LOW-COST CONTROL FOR CARBON DIOXIDE CONDENSING UNIT

Abstract

A system may include a condenser unit including a compressor configured to receive a refrigerant from a condenser unit input port and provide a compressed refrigerant; a gas cooler configured to receive the compressed refrigerant and provide a first cooled refrigerant at a gas cooler discharge port; an expansion valve configured to receive the first cooled refrigerant and provide a second cooled refrigerant to a condenser unit discharge port; and a first controllable valve configured to receive the first cooled refrigerant and provide a first metered refrigerant combined with the second cooled refrigerant into a combined refrigerant provided to the condenser unit discharge port, the first controllable valve configured to selectively open when a first temperature at the gas cooler discharge port is below a first temperature threshold.

Claims

1. A system, the system comprising: a condenser unit, the condenser unit comprising: a compressor configured to receive a refrigerant from a condenser unit input port and provide a compressed refrigerant; a gas cooler configured to receive the compressed refrigerant and provide a first cooled refrigerant at a gas cooler discharge port; an expansion valve configured to receive the first cooled refrigerant and provide a second cooled refrigerant to a condenser unit discharge port; and a first controllable valve configured to receive the first cooled refrigerant and provide a first metered refrigerant combined with the second cooled refrigerant into a combined refrigerant provided to the condenser unit discharge port, the first controllable valve configured to selectively open when a first temperature at the gas cooler discharge port is below a first temperature threshold.

2. The system of claim 1, wherein the expansion valve is a fixed differential expansion valve.

3. The system of claim 1, wherein the first controllable valve is a shut off valve.

4. The system of claim 1, further comprising: a first temperature sensor physically attached to the first controllable valve, the first temperature sensor configured to directly activate a first controllable valve actuator configured to operate the first controllable valve.

5. The system of claim 1, wherein the first temperature threshold corresponds to a critical temperature of carbon dioxide.

6. The system of claim 1, the system further comprising: an evaporator unit, the evaporator unit comprising: a second controllable valve configured to receive at least one of the first cooled refrigerant and the first metered refrigerant from the condenser unit discharge port and provide a second metered refrigerant; and an evaporator configured to receive the second metered refrigerant and provide an evaporated refrigerant at an evaporator discharge port configured to be coupled to the condenser unit input port, wherein the second metered refrigerant in the evaporator is configured to cool an adjacent space, wherein the second controllable valve is configured to selectively open when a second temperature at the evaporator discharge port is below a second temperature threshold.

7. The system of claim 6, wherein the second controllable valve is a shut off valve.

8. The system of claim 6, further comprising: a second temperature sensor physically attached to the second controllable valve, the second temperature sensor configured to directly activate a second controllable valve actuator configured to operate the second controllable valve.

9. The system of claim 6, further comprising: a first temperature sensor physically separated from the first controllable valve, the first temperature sensor configured to provide a first temperature signal representative of the first temperature at the gas cooler discharge port; a second temperature sensor physically separated from the second controllable valve, the second temperature sensor configured to provide a second temperature signal representative of the second temperature at the evaporator discharge port, the second temperature signal transmitted through a second temperature port as a transmitted second temperature signal; and a controller configured to compare the first temperature signal with a first temperature threshold signal representative of the first temperature threshold, the controller configured to assert a first control signal to indirectly activate a first controllable valve actuator configured to open the first controllable valve when the first temperature is below the first temperature threshold, the controller configured to compare the transmitted second temperature signal with a second temperature threshold signal representative of the second temperature threshold, the controller configured to assert a second control signal, the second control signal transmitted through a second control port as a transmitted second control signal to indirectly activate a second controllable valve actuator configured to open the second controllable valve when the second temperature is below the second temperature threshold.

10. The system of claim 9, wherein the controller is configured to selectively activate at least one of the first controllable valve actuator and the second controllable valve actuator with pulse width modulation.

11. The system of claim 9, wherein the second controllable valve is one of a thermally controlled valve, an electronic expansion valve, and a pulse width modulated valve.

12. A method, comprising: condensing a compressed refrigerant with a gas cooler having a gas cooler discharge port to provide a first cooled refrigerant; expanding the first cooled refrigerant to provide a second cooled refrigerant to a condenser unit discharge port; detecting a first temperature at the gas cooler discharge port; and conducting at least a portion of the first cooled refrigerant to combine with the second cooled refrigerant into a combined refrigerant at the condenser unit discharge port when the first temperature is below a first temperature threshold.

13. The method of claim 12, wherein conducting the portion of the first cooled refrigerant to combine with the second cooled refrigerant into the combined refrigerant at the condenser unit discharge port when the first temperature is below the first temperature threshold includes: controlling a first controllable valve configured to receive the first cooled refrigerant and provide a first metered refrigerant combined with the second cooled refrigerant into the combined refrigerant provided to the condenser unit discharge port.

14. The method of claim 13, wherein controlling the first controllable valve configured to receive the first cooled refrigerant and provide the first metered refrigerant combined with the second cooled refrigerant into the combined refrigerant provided to the condenser unit discharge port includes: activating a first controllable valve actuator configured to open the first controllable valve.

15. The method of claim 14, wherein activating the first controllable valve actuator includes one of directly activating through a physical connection and indirectly activating through an electronic connection.

16. The method of claim 12, further comprising: compressing a refrigerant from a condenser unit input port to provide the compressed refrigerant.

17. The method of claim 12, further comprising: absorbing heat from an adjacent space with an evaporator having an evaporator discharge port; detecting a second temperature at the evaporator discharge port; and conducting the combined refrigerant to the evaporator when the second temperature is below a second temperature threshold, the evaporator providing an evaporated refrigerant to a condenser unit input port.

18. The method of claim 17, wherein conducting the combined refrigerant to the evaporator when the second temperature is below the second temperature threshold includes: controlling a second controllable valve configured to receive the combined refrigerant and provide a second metered refrigerant to the evaporator.

19. The method of claim 18, wherein controlling the second controllable valve configured to receive the combined refrigerant and provide the second metered refrigerant to the evaporator includes: activating a second controllable valve actuator configured to open the second controllable valve.

20. The method of claim 19, wherein activating the second controllable valve actuator includes one of directly activating through a physical connection and indirectly activating through an electronic connection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a more complete understanding of the present disclosure, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

[0013] FIG. 1 illustrates a block diagram view of a system, according to an example;

[0014] FIG. 2 illustrates a block diagram view of a system, according to another example; and

[0015] FIGS. 3A-3C illustrate a method of operating a cooling system, according to an example.

[0016] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0017] This disclosure provides a low-cost method for controlling and operating cooling systems with carbon dioxide (CO.sub.2) condensing units, resulting in relatively lower performance at non rating points, and with a lower initial cost, while still achieving minimum performance levels required by various United States Department of Energy (DoE) and Air Conditioning, Heating, and Refrigeration Institute (AHRI) standards, for example.

[0018] Hereinafter, a description will be given of respective examples of the present disclosure with reference to the drawings. Note that the disclosure is merely an example, and appropriate changes, which maintain the spirit thereof and are easily conceivable by those skills in the relevant art, are naturally included in the scope of the present disclosure. Moreover, in some cases, in the present specification and the respective drawings, the same reference numerals are assigned to elements similar to those mentioned above regarding the already-discussed drawings, and a detailed description thereof is omitted as appropriate.

[0019] FIG. 1 illustrates a block diagram view of a system 100, according to an example. System 100 may include a condenser unit 102 cand an evaporator unit 104 which together may comprise system 100, also denoted as a cooling system 100. Condenser unit 102 may be a modular component of cooling system 100 that is separate from evaporator unit 104 which may be another modular component of cooling system 100, for example. In this manner, condenser unit 102 and evaporator unit may be fabricated separately and assembled into cooling system 100 in a factory setting or a field setting, for example. Condenser unit 102 may be releasably coupled to evaporator unit 104 where the corresponding refrigerant and/or electrical connections may be connected and disconnected for assembly, testing, and maintenance, for example. Condenser unit 102 may also be denoted as a cooling unit 102 or a carbon dioxide (CO.sub.2) cooling unit 102 and may include a compressor 118 configured to receive a refrigerant 120 from a condenser unit input port 122 and compressor 118 may provide a compressed refrigerant 124. As described, refrigerant 120 may include carbon dioxide (CO.sub.2) or may be composed entirely of carbon dioxide.

[0020] Condenser unit 102 may include a gas cooler 128 (e.g., a condensing coil or heat exchanger) with a gas cooler inlet (e.g., an input port) that is configured to receive compressed refrigerant 124 and provide a first cooled refrigerant 130 at a gas cooler discharge port 132. Gas cooler 128 may include a plurality of coils with radiating fins configured to receive compressed refrigerant 124 at a high temperature and pressure and provide first cooled refrigerant 130 at a lower temperature and pressure by radiation, convection, and conduction of heat from compressed refrigerant 124 to an adjacent first space 194, such as an outdoor region, or other surrounding area. Thus, gas cooler 128 may release heat from compressed refrigerant 124 into adjacent first space 194 as compressed refrigerant 124 cools. Further, gas cooler 128 may cool compressed refrigerant 124 without changing state of compressed refrigerant 124 from gas to liquid, but this is not considered limiting. In some examples, gas cooler 128 may change the state from gas to liquid of compressed refrigerant 124.

[0021] Condenser unit 102 may also include an expansion valve 138 configured to receive first cooled refrigerant 130 at a higher pressure and provide a second cooled refrigerant 140 at a lower pressure to a condenser unit discharge port 144. In this manner, expansion valve 138 may cause resistance to the flow of first cooled refrigerant 130 with high pressure, between about 90-100 bar (9-10 MegaPascals), on an inlet side of expansion valve 138 and a low pressure, between about 35-60 bar (3.5-6 MPa), on a discharge side of expansion valve 138, for example. Expansion valve 138 may be a fixed differential expansion valve 138 (e.g., to save costs) having a fixed orifice configured to regulate refrigerant flow at a fixed rate and maintain the inlet and discharge pressures within an acceptable range, above. Alternatively, expansion valve 138 may be implemented as a pin-type, small orifice tube.

[0022] Condenser unit 102 may also include a first controllable valve 148 configured to receive first cooled refrigerant 130 and provide a first metered refrigerant 150 combined with second cooled refrigerant 140 into a combined refrigerant 142 that may be provided to condenser unit discharge port 144. First controllable valve 148 may be a shut off valve configured to selectively open when a first temperature 134 at gas cooler discharge port 132 is below a first temperature threshold 112 which may correspond to a sub-critical temperature within a range of temperatures from a sub-critical temperature 75 F. (or 23.9 C.) to a critical temperature of carbon dioxide 87.98 F. (or 31.1 C.) at a pressure of 73.8 bar (or 7.38 MPa). Operation of gas cooler 128 or other components at a temperature and/or pressure above the critical point may correspond to trans-critical operation. Condenser unit 102 may include a first temperature sensor 156 disposed in a region adjacent to a gas cooler discharge port 132 to measure first temperature 134 and either directly or indirectly operate first controllable valve 148.

[0023] First controllable valve 148 may include a first controllable valve actuator 154 operatively coupled with first controllable valve 148 and configured to selectively open first controllable valve 148 from a fully closed state where no amount of first cooled refrigerant 130 is able to pass through first controllable valve 148, to a partially opened state where some amount of first cooled refrigerant 130 is able to pass through first controllable valve 148, and finally to a fully opened state where a maximal amount of first cooled refrigerant 130 is able to pass through first controllable valve 148, or to any opened state between fully closed to fully open, inclusively. First controllable valve actuator 154 may include a solenoid element that may be operated according to a duty cycle to selectively open first controllable valve 148, for example. In this manner, first controllable valve actuator 154 may be configured to selectively open first controllable valve 148 based on first temperature sensor 156. Stated differently, when first controllable valve 148 is at least partially opened, at least a portion of first cooled refrigerant 130 may be combined with second cooled refrigerant 140 at condenser unit discharge port 144 when first temperature 134 is below first temperature threshold 112. In one example, first controllable valve 148 may remain closed while first temperature 134 is less than 75 F. (or 23.9 C.) and first controllable valve 148 may begin to open above this temperature. In another example, first controllable valve 148 may remain closed while first temperature 134 is less than 87.98 F. (or 31.1 C.) and first controllable valve 148 may begin to open above this temperature. Thus, first controllable valve 148 may be configured to receive first cooled refrigerant 130 and provide first metered refrigerant 150 combined with second cooled refrigerant 140 which may be combined into a combined refrigerant 142 at condenser unit discharge port 144.

[0024] Condenser unit 102 may include a controller 106 configured to receive electronic sensor signals and/or assert electronic control signals to various components in order to perform one or more operations described in relation to condenser unit 102. For example, controller 106 may include a programmable device such as a processor 108 configured to read, decode, and execute instructions to manipulate data to perform operations of controller 106 and condenser unit 102. Controller 106 may include a memory 110 configured to store and retrieve instructions and/or data used to perform operations of controller 106 and condenser unit 102. Controller 106 may include a first temperature threshold 112 and a second temperature threshold 114 that may be implemented as values stored in a register within processor 108 and/or in predetermined memory locations within memory 110.

[0025] First temperature threshold 112 may be implemented as a first temperature threshold signal 112S, while second temperature threshold 114 may be implemented as a second temperature threshold signal 114S, as will be described more fully below. For example, both first temperature threshold signal 112S and second temperature threshold signal 114S may be generated by a digital-to-analog (DAC) converter based on the corresponding stored values for first temperature threshold 112 and second temperature threshold 114, respectively. In this manner, first temperature threshold signal 112S and second temperature threshold signal 114S may be compared with corresponding sensor signals, using various comparator and logic elements within controller 106, for example. Further, first temperature threshold 112 may be implemented as a first embedded microcode value and second temperature threshold 114 may be implemented as a second embedded microcode value in a combined logic chip in place of processor 108 and memory 110 to perform the operations described herein.

[0026] Processor 108 may be implemented as a special purpose computer, a microprocessor, a microcomputer, or a microcontroller configured to retrieve and execute program instructions from memory 110, for example. Alternatively, processor 108 may be implemented as a programmable logic circuit and/or a state machine configured to follow embedded microcode instructions in a portion of programmable logic circuit designated as memory 110 or according to hard-wired instructions. Some or all of processor 108 and/or memory 110 may be replaced to change, modify, or upgrade readable or microcoded instructions, for example. In this manner, memory 110 may be considered as a computer readable medium component including instructions stored in memory 110, for example.

[0027] Controller 106 may also include a pulse width modulation (PWM) control unit 116 configured to assert pulse width modulation control signals to operate various components within cooling system 100 under direction by processor 108, as will be described more fully below. Controller 106 may receive a first temperature signal 158 asserted by first temperature sensor 156 disposed adjacent to gas cooler discharge port 132. First temperature signal 158 may be representative of a first temperature adjacent to gas cooler discharge port 132, and may be an ambient temperature (e.g., environmental air temperature) at that location. Further, first temperature sensor 156 may be in contact with gas cooler discharge port 132, in some examples. Controller 106 may be configured to compare first temperature signal 158 with first temperature threshold signal 112S representative of first temperature threshold 112 and determine whether first temperature 134 is below first temperature threshold 112.

[0028] When first temperature 134 is below first temperature threshold 112, controller 106 may cause pulse width modulation control unit 116 to assert (e.g., to activate) a first control signal 152 to directly activate first controllable valve actuator 154 in order to indirectly activate and selectively open first controllable valve 148, as described above. A pulse width modulated signal may have a duty cycle corresponding to an on-time (e.g., active) and an off-time (e.g., inactive) and a waveform having a predetermined frequency or wavelength. In this manner, controller 106 may indirectly operate first controllable valve 148 based on first temperature signal 158 given various predetermined dynamic characteristics of controllable valve 148 according to various vendor specifications. Thus, controller 106 may be suitably programmed to operate first controllable valve 148 available from different vendors. Finally, when first temperature 134 is equal to or greater than first temperature threshold 112, controller 106 may cause pulse width modulation control unit 116 to de-assert (e.g., to de-activate) first control signal 152 to first controllable valve actuator 154 in order to selectively close controllable valve 148.

[0029] Evaporator unit 104 may include a second controllable valve 160, an evaporator 168, and a second temperature sensor 178. Similar to the description above, second controllable valve 160 may receive combined refrigerant 142 from condenser unit discharge port 144 and provide a second metered refrigerant 162 under the control of a second controllable valve actuator 164 configured to selectively open second controllable valve 160. Second metered refrigerant 162 may be applied to an inlet (e.g., an input port) of evaporator 168. In evaporator 168, second metered refrigerant 162 may be converted from liquid to gas, absorbing heat from surrounding air in a second space or compartment 196. Thus, warmer air applied to evaporator 168 may be cooled and may be used to cool second space or compartment 196.

[0030] A fan may be used in conjunction with evaporator 168 to move air through evaporator 168 and into second space or compartment 196, for example. Ducting may be used to transport air to and from evaporator 168, or evaporator 168 may be disposed partially or entirely within compartment 196. Evaporator 168 may receive second metered refrigerant 162 in liquid form and provide an evaporated refrigerant 170 in gas form at an outlet (e.g., an output port) of evaporator 168. This evaporated refrigerant 170 may be applied in gas form to condenser unit input port 122 and then be applied in gas form to compressor 118, as discussed above. In this manner, refrigerant 120 may circulate through condenser unit 102 and evaporator unit 104.

[0031] Second controllable valve 160 may be a shut off valve configured to selectively open when a second temperature 174 at an evaporator discharge port 172 is below second temperature threshold 114 which may correspond to a minimum allowed room temperature of evaporator 168. For example, second temperature threshold may be between about 2-5 F. (or 1-3 C.) lower than (e.g., several degrees away from) a required room temperature set by controller 106 and compared to the output of a room thermostat (not shown). Second controllable valve 160 may be one of a thermally controlled valve (TXV), an electronic expansion valve (EEV), or a pulse width modulated valve (PMV) with a solenoid, for example.

[0032] A second temperature sensor 178 may be disposed adjacent to evaporator discharge port 172 and may provide a second temperature signal 180 that may be representative of a second temperature adjacent to evaporator discharge port 172, and may be considered to be ambient temperature (e.g., environmental air temperature) at that location. Further, second temperature sensor 178 may be in contact with evaporator discharge port 172, in some examples. Second temperature signal 180 may be transmitted through a second temperature port 182 at the interface between condenser unit 102 and evaporator unit 104 as a transmitted second temperature signal 184 applied as an input signal to controller 106.

[0033] Similar to the processing of first temperature signal 158 above, controller 106 may be configured to compare transmitted second temperature signal 184 with second temperature threshold signal 114S representative of the second temperature threshold 114. Controller 106 may be configured to assert a second control signal 188 transmitted through a second control port 190 as a transmitted second control signal 192 to activate a second controllable valve actuator 164 and indirectly activate second controllable valve 160. Thus, controller 106 may be configured to selectively open the second controllable valve when second temperature 174 is below second temperature threshold 114.

[0034] FIG. 2 illustrates a block diagram view of a system 200, according to another example that is similar to but also different in some ways from the example of FIG. 1. System 200 may include a condenser unit 202 and an evaporator unit 204 which together may comprise system 200, also denoted as a cooling system 200. Condenser unit 202 may be a modular component of cooling system 200 that is separate from evaporator unit 204 which may be another modular component of cooling system 200, for example. As described above in reference to cooling system 100, condenser unit 202 and evaporator unit may be fabricated separately and assembled into cooling system 200 in a factory setting or a field setting, for example. Condenser unit 202 may be releasably coupled to evaporator unit 204 where the corresponding refrigerant connections may be connected and disconnected for assembly, testing, and maintenance.

[0035] In reference to both FIG. 1 and FIG. 2, condenser unit 202 may also be denoted as a cooling unit 202 or a carbon dioxide (CO.sub.2) cooling unit 202 and may include a compressor 118 configured to receive a refrigerant 120 from a condenser unit input port 122 and compressor 118 may provide a compressed refrigerant 124. As described, refrigerant 120 may include carbon dioxide (CO.sub.2) or may be composed entirely of carbon dioxide.

[0036] Condenser unit 202 may include a gas cooler 128 (e.g., a condensing coil or heat exchanger) with a gas cooler inlet (e.g., an input port) that is configured to receive compressed refrigerant 124 and provide a first cooled refrigerant 130 at a gas cooler discharge port 132. Gas cooler 128 may include a plurality of coils with radiating fins configured to receive compressed refrigerant 124 at a high temperature and pressure and provide first cooled refrigerant 130 at a lower temperature and pressure by radiation, convection, and conduction of heat from compressed refrigerant 124 to an adjacent first space 194, such as an outdoor region, or other surrounding area. Thus, gas cooler 128 may release heat from compressed refrigerant 124 into adjacent first space 194 as compressed refrigerant 124 cools. Further, gas cooler 128 may cool compressed refrigerant 124 without changing state of compressed refrigerant 124 from gas to liquid, but this is not considered limiting. In some examples, gas cooler 128 may change the state from gas to liquid of compressed refrigerant 124.

[0037] Condenser unit 202 may also include an expansion valve 138 configured to receive first cooled refrigerant 130 at a higher pressure and provide a second cooled refrigerant 140 at a lower pressure to a condenser unit discharge port 144. In this manner, expansion valve 138 may cause resistance to the flow of first cooled refrigerant 130 with high pressure on an inlet side of expansion valve 138 and a low pressure on a discharge side of expansion valve 138, for example. Expansion valve 138 may be a fixed differential expansion valve 138 having a fixed orifice configured to regulate refrigerant flow at a fixed rate and maintain the inlet and discharge pressures within an acceptable range, above.

[0038] Condenser unit 202 may also include a first controllable valve 248 configured to receive first cooled refrigerant 130 and provide a first metered refrigerant 150 combined with second cooled refrigerant 140 into a combined refrigerant 142 that may be provided to condenser unit discharge port 144. First controllable valve 248 may be a shut off valve configured to selectively open when a first temperature 134 at gas cooler discharge port 132 is below a first temperature threshold 112 which may correspond to a critical temperature of carbon dioxide 87.98 F. (or 31.1 C.) at a pressure of 73.8 bar (or 7.38 Mpa). Operation of gas cooler 128 or other components at a temperature and/or pressure above the critical point may correspond to trans-critical operation. Condenser unit 202 may include a first temperature sensor 256 disposed in a region adjacent to a gas cooler discharge port 132 to measure first temperature 134 and directly operate first controllable valve 248.

[0039] First controllable valve 248 may include a first controllable valve actuator 254 operatively coupled with first controllable valve 248 and configured to selectively open first controllable valve 248 from a fully closed state where no amount of first cooled refrigerant 130 is able to pass through first controllable valve 248, to a partially opened state where some amount of first cooled refrigerant 130 is able to pass through first controllable valve 248, and finally to a fully opened state where a maximal amount of first cooled refrigerant 130 is able to pass through first controllable valve 248, or to any opened state between fully closed to fully open, inclusively. In this manner, first controllable valve actuator 254 may be configured to selectively open first controllable valve 248 based on first temperature sensor 256. Stated differently, when first controllable valve 248 is at least partially opened, at least a portion of first cooled refrigerant 130 may be combined with second cooled refrigerant 140 at condenser unit discharge port 144 when first temperature 134 is below first temperature threshold 112. Thus, first controllable valve 248 may be configured to receive first cooled refrigerant 130 and provide first metered refrigerant 150 combined with second cooled refrigerant 140 which may be combined into a combined refrigerant 142 at condenser unit discharge port 144.

[0040] Evaporator unit 204 may include a second controllable valve 260, an evaporator 168, and a second temperature sensor 278. Similar to the description above, second controllable valve 260 may receive combined refrigerant 142 from condenser unit discharge port 144 and provide a second metered refrigerant 162 under the control of a second controllable valve actuator 264 configured to selectively open second controllable valve 160. Second metered refrigerant 162 may be applied to an inlet (e.g., an input port) of evaporator 168. In evaporator 168, second metered refrigerant 162 may be converted from liquid to gas, absorbing heat from surrounding air in a second space or compartment 196. Thus, warmer air applied to evaporator 168 may be cooled and may be used to cool second space or compartment 196.

[0041] A fan may be used in conjunction with evaporator 168 to move air through evaporator 168 and into compartment 196, for example. Ducting may be used to transport air to and from evaporator 168, or evaporator 168 may be disposed partially or entirely within compartment 196. Evaporator 168 may receive second metered refrigerant 162 in liquid form and provide an evaporated refrigerant 170 in gas form at an outlet (e.g., an output port) of evaporator 168. This evaporated refrigerant 170 may be applied in gas form to condenser unit input port 122 and then be applied in gas form to compressor 118, as discussed above. In this manner, refrigerant 120 may circulate through condenser unit 202 and evaporator unit 204.

[0042] Second controllable valve 260 may be a shut off valve configured to selectively open when a second temperature 174 at an evaporator discharge port 172 is below second temperature threshold 114 which may correspond to a minimum allowed room temperature of evaporator 168. For example, second temperature threshold may be between about 2-5 F. (or 1-3 C.) lower than a required room temperature set by controller 106. Second controllable valve 260 may be one of a thermally controlled valve (TXV), an electronic expansion valve (EEV), or a pulse width modulated valve (PMV).

[0043] A second temperature sensor 278 may be disposed adjacent to evaporator discharge port 172 and may provide a second temperature signal 280 that may be representative of a second temperature adjacent to evaporator discharge port 172, and may be considered to be ambient temperature (e.g., environmental air temperature) at that location. Further, second temperature sensor 278 may be in contact with evaporator discharge port 172, in some examples.

[0044] FIGS. 3A-3C illustrate a method 300 of operating a system, such as a cooling system 100, according to an example. In addition to the description of FIGS. 1-2, FIG. 3 illustrates method 300 may begin with a step of compressing 304 a refrigerant 120 from a condenser unit input port 122 to provide a compressed refrigerant 124. Method 300 may continue with a step of condensing 308 compressed refrigerant 124 with a gas cooler 128 having a gas cooler discharge port 132 to provide a first cooled refrigerant 130. Method 300 may continue with a step of expanding 312 first cooled refrigerant 130 to provide a second cooled refrigerant 140 to a condenser unit discharge port 144. Method 300 may continue with a step of detecting 316 a first temperature 134 at gas cooler discharge port 132. Method 300 may continue with a step of conducting 320 at least a portion of first cooled refrigerant 130 to combine with second cooled refrigerant 140 into a combined refrigerant 142 at condenser unit discharge port 144 when first temperature 134 is below a first temperature threshold 112.

[0045] Method 300 may continue with a step of absorbing 332 heat from an adjacent space or compartment 196 with an evaporator 168 having an evaporator discharge port 172. Method 300 may continue with detecting 336 a second temperature 174 at evaporator discharge port 172. Method 300 may continue with conducting 340 combined refrigerant 142 to the evaporator 168 when second temperature 174 is below a second temperature threshold 114. Method 300 may conclude with providing 344 an evaporated refrigerant 170 to condenser unit input port 122. As described above, refrigerant 120 may circulate through condenser unit 102 and evaporator unit 104, and the described method may repeat.

[0046] In reference to the above method step of conducting 320 the portion of first cooled refrigerant 130 to combine with second cooled refrigerant 140 into combined refrigerant 142 at condenser unit discharge port 144 when the first temperature is below first temperature threshold 112, method 300 may continue with a step of controlling 324 a first controllable valve 148 (248) configured to receive first cooled refrigerant 130 and provide a first metered refrigerant 150 combined with second cooled refrigerant 140 into combined refrigerant 142 provided to the condenser unit discharge port 144. In reference to the above method step of controlling 324 first controllable valve 148 (248) configured to receive first cooled refrigerant 130 and provide first metered refrigerant 150 combined with second cooled refrigerant 140 into combined refrigerant 142 provided to condenser unit discharge port 144, method 300 may continue with a step of activating 328 a first controllable valve actuator 154 (254) configured to open first controllable valve 148 (248). As described, the step of activating 328 first controllable valve actuator 154 (254) may include either directly activating first controllable valve actuator 154 (254) through a physical connection or first controllable valve actuator 154 (254) indirectly activating through an electronic connection.

[0047] In reference to the above method step of conducting 340 combined refrigerant 142 to evaporator 168 when second temperature is below second temperature threshold 114, method 300 may continue with a step of controlling 344 a second controllable valve 160 (260) configured to receive combined refrigerant 142 and provide a second metered refrigerant 162 to evaporator 168. In reference to the above method step of controlling 344 second controllable valve 160 (260), method 300 may continue with a step of activating 348 a second controllable valve actuator 164 (264) configured to open second controllable valve 160 (260). As described, the step of activating 348 second controllable valve actuator 164 (264) may include either directly activating second controllable valve actuator 164 (264) through a physical connection or second controllable valve actuator 164 (264) indirectly activating through an electronic connection.

[0048] Modifications, additions, or omissions may be made to processes of method 300 depicted in reference to FIGS. 1-3. The processes of method 300 may include more, fewer, or other operations. For example, operations may be performed in parallel or in any suitable order.

[0049] While several examples have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

[0050] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

[0051] To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants note that they do not intend any of the appended claims to invoke 35 U.S.C. 112 (f) as it exists on the date of filing hereof unless the words means for or step for are explicitly used in the particular claim. Further, the closed form phrase consisting of may be used in the place of open form term comprising to indicate a disclosed system, apparatus, device, or method having only the recited elements.