Description:FIELD OF INVENTION
[0001] Embodiments of the present disclosure relate generally to ground‐based aircraft environmental control systems. Particularly, but not exclusively, embodiments of the present disclosure relate to pre-conditioned air unit, system and method for providing pre-conditioned air to parked aircrafts – ensuring dynamic adjustments responsive to individual aircraft requirements and real-time environmental loads.
BACKGROUND
[0002] Modern commercial airliners demand meticulously pre-conditioned air to sustain passenger comfort, avionics reliability, and cabin pressurization throughout all phases of operation. In‐flight environmental control systems (ECS) conventionally exploit engine bleed air or auxiliary power units to pressurize, dehumidify, and thermally regulate air circulated within the cabin. However, once the aircraft is parked and engines are shut down – often for safety, fuel conservation, and noise abatement, these onboard assets become unavailable.
[0003] Ground-based Pre-Conditioned Air (PCA) units address this exigency by drawing ambient air, subjecting the ambient air to one or more thermal exchange processes before delivering the pre-conditioned airstream into the aircraft. These PCA units may be electrically driven or powered by dedicated engines, yet they all contend with the challenge of transforming fluctuating ambient air into a stable, comfortable cabin environment.
[0004] The thermal load imposed on PCA units is inherently capricious, varying widely with geographic locale (tropical humidity versus arctic chill), diurnal and seasonal swings, solar irradiation on exposed fuselage surfaces, aircraft class (narrow-body versus wide-body), and disparate crew or passenger comfort requirements. Under such instable and divergent conditions and since conventional PCA designs often employ fixed-capacity conditioning stages and manual controls, the traditional approaches result in suboptimal energy efficiency, temperature overshoot or undershoot at the aircraft inlet, limited responsiveness to real-time environmental fluctuations, delayed attainment of target temperatures, and compromised cabin climate control.
[0005] Compounding these challenges, most extant PCA units are architected to serve only a single aircraft at a time. While some units provision multiple discharge outlets, these outlets draw from a common conditioning stream and lack the independent modulation of temperature, pressure, and flow rate necessary to satisfy the unique demands of multiple aircraft simultaneously. Attempts to connect more than one airplane to such units invariably lead to uneven airflow distribution, compromised cabin climate control, and an inability to meet each aircraft’s unique thermal demands in tandem.
[0006] Accordingly, there exists a pressing need for an advanced ground-based PCA solution that delivers dynamically adjustable, multi-stage conditioning – capable of both sub-freezing and non-sub-freezing output – while concurrently and independently serving multiple parked aircrafts. Such a system must seamlessly adapt to real-time thermal loads, facilitate precise temperature, pressure, and flow-rate control per aircraft, and integrate with airport docking and control systems to automate operation with minimal manual entry, thereby maximizing responsiveness, reliability, and operational efficiency.

BRIEF DESCRIPTION
[0007] In accordance with an embodiment of the present disclosure, a system for providing pre-conditioned air to a plurality of parked aircrafts is provided. The system comprises a pre-conditioned air unit that comprises a plurality of duct structures, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure is configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective air flow path, wherein the one or more thermally coupled heat exchange modules comprises: a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and a plurality of secondary heat exchange modules; a main control unit configured to control operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures; a plurality of secondary control units, each secondary control unit configured to control a respective secondary heat exchange module disposed in the plurality of duct structures; and a memory storing a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts; a plurality of sensors disposed along the respective duct structure and configured to provide a sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules; and a processing module coupled to the memory, the main control unit, and the plurality of secondary control units, wherein the processing module configured to configured to: calculate real-time thermal load based on the sensor data received in real-time; receive one or more aircraft identifiers from an operator interface; retrieve, for the one or more aircraft identifiers, a corresponding predefined operating configuration indicating a target supply air condition from the memory; determine, based on corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determine whether one or more of its corresponding plurality of outlets are to be activated; and based on the determination and the real-time thermal load, dynamically adjust operation of the main control unit and the secondary control units to cater pre-conditioned air at the target supply air condition at each active air outlet.
[0008] In accordance with another embodiment of the present disclosure, a method for providing pre-conditioned air to one or more parked aircrafts comprising: conveying ambient air through a plurality of duct structures, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective airflow path, wherein the one or more thermally coupled heat exchange modules comprises a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and a plurality of secondary heat exchange modules; controlling operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures via a main control unit; controlling operation of each secondary heat exchange module disposed in the plurality of duct structures via a respective secondary control unit; storing a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts in a memory; receiving sensor data via a plurality of sensors disposed along each duct structure, the sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules; calculating real-time thermal load based on the sensor data received in real-time; receiving one or more aircraft identifiers from an operator interface; retrieving, for the one or more aircraft identifiers, a corresponding predefined operating configuration indicating a target supply air condition from the memory; determining, based on the corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determining whether one or more of its corresponding plurality of outlets are to be activated; and based on the determination and the real-time thermal load, dynamically adjusting operation of the main control unit and the secondary control units to cater pre-conditioned air at the target supply air condition at each active air outlet.
[0009] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:
[0011] FIG. 1 illustrates a schematic diagram of a pre-conditioned air unit for providing pre-conditioned air to one or more parked aircrafts, in accordance with an example implementation of the present subject matter;
[0012] FIG. 2 illustrates a schematic diagram of vapour-compression refrigeration circuit forming secondary heat exchange module disposed across the airflow path of a duct structure, in accordance with an example implementation of the present subject matter;
[0013] FIGS. 3A-3B illustrate a closed view and a partial view of an enclosure housing the pre-pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter;
[0014] FIGS. 4A-4B illustrate a partial view of the pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter;
[0015] FIG. 5 illustrates a schematic view of blower provided in the pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter;
[0016] FIG. 6 illustrates a partial view of chilled water circuit provided in the pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter;
[0017] FIG. 7 illustrates a schematic view of different components of the vapour-compression refrigeration circuit provided in the pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter;
[0018] FIG. 8 illustrates a block diagram of a control system causing operation of the PCA unit forming a system for providing pre-conditioned air to one or more aircrafts, in accordance with an example implementation of the present subject matter;
[0019] Fig. 9 illustrates an example implementation of the system for providing pre-conditioned air to one or more parked aircrafts at a MARS gate, in accordance with an example implementation of the present subject matter;
[0020] Figs. 10A-10B illustrate a method for providing pre-conditioned air to one or more parked aircrafts, in accordance with an example implementation of the present subject matter;
[0021] Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
DETAILED DESCRIPTION
[0022] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.
[0023] The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more devices or subsystems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, sub-systems, elements, structures, components, additional devices, additional sub-systems, additional elements, additional structures or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.
[0024] The term “plurality,” as used herein, means two or more, i.e., it encompasses two, three, four, five, etc. For example, the expression “plurality of duct structures” may include two duct structures, three duct structures and so on.
[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
[0026] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
[0027] FIG. 1 illustrates a schematic diagram of a pre-conditioned air unit 100 for providing pre-conditioned air to one or more parked aircrafts, in accordance with an example implementation of the present subject matter. In some implementations, the pre-conditioned air unit 100 may be configured as a stationary, pit-based air delivery pre-conditioned air unit integrated into the airport gate infrastructure. Unlike mobile pre-conditioned air units, such as cart-based units that are maneuvered to the aircraft and coupled via external ducts and flexible hoses, the pit-based implementation enables air delivery through fixed ducts and flexible hoses embedded below the apron surface, with outlets located in proximity to the aircraft stand. This stationary architecture allows for minimized obstruction on the tarmac, reduced deployment time, and integration with gate utilities and building management systems. In alternative implementations, the pre-conditioned air unit may be configured for modular deployment with semi-fixed conduits and enclosures, allowing adaptation to gate layout variations or retrofit scenarios, without departing from the scope of the present subject matter.
[0028] As shown therein, the pre-conditioned air unit 100 comprises a plurality of duct structures 100A and 100B. Each duct structure 100A, 100B define a respective airflow path extending from a corresponding air inlet 118A, 118B to a corresponding plurality of air outlets 112A-1, 112A-2, 112B-1, 112B-2, each duct structure 100A, 100B is configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules 106A, 106B, 108A-1 to 108A-3, 108B-1 to 108B-3 positioned along the respective air flow path. For example, the duct structure 100A has one or more thermally coupled heat exchange modules 106A, and 108A-1 to 108A-2 disposed along the airflow path defined by the air inlet 118A and the plurality of air outlets 112A-1, and 112A-2. Similarly, the duct structure 100B has one or more thermally coupled heat exchange modules 106B, and 108B-1 to 108B-2 disposed along the airflow path defined by the air inlet 118B and the plurality of air outlets 112B-1, and 112B-2. Each of the one or more thermally coupled heat exchange modules 106A, and 108A-1 to 108A-3, 106B, and 108B-1 to 108B-3 in a respective duct structure is operable independently or simultaneously of the each of the one or more thermally coupled heat exchange modules in the other duct structure based on the real-time thermal load and the target supply air condition associated with the each active air outlet.
[0029] The ambient air is drawn into the respective duct structure 100A, 100B via the respective air inlet 118A, 118B by a respective blower 104A, 104B upon passing through a respective air filter assembly 102A, 102B. For example, in duct structure 100A, ambient air enters through air inlet 118A and first encounters air filter assembly 102A, which is configured to remove particulate matter, airborne contaminants, and other undesirable impurities from the incoming air stream. The air filter assembly 102A may comprise one or more filter elements, such as pre-filters, HEPA filters, or washable mesh filters, adapted for operational environments near aircraft aprons, where high dust and pollutant loads are expected. After filtration, the cleaned air is directed into the blower 104A, which is operatively coupled downstream of the filter assembly 102A and is configured to generate a negative pressure at the inlet side and a corresponding positive pressure at the outlet side to induce and sustain airflow along the defined airflow path of duct structure 100A. The blower 104A may be of a centrifugal or axial type and may be powered by a dedicated electric motor or any actuator. In an exemplary implementation, the electric motor driving the blower is operatively coupled to a Variable Frequency Drive (VFD) controller circuit via a VFD panel. The VFD enables continuous and real-time modulation of blower speed based on airflow requirements, back-pressure in the duct, or ambient air conditions. This allows for optimal air delivery performance while reducing energy consumption, mechanical wear, and operational noise. Similarly, in duct structure 100B, ambient air passes through filter assembly 102B and is propelled forward by blower 104B to establish a continuous air stream through the respective thermal conditioning stages. In an example, the blower at the respective duct structure is configured to provision air at a pressure and a flow rate same or different from the blower of the other duct structure, based on the determination and the real-time thermal load.
[0030] Each blower 104A, 104B may be controllable via a programmable logic controller (PLC) and may include sensors or feedback systems to modulate blower speed, flow rate, or static pressure in response to real-time temperature demands, aircraft cooling load, or downstream flow resistance. This allows the pre-conditioned air unit 100 to maintain optimal airflow and ensures that the downstream thermal exchange modules receive a stable and predictable volume of air for conditioning. In some implementations, the filter assemblies 102A, 102B and blowers 104A, 104B may be arranged within a compact modular frame positioned near or partially recessed below the aircraft service apron, such as in a pit-mounted configuration, thereby minimizing equipment footprint and reducing acoustic and thermal impact in the surrounding gate environment.
[0031] The one or more thermally coupled heat exchange modules 106A, 106B, 108A-1 to 108A-2, 108B-1 to 108B-3 include a primary heat exchange module 106A, 106B and a plurality of secondary heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3. Each primary heat exchange module 106A, 106B comprises a chilled water coil positioned in thermal proximity to the duct structure 100A, 100B and configured to reduce temperature of the air via heat transfer to a chilled water circuit 114A, 114B. As shown in Fig. 1, the pre-conditioned air unit 100 includes a chilled water circuit 114 that enables thermal conditioning of ambient air by utilizing chilled water supplied from an external chiller plant and routes the chilled water into respective chilled water coil. Each chilled water coil is disposed downstream of the respective air filter assembly and serves as an initial stage of heat exchange for reducing the temperature of hot and filter ambient air entering the respective duct structure 100A, 100B. The primary heat exchange module may be configured to reduce the temperature of the ambient air in the airflow path at a target discharge air temperature between approximately 7°C and 9°C upon exiting the chilled water coil.
[0032] The chilled water circuit 114 includes a 3-way valve disposed between the plurality of duct structures 100A, 100B and an inlet conduit connecting the chilled water circuit to the external chiller plant. Further, the chilled water circuit 114 includes an actuator assembly configured to regulate the flow of chilled water between at least two pathways by operating the 3-way valve in two positions. In a first position, the 3-way valve of the chilled water circuit 114 is configured to direct incoming chilled water into the respective duct structures 100A and 100B for active heat exchange with the incoming ambient air. In this position, the 3-way valve actuates to allow chilled water from a chilled water source such as a centralized chiller plant or chilled water supply header to enter the upstream portion of the chilled water circuit associated with each duct structure 100A, 100B. In this position, the chilled water flows sequentially through one or more chilled water coils disposed in the first-stage thermal exchange modules (e.g., modules 106A and 106B) and subsequently through one or more downstream heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3 via a respective water inlet conduits 114A-1 to 114A-3, 114B-1 to 114B-3 as detailed further in the specification.
[0033] As the chilled water absorbs thermal energy from the ambient air via the heat exchange surfaces, it exits each respective duct structure 100A, 100B at respective heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3 and is conveyed downstream via respective outlet ducts/conduits 114A’-1, 114A’-2, 114B’-1, 114B’-2(for brevity, depicted only for heat exchange modules 108A-1, 108B-1) toward corresponding discharge manifolds 114A’ and 114B’. Each discharge manifold 114A’, 114B’ serves as a collection conduit for the warmed chilled water exiting the thermal exchange modules. In some implementations, each discharge manifold 114A’, 114B’ is fluidly coupled with a corresponding pressure-independent control valve 116A, 116B, configured to regulate the flow rate irrespective of upstream or downstream pressure fluctuations, thereby ensuring consistent chilled water return flow.
[0034] The pressure-independent valves 116A, 116B may be electronically actuated and governed by a programmable logic controller (PLC) to maintain desired flow rates, pre-conditioned air unit balance, and thermal performance. After exiting the discharge manifolds 114A’, 114B’, the used chilled water is directed via the corresponding pressure-independent valves 116A, 116B toward the return loop of the chiller plant via a respective booster pump assembly. The booster pump provides sufficient hydraulic head to overcome piping resistance and elevation differentials, ensuring reliable return flow of the thermally exchanged chilled water to the chilled water plant for recirculation and re-cooling. Thus, the integration of the 3-way valve, pressure-independent valve, and booster pump enables flexible and efficient management of chilled water flow paths depending on operational mode, load conditions, or maintenance requirements. In a second position, the 3-way valve selectively bypasses the chilled water coil and instead diverts chilled water directly to the discharge line, effectively isolating the chilled water from the flow path. This configuration enables flexible thermal control, supports maintenance operations, and prevents unnecessary flow through inactive pre-conditioned air unit branches. The primary heat exchange module 106A, 106B is configured to reduce the temperature of the ambient air in the airflow path at a target discharge air temperature between approximately 7°C and 9°C upon exiting the chilled water coil.
[0035] Further, the primary heat exchange module 106A, 106B and the plurality of secondary heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3 are arranged sequentially along the respective duct structure 100A, 100B such that the primary heat exchange module 106A, 106B is disposed downstream of a respective air filter assembly 102A, 102B, through which ambient air enters the respective duct structure 100A, 100B. The first heat exchange module 108A-1, 108B-1 of the plurality of secondary heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3 is arranged downstream of the respective primary heat exchange module 106A, 106B, followed by the second heat exchange module 108A-2, 108B-2, and then the third heat exchange module 108A-3, 108B-3. A heating module 110A, 110B is disposed between the second and third heat exchange modules, i.e., downstream of 108A-2, 108B-2 and upstream of 108A-3, 108B-3, and comprises one or more heating elements thermally coupled to the duct structure 100A, 100B and configured to selectively raise the ambient air temperature.
[0036] In an example, the heating module 110A, 110B includes two electric heaters, each rated at 11kW, with thyristor-based control for precise heating regulation. The heaters are configured to operate particularly under sub-freezing conditions, in compliance with IATA AHM 997 and AHM 974 standards and aircraft manufacturer recommendations regarding functional specification and aircraft inlet air with specific humidity and temperature. Specifically, the heaters are activated when the air temperature delivered to the aircraft is below 2°C but above -8°C, a condition under which air is intentionally cooled to a level below the target temperature to reduce specific humidity (i.e., moisture content), and then reheated using the heating module to reach the final delivery temperature. This staged cooling and reheating strategy ensures that the moisture content of the air is reduced to less than 2 grams of water per kilogram of dry air, thereby achieving dehumidification requirements for low-temperature operation. The inclusion of the heating module at this location in the airflow path allows the pre-conditioned air unit to maintain optimal cabin comfort and operational compliance while preserving thermal control flexibility. Each of the secondary heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3 comprises a respective vapour-compression refrigeration circuit (detailed description provided later in this disclosure).
[0037] In an example, the first heat exchange module 108A-1, 108B-1 may be configured to operate with an evaporating temperature of approximately -10°C, a condensing temperature of approximately 13-20°C, and to provide the ambient air at a target discharge air temperature of approximately -5°C upon exiting the first heat exchange module. The second heat exchange module 108A-2, 108B-2 may be configured to operate with an evaporating temperature of approximately -20°C, a condensing temperature of approximately 13-20°C, and to provide the ambient air at a target discharge air temperature of approximately -15°C upon exiting the second heat exchange module and the third heat exchange module 108A-3, 108B-3 may be configured to operate with an evaporating temperature of approximately -30°C, a condensing temperature of approximately 13-20°C, and to provide the ambient air at a target discharge air temperature of approximately -25°C upon exiting the third heat exchange module.
[0038] After being drawn through the respective air inlet 118A, 118B and sequentially pre-conditioned via the primary heat exchange module 106A, 106B and one or more downstream secondary heat exchange modules 108A-1 to 108A-3 and 108B-1 to 108B-3 the ambient air is progressively cooled and treated along the airflow path defined within the respective duct structures 100A and 100B. The pre-conditioned air exiting the downstream end of each duct structure 100A, 100B is received into a respective internal plenum chamber 112A, 112B formed proximate to the downstream terminal end of the airflow path. From the respective plenums 112A, 112B, the pre-conditioned air is directed outward through a corresponding plurality of air delivery outlets, including but not limited to outlets 112A-1, 112A-2, 112B-1, and 112B-2, for delivery to one or more parked aircrafts.
[0039] Fig. 2 illustrates a schematic diagram of vapour-compression refrigeration circuit 200 forming secondary heat exchange module 108A-1 to 108A-3, 108B-1 to 108B-3 disposed across the airflow path of a duct structures 100A, 100B, in accordance with an example implementation of the present subject matter. Referring to FIG. 2, there is shown a refrigeration circuit 200 integrated within a duct structure 202 of a modular pre-conditioned air (PCA) 100 designed to supply temperature-controlled air to parked aircrafts. It may be noted that the duct structure 202 is same as the duct structures 100A, 100B. The circuit 200 operates on a closed-loop vapor-compression refrigeration cycle and is configured to deliver cooled or sub-cooled air as demanded. The circuit comprises a hermetically sealed scroll compressor 206 (S2-CMP1A) which receives low-pressure vaporized refrigerant from an accumulator 205 via a suction line and compresses it into a high-pressure, high-temperature vapor. This high-pressure vapor exits the compressor 206 through a discharge line fitted with a non-return valve (NRV), and flows toward a water-cooled condenser 208, the NRV is to prevent reverse migration of liquid refrigerant into the compressors during idle states. This feature protects compressor integrity and avoids hydraulic lock, thus enhancing equipment durability and reducing maintenance intervals. Complementing the compression cycle, the system employs brazed plate heat exchanger (BPHE) condensers in each refrigeration stage. These BPHEs utilize counterflow chilled water to effectively condense high-pressure refrigerant gas into liquid form. The modular plate structure of the BPHE offers excellent thermal transfer with minimal footprint, while the consistent condensing temperature design of 13-20°C across stages ensures uniform and predictable performance. This configuration allows the system to achieve high energy efficiency and tight control over outlet refrigerant conditions. In some implementations, variable-speed (inverter-driven) compressors may be used for part-load efficiency and soft start/stop capability. Particularly, the compressor 206 is fluidly coupled to the evaporator coil 204, for example, fin-tube evaporator coils, via the accumulator 205 and configured to circulate the refrigerant and the compressor 206 is fluidly coupled to the condenser 208. Each compressor 206 within the respective refrigeration circuit 200 may be operatively coupled to a VFD controller to allow adaptive modulation of compression speed in response to pre-conditioned air unit load, evaporator temperature, and feedback from the electric expansion valve, thereby enhancing thermal efficiency and compressor lifespan. Preferably, in an example, the PCA unit employs high-efficiency scroll compressors operating with R410A/R32 refrigerant, configured in both variable and fixed speed variants to accommodate varying thermal loads. These compressors are engineered to deliver high-pressure refrigerant gas while achieving deep evaporating temperatures of -10°C, -20°C, and -30°C across respective cooling stages, with consistent condensing temperatures maintained at 13-20°C. Integrated features such as oil separators with sight glass, internal oil filtration, and crankcase belt heaters enhance operational reliability and longevity. The ability to reach sub-freezing evaporating temperatures supports rapid thermal draw-down during high-demand cooling cycles, offering a critical advantage for applications at hot and humid airport environments or during quick turnaround schedules.
[0040] The flow is monitored and regulated by a pair of low-pressure and high-pressure switches and pressure transducers interfaced with a programmable logic controller (PLC), thereby enabling real-time safety monitoring and modulation of compressor performance. The condenser 208 being and thermally coupled to the chilled water circuit 114 and configured to circulate the refrigerant, is cooled by chilled water entering from inlet conduits 114A-1 to 114A-3, 114B-1 to 114B-3 that is selectively routed through a three-way valve 210, which can direct the flow of chilled water into the condenser 208 or bypass it entirely based on operational requirements. For example, Chilled water enters the condenser 208 via a “water in” inlet and exits through a “water out” port, forming a thermally coupled loop that removes heat from the refrigerant, thereby condensing it into a subcooled high-pressure liquid. This condensed refrigerant enters a liquid receiver 212 which stabilizes flow and compensates for volume fluctuations across operating conditions. To mitigate over-pressurization risks, a pressure relief valve is mounted above the receiver 212, calibrated to discharge at 42 bar, thereby ensuring system safety compliance and safeguarding components from mechanical failure due to pressure surges.
[0041] As illustrated in Figs. 1 and 2, it may be noted that each secondary heat exchange module 108A-1 to 108A-3, 108B-1 to 108B-3 is fluidly coupled to the chilled water circuit 114 through a respective three-way valve that selectively directs the flow of chilled water into the corresponding condenser coil 208. For example, when the chilled water circuit is operational, chilled water enters the first condenser 208 positioned within a first secondary heat exchange module 108A-1, 108B-1 via chilled water line 114A-1, 114B-1 through a corresponding three-way valve. Similarly, chilled water is supplied to the second and third condenser coils, positioned within the second and third secondary heat exchange modules 108A-2, 108A-3, 108B-2, 108B-3, respectively, via chilled water lines 114A-2, 114A-3, 114B-2, 114B-3 respectively, each of which is likewise provided with a corresponding three-way valve to control fluid admission. In this manner, each condenser in the plurality of secondary heat exchange modules independently receives chilled water through its own regulated or dedicated path, ensuring modular thermal management and preventing undesired crossflow or thermal coupling between different condenser stages.
[0042] From the receiver 212, the liquid refrigerant is routed through a filter/drier 214 to remove particulates, moisture, and acids, and subsequently through a sight glass 216 for visual charge inspection. The drier/filter 214 includes silica gel to adsorb moisture and capture particulate contaminants. This ensures the refrigerant circuit remains dry and clean, minimizing corrosion, freezing, and expansion valve blockage. Sight glasses equipped with moisture-sensitive visual indicators provide operators with a real-time assessment of system dryness, enabling predictive maintenance and quality assurance. Further, solenoid valves installed on both liquid and hot gas lines offer precise control over refrigerant routing. These valves, actuated by electric current, enable fast and automated switching, supporting real-time flow regulation under PLC control to meet dynamically changing cooling demands. The refrigerant then enters a solenoid valve 220 which is normally closed and is actuated open under control signals from the PLC leading to an electric expansion valve 224.
[0043] Under normal cooling operation, the electric expansion valve 224 modulated by superheat control logic or valve driver or PLC, meters the flow of refrigerant into the evaporator coil 204 where the refrigerant undergoes isenthalpic expansion and evaporates into a low-pressure vapor. Concurrently, hot ambient air is directed over the evaporator coil 204. Particularly, evaporator coil 204 is positioned in thermal proximity to the duct structure 100A, 100B, 202 and configured to absorb heat from the air using a refrigerant, where it transfers sensible and latent heat to the refrigerant, thereby cooling the air and causing the refrigerant to vaporize. The cooled air progresses through the respective duct structure 100A, 100B, 202 until it is delivered to the aircraft. The bypass path defined at the exit of the compressor 206 via the hot gas bypass valve 218, 222 is selectively enabled during low-load or anti-freeze operations, directing a portion of high-pressure discharge vapor to bypass the expansion valve and enter the evaporator coil 204 directly, thereby maintaining a minimum evaporator pressure and preventing coil icing. Further, the evaporator coil 204 being fin and tube heat exchangers are inherently optimized for maximum surface area contact with forced air, allowing efficient latent heat absorption from the airflow and supporting evaporating temperatures down to -30°C, which is critical for fast cabin cooling.
[0044] In other words, to mitigate excessive compressor discharge temperatures and maintain thermal stability within the refrigerant circuit, the PCA unit incorporates a de-superheating valve configured to reduce the superheat of the refrigerant gas downstream of the compressor. Specifically, a de-superheating valve fluidly coupled between a liquid refrigerant line extending from the receiver 212 and the suction-side accumulator 205 is arranged to divert a metered portion of high-pressure liquid refrigerant from the receiver into the accumulator 205. The diverted liquid refrigerant is routed through a thermostatically controlled expansion device, such as a mechanical thermostatic expansion valve actuated by a solenoid valve, which reduces the pressure and temperature of the liquid refrigerant prior to its entry into the accumulator 205. Upon entering the accumulator 205, the cooled refrigerant mixes with the suction vapor, thereby lowering the effective superheat of the return gas entering the compressor 206. This controlled de-superheating process moderates compressor discharge temperatures, enhances system efficiency, and extends compressor life by maintaining thermal conditions within design tolerances.
[0045] As may be noted, the solenoid valve 220 is strategically placed downstream of the filter/dryer 214 and sight glass 216, and upstream of the electric expansion valve 224, in the high-pressure liquid line of the vapor-compression refrigeration loop. Unlike conventional thermostatic or capillary expansion devices, the electric expansion valve 224 operates using a stepper motor or pulse-width modulated actuator, which allow fine-resolution control over the valve opening in real time. This precise modulation enables the valve to dynamically respond to thermal requirements as explained later in this disclosure.
[0046] The primary purpose of the solenoid valve 220 is to initiate or interrupt the flow of high-pressure liquid refrigerant into the evaporator coil 204 based on pre-conditioned air unit 100 demand. When cooling is required such as during aircraft boarding or ground servicing the control PLC energizes the solenoid coil, lifting the internal plunger and thereby opening the valve to permit refrigerant flow to the expansion valve. Conversely, when cooling is not required e.g., when the aircraft is disconnected, cabin temperature is stable, or during defrost or maintenance modes, the solenoid valve is de-energized, closing the valve and effectively cutting off refrigerant flow to the evaporator, preventing unwanted heat exchange or pressure buildup. This binary control capability provides a critical energy-saving and safety function, preventing flooding of the evaporator and ensuring that refrigerant does not pool during pre-conditioned air unit idle states, which could lead to compressor slugging upon restart. It also allows the pre-conditioned air unit 100 to respond rapidly to changing load conditions or fault states by immediately halting refrigerant movement.
[0047] In some embodiments, the solenoid valve may also work in coordination with hot gas bypass control, low-pressure cutout logic, or time-delay restart logic, enhancing pre-conditioned air unit stability and compressor protection. The valve 220 is typically a normally closed type, meaning it remains shut unless actively energized, offering a fail-safe configuration in the event of power loss.
[0048] Upon completion of heat exchange, the vaporized refrigerant exits the evaporator 204 and flows into the accumulator 205 which separates and retains any residual liquid to protect the compressor from slugging. The accumulator volume is sized to 50% of the total refrigerant charge, balancing system safety and operational reliability. The vapor then returns to the compressor 206 (S2–CMP1A) to complete the cycle. The refrigeration circuit is fully instrumented with pressure switches, transducers, temperature sensors, and flow controls, all monitored by a slave programmable logic controller (PLC) dedicated to refrigeration control, which is in communication with a main PLC coordinating the overall (PCA) pre-conditioned air unit. The electric expansion valve, solenoid valves, and hot gas bypass valve are all driven via control outputs based on temperature setpoints, ambient conditions, hose-end thermocouples, and aircraft-specific cooling recipes.
[0049] The refrigerants may include, but are not limited to R-410A, R-407C, and R-32, and may be adapted to future low-GWP refrigerants such as R-454B or natural refrigerants like R-290 or R-744, subject to compatibility and safety regulation compliance. Thus, the integration of a dual-path three-way valve, hot gas bypass, and electric expansion valve allows fine-tuned performance control, fast pulldown, and protection against frost conditions, thereby enabling rapid response to variable aircraft cooling loads.
[0050] Further, during operation, as ambient air passes over the chilled water coil in the primary heat exchange module 106A, 106B and the evaporator coils 204 in the secondary heat exchange modules 108A-1 to 108A-3, 108B-1 to 108B-3, moisture present in the air condenses upon contact with the cooled coil surfaces, resulting in condensate water formation within the duct structure 100A, 100B. To effectively manage the accumulated condensate and prevent pooling or recirculation within the duct structure 100A, 100B, the condensate outlets from each chilled water coil and evaporator coil are fluidly connected to a dedicated condensate line 120A, 120B. This common condensate line is routed downward along the length of the duct structure and is connected to a condensate water tank 122 via a dedicated condensate pump. The condensate pump is operable to transport the collected condensate to the tank during active pre-conditioned air unit operation. A respective non-return valve (NRV) is positioned downstream of the pump and upstream of the condensate tank to prevent backflow and ensure unidirectional movement of condensate water into the tank. This configuration provides a gravity-assisted and pump-assisted mechanism for continuous drainage of condensate from multiple stages of cooling and is particularly advantageous in multi-stage cooling duct systems where prolonged operation of heat exchange modules, especially under high humidity conditions, can result in significant condensate accumulation. The centralized condensate collection approach also facilitates easier maintenance and enhances hygiene by avoiding localized water stagnation in individual heat exchange modules.
[0051] Not shown in the Figs. 1 and 2 for brevity, however, a plurality of sensors are disposed along the respective duct structure 100A, 100B and are configured to provide a sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules.
[0052] FIGS. 3A-3B illustrate a closed view and a partial view of an enclosure housing the pre-conditioned air unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter. Referring to Fig. 3A, the pre-conditioned air (PCA) unit 300 comprises a pair of functionally integrated sub-units or modules 300A, 300B, physically conjoined to form a composite unit. The two conjoined units are mechanically coupled via a common support frame, chassis, or structural base, and may share one or more operational subsystems such as power distribution, control logic, chilled water distribution lines, or refrigerant lines. In some embodiments, each unit may be independently operable but collectively configured to function in a synchronized manner under the supervision of a centralized or distributed control system. This modular and conjoined configuration facilitates support for larger aircraft (e.g., Code E or F aircraft), enables redundancy, and allows for scalable deployment in space-constrained apron or gate areas.
[0053] In an example, the pre-conditioned air (PCA) unit 300 is enclosed within an acoustic housing that is configured to minimize airborne noise emissions and mitigate environmental disturbances during operation. The acoustic housing fully or partially encapsulates the PCA unit, thereby providing both sound attenuation and physical protection. The acoustic housing may be fabricated from noise-dampening composite materials, such as multi-layered panels comprising an inner layer of perforated galvanized steel or aluminum, a middle core of sound-absorbing mineral wool or foam (e.g., polyurethane or melamine-based), and an outer weather-resistant casing formed of powder-coated sheet metal, fiber-reinforced polymer (FRP), or corrosion-resistant stainless steel. This may also include vibration isolation mounts and gasket-sealed access panels to prevent transmission of structural-borne noise. In another example, the acoustic housing is rated to meet or exceed relevant noise reduction criteria (e.g., achieving a sound transmission class (STC) or noise reduction coefficient (NRC) above a predetermined threshold), in accordance with airport environmental compliance requirements and international standards such as ICAO Annex 16 or equivalent national standards. The housing may further include ventilation louvers with acoustic baffles, strategically positioned for adequate airflow while maintaining acoustic performance.
[0054] Additionally, the acoustic housing is configured to be modular and service-accessible, allowing maintenance personnel to access internal components without requiring full disassembly, and is structurally reinforced to withstand outdoor environmental conditions including wind load, rain, UV exposure, and temperature variations. In certain configurations, the housing may also contribute to thermal insulation and support compliance with environmental safety regulations by reducing the emission of both noise and airborne particulate matter during operation.
[0055] The pre-conditioned air unit 300 is same as pre-conditioned air unit 100 shown in Fig. 1 and includes an opening 302 through which the ambient air enters the respective air filter assembly of the respective duct structure of the respective subunit 300A, 300B. Fig. 3B read in light of Figs. 1 and 2, shows compressor 306A, 306B (206 in Fig. 2) in subunits 300A, 300B. The housing may include a base frame 308, side frames unified as required, and a canopy 304 forming the acoustic housing. Further, Fig. 3B illustrates control panel 312 comprising a main control unit and a plurality of secondary control units and a VFD panel 310. The main control unit may be configured to control operation of the chilled water circuit 114 and the primary heat exchange module 106A, 106B disposed of the plurality of duct structures 100A, 100B. Further, the plurality of secondary control units, each may be configured to control a respective secondary heat exchange module 108A-1 to 108A-3, 108B-1 to 108B-3 and heating modules 100A, 110B disposed in the plurality of duct structures 100A, 100B.
[0056] FIGS. 4A-4B illustrate a partial view of the pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter. Referring to Figs. 1, 2, and 4A-4B, the pre-conditioned air unit 400 is shown including blowers 404A, 404B, compressors 406A-1 to 406A-3, 406B-1 to 406B-3, same as compressor 206, 306 and condenser 408, same as 208 shown in Fig. 2 provided at each secondary heat exchange module (108A-1 to 108A-3, 108B-1 to 108B-3 shown in Fig. 1).
[0057] FIG. 5 illustrates a schematic view of blower provided in the pre-conditioned air (PCA) unit illustrated in Fig.1, in accordance with an example implementation of the present subject matter. Referring to Figs. 1 and 5, blower 504 is shown, the blower 504 is same as the blowers 104A, 104B. The ambient air enters through the opening 502 and upon passing through respective air filter provided in the respective airflow path is drawn by the respective blower 504 into the respective duct structure 100A, 100B.
[0058] FIG. 6 illustrates a partial view of the chilled water circuit provided in the pre-conditioned air (PCA) unit illustrated in FIG. 1, in accordance with an example implementation of the present subject matter. Referring to FIGS. 1 and 6 collectively, a chilled water circuit 614 and Evaporator coils circuit 614A-1, 614A-2, and 614A-3 is illustrated in FIG. 6. The chilled water circuit 614, 614A-1, 614A-2, and 614A-3 correspond to and represent the same chilled water circuit respectively identified in FIG. 1 as 114, 114A-1, 114A-2, and 114A-3, which extend through the duct structure 100A. Similarly, chilled water lines 114B-1, 114B-2, and 114B-3 shown in FIG. 1 are structurally and functionally analogous to those provided for the duct structure 100B and are considered as parallel counterparts to 614A-1 to 614A-3 for the second duct structure 100B.
[0059] Further referring to Figs. 1 and 6, a plenum 612A and plenum 612B are illustrated in FIG. 6, which are respectively the same as plenum 112A and plenum 112B shown in FIG. 1. These plenums are structurally integrated into the duct structures 100A and 100B and serve to homogenize the flow of pre-conditioned air before it is discharged to the aircraft or terminal hose assembly.
[0060] FIG. 7 illustrates a schematic view of different components of the vapour-compression refrigeration circuit provided in the pre-conditioned air (PCA) unit as illustrated in FIG. 1, in accordance with an example implementation of the present subject matter. The components depicted in FIG. 7 correspond to those shown in the functional layout of the PCA unit in FIG. 2 and are described herein with reference to both figures for continuity and clarity. Referring collectively to Figs. 2 and 7, a drier 714 is shown in FIG. 7, where the drier 714 is the same component as the drier/filter 214 shown in FIG. 2 and functions to remove moisture and particulates from the refrigerant stream to ensure efficient and reliable operation of the refrigeration circuit. Similarly, a compressor 706 is depicted, and the compressor 706 is the same as the compressor 206 shown in FIG. 2, configured to compress low-pressure refrigerant vapor to a high-pressure, high-temperature state as part of the thermodynamic cycle. Further, a condenser 708 is illustrated in FIG. 7, which is the same as the condenser 208 in FIG. 2, and is configured to reject heat from the refrigerant to the ambient or to a secondary heat transfer medium, thereby condensing the refrigerant into a liquid state.
[0061] Also depicted is an accumulator 705, which is the same as the accumulator 205 shown in FIG. 2; the accumulator 705 is configured to prevent liquid refrigerant from entering the suction line of the compressor 706, thereby protecting the compressor from potential damage due to liquid slugging. Furthermore, a sight glass 716 is shown, the sight glass 716 is the same as the sight glass 216 in FIG. 2 and is provided for visual inspection of the refrigerant flow and condition (e.g., presence of bubbles indicating vapor entrainment or inadequate charge). Additionally, a receiver 712 is shown in FIG. 7, which corresponds to the receiver 212 illustrated in FIG. 2, and serves to store excess liquid refrigerant within the system and ensure a steady supply of liquid refrigerant to the expansion valve regardless of variations in system load or environmental conditions.
[0062] In accordance with an embodiment of the present disclosure, a system for providing pre-conditioned air to a plurality of parked aircrafts is provided. The system comprises a pre-conditioned air unit that comprises a plurality of duct structures, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure is configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective air flow path, wherein the one or more thermally coupled heat exchange modules comprises: a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and a plurality of secondary heat exchange modules; a main control unit configured to control operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures; a plurality of secondary control units, each secondary control unit configured to control a respective secondary heat exchange module disposed in the plurality of duct structures; and a memory storing a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts; a plurality of sensors disposed along the respective duct structure and configured to provide a sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules; and a processing module coupled to the memory, the main control unit, and the plurality of secondary control units, wherein the processing module configured to configured to: calculate real-time thermal load based on the sensor data received in real-time; receive one or more aircraft identifiers from an operator interface; retrieve, for the one or more aircraft identifiers, a corresponding predefined operating configuration indicating a target supply air condition from the memory; determine, based on corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determine whether one or more of its corresponding plurality of outlets are to be activated; and based on the determination and the real-time thermal load, dynamically adjust operation of the main control unit and the secondary control units to cater pre-conditioned air at the target supply air condition at each active air outlet.
[0063] FIG. 8 illustrates a block diagram of a control system causing operation of the PCA unit forming the system for providing pre-conditioned air to one or more aircrafts, in accordance with an example implementation of the present subject matter. As shown therein, the control system 800 may comprise a processor(s) 802, a memory(s) 804 coupled to and accessible by the processor(s) 802, and a communication interface 806 coupled to the memory(s) 804. The functions of various elements shown in the figs., including any functional blocks labeled as "processor(s)", may be provided through the use of dedicated hardware as well as hardware capable of executing instructions. Other hardware, standard and/or custom, may also be coupled to the processor(s) 802. The control system 800 may further include other components such as, but not limited to, I/O interfaces, sensors, logic circuits etc.
[0064] The memory(s) 804 may be a computer-readable medium, examples of which comprise volatile memory (e.g., RAM), and/or non-volatile memory (e.g., Erasable Programmable read-only memory, i.e.. EPROM, flash memory, etc.). The control system 800 may further include a communication interface 806 that may allow the connection or coupling of the control system 800 with one or more other devices, through a wired connection or through a wireless connection, for example, Local Area Network, i.e., LAN, or any industrial control protocols such as Profinet, or Modbus RTU/TCP, or Modbus TCP/IP, Serial Communication (like RS232, RS485) with optional use of analog signal lines or digital I/O where appropriate for example, for connecting to the operator device (for example, remote device) for connecting via HMI 800’ or any other systems or devices like a visual docking guidance system 801, VFD panels, and control panel.
[0065] Further, the communication interface 806 may also enable communication between the control system 800 and control panel 312 operating the pre-conditioned air unit 100 shown in fig. 1.
[0066] Further, the control system 800 may include module(s) 808. The module(s) 808 may include a receiving module 808A, a retrieving module 808B, a processing module 808C, sending module 808D, and a correction module 808E. The system 800 may include other modules (s) 808F and may implement similar or extended functionalities of the control system 800. In one example, the module(s) 808 may be implemented as a combination of hardware and firmware. In an example described herein, such combinations of hardware and firmware may be implemented in several different ways. For example, the firmware for module(s) 808 may be processor 802 executable instructions stored on a non-transitory machine-readable storage medium and the hardware for the module(s) 808 may include a processing resource (for example, implemented as either single processor or combination of multiple processors), to execute such instructions.
[0067] In the present examples, the non-transitory machine-readable storage medium may store instructions that, when executed by the processing resource, implement the functionalities of modules(s) 808. In such examples, the control system 800 may include the machine-readable storage medium storing the instructions and the processing resource to execute the instructions. In other examples of the present subject matter, the machine-readable storage medium may be located at a different location but accessible to the control system 800 and the processor(s) 802.
[0068] The control system 800 may include data 810 configured to store data which may include. Further, the data 810 may include other data (not shown) which may include data processed, generated, retrieved, stored as a result of functions implemented by the control system 800. The data may include aircraft identifier(s) 810A, predefined operating configurations 810B, mapping(s) 810C, other data 810D.
[0069] In operation, the visual docking guidance system (VDGS) 801 is configured to detect and identify an arriving aircraft at a designated gate, determining the aircraft type, model, or specific identifier (e.g., ICAO code, airline-specific ID, or gate-specific mapping), and transmit this data to the control system 800. The receiving module 808A of the control system 800 receives the transmitted aircraft identification data. Based on this received input, the retrieving module 808B accesses a data structure within memory 804 containing a plurality of mappings 810C, which associate each aircraft identification data with a respective aircraft identifier 810A with a respective predefined operating configuration 810B. These predefined configurations represent target supply air conditions tailored to the identified aircraft, such as airflow rate, temperature, humidity, and pressure levels suitable for effective and safe pre-conditioned air (PCA) delivery.
[0070] In an example, when multiple aircraft have arrived at the designated gate, the VDGS 801 may be configured to detect and identify the type, model, or specific identifier (e.g., ICAO code, airline-specific ID, or gate-specific mapping) for each aircraft, and transmit this data to the control system 800. The receiving module 808A of the control system 800 receives the transmitted aircraft identification data. Based on this received input, the retrieving module 808B accesses a data structure within memory 804 that contains a plurality of mappings 810C, each mapping associating the received aircraft identification data with a respective aircraft identifier 810A, and further associating each aircraft identifier 810A with a corresponding predefined operating configuration 810B.
[0071] The processing module 808C, coupled to the memory 804, the main control unit 312A, and one or more secondary control units 312B may be configured to execute a control logic pipeline as follows: first, the processing module 808C may be configured to calculate a real-time thermal load based on sensor data received from the PCA unit and/or ambient environment, thereby determining the dynamic cooling demand. In parallel, the processing module 808C may be configured to confirm the aircraft identifier 810A automatically via VDGS which may be manually overridden via operator input on the HMI 800’. For the verified identifier, the processing module retrieves the corresponding predefined operating configuration 810B from the memory 804. The HMI 800’ may be configured to enable role-based access to modify or update the predefined operating configurations associated with the respective aircraft identifiers corresponding to the aircraft.
[0072] Using the predefined operating configuration 810B as a reference, the processing module 808C may determine whether one or both of the available duct structures are to be activated. For each selected duct structure, the module 808C further determines which of its associated air outlets should be enabled, ensuring precision in localized air delivery. The processing module then communicates via the sending module 808D appropriate commands/control signals to the main control unit 312A and the plurality of secondary control units 312B, which in turn actuate components of the PCA system such as valve positions, fan speeds, and compressor stages via the VFD panel 310 or other electrical control mechanisms identified as programmed control logic in this disclosure. This closed-loop process ensures that pre-conditioned air is delivered at the specified target supply air condition to each active outlet, dynamically adjusting operation based on both the retrieved configuration and current thermal load conditions.
[0073] With each aircraft connected to one or more outlets of the plurality of air outlets via a respective hosepipe, the hose heat gain correction module 808E may be configured to measure a temperature difference between pre-conditioned air at the one or more outlets and at an aircraft-end of the respective hosepipe and adjust the operation of the main control unit and the secondary control units to compensate for heat gain in the respective hosepipe, thereby maintain the target supply air condition at the aircraft-end of the respective hosepipe despite heat gain along the respective hosepipe. The control system 800 operatively coupled with the pre-conditioning unit 100 collectively form the system for providing pre-conditioned air to one or more aircrafts parked on ground.
[0074] Fig. 9 illustrates an example implementation of the system for providing pre-conditioned air to one or more parked aircrafts 920A-920C at a MARS gate, using a pre-conditioned air (PCA) unit 910 in accordance with an example implementation of the present subject matter. Referring now to Fig. 9, the PCA unit 910 delivers ultra sub-freezing pre-conditioned air via dual plenums 912A and 912B, which serve as air distribution trunks. Each plenum 912A and 912B is connected to a pair of flow control valves 912A-1, 912A-2 and 912B-1, 912B-2, respectively, which regulate the flow of conditioned air through downstream hoses 917A-1, 917A-2, 917B-1, and 917B-2. These hoses 917A-1, 917A-2, 917B-1, and 917B-2 terminate at dedicated pre-conditioned air delivery pits 918-1, 918-2, and 918-3, each positioned at one of three aircraft stands within the MARS gate. The system is thus configured to serve all three aircraft simultaneously, regardless of size, by distributing air through parallel delivery paths, each independently controllable via the associated valve and hose. Upon arrival of an aircraft at a given stand, the visual docking guidance system (VDGS) identifies the aircraft type and stand occupancy, and transmits this information to a gate programmable logic controller (Gate PLC) or control system 800. Based on this input, the control system actuates the corresponding valve(s) to initiate flow of ultra sub-freezing pre-conditioned air to the respective aircraft via its assigned pit and hose. This architecture ensures that a wide-body aircraft and two narrow-body aircraft can be simultaneously serviced, enhancing gate throughput and thermal readiness across varied aircraft configurations.
[0075] The control system 800 receives the aircraft identification data and, upon confirmation by the operator through the Human-Machine Interface (HMI), retrieves for each aircraft a corresponding predefined operating configuration from the memory. This configuration, also referred to as an aircraft recipe, defines the target supply air condition such as outlet temperature, flow rate, and pressure required to cater the identified aircraft. Based on the predefined operating configuration, the control panel 310 may calculate the operating values. For each stand, the control system 800 determines the necessary activation of duct structures 100A, 100B and associated outlets based on the retrieved configuration. Upon this determination, the control panel, particularly, main control unit 312A and a plurality of secondary control units 312B may receive real-time ambient sensor data and based on the ambient sensor data and the predefined operating configuration, the control panel 310 may be configured to calculate operating values of the different components of the PCA unit. Further, based on the real-time ambient sensor data and the sensor data including temperature, humidity, and air pressure, the control panel 310 may dynamically update the operating values from the PCA unit, ensuring optimal and efficient delivery of preconditioned air to each of the identified aircraft. For example, the plurality of sensors may include one or more mass flow sensors positioned along each duct structure or at each active air outlet, the mass flow sensors may be configured to measure real-time mass flow rate of pre-conditioned air and the processing module may be configured to dynamically adjust the operation of the main control unit and the secondary control units to maintain the target supply air condition based on the to the reduced mass flow rate. The processing module 808C may be configured to automatically select between sub-freezing (0°C to -25°C) and non-sub-freezing (>0 °C) operating modes based on the retrieved predefined operating configuration and the real-time thermal load.
[0076] In an example, the processing module 808C may be configured to enable the control panel 312 to cause activation of the primary heat exchange module and the plurality of secondary heat exchange modules in a respective duct structure independently or in sequence such that each downstream heat exchange module is activated only after its immediately upstream heat exchange module has reached a respective target discharge air temperature.
[0077] For each stand, the control system 800 determines the necessary activation of duct structures and associated outlets based on the retrieved configuration and real-time thermal load. The control system 800 issues commands to the USFPCA unit to initiate pre-conditioned air delivery accordingly. For instance, for the code-C aircraft 920A at stand-A, the control system 800 opens valve 912A-1 to route pre-conditioned air from plenum 912A to PIT 918-1. For stand-C, which accommodates the larger Code-E aircraft 920B, the system 800 opens valves 912A-2, 912B-2 to route air to PIT 918-2, and may adjust flow rate and pressure to account for higher cabin volume. Simultaneously, valve 912B-1 is activated to deliver air via plenum 912B to PIT 918-3, servicing the code-C aircraft 920C at stand-B. Insulated hosepipes connect each pit to the respective aircraft inlet.
[0078] This architecture enables parallel and independent delivery of preconditioned air to multiple aircraft at the MARS gate, with intelligent distribution managed by the USFPCA control system. Real-time closed-loop feedback from environmental sensors and airflow instrumentation allows the system to fine-tune delivery in accordance with the predefined configuration, maintaining efficient, aircraft-specific air conditioning performance across all active stands.
[0079] In accordance with another embodiment of the present disclosure, a method for providing pre-conditioned air to one or more parked aircrafts comprising: conveying ambient air through a plurality of duct structures, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective airflow path, wherein the one or more thermally coupled heat exchange modules comprises a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and a plurality of secondary heat exchange modules; controlling operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures via a main control unit; controlling operation of each secondary heat exchange module disposed in the plurality of duct structures via a respective secondary control unit; storing a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts in a memory; receiving sensor data via a plurality of sensors disposed along each duct structure, the sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules; calculating real-time thermal load based on the sensor data received in real-time; receiving one or more aircraft identifiers from an operator interface; retrieving, for the one or more aircraft identifiers, a corresponding predefined operating configuration indicating a target supply air condition from the memory; determining, based on the corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determining whether one or more of its corresponding plurality of outlets are to be activated; and based on the determination and the real-time thermal load, dynamically adjusting operation of the main control unit and the secondary control units to cater pre-conditioned air at the target supply air condition at each active air outlet.
[0080] Figs. 10A-10B illustrate a method for providing pre-conditioned air to one or more parked aircrafts, in accordance with an example implementation of the present subject matter. Although the method 1000 may be implemented in a variety of implementations, for ease of explanation, the description of method 1000 is provided in reference to the above-described system for providing pre-conditioned air to one or more parked aircrafts. The order in which the method 1000 are described is not intended to be construed as a limitation, and any number of the method blocks described may be combined in any order to implement the method 1000, or an alternative method.
[0081] At block 1002, ambient air through a plurality of duct structures may be conveyed, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective airflow path, wherein the one or more thermally coupled heat exchange modules comprises a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and a plurality of secondary heat exchange modules.
[0082] At block 1004, operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures may be controlled via a main control unit.
[0083] At block 1006, operation of each secondary heat exchange module disposed in the plurality of duct structures via a respective secondary control unit may be controlled;
[0084] At block 1008, a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts may be stored in a memory;
[0085] At block 1010, sensor data may be received from a plurality of sensors disposed along each duct structure, the sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules.
[0086] At block 1012, real-time thermal load based on the sensor data received in real-time may be calculated.
[0087] At block 1014, one or more aircraft identifiers may be received from an operator interface.
[0088] At block 1016, for the one or more aircraft identifiers, a corresponding predefined operating configuration may be retrieved indicating a target supply air condition from the memory.
[0089] At block 1018, based on the corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determining whether one or more of its corresponding plurality of outlets are to be activated may be determined.
[0090] At block 1020, based on the determination and the real-time thermal load, operation of the main control unit and the secondary control units may be dynamically adjusted to cater pre-conditioned air at the target supply air condition at each active air outlet.
[0091] Collectively, the present subject matter overcomes the limitations of conventional ground-based PCA units by enabling dynamically adjustable, recipe-based, multi-stage air conditioning that concurrently serves multiple parked aircraft with independent control per outlet. The system is configured to interface with a VDGS to automatically detect and identify incoming aircraft and retrieve corresponding predefined operating configurations also known as aircraft recipes based on aircraft type, model, or gate location. These recipes define the target outlet temperature, pressure, and flow rate specific to each aircraft’s environmental and structural requirements. By using a main control unit in coordination with distributed secondary control units, the system processes real-time ambient sensor data including temperature, humidity, and atmospheric pressure to calculate thermal load and adjust operation of the internal subsystems accordingly. This architecture enables closed-loop control of individual plenums, duct structures, and outlet assemblies, ensuring precise, on-demand air delivery to each aircraft stand.
[0092] Through its modular multi-duct structure and independent outlet control, the USFPCA system eliminates the airflow imbalances and cross-contamination issues that arise when traditional systems attempt to serve more than one aircraft from a shared conditioning stream. Its integration with Gate PLCs and HMI interfaces allows for semi-automated operation, significantly reducing manual input while improving operational responsiveness. Furthermore, the system’s real-time adaptability to ambient conditions enhances energy efficiency by activating only the components necessary to meet the dynamic cooling or heating demand, minimizing overshoot, undershoot, and unnecessary compressor or fan activity. The ability to provide both sub-freezing and non-sub-freezing output expands the system’s applicability to aircraft with diverse operational needs, including avionics cooling and cabin comfort during extreme weather conditions. By supporting simultaneous, independent service to multiple aircraft, and dynamically adjusting to varying external and internal conditions, the invention ensures faster cabin temperature stabilization, reduced turnaround times, improved passenger comfort, and significant reductions in power consumption and equipment wear representing a substantial advancement over existing PCA technologies.
[0093] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the disclosure and are not intended to be restrictive thereof.
[0094] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.
[0095] The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, the order of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.
, Claims:WE CLAIM:
1. A system for providing pre-conditioned air to a plurality of parked aircrafts comprising:
a pre-conditioned air unit comprising:
a plurality of duct structures, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure is configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective air flow path,
wherein the one or more thermally coupled heat exchange modules comprises:
a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and
a plurality of secondary heat exchange modules;
a main control unit configured to control operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures;
a plurality of secondary control units, each secondary control unit configured to control a respective secondary heat exchange module disposed in the plurality of duct structures;
a memory storing a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts; and
a plurality of sensors disposed along the respective duct structure and configured to provide a sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules; and
a processing module coupled to the memory, the main control unit, and the plurality of secondary control units, wherein the processing module configured to configured to:
calculate real-time thermal load based on the sensor data received in real-time;
receive one or more aircraft identifiers from an operator interface;
retrieve, for the one or more aircraft identifiers, a corresponding predefined operating configuration indicating a target supply air condition from the memory;
determine, based on corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determine whether one or more of its corresponding plurality of outlets are to be activated; and
based on the determination and the real-time thermal load, dynamically adjust operation of the main control unit and the secondary control units to cater pre-conditioned air at the target supply air condition at each active air outlet.
2. The system as claimed in claim 1, wherein each secondary heat exchange module comprises a respective vapour-compression refrigeration circuit, each comprising:
an evaporator coil positioned in thermal proximity to the duct structure and configured to absorb heat from the air using a refrigerant;
a compressor fluidly coupled to the evaporator coil and configured to circulate the refrigerant; and
a condenser coil fluidly coupled to the compressor and thermally coupled to the chilled water circuit and configured to circulate the refrigerant,
wherein the chilled water circuit comprises:
an inlet conduit;
an outlet conduit; and
a manifold fluidically connected to the chilled water coil and to each of the condenser coils.
3. The system as claimed in claim 1, wherein each of the one or more thermally coupled heat exchange modules in a respective duct structure is operable independently or simultaneously of the each of the one or more thermally coupled heat exchange modules in the other duct structure based on the real-time thermal load and the target supply air condition associated with the each active air outlet.
4. The system as claimed in claim 1, wherein the primary heat exchange module is configured to reduce the temperature of the ambient air in the airflow path at a target discharge air temperature between approximately 7°C and 9°C upon exiting the chilled water coil.
5. The system as claimed in claim 1, wherein the one or more thermally coupled heat exchange modules are arranged sequentially along the respective duct structure such that the primary heat exchange module is disposed downstream to a respective air filter assembly through which the ambient air enters the respective duct structure, the first heat exchange module of the plurality of secondary heat exchange modules is arranged downstream of the primary heat exchange module, the second heat exchange module of the plurality of secondary heat exchange modules is arranged downstream of the first heat exchange module, and wherein a third heat exchange module is arranged downstream of the second heat exchange module with a heating module disposed between the second heat exchange module and the third heat exchange module, wherein the heating module comprises one or more heating elements thermally coupled to the duct structure and configured to selectively raise the ambient air temperature.
6. The system as claimed in claim 5, wherein the first heat exchange module is configured to operate with an evaporating temperature of approximately -10°C, a condensing temperature of approximately 13-20°C, and to provide the ambient air at a target discharge air temperature of approximately -5°C upon exiting the first heat exchange module.
7. The system as claimed in claim 5, wherein the second heat exchange module is configured to operate with an evaporating temperature of approximately -20°C, a condensing temperature of approximately 13-20°C, and to provide the ambient air at a target discharge air temperature of approximately -15°C upon exiting the second heat exchange module.
8. The system as claimed in claim 5, wherein the third heat exchange module is configured to operate with an evaporating temperature of approximately -30°C, a condensing temperature of approximately 13-20°C, and to provide the ambient air at a target discharge air temperature of approximately -25°C upon exiting the third heat exchange module.
9. The system as claimed in claim 5, wherein the respective air filter assembly is positioned at the respective air inlet, wherein the respective air filter assembly air filter comprises:
an air filter configured to receive and remove particulate matter from ambient air entering the respective duct structure;
a blower positioned downstream of the air filter and configured to draw filtered ambient air through the respective duct structure, wherein the blower at the respective duct structure is configured to provision air at a pressure and a flow rate same or different from the blower of the other duct structure, based on the determination and the real-time thermal load.
10. The system as claimed in claim 5, wherein the processing module is further configured to cause activation of the primary heat exchange module and the plurality of secondary heat exchange modules in a respective duct structure independently or in sequence such that each downstream heat exchange module is activated only after its immediately upstream heat exchange module has reached a respective target discharge air temperature.
11. The system as claimed in claim 1, wherein to receive one or more aircraft identifiers from an operator interface comprises:
receive data indicative of an aircraft stand and an aircraft type corresponding to each of the plurality of aircrafts based on automatic identification of the plurality of aircrafts using a visual docking guidance system (VDGS); and
cause to display the data on a human-machine interface (HMI) for confirmation or for override by an operator.
12. The system as claimed in claim 1, wherein each aircraft is connected to one or more outlets of the plurality of air outlets via a respective hosepipe and the system comprises:
a hose heat gain correction module configured to:
measure a temperature difference between pre-conditioned air at the one or more outlets and at an aircraft-end of the respective hosepipe;
adjust the operation of the main control unit and the secondary control units to compensate for heat gain in the respective hosepipe; and
thereby maintain the target supply air condition at the aircraft-end of the respective hosepipe despite heat gain along the respective hosepipe.
13. The system as claimed in claim 1, wherein the plurality of sensors further comprises one or more mass flow sensors positioned along each duct structure or at each active air outlet, the mass flow sensors configured to measure real-time mass low rate of pre-conditioned air, and wherein the processing module is configured to dynamically adjust the operation of the main control unit and the secondary control units to maintain the target supply air condition based on the to the reduced mass flow rate.
14. The system as claimed in claim 14, wherein the HMI is configured to enable role-based access to modify or update the predefined operating configurations associated with the respective aircraft identifiers corresponding to the aircrafts.
15. The system as claimed in claim 1, wherein the processing module is further configured to automatically select between sub-freezing (0°C to -25°C) and non-sub-freezing (>0 °C) operating modes based on the retrieved predefined operating configuration and the real-time thermal load.
16. A method for providing pre-conditioned air to one or more parked aircrafts comprising:
conveying ambient air through a plurality of duct structures, each defining a respective airflow path extending from a corresponding air inlet to a corresponding plurality of air outlets, each duct structure configured to convey ambient air through the respective airflow path such that the ambient air is progressively pre-conditioned by respective one or more thermally coupled heat exchange modules positioned along the respective airflow path, wherein the one or more thermally coupled heat exchange modules comprises a primary heat exchange module comprising a chilled water coil positioned in thermal proximity to the duct structure and configured to reduce temperature of the air via heat transfer to a chilled water circuit; and a plurality of secondary heat exchange modules;
controlling operation of the chilled water circuit and the primary heat exchange module disposed in the plurality of duct structures via a main control unit;
controlling operation of each secondary heat exchange module disposed in the plurality of duct structures via a respective secondary control unit;
storing a plurality of predefined operating configurations associated with respective aircraft identifiers corresponding to the aircrafts in a memory;
receiving sensor data from a plurality of sensors disposed along each duct structure, the sensor data comprising at least one of ambient air temperature, chilled water temperature, ambient air temperature at locations downstream of the one or more thermally coupled heat exchange modules and respective temperature or pressure of the refrigerant at the plurality of secondary heat exchange modules;
calculating real-time thermal load based on the sensor data received in real-time;
receiving one or more aircraft identifiers from an operator interface;
retrieving, for the one or more aircraft identifiers, a corresponding predefined operating configuration indicating a target supply air condition from the memory;
determining, based on the corresponding predefined operating configuration, whether one or both of the plurality of duct structures are to be activated, and, for each activated duct structure, determining whether one or more of its corresponding plurality of outlets are to be activated; and
based on the determination and the real-time thermal load, dynamically adjusting operation of the main control unit and the secondary control units to cater pre-conditioned air at the target supply air condition at each active air outlet.

Dated this 25th day of July 2025
Signature

Manish Kumar
Patent Agent (IN/PA-5059)