DESC:TECHNICAL FIELD OF THE INVENTION
[1] The present invention relates to refrigerant systems and method of circulating a refrigerant in a variable refrigerant flow (VRF) system and a VRF system thereof.

BACKGROUND OF THE INVENTION
[2] A variable refrigerant flow (VRF) system is a sophisticated centralized air-conditioning system that heats or cools large multi-zone spaces with varying heating and cooling demands by regulating refrigerant flow through intelligent controls. This results in tremendous power savings as the system is smart enough to know where to cool or heat, and when. Therefore, modern VRF systems are more efficient than conventional water-cooled and HVAC systems.
[3] The refrigerant circulates throughout the VRF system by means of refrigerant loops connecting a plurality of indoor units with at least one outdoor unit. In the refrigerant loop, the refrigerant leaves the evaporator and enters an accumulator. The accumulator only allows refrigerant gas to enter a compressor where the pressure of the refrigerant is increased, changing its condensation point. The compressed refrigerant leaves the compressor and passes through an oil separator where oil and refrigerant get separated from the mixture of refrigerant and oil. This refrigerant then enters a condenser where it is condensed from a vapor to a liquid refrigerant by heat exchange with a cooling medium. The liquid refrigerant is then returned, by means of an expansion device, to the evaporator to continue the cycle through the refrigerant loop.
[4] Pressure and temperature of the refrigerant circulating in any VRF system varies according to operating conditions. High pressures and high temperatures which are not desirable are developed during refrigeration cycle which may affect wear and tear various components and decrease the efficiency of the VRF system. Further, in sufficient oil may also affect the compressor working. Such affected components need to be replaced and thus, adversely increases the cost associated with the VRF system.
[5] As a safety precaution separate temperature and pressure sensors, separate valves and separate pipes for each of temperature, pressure control operations are used for effectively maintaining the VRF system. Further, for maintaining sufficient oil in the VRF system separate piping and sensors are used. Intelligent control systems configured with these separate temperature and pressure sensors, separate valves and separate pipes, control and regulate refrigerant flow and oil supply in the VRF system.
[6] However, a system having a separate piping circuit for circulating refrigerant flow and oil supply for attaining desirable conditions adversely increases the complexity and costs of the VRF system. Therefore, there is a requirement to ensure safe working of the VRF system at operable conditions without high costs associated therewith.

SUMMARY OF THE INVENTION
[7] Accordingly, an aspect of the present invention discloses a method of circulating a refrigerant within closed loops of a variable refrigerant flow (VRF) system comprising the steps of: configuring an eductor having a decreased cross section nozzle in a suction line between a high-pressure side and a low-pressure side; and providing a controller, which upon sensing a temperature or a pressure or an oil limit, higher or lower than predefined set limits and conditions, selectively or collectively operates to open (ON) or close (OFF) at least one or more solenoid valves, for a predetermined time, within at least one or more said closed loops at a specific time, for regulating/diverting a predetermined refrigerant flow and oil supply through said eductor when open (ON).
[8] According to an embodiment, an inlet end of said eductor is configured to suction a high-pressure vapour refrigerant and output high velocity, high pressure vapour refrigerant, mixes with a low-pressure gas refrigerant, oil, input at an outlet end, for outputting a mixture of low-pressure gas and liquid refrigerant.
[9] In the embodiment, the controller in an eductor-accumulator- inverter compressor closed loop: senses a discharge line temperature (DLT) temperature higher than said predefined set limit, continuous for a predetermined time, and upon detection, operates to open (ON) a fourth solenoid valve for regulating/diverting said high-pressure liquid refrigerant into said eductor, which outputs said low pressure gas, liquid refrigerant to suction of said accumulator; and upon regulating/diverting said refrigerant, detects said temperature within said predefined set limit and upon detection, operates to close (OFF) said fourth solenoid valve, thereby restricts high DLT of said inverter compressor.
[10] In the embodiment, the controller in an inverter compressor- eductor- accumulator- inverter compressor closed loop: senses a pressure higher than said predefined set limit, continuous for said predetermined time, and upon detection, operates to open (ON) a first solenoid valve for regulating/diverting said high pressure vapour refrigerant into said eductor, which outputs low pressure gas refrigerant to suction of said accumulator; and upon regulating/diverting said refrigerant, detects said pressure within said predefined set limit and upon detection, operates to close (OFF) said first solenoid valve, thereby equalizing said pressure from said high-pressure side to said low-pressure side.
[11] In the embodiment, the controller in an oil separator- inverter compressor closed loop: senses an oil limit in said inverter compressor below than said predefined set limit, continuous for said predetermined time and upon detection, operates to open (ON) a second solenoid valve for regulating/diverting oil supply from said oil separator to said inverter compressor; and upon regulating/diverting said oil, detects said oil limit equal to said predefined set limit and upon detection, operates to close (OFF) said second solenoid valve, thereby maintains sufficient oil supply in said refrigerant system and said inverter compressor.
[12] In the embodiment, the controller in a (ODU2) inverter compressor- (ODU1) eductor- (ODU1) accumulator- (ODU1) inverter compressor closed loop: senses an oil limit in a first outdoor unit (ODU1) below than said predefined set limit, continuous for said predetermined time, senses sufficient oil limit in a second outdoor unit and upon detection, operates to open (ON) a third solenoid valve of said second out door unit (ODU2) and simultaneously opens (ON) first, second and fifth solenoid valves of said first out door unit (ODU1), such that due to low pressure suction of said eductor, refrigerant gas along with oil flows into said accumulator; upon regulating/diverting said refrigerant gas along with oil, detects said oil limit in said first door unit (ODU1) equal to said predefined set limit and upon detection, operates to close (OFF) said third solenoid valve of said second out door unit (ODU2) and first and fifth solenoid valves of said first out door unit (ODU1); and upon detecting sufficient oil limit in said first outdoor unit (ODU1), closes (OFF) said second solenoid valve of said first out door unit (ODU1), thereby facilitates oil swap.
[13] According to the embodiment, the predetermined time is 10 seconds, said DLT temperature set limit is 85 degrees Celsius, said predefined pressure set limit is in the range of 120 to 210 PSIG (pounds per square in gauge), and said predefined oil limit level value is above 30% of oil level.
[14] According to the embodiment, the controller after equalization of pressure, maintains the difference between high pressure and low pressure at less than 50 PSIG (pounds per square in gauge).
[15] According to the embodiment, the refrigerant temperature at the outlet of the eductor is in range of -3 degrees Celsius to 20 degrees Celsius and the refrigerant temperature at the inlet of the eductor is in range of 38 degrees Celsius to 66 degrees Celsius.
[16] According to the embodiment, the the inlet pressure range of the refrigerant in the eductor is 300 to 620 PSIG (pounds per square in gauge) and pressure range at the outlet of the eductor is of 150 to 350 PSIG (pounds per square in gauge).
[17] According to another aspect, the present invention discloses, a variable refrigerant flow (VRF) system comprising: a plurality of indoor units and at least one outdoor unit; an accumulator interposed between at least one evaporator and at least one inverter compressor; an oil separator; a plurality of condensers; a heat-sink interconnecting the plurality of condensers; an expansion valve communicating between the heat-sink and said at least one evaporator; a plurality of pipes; a plurality of sensors; a plurality of solenoid valves having an inlet end and outlet end interposed therein the plurality of pipes; an eductor having a decreased cross section nozzle configured in a suction line between a high-pressure side and a low-pressure side; and
a controller for determining a temperature or a pressure or an oil limit, higher or lower than predefined set limits and conditions, thereby selectively or collectively opening (ON) or closing (OFF) at least one or more solenoid valves, for a predetermined time, within at least one or more said closed loops, for regulating/diverting a predetermined refrigerant flow and oil supply through said eductor when open (ON).

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[18] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
Figure 1 shows a circuit layout of a cool mode VRF system, according to an aspect of the present invention;
Figure 1A shows a detailed view of an eductor, according to an embodiment of the present invention;
Figure 2 shows an enlarged view of the eductor under operation for maintaining a discharge line temperature (DLT), according to an embodiment of the present invention;
Figure 3 shows an enlarged view of the eductor under operation for obtaining pressure equalization, according to the embodiment of the present invention;
Figure 4 shows an enlarged view of a second self-oil recovery operation valve in operation within an outdoor unit (ODU1), according to the embodiment of the present invention;
Figure 4A shows a flowchart for the operation of self-oil recovery within the outdoor unit (ODU1), according to the embodiment of the present invention;
Figure 5 shows a circuit layout for facilitating oil swap operation between two outdoor units ODU, according to the embodiment of the present invention; and
Figure 5A shows a flowchart for facilitating oil swap operation between two outdoor units ODU, according to the embodiment of the present invention.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and units.

DETAILED DESCRIPTION OF THE INVENTION
[19] In general, the present invention claims a method for circulating a refrigerant within closed loops of a variable refrigerant flow (VRF) system by providing an eductor and a controller that defines and monitors a predefined set limits, conditions, and regulates a predetermined refrigerant flow and oil supply therethrough the educator. The controller thus maintains a discharge line temperature (DLT), equalizes pressure from a high-pressure side to a low-pressure side, maintains a sufficient oil supply in the refrigerant system and an inverter compressor, and facilitates oil swap between at least two the outdoor units.
[20] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
[21] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
[22] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. For example, number of solenoid valves, outdoor units, sensors, temperatures, pressures, predefined set limits, and type of refrigerant etc. are referred in the description for the purpose of the understanding and nowhere limit the invention.
[23] Figures discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure and not to scaled. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged environment. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions in no way limit the scope of the invention.
[24] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment includes elements A, B, and C, and a second embodiment includes elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[25] Referring figures 1-5 shows a VRF system (100), a plurality of indoor units (115), at least one outdoor unit (116), an eductor (106), an accumulator (101), at least one inverter compressor (102), an oil separator (103), a plurality of air cooled heat exchangers used as condensers (104), a heat-sink (105), a plurality of pipes (118), and a plurality of solenoid valves (107, 108, 109, 110 and 111), a discharge line temperature (DLT), DLT sensor (112), a low-pressure sensor (114), a capillary out temperature sensor (113), nozzle (1), an inlet (2), an output (3), nozzle output (4), outdoor units (116 ODU1, 116 ODU 2, (117 ODU2)), controller (150) and method (200).
[26] Referring Figure 1 through Figure 1A shows a circuit layout of a cool mode VRF system (100) according to the embodiment of the present invention. According to the embodiment, the VRF system may have a plurality of indoor units (115) connected with at least one outdoor unit (116) and at least one evaporator (not shown). The eductor (106) having a decreased cross section a nozzle configured to low pressure suction is interposed in a suction line between a high-pressure side and a low-pressure side.
[27] According to the embodiment, the VRF system (100) also includes an accumulator (101) interposed between the evaporator and at least one inverter compressor (102), an oil separator (103), a plurality of air cooled heat exchangers used as condensers (104), a heat-sink (105) interconnecting the plurality of condensers (104), an expansion valve (not shown) communicating between the heat-sink (105) and at least one evaporator, a plurality of pipes (118), and a plurality of solenoid valves (107, 108, 109, 110 and 111) having an inlet end and outlet end interposed therein the plurality of pipes (118) for varying the refrigerant and oil supply flowing therethrough the eductor (106).
[28] According to the embodiment, the first pressure solenoid valve (107) interposed therebetween the inverter compressor (102) and the eductor (106) is configured to equalize pressure flow of the refrigerant from a high compressor (102) pressure side to a low-pressure eductor side (106) and operate oil swap between two outdoor units (116). During Normal operation compressor speed varies between minimum 15 rps to maximum 100 rps.
[29] According to the embodiment, the second solenoid valve (108) interposed therebetween the oil separator (103) and the inverter compressor (102) is configured to regulate oil and operate in a self-oil recovery process.
[30] According to the embodiment, the third solenoid valve (109) interposed therebetween the inverter compressor (102) and the eductor (106) is configured to regulate output flow of oil push out from the compressor (102).
[31] According to the embodiment, the fourth solenoid valve (110) interposed therebetween the heatsink (105) and the eductor (106) is configured to regulate flow of liquid refrigerant injection into the eductor (106).
[32] According to the embodiment, the fifth solenoid valve (111) interposed therebetween an evaporator and the eductor (106) is configured to regulate flow of the gas refrigerant into the eductor (106) and operate oil swap between two outdoor units (116).
[33] According to the embodiment, the present invention includes a plurality of non-return one-way valves, a first non-return valve intermediate to the compressor (102) and the oil separator (103) and a second non-return valve intermediate to the evaporator and the eductor (106).
[34] According to the embodiment, the present invention includes a plurality of sensors configured to detect high pressures and temperatures in the VRF system. A discharge line temperature (DLT) sensor (112) connected to a discharge of the compressor (102) is configured to restrict high temperatures of discharge, a low-pressure sensor (114) is connected to the accumulator (101) and a capillary out temperature sensor (113) is connected to the compressor (102).
[35] According to the embodiment, the present invention includes a controller (150) having a processor operatively interconnected to the plurality of sensing means (112, 113, 114) and the plurality of solenoid valves (107, 108, 109, 110 and 111). The controller (150) upon sensing temperatures or pressures or oil limit, higher or lower than the predefined set limits and conditions, selectively or collectively operates opening (ON) or closing (OFF) of at least one or more plurality of solenoid valves (107, 108, 109, 110 and 111) for a predetermined time within at least one or more closed loops at a specific time. Thus, the controller (150) regulates and diverts a predetermined refrigerant flow and oil supply therethrough the eductor (106) when open (ON) and thereby maintains the discharge line temperature (DLT), equalizes pressure from a high-pressure side to a low-pressure side, maintains a sufficient oil supply in the refrigerant system and the inverter compressor, and facilitates oil swap between at least two outdoor units. According to the exemplary embodiment, the predefined DLT temperature is below 85 Degrees Celsius and the detected DLT temperature range is minimum 40 Degrees Celsius, maximum 110 Degrees Celsius. According to the embodiment, the temperature, pressure and oil level values are measured for a predefined time limit of every 10 seconds. Based on the values the Solenoid valve is also controlled the predefined time limit is for every 10 seconds.
[36] In Figure 1A, an inlet end of the eductor (106) is configured to suction a high-pressure vapour refrigerant and output high velocity, high pressure vapour refrigerant, therein mix with a low-pressure gas refrigerant, oil input at an outlet end to output a mixture of low-pressure gas, liquid refrigerant.
[37] For example, in Figure 1A, a high pressure R410a vapor enters through the input of nozzle (1) and a low pressure R410a gas along with oil inputs an inlet (2) near the nozzle output (4). Due to large pressure difference created therein the eductor R410a gas along with oil gets sucked through the inlet inside the eductor (106). Due to the low-pressure suction the output (3) of eductor (106) is a low pressure R410a vapour along with oil. When only high-pressure refrigerant is passing through decreasing cross section area, pressure drop takes place and output is low pressure refrigerant.
[38] According to an exemplary embodiment, the refrigerant temperature at the outlet (3) of the eductor (106) has range from -3 Degrees Celsius to 20 Degrees Celsius and the refrigerant temperature at the inlet (1) of the eductor (106) has range from 38 Degrees Celsius to 66 Degrees Celsius.
In the exemplary embodiment, the high-pressure refrigerant is passed through the eductor (106) and then expands, so the inlet pressure range of the refrigerant is 300 to 620 PSIG (pounds per square in gauge). The outlet (2) of the eductor (106) is connected to low pressure side having pressure range of 150 to 350 PSIG (pounds per square in gauge).
[39] Referring Figure 2 shows an enlarged view of the eductor (106) under operation for maintaining the discharge line temperature (DLT) according to the embodiment of the present invention. The arrows show the sequence of refrigerant flow. The controller (150) therein an eductor (106)-accumulator (101)- inverter compressor (102) closed loop detects a DLT temperature higher than the predefined set limit and continuous for a predetermined time. Upon detection, the controller (150) opens (ON) the fourth solenoid valve (110) thereby regulates a high-pressure liquid refrigerant injection into the eductor (106). Then, the eductor (106) outputs low pressure gas, liquid refrigerant to suction of the accumulator (101). When the low-pressure gas, liquid refrigerant is diverted, the controller (150) detects that the temperature is within the predefined set limit and therefore closes (OFF) the fourth solenoid valve (110), thereby restricts high DLT of the inverter compressor (102).
[40] Referring Figure 3 shows an enlarged view of the eductor (106) under operation for obtaining pressure equalization according to the embodiment of the present invention. The arrows show the sequence of refrigerant flow. The controller (150) therein an inverter compressor (102) - eductor (106) - accumulator (101)- inverter compressor (102) closed loop detects a pressure higher than the predefined set limit and continuous for a predetermined time. Upon detection, the controller (150) opens (ON) the first solenoid valve (107) thereby regulates high pressure vapour refrigerant injection into the eductor (106). The eductor (106) outputs low pressure gas refrigerant to suction of the accumulator (101). Upon diverting the refrigerant, the controller (150) detects that the pressure is within the predefined set limit and therefore, closes (OFF) the first solenoid valve (107), thereby equalizes the pressure.
[41] According to the embodiment, pressure equalization is when high pressure and low pressure are matched or made equal. The pressure equalization range is from 120 to 210 PSIG. According to the embodiment, the difference between high Pressure and Low Pressure is less than 50 PSIG after equalization. In the embodiment, high Pressure is detected in range of 300 to 620 PSIG (pounds per square in gauge). Low Pressure is detected in 70 to 180 PSIG (pounds per square in gauge).
[42] Referring Figure 4 through Figure 4A shows an enlarged view of a second self-oil recovery operation valve and a flowchart for the operation of self-oil recovery within an outdoor unit (ODU1) according to the embodiment of the present invention. The arrows show the sequence of oil flow. When oil in the compressor (102) is less, oil from the oil separator (103) is diverted through the second solenoid valve (108) into the compressor (102) and thus sufficient oil is maintained in the VRF system (100).
[43] In Figure 4A, the controller (150) therein an oil separator (103) - inverter compressor (102) closed loop, detects an oil limit in the inverter compressor (102) below than the predefined set limit for a continuous predetermined time. Upon detection, the controller (150) opens (ON) the second solenoid valve (108) to regulate and divert oil supply from the oil separator (103) to the inverter compressor (102). Upon diverting the oil, the controller (150) detects that the oil limit in the compressor is equal to the predefined set limit and therefore, closes (OFF) the second solenoid valve (103), thereby maintaining sufficient oil in the VRF system and the compressor.
According to the embodiment, the predefined oil level limit value is above 30% of the oil level and the desired oil level detected according to the exemplary embodiment is varies from 0% to 100%.
[44] According to the embodiment, during oil recovery compressor speed is 60 RPS. The predetermined refrigerant flow and oil supply through said eductor (106) is determined by the controller (150).
[45] Referring Figure 5 through Figure 5A shows a circuit layout between two outdoor units (116 ODU1 and 116 ODU 2) and a flow chart for facilitating oil swap operation between two outdoor units ODU according to the embodiment of the present invention. When the controller (150) detects that oil within the first outdoor unit (116 ODU1) is not sufficient, oil is swapped from the next outdoor unit (117 ODU2). The arrows show the sequence of oil flow.
[46] In Figure 5A, the controller (150) therein an outdoor unit (117 ODU2) inverter compressor (102 ODU2)- outdoor unit (116 ODU1) eductor (106) - outdoor unit (ODU1) accumulator (101)- outdoor unit (ODU1) inverter compressor (102 ODU1) closed loop, detects an oil limit in a first outdoor unit (ODU1) below than the predefined set limit for a continuous predetermined time. Then the controller (150) checks for sufficient oil limit in a second outdoor unit (117 ODU2) and upon detection that sufficient oil is available, opens (ON) a third solenoid valve (109 ODU2) of the second outdoor unit (117 ODU2) and simultaneously opens (ON) the first (107), second (108) and fifth (111) solenoid valves of the first outdoor unit (116 ODU1).
[47] According to the present invention, due to low pressure suction of the eductor (106), refrigerant gas along with oil flows therein to the accumulator (101). The controller (150) upon diverting the refrigerant gas along with oil, detects oil limit in the first door unit (116 ODU1) equal to the predefined set limit and closes (OFF) the third solenoid valve (109 ODU2) of the second outdoor unit (117 ODU2) and first (107) and fifth (111) solenoid valves of the first outdoor unit (116 ODU1). When the controller (150) detects sufficient oil limit in the first outdoor unit (116 ODU1), closes (OFF) the second solenoid valve (108) of the first outdoor unit (116 ODU1), thereby facilitates oil swap between the two outdoor units.
[48] According to the embodiment, during Oil Swap second outdoor unit (117 ODU2) compressor speed is 65 RPS and first outdoor unit (116 ODU1) compressor speed is 40 RPS.
[49] According to the embodiment, the controller having the processor and memory stores the predefined set temperature, pressure and oil limits and predetermined time periods in a memory. During operation, the controller measures real-time temperature, pressure and oil limits and compares the sensed / determined real-time temperature, pressure and oil limits with stored predefined set temperature, pressure and oil limits and invokes corresponding signals within the plurality of closed loops to pass the refrigerant through the eductor thereby maintains a discharge line temperature (DLT), equalizes pressure from a high-pressure side to a low-pressure side, maintains a sufficient oil supply in the refrigerant system (100) and an inverter compressor (102), and facilitates oil swap between at least two the outdoor units (116, 117). The real time values are determined by said microcontroller, during continuous operation of the system and compressor.
[50] According to another aspect, the present invention discloses a variable refrigerant flow (VRF) system (100) comprising a plurality of indoor units (115) and at least one outdoor unit (116); an accumulator (101) interposed between at least one evaporator and at least one inverter compressor (102); an oil separator (103); a plurality of condensers (104); a heat-sink (105) interconnecting the plurality of condensers (104); an expansion valve communicating between the heat-sink (105) and said at least one evaporator; a plurality of pipes (118); a plurality of sensors (112, 113, 114); a plurality of solenoid valves (107, 108, 109, 110 and 111) having an inlet end and outlet end interposed therein the plurality of pipes (118); an eductor (106) having a decreased cross section nozzle configured in a suction line between a high-pressure side and a low-pressure side; and a controller (150) for determining a temperature or a pressure or an oil limit, higher or lower than predefined set limits and conditions, thereby selectively or collectively opening (ON) or closing (OFF) at least one or more solenoid valves (107, 108, 109, 110 and 111), for a predetermined time, within at least one or more said closed loops, for regulating/diverting a predetermined refrigerant flow and oil supply through said eductor (106) when open (ON).
[51] The embodiments of the present invention eliminate the need for separate piping and ensures safety of the VRF system. The present invention discloses the use of a simple low-pressure suction method, simplified piping and smart solenoid valve operation. Therefore, the high costs associated with separate piping in VRF system are reduced to an extent of 4% for a standard 12HP IVRF system. Similarly, separate piping required for connecting multiple outdoor units is also eliminated by using only a gas valve line and a liquid valve line.
[52] There have been described and illustrated herein embodiments circulating refrigerant in a cool mode variable refrigerant flow (VRF) systems. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular types of temperatures, pressures, time periods, refrigerant types, higher and lower limits, normal and desired changes have been disclosed, it will be appreciated they are not limited to those described herein above.
[53] In the foregoing detailed description of aspects embodiments of the invention, various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the detailed description of aspects, embodiments of the invention, with each claim standing on its own as a separate embodiment.
[54] It is understood that the above description and drawings are intended to be illustrative, and not restrictive. Description and drawings are intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” is used as the plain-English equivalent of the respective term “comprising” respectively.
,CLAIMS:
1. A method (200) of circulating a refrigerant within closed loops of a variable refrigerant flow (VRF) system (100) comprising the steps of:
a) configuring an eductor (106) having a decreased cross section nozzle in a suction line between a high-pressure side and a low-pressure side; and
b) providing a controller (150), which upon sensing a temperature or a pressure or an oil limit, higher or lower than predefined set limits and conditions, selectively or collectively operates to open (ON) or close (OFF) at least one or more solenoid valves (107, 108, 109, 110 and 111), for a predetermined time, within at least one or more said closed loops, for regulating/diverting a predetermined refrigerant flow and oil supply through said eductor (106) when open (ON).

2. The method (200) as claimed in claim 1, wherein an inlet end (1) of said eductor (106) is configured to suction a high-pressure vapour refrigerant and output high velocity, high pressure vapour refrigerant, mixes with a low-pressure gas refrigerant, oil, input (2) at an outlet end (4), for outputting a mixture of low-pressure gas and liquid refrigerant.

3. The method (200) as claimed in claims 1 or 2, wherein said controller (150) in an eductor (106) - accumulator (101) - inverter compressor (102) closed loop:
a) senses a discharge line temperature (DLT) temperature higher than said predefined set limit, continuous for a predetermined time, and upon detection, operates to open (ON) a fourth solenoid valve (110) for regulating/diverting said high-pressure liquid refrigerant into said eductor (106), which outputs said low pressure gas, liquid refrigerant to suction of said accumulator (101); and
b) upon regulating/diverting said refrigerant, detects said temperature within said predefined set limit and upon detection, operates to close (OFF) said fourth solenoid valve (110), thereby restricts high DLT of said inverter compressor (102).

4. The method (200) as claimed in anyone of claims 1-3, wherein said controller (150) in an inverter compressor (102) - eductor (106) – accumulator (101) - inverter compressor (102) closed loop:
a) senses a pressure higher than said predefined set limit, continuous for said predetermined time, and upon detection, operates to open (ON) a first solenoid valve (107) for regulating/diverting said high pressure vapour refrigerant into said eductor (106), which outputs low pressure gas refrigerant to suction of said accumulator (101); and
b) upon regulating/diverting said refrigerant, detects said pressure within said predefined set limit and upon detection, operates to close (OFF) said first solenoid valve (107), thereby equalizing said pressure from said high-pressure side to said low-pressure side.
5. The method (200) as claimed in anyone of claims 1-4, wherein said controller (150) in an oil separator (103) - inverter compressor (102) closed loop:
a) senses an oil limit in said inverter compressor (102) below than said predefined set limit, continuous for said predetermined time and upon detection, operates to open (ON) a second solenoid valve (108) for regulating/diverting oil supply from said oil separator (103) to said inverter compressor (102); and
b) upon regulating/diverting said oil, detects said oil limit equal to said predefined set limit and upon detection, operates to close (OFF) said second solenoid valve (108), thereby maintains sufficient oil supply in said refrigerant system (100) and said inverter compressor (102).

6. The method (200) as claimed in anyone of claims 1-5, wherein said controller (150) in a (ODU2) inverter compressor (102) - (ODU1) eductor (106) - (ODU1) accumulator (101) - (ODU1) inverter compressor (102) closed loop:
a) senses an oil limit in a first outdoor unit (116 ODU1) below than said predefined set limit, continuous for said predetermined time, senses sufficient oil limit in a second outdoor unit (117ODU) and upon detection, operates to open (ON) a third solenoid valve (109) of said second out door unit (117 ODU2) and simultaneously opens (ON) first (107), second (108) and fifth (111) solenoid valves of said first out door unit (116 ODU1), such that due to low pressure suction of said eductor (106), refrigerant gas along with oil flows into said accumulator (101);
b) upon regulating/diverting said refrigerant gas along with oil, detects said oil limit in said first door unit (ODUs1) equal to said predefined set limit and upon detection, operates to close (OFF) said third solenoid valve (109) of said second outdoor unit (117 ODU2) and first (107) and fifth (111) solenoid valves of said first outdoor unit (116 ODU1); and
c) upon detecting sufficient oil limit in said first outdoor unit (116ODU1), closes (OFF) said second solenoid valve (108) of said first outdoor unit (116 ODU1), thereby facilitates oil swap.

7. The method (200) as claimed in anyone of claims 1-6, wherein said predetermined time is 10 seconds, said DLT temperature set limit is 85 degrees Celsius, said predefined pressure set limit is in the range of 120 to 210 PSIG (pounds per square in gauge), and said predefined oil limit level value is above 30% of oil level.

8. The method (200) as claimed in anyone of claims 1-7, wherein the Controller (150) after equalization of pressure, maintains the difference between high pressure and low pressure at less than 50 PSIG (pounds per square in gauge).

9. The method (200) as claimed in anyone of claims 1-8, wherein refrigerant temperature at the outlet (3) of the eductor (106) is in range of -3 degrees Celsius to 20 degrees Celsius and the refrigerant temperature at the inlet (1) of the eductor (106) is in range of 38 degrees Celsius to 66 degrees Celsius.
10. The method (200) as claimed in anyone of claims 1-9, wherein the inlet pressure range of the refrigerant in the eductor (106) is 300 to 620 PSIG (pounds per square in gauge) and pressure range at the outlet (2) of the eductor (106) is of 150 to 350 PSIG (pounds per square in gauge).

11. A variable refrigerant flow (VRF) system (100) comprising:
a plurality of indoor units (115) and at least one outdoor unit (116);
an accumulator (101) interposed between at least one evaporator and at least one inverter compressor (102);
an oil separator (103);
a plurality of condensers (104);
a heat-sink (105) interconnecting the plurality of condensers (104);
an expansion valve communicating between the heat-sink (105) and said at least one evaporator;
a plurality of pipes (118);
a plurality of sensors (112, 113, 114);
a plurality of solenoid valves (107, 108, 109, 110 and 111) having an inlet end and outlet end interposed therein the plurality of pipes (118);
an eductor (106) having a decreased cross section nozzle configured in a suction line between a high-pressure side and a low-pressure side; and
a controller (150) for determining a temperature or a pressure or an oil limit, higher or lower than predefined set limits and conditions, thereby selectively or collectively opening (ON) or closing (OFF) at least one or more solenoid valves (107, 108, 109, 110 and 111), for a predetermined time, within at least one or more said closed loops, for regulating/diverting a predetermined refrigerant flow and oil supply through said eductor (106) when open (ON).