Claims:We Claim:

1. An improved air conditioning system, the system (100) comprising:
at least one pre-cooling coil (1) positioned at an input side receiving supply air;
at least one evaporator coil (2) positioned adjacent to the pre-cooling coil (1) before a supply fan/indoor fan (3) and configured to receive the supply air passed through the pre-cooling coil (1) and conduct heat to a refrigerant flowing through the evaporator coil (2);
a co-axial heat exchanger (13) positioned in a refrigerant circuit at an outlet of the evaporator coil (2) for exchanging heat with the refrigerant exiting the evaporator coil (2);
a compressor (4) connected to the co-axial heat exchanger (13) to pressurize the refrigerant coming out from the co-axial heat exchanger (13);
a condenser (6) positioned downstream of the compressor in the refrigerant circuit that exchanges heat from the hot refrigerant with the evaporatively cooled air;
an evaporative cooling pad (5) positioned in the air stream upstream of the condenser (6) to cool the air stream and enhance the heat exchange from the condenser (6); and
a sub-cooler (11) positioned downstream of the condenser (6) in the refrigerant circuit.

2. The improved air conditioning system as claimed in claim 1, wherein the system further comprises a tank (9) filled with water, a pump (8) and , a water distribution system comprising a plurality of pipes and flow control devices, said tank is connected with the pre-cooling coil (1) and co-axial heat exchanger (13) for exchanging heat with water.

3. The improved air conditioning system as claimed in claim 1, wherein the system further comprises an expansion device (14), wherein said expansion device is an electronic expansion valve.

4. The improved air conditioning system as claimed in claim 1, wherein the condenser (6) is positioned in front of condenser fan (7).

5. The improved air conditioning system as claimed in claim 1, wherein the evaporative cooling pad (5) is positioned between a condenser fan (7), and the condenser (6).

6. The improved air conditioning system as claimed in claim 1, wherein a portion of the condenser (6) is immersed in the water tank to increase the heat discharge capacity of the condenser.

7. The improved air conditioning system as claimed in claim 1, wherein an additional direct evaporative cooling section is positioned in series with and after the pre-cooling coil (1).

8. A method for an improved air conditioning, the method comprising:
pre-cooling supply sir received through, at least one pre-cooling coil (1) positioned at an input side;
evaporatively cooling and dehumidifying the supply air passed through the pre-cooling coil (1) by the evaporator coil (2);
evaporating a refrigerant flowing through the evaporator coil (2) at constant pressure by exchanging heat with the refrigerant and outputting the refrigerant with cooled air by the evaporator coil (2);
super heating the refrigerant at constant pressure at a co-axial heat exchanger (13) positioned at an outlet of the evaporator coil (2) by exchanging heat with the refrigerant exiting the evaporator coil (2);
increasing the pressure of the refrigerant exiting from the co-axial heat exchanger (13) by a compressor (4);
condensing the refrigerant at constant pressure by a condenser (6) using the evaporatively cooled air;
cooling the air stream upstream of the condenser (6) and enhancing the heat exchange from the condenser (6) by an evaporative cooling pad (5); and
sub-cooling the refrigerant by exchanging the heat at a sub-cooler (11) positioned downstream of the condenser (6).

9. The method as claimed in claim 8, wherein the method further comprises circulating the refrigerant by controlling an electronic expansion valve (14).

10. The method as claimed in claim 8, wherein the supply air is pre-cooled by exchanging heat with water received from a water tank (9).

11. The method as claimed in claim 8, wherein the refrigerant is super-heated at constant pressure by exchanging heat with water received from a water tank (9). , Description:TECHNICAL FIELD
[0001] The present disclosure relates to the field of air conditioning system, and more specifically relates to air condition systems integrating evaporative cooling and conventional vapor compression.

BACKGROUND
[0002] Air conditioners have now become the norm in commercial as well as residential building. However, air conditioning devices consume significant amount of energy during cooling. The energy consumption of the device could be attributed to the operating conditions under which the device work using the conventional vapour compression system that are based on refrigerants. There is a need and an opportunity to design and produce an energy efficient air conditioner.

SUMMARY
[0003] In one aspect of the present disclosure, a method for an improved air conditioning is disclosed. The method comprises pre-cooling supply air received at a pre-cooling coil positioned at an input side, evaporatively cooling and dehumidifying the supply air passed through the pre-cooling coil by the evaporator coil, evaporating a refrigerant flowing through the evaporator coil at constant pressure by exchanging heat with the refrigerant and outputting the refrigerant with cooled air by the evaporator coil, and super heating a refrigerant in a co-axial heat exchanger using water, wherein the refrigerant is heated at constant pressure. The method further may comprise increasing the pressure of the refrigerant exiting from the co-axial heat exchanger by a compressor, condensing the refrigerant at constant pressure at by a condenser using the evaporatively cooled air, cooling the air stream upstream of the condenser and enhancing the heat exchange from the condenser by an evaporative cooling pad and sub-cooling the refrigerant by exchanging the heat at a sub-cooler positioned downstream of the condenser. The cooled water is used in three ways: to pre-cool the supply air and thus reduce the load on the evaporator, to evaporatively cool air that is used to condense the refrigerant in the condenser, and then further to sub-cool the refrigerant.

[0004] In another aspect of the present disclosure, an improved air conditioning system is disclosed. The system may comprise a pre-cooling coil positioned at an input side receiving supply air, an evaporator coil positioned adjacent to the pre-cooling coil and before a supply fan/indoor fan . The evaporator coil is configured to receive the supply air passed through the pre-cooling coil and conduct heat to a refrigerant flowing through the evaporator coil. The system may further comprise a co-axial heat exchanger positioned in a refrigerant circuit at an outlet of the evaporator coil for exchanging heat with the refrigerant exiting the evaporator coil and a rotary compressor at the outlet of a super heater/co-axial heat exchanger to pressurize the refrigerant coming out from the co-axial heat exchanger. Further, a condenser may be positioned downstream of the compressor in the refrigerant circuit for exchanging heat from the hot refrigerant with the evaporatively cooled air. The system may further comprise an evaporative cooling pad positioned in the air stream upstream of a condenser to cool the air stream and enhance the heat exchange from the condenser and a sub-cooler positioned downstream of the condenser in the refrigerant circuit.

BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The detailed description of the invention is described with reference to the accompanying figures.
[0006] Figure 1 illustrates a top view of an improved air condition system in accordance with an aspect of the present disclosure.
[0007] Figure 2 illustrates a side view of an improved air condition system in accordance with an aspect of the present disclosure.
[0008] Figure 3 illustrates a front view of an improved air condition system in accordance with an aspect of the present disclosure.
[0009] Figure 4 illustrates a schematic of operation for an improved air conditioning system in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure relates to an improved air conditioning system and method integrating evaporative cooling and vapour compression to achieve year-round cooling with reduced energy consumption. The improved air conditioning system integrates an evaporatively-cooled condenser and a sensible-cooling coil with the conventional refrigeration system. The sensible cooling coil pre-cools the air returned from the room that is then subsequently cooled and dehumidified by the evaporator coil of the conventional vapour compression system. The operating conditions of the evaporator are determined by the temperature and relative humidity of the return air, which in turn reflects the condition in the room and the variance from desired conditions. The refrigeration system as disclosed in the present system incorporates all the energy efficient features of a conventional air conditioner that operates on the vapour compression principle including allowance for using fresh outside air.

[0011] A conventional vapour compression air conditioning system comprises an evaporator coil, compressor, condenser coil and an expansion device. In a normal air conditioning device, the condenser coil is part of the “external unit”, and the evaporator coil is part of the “internal unit”. The supply air passes over the evaporator section and is cooled to the required condition. The heat from the supply air is absorbed by the evaporator and is rejected via the condenser coil. “Supply air” refers to the air that must be cooled and supplied to the end application. Supply air may be ambient air or return air from the room. “Exhaust air” refers to the air used to cool the condenser and is rejected from the device. Exhaust air may be ambient air or air from the room.

[0012] In an embodiment of the present disclosure, the condenser coil is cooled using the exhaust ambient air that is first passed through a direct evaporative cooling section, e.g., a cooling pad, to form an evaporatively-cooled condenser. The cooling pad has an advantage of cooling the exhaust ambient air up to its wet bulb temperature and thus, the lower temperature air of the pad reduces the condensing temperature of the refrigerant in the condensing coil. Thus, the cooling pad substantially improves the performance of the vapour compression system particularly when the exhaust air is hot and dry.

[0013] In accordance with an exemplary embodiment the present disclosure, the present system may comprise a water tank that contains the water, a pump, a water distribution system comprising a plurality of pipes and optionally, a plurality of flow control devices, and the direct evaporative cooling component such as a cooling pad.

[0014] The water in the tank of the evaporatively-cooled section is consequently cooled close to the wet bulb temperature of the outdoor condition. The wet bulb temperature depends on the design and size of the evaporatively cooled section. The internal unit comprises the evaporator and another coil or other type of heat exchanger that is placed upstream before the evaporator. The water from the tank runs through this first heat exchanger to partially cool the supply air. Since only the temperature of the supply air is reduced, this process is referred to as sensible cooling. And since the heat exchanger is placed before the evaporator, this heat exchanger is termed the pre-cooling heat exchanger/coil. Hence, the second heat exchanger serves as a sensible pre-cooling heat exchanger to partially cool the supply air before it enters the evaporator.

[0015] The sensible pre-cooling heat exchanger has the effect of reducing the quantity of heat to be absorbed by the evaporator, which is a part of the vapour compression system. The sensible pre-cooling heat exchanger reduces the load on the vapour compression cycle, allowing the cycle to be made either smaller in size or operate at a higher refrigerant temperature in the evaporator. Making the evaporator smaller in size, can reduce the overall cost. Raising the refrigerant temperature in the evaporator can improve the efficiency of the vapour compression system.

[0016] Under certain conditions, when the supply air is sufficiently dry (low relative humidity) or the heat load in the application is low, the supply air need not be cooled and de-humidified by the evaporator coil. In such cases, if additional cooling is needed after the sensible pre-cooling heat exchanger, then an optional direct evaporative cooling section, placed in series and after the sensible pre-cooling heat exchanger. The optional direct evaporative cooling section may be used to further reduce the temperature of the supply air. The system operated in this way is a 2-stage evaporative cooling device. The direct evaporative cooling section in the internal unit is always placed downstream of the sensible pre-cooling heat exchanger. However, it can be placed upstream or downstream of the evaporator. The size of the sensible pre-cooling heat exchanger is designed as per the annual weather conditions at the location, and may cover the evaporator coil either partially or fully. Further, the direct evaporative cooling section may cover the evaporator coil either partially or fully.

[0017] Thus, the system is designed as an integrated evaporative cooling system with a conventional refrigerant-based vapour compression system in which the sensible pre-cooling heat exchanger reduces the load on the energy-inefficient vapour compression system. In addition, the vapour compression cycle is made more efficient by using an evaporatively-cooled condenser. In addition, under certain conditions, the vapour compression system may not be operated at all. A proprietary control system decides the mode of operation based on use of sensors that measure the temperature and humidity of the exhaust air and the supply air. The whole system is usually made as a single machine. In some implementations, a separate “external unit” comprising the evaporatively-cooled condenser from the internal unit comprising the sensible pre-cooling heat exchanger and evaporator and an optional direct evaporative cooling section may be preferred.

[0018] In accordance with an exemplary embodiment the present disclosure, a supply air, which may be the room return air, is induced by a supply fan, and first passed over a sensible pre-cooling coil, and then through an evaporator coil. In the first stage with the pre-cooling coil, the supply air is pre-cooled by the water from a water tank. A pump is used to circulate the water from the tank, first through a “super heater”/ co-axial heat exchanger, where the water exchanges heat with the refrigerant that exits the evaporator coil. The refrigerant is usually colder than the water, and is slightly heated, while simultaneously cooling the water. This water at lower temperature passes through the sensible pre-cooling coil to cool the supply air. Pre-cooled supply air is further cooled and dehumidified in the evaporator coil where the evaporating refrigerant picks up the heat load before passing through the supply fan. Pre-cooling reduces the required cooling in the evaporator of the vapour compression system and enables reduction in the size of the compressor and further reduces the energy consumed. The heating of the refrigerant after the evaporator helps protects the compressor.

[0019] In another embodiment, supply air may be sufficiently dry, and / or if the heat load is low, the vapour compression system will operate at partial load because the supply air is pre-cooled within the pre-cooling coil section next to the evaporator before passing through the supply fan. This sensible cooling reduces the load on the evaporator and thereby enables significant energy saving during such operating periods. The pre-cooling coil may cover the evaporator coil partially or fully. Further the supply fan may be a variable speed fan.

[0020] Further a sub-cooling heat exchanger may be provided downstream of the condenser in the refrigerant circuit/system. In this, the hot refrigerant exiting the condenser is further cooled by exchanging its heat with a stream of colder water in the sub-cooling heat exchanger. The sub-cooling of the refrigerant is used to ensure the entire refrigerant reaches the expansion valve or device in liquid form. Indirectly, sub-cooling of the refrigerant also helps increase the refrigeration capacity of the system, and thus its efficiency.

[0021] In another exemplary embodiment, the last portion of the condenser coils may be immersed in the water tank to increase the heat discharge capacity of the condenser. The choice depends on the various factors such as cost and ease of maintenance.

[0022] In accordance with an exemplary embodiment of the present disclosure the single tank contains all the water and the pump. Water condensing from the evaporator coil is also collected in this tank and this in addition to the water being cooled by evaporative cooling, lowers the temperature of the water already in the tank. The level of water in this tank can be maintained by a device such as a float valve, and the deficiency in water is made up by using water from another source. Hence, this device can be used even when there is insufficient volume of condensate generated at the evaporator coil.

[0023] As the water in the tank is partially cooled by evaporation in a cooling pad and is then used in a pre-cooling coil to sensibly pre-cool the air, this portion of the device is a form of indirect evaporative cooling. A controller may further be provided and configured to decide the modes of the operation of the device, e.g., as a sensible cooler alone or augmented by the vapour compression system. The controller also decides the operation of the electronic expansion value to ensure the evaporator operating temperature is as high as possible to supply the cooling requirement.

[0024] In yet another embodiment, the present disclosure enables fresh or outside air to be let into the space being cooled. The system may comprise damper that can be opened or closed by various ways such as a button, a pull-type lever or sliding lever, and permits outside air to be sucked into the path of the cold air being blown into the room. Using fresh air dilutes the air inside the room and reduces the level of impurities such as carbon dioxide, odour-forming chemicals, and biological material. The input of fresh air into closed spaces has been shown to improve the health and productivity of people in these spaces and is gaining more importance in recent times. Fresh air may be let in continuously or intermittently.

[0025] Now referring to Figure 1, illustrates an improved air conditioning system in accordance with the present disclosure. The system (100) as disclosed comprises a pre-cooling coil (1), wherein supply air i.e., primarily the room return air, is induced by a supply fan/indoor fan (3) and first passed over the pre-cooling coil (1). Further, the supply air is then passed through an evaporator coil (2). At this stage, the pre-cooling coil (1) is provided water from a water tank (9) and the same is used to pre-cool the supply air. Further a water pump (8) may be used to circulate the water from the tank and through a “super heater” where it exchanges heat with a refrigerant that exits the evaporator coil (2). The water from the super heater at lower temperature passes through the sensible pre-cooling coil (1) to cool the supply air. Pre-cooled supply air is further cooled and dehumidified in the evaporator coil (2), where the evaporating refrigerant picks up the heat load before passing through the supply fan. Pre-cooling helps reduce the required cooling in the evaporator of the vapour compression system.

[0026] The system (100) further comprises a compressor (4) provided to pressurize the refrigerant coming out of the evaporator and the super heater/co-axial heat exchanger (13). Further, the hot refrigerant exiting a condenser (6) is further cooled by exchanging its heat with a stream of ambient air that has been cooled by passing over a water-wetted evaporative cooling pad (5). The evaporative cooling pad (5) is positioned between a condenser fan (7), and the condenser (6). In another possible embodiment, a portion, or the last portion of the condenser coils (6) may be immersed in the water tank (9) to increase the heat discharge capacity of the condenser. Sub-cooling of the refrigerant is used to ensure the entire refrigerant reaches an expansion valve/electronic expansion valve (14) or device in liquid form. The expansion valve (14) is connected to sub-cooling heat exchanger (11). Indirectly, sub-cooling of the refrigerant also helps increase the refrigeration capacity of the system, and thus its efficiency. Further, the condenser coils (6) may be positioned in front of condenser fan (7). The water tank (9) is connected with the pre-cooling coil (1) and co-axial heat exchanger (13) for exchanging heat with water. The system further may comprise a water distribution system comprising a plurality of pipes and flow control devices. In some implementations, an additional direct evaporative cooling section is positioned in series with and after the pre-cooling coil (1).

[0027] Now referring to Figure 4, illustrates a method for improved air conditioning in accordance with the present disclosure. The method as disclosed may be segregated into a refrigeration cycle and water cycle. Further, a liquid refrigerant is circulated by controlling an electronic expansion valve (14). The liquid refrigerant takes heat from the air to be cooled (Step 1-2) and then passes through a coaxial heat exchanger / super-heater, and water from a tank (9) is also provided to this heat exchanger, wherein heat transfer between the liquid refrigerant and water occurs (Step 2-3). The liquid refrigerant evaporates and may be superheated at constant pressure while the water temperature decreases, during heat transfer in the pre-cooler heat exchanger. Further in the co-axial heat exchanger/super heater water temperature drops due to super heating of refrigerant, wherein the refrigerant is super-heated at constant pressure by exchanging heat with water received from a water tank (9). Then, the refrigerant is compressed using a compressor (REF DC COMP).

[0028] In yet another embodiment, the present invention discloses a method for an improved air conditioning. The method comprises pre-cooling supply sir received at a pre-cooling coil positioned at an input side, evaporatively cooling and dehumidifying the supply air passed through the pre-cooling coil by the evaporator coil, evaporating a refrigerant flowing through the evaporator coil at constant pressure by exchanging heat with the refrigerant and outputting the refrigerant with cooled air by the evaporator coil, and super heating a refrigerant in a co-axial heat exchanger using water, wherein the refrigerant is heated at constant pressure. The method further may comprise increasing the pressure of the refrigerant exiting from the co-axial heat exchanger by a compressor, condensing the refrigerant at constant pressure at by a condenser using the evaporatively cooled air, cooling the air stream upstream of the condenser and enhancing the heat exchange from the condenser by an evaporative cooling pad and sub-cooling the refrigerant by exchanging the heat at a sub-cooler positioned downstream of the condenser. The cooled water is used in three ways: to pre-cool the supply air and thus reduce the load on the evaporator, to evaporatively cool air that is used to condense the refrigerant in the condenser, and then further to sub-cool the refrigerant.

[0029] The evaporatively-cooled condenser can be of various designs including direct spray of water in the air stream at or before the condenser coils. Water may be sprayed onto the coils and ambient air can flow over them. Such condensers save on energy consumed by eliminating the pressure drop experienced by the air passing through the cooling pad described in the embodiment in the present disclosure. The cooling pad can be made of different materials to increase the evaporation of water into the flowing air. The sensible pre-cooling coil can be of various designs. If water is available at a temperature below the wet bulb temperature of the ambient, the cool water can be used directly in the pre-cooling coil and the condenser section or mixed with the water condensing from the evaporator (for condensate). The system has a provision to use fresh or outside air. As described in above embodiments, the use of fresh air is again gaining prominence. The system may have a different types of provisions to permit fresh air and such provisions may consider to be an essential feature of the system.

[0030] The present air conditioning system reduces the annual energy consumed when operating the room air conditioner without substantially increasing the cost of the air conditioner. In the present invention, water is used as a cooling medium in addition to the refrigerant in a conventional vapour compression system. Reducing the mass of refrigerant is desirable as it is reasonably expensive, and requires special handling due to safety and global warming potential considerations. The size of the system need not be much larger than a normal window air-conditioner and hence, the proposed system is eminently suited to cool rooms in residences as well as offices. Since all the components are easily available, the incremental cost to a conventional window-type room air conditioner is not significant. The present system of room air conditioner can be adapted to operate on various green (environmentally-friendly) and even, natural refrigerants such as R290 (propane).

[0031] The following table further refers to reference numerals as disclosed in figure 1:

REFERENCE NUMERAL DESCRIPTION
1 Pre-Cooling Coil
2 Evaporator Coil
3 Indoor Fan
4 Rotary Compressor DC
5 Evaporative cooling Pad
6 Condenser Coil
7 Condenser Fan
8 Water Pump
9 Water Storage Tank
10 Supply Air Louver
11 Subcooling Pipe
12 Water Distribution Pipe
13 Co-Axial Heat Exchanger
14 Electronic Expansion Valve

[0032] The following table further refers to the step of the method as disclosed in figure 4:

Legend Description
CDS Fin Tube Heat Exchanger + Evaporative Pad
SC-HX Sub Cooler
EEV Electronic Expansion Valve
EVP Fin Tube Hex Ref Side+ Fin Tube Hex Water Side
TS Temperature Sensor
PS Pressure Sensor
CO-AX-HX Co Axial Heat Exchanger - Super Heater
REF DC COMP DC - Compressor
DC FAN DC Fans
PUMP DC Pump
Refrigeration Side Cycle
1-2 Liquid Refrigerant Evaporates At Constant Pressure
2-3 Constant Pressure Super Heating Of Refrigerant
3-4 Isentropic Compression
4-6 Constant Pressure Condensation
6-7 Constant Pressure Sub Cooling
7-1 Isentropic Expansion Of Refrigerant
Water Side Cycle
A Make-Up Water Line
G Condensate Water From Evaporator Into Tank
K Drain Water Line
B-C Water Temperature Drops Due To Super Heating Of Refrigerant
C-D Water Temperature Increases In Pre Cooler Heat Exchanger
D-E Water Temperature Drops In Evaporative Pads
E-F Water Temperature Increases In Sub Cooling Heat Exchanger
H Water Drain Line
J Water Tank Overflow Line

[0033] Although the present disclosure has been described in the context of certain aspects and embodiments, it will be understood by those skilled in the art that the present disclosure extends beyond the specific embodiments to alternative embodiments and/or uses of the disclosure and obvious implementations and equivalents thereof. Thus, it is intended that the scope of the present disclosure described herein should not be limited by the disclosed aspects and embodiments above.