Methods and systems for supplemental flow control of working fluid through a climate control circuit

A method for providing supplemental flow control of working fluid through a transport climate control circuit during a start-stop cooling operation mode is provided. The method includes closing a main liquid suction solenoid valve disposed between a condenser and an evaporator of the transport climate control circuit when the compressor is OFF. The method also includes monitoring a climate controlled space temperature within a climate controlled space. When the climate controlled space temperature is greater than or equal to a setpoint temperature, the method includes turning a compressor ON, and opening the main liquid suction solenoid valve when a suction pressure at the suction port of the compressor is less than or equal to a predetermined suction pressure threshold. When the climate controlled space temperature is less than or equal to the setpoint temperature, the method includes turning the compressor OFF, and closing the main liquid suction solenoid valve.

FIELD

Embodiments of this disclosure relate generally to a climate control system for a transport unit. More specifically, the embodiments relate to methods and systems for supplemental flow control of working fluid through a transport climate control circuit.

BACKGROUND

A climate control system, a transport climate control system (TCCS) for a transport unit (e.g., a truck, a container (such as a container on a flat car, an intermodal container, marine container, etc.), a box car, a semi-tractor, a bus, or other similar transport unit), etc. may be included on the transport unit to condition air of a climate controlled space (e.g., internal space, cargo space, etc.) of the transport unit. In some transport units, the climate control system can be installed externally (e.g., on a rooftop of the transport unit, on a front wall of the transport unit, etc.). The climate control system can provide a desired environment for cargo stored in the transport unit.

SUMMARY

This disclosure relates generally to a climate control system for a transport unit. More specifically, the embodiments relate to methods and systems for supplemental flow control of working fluid through a transport climate control circuit.

In particular, the embodiments described herein stage operation of various valves in the transport climate control circuit relative to the starting and stopping of a compressor of the transport climate control circuit to provide increased flow control of working fluid within the transport climate control circuit. Accordingly, the embodiments described herein can provide tighter temperature control within a climate controlled space of the transport unit. That is, the embodiments described herein can reduce temperature swing fluctuations within the climate controlled space of the transport unit.

The embodiments described herein can provide supplemental flow control for a transport climate control circuit that includes a compressor with an auxiliary or intermediate suction port (also referred to as an economizer port, a vapor injection port, etc.) in combination with a main suction port and a discharge port.

The embodiments described herein can be used with a fixed speed (e.g., two-speed compressor) or a variable speed compressor. The embodiments described herein can reduce the flow of working fluid through the transport climate control circuit beyond what can be accomplished with a variable speed compressor.

The embodiments described herein can increase the amount of time the compressor is ON and/or the amount of time the compressor is OFF during a start-stop cooling cycle relative to a conventional start-stop cooling operation mode. Accordingly, the number of cycles that the compressor is turned ON and OFF during a set period of time can be reduced and the amount of time for a single cycle in which the compressor is turned ON and then OFF can be increased.

An advantage of the embodiments described herein is that increased capacity control of a compressor of the transport climate control circuit can be provided in order to improve temperature control in a climate controlled space of the transport unit. The embodiments described herein can also minimize relative power consumption of the compressor and thereby the power consumption of the climate control system. Also, the embodiments, described herein can improve startup conditions of the transport climate control circuit and thereby avoid, for example, hydraulic locking of the compressor due to too much liquid working fluid and/or wet working fluid foam entering the compressor. Further, the embodiments described herein can reduce a discharge pressure at the discharge port of the compressor.

In one embodiment, a method for providing supplemental flow control of working fluid through a transport climate control circuit during a start-stop cooling operation mode is provided. The climate control circuit is part of a climate control system that provides climate control within a climate controlled space of a transport unit. The transport climate control circuit includes a condenser, an expansion device, an evaporator, and a compressor with a main suction port, an auxiliary port and a discharge port. The method includes closing a main liquid suction solenoid valve disposed between a condenser and an evaporator of the transport climate control circuit when the compressor is OFF. The method also includes monitoring a climate controlled space temperature within the climate controlled space. When the monitored climate controlled space temperature is greater than or equal to a predetermined setpoint temperature, the method includes turning the compressor ON, and opening the main liquid suction solenoid valve when a suction pressure at a suction port of the compressor is less than or equal to a predetermined suction pressure threshold. When the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature, the method includes turning the compressor OFF, and closing the main liquid suction solenoid valve.

In another embodiment, a climate control system for providing climate control within a climate controlled space of a transport unit is provided. The climate control system includes a controller and a transport climate control circuit. The transport climate control circuit includes a condenser, an expansion device, an evaporator, and a compressor that includes a main suction port, an auxiliary port, and a discharge port. The controller is configured to: close a main liquid suction solenoid valve disposed between the condenser and the evaporator of the transport climate control circuit when the compressor is OFF, and monitor a climate controlled space temperature within the climate controlled space. When the monitored climate controlled space temperature is greater than or equal to a predetermined setpoint temperature, the controller is configured to turn the compressor ON, and open the main liquid suction solenoid valve when a suction pressure at the suction port of the compressor is less than or equal to a predetermined suction pressure threshold. When the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature, the controller is configured to turn the compressor OFF, and close the main liquid suction solenoid valve.

DETAILED DESCRIPTION

This disclosure relates generally to a climate control system for a transport unit. More specifically, the embodiments relate to methods and systems for supplemental flow control of working fluid through a transport climate control circuit.

In particular, the embodiments described herein stage operation of various valves in the transport climate control circuit relative to the starting and stopping of a compressor of the transport climate control circuit to provide increased flow control of working fluid within the transport climate control circuit.

An advantage of the embodiments described herein is that increased capacity control of a compressor of the transport climate control circuit can be provided in order to improve temperature control in a climate controlled space of the transport unit. The embodiments described herein can also minimize relative power consumption of the compressor and thereby the power consumption of the climate control system. Also, the embodiments, described herein can improve startup conditions of the transport climate control circuit and thereby avoid, for example, hydraulic locking of the compressor due to too much liquid working fluid and/or wet working fluid foam entering the compressor. Further, the embodiments described herein can reduce a discharge pressure at the discharge port of the compressor. Moreover, the embodiments described herein can minimize the amount of time the compressor is OFF in a start-stop cooling mode and increase the amount of time the compressor is ON in the start-stop cooling mode.

The embodiments described herein can provide supplemental flow control for a transport climate control circuit that includes a compressor with an auxiliary or intermediate suction port (also referred to as an economizer port, a vapor injection port, etc.) in combination with a main suction port and a discharge port.

A climate control system may be generally configured to control one or more environmental conditions (e.g., temperature, humidity, atmosphere, air quality, etc.) in a climate controlled space (e.g., internal space, cargo space, etc.) of a transport unit (e.g., a truck, a container (such as a container on a flat car, an intermodal container, a marine container, etc.), a box car, a semi-tractor, etc.). Generally, the internal space of a transport vehicle can be supplied with fresh air (e.g., outside air) and/or conditioned air (e.g., air conditioned by a transport climate control circuit of the climate control system) by the climate control system.

FIG. 1Aillustrates one embodiment of a climate controlled transport unit102attached to a tractor103. The climate controlled transport unit102includes a climate control system100for a transport unit105. The tractor103is attached to and is configured to tow the transport unit105. The transport unit105shown inFIG. 1Ais a trailer. It will be appreciated that the embodiments described herein are not limited to tractor and trailer units, but can apply to any type of transport unit (e.g., a truck, a container (such as a container on a flat car, an intermodal container, a marine container, etc.), a box car, a semi-tractor, a bus, or other similar transport unit), etc.

The climate control system100includes a climate control unit (CCU)110that provides environmental control (e.g. temperature, humidity, air quality, etc.) within a climate controlled space106of the transport unit105. The climate control system100also includes a programmable climate controller107and one or more sensors (not shown) that are configured to measure one or more parameters of the climate control system100(e.g., an ambient temperature outside of the transport unit105, a space temperature within the climate controlled space106, an ambient humidity outside of the transport unit105, a space humidity within the climate controlled space106, etc.) and communicate parameter data to the climate controller107.

The CCU110is disposed on a front wall108of the transport unit105. In other embodiments, it will be appreciated that the CCU110can be disposed, for example, on a rooftop or another wall of the transport unit105. The CCU110includes a transport climate control circuit (seeFIG. 2) that connects, for example, a compressor, a condenser, an evaporator and an expansion valve to provide conditioned air within the climate controlled space106.

The climate controller107may comprise a single integrated control unit112or may comprise a distributed network of climate controller elements112,113. The number of distributed control elements in a given network can depend upon the particular application of the principles described herein. The climate controller107is configured to control operation of the climate control system100including the transport climate control circuit.

FIG. 1Billustrates a container115that includes a climate controlled space116that is conditioned by a climate control system117. The climate control system117includes a CCU118provided on a front wall119of the container115. The CCU118provides environmental control (e.g. temperature, humidity, air quality, etc.) within the climate controlled space116. In some embodiments, the CCU118can control a supply air temperature of supply air that is brought into the climate controlled space116. The CCU118includes a transport climate control circuit (seeFIG. 2) that connects, for example, a compressor, a condenser, an evaporator and an expansion valve to provide conditioned air within the climate controlled space116.

The climate control system100also includes a programmable climate controller114and one or more sensors (not shown) that are configured to measure one or more parameters of the climate control system100(e.g., an ambient temperature outside of the container115, a space temperature within the climate controlled space116, an ambient humidity outside of the container115, a space humidity within the climate controlled space116, etc.) and communicate parameter data to the climate controller114. The climate controller114is configured to control operation of the climate control system100including the transport climate control circuit.

FIG. 1Cdepicts a temperature-controlled straight truck120that includes a climate controlled space122for carrying cargo and a climate control system124. The climate control system124includes a CCU126that is mounted to a front wall128of the load space112. The CCU126is controlled via a climate controller130to provide climate control within the climate controlled space122. The CCU126can include, amongst other components, a transport climate control circuit (seeFIG. 2) that connects, for example, a compressor, a condenser, an evaporator and an expansion valve to provide climate control within the climate controlled space122.

The climate control system124also includes a programmable climate controller130and one or more sensors (not shown) that are configured to measure one or more parameters of the climate control system124(e.g., an ambient temperature outside of the truck120, a space temperature within the climate controlled space122, an ambient humidity outside of the truck120, a space humidity within the climate controlled space122, etc.) and communicate parameter data to the climate controller130. The climate controller130is configured to control operation of the climate control system124including the transport climate control circuit.

FIG. 1Ddepicts a temperature-controlled van130that includes a climate controlled space132for carrying cargo and a climate control system135for providing climate control within the climate controlled space132. The climate control system135includes a CCU140that is mounted to a rooftop134of the climate controlled space132. The climate control system135can include, amongst other components, a transport climate control circuit (seeFIG. 2) that connects, for example, a compressor, a condenser, an evaporator and an expansion valve to provide climate control within the climate controlled space132.

The climate control system135also includes a programmable climate controller145and one or more sensors (not shown) that are configured to measure one or more parameters of the climate control system135(e.g., an ambient temperature outside of the van130, a space temperature within the climate controlled space132, an ambient humidity outside of the van130, a space humidity within the climate controlled space132, etc.) and communicate parameter data to the climate controller130. The climate controller145is configured to control operation of the climate control system124including the transport climate control circuit.

FIG. 2illustrates a schematic of a transport climate control circuit200for a climate control system, according to one embodiment. The transport climate control circuit200can be used, for example, with the climate control units110,118,126and140shown inFIGS. 1A-1D. The transport climate control circuit200can be controlled by a controller (e.g., the climate controllers107,114,130,145shown inFIGS. 1A-1D). The transport climate control circuit200includes a compressor205, a condenser210, a main thermal expansion device215, and an evaporator220. The transport climate control circuit200also includes a receiver225, an economizer heat exchanger230, a plurality of valves232,236,238,240,242,244, and an economizer expansion device234. As will be discussed in more detail below, in some embodiments the valve232and the expansion device234can be replaced with optional valve232′ and optional expansion device234′.

The compressor205is configured to direct a working fluid (e.g., refrigerant) within the circuit200. The compressor200includes a main suction port206, an auxiliary suction port207and a discharge port208. It will be appreciated that the auxiliary port207can also be referred to as an economizer port, a vapor injection port, an intermediate suction port, etc.

In the embodiments described herein, the compressor205is configured to not operate or is incapable of operating as a digital compressor that can modulate (e.g., load and unload) the amount of working fluid being compressed at any given time. Accordingly, when the circuit200is instructed to operate at less than a full capacity, the compressor205operates in a start-stop cooling operation mode in which the compressor205cycles between being ON and OFF to control the amount of working fluid being compressed and directed through the circuit200. In some embodiments, the start-stop cooling operation mode can cause the compressor205to rapidly cycle between being ON and OFF.

The compressor205can be, for example, a screw compressor, a scroll compressor, a centrifugal compressor, etc. In some embodiments, the compressor205can be a two stage compressor in which the auxiliary suction port207is connected to the middle of the two stage compressor.

In some embodiments, the compressor205can be a fixed speed (e.g., two-speed) compressor. In other embodiments, the compressor205can be a variable speed compressor.

In operation, working fluid compressed by the compressor205is directed from the discharge port208to the condenser210via discharge line245. Working fluid passing through the condenser210is directed to the receiver225via a liquid line250. A first portion of the working fluid passing through the receiver225is directed through the economizer heat exchanger230to a main liquid solenoid valve236via a sub-cooled liquid line255. The working fluid then passes through the main liquid solenoid valve236and the main expansion device215to the evaporator220. The working fluid passing through the evaporator220is then directed to the main suction port206via a main suction line260. The circuit200also includes an expansion device bypass valve244that allows working fluid directed from the main liquid solenoid valve236to bypass the expansion device215and go to the evaporator220. In some embodiments, the expansion device bypass valve244can be sized to roughly match the mass flow of working fluid through the expansion device244when the compressor205is ON.

A second portion of the working fluid passing through the receiver225is directed via an economizer liquid line265through an economizer liquid solenoid valve232and an economizer expansion device234to the economizer heat exchanger230to provide heat exchange with the first portion of the working fluid. The second portion of the working fluid is then directed through an economizer suction line270to the auxiliary suction port207. The second portion of the working fluid can also be directed through an economizer bypass valve240to the main suction port206instead of the auxiliary suction port207.

A third portion of the working fluid passing through the receiver225is directed to a liquid injection valve238via a liquid injection line275and then to the auxiliary suction port207. In some embodiments, the liquid injection valve238can be a pulsing valve.

The circuit200also includes a hot gas bypass line280that directs working fluid from the discharge port208of the compressor205to a hot gas bypass valve242before being combined with the second portion of the working fluid directed to the economizer heat exchanger230.

In some embodiments, the main liquid solenoid valve236and the main expansion device215can be replaced with an electronic expansion valve with, for example, a stepper motor, a fast pulsing valve, etc.

In some embodiments, the circuit200can include a downstream economizer configuration in which the economizer liquid solenoid valve232, the economizer expansion device234and the economizer liquid line265are replaced with an optional downstream economizer liquid solenoid valve232′, an optional downstream economizer expansion device234′, and an optional downstream economizer liquid line265′. In operation, a portion of working fluid passing from the receiver225through the economizer heat exchanger230to the main liquid solenoid valve236can be redirected through the optional downstream economizer liquid line265′ to the optional downstream economizer liquid solenoid valve232′ and the optional downstream expansion device234′ to the economizer heat exchanger230to provide heat exchange with the working fluid passing through the economizer heat exchanger230to the main liquid solenoid valve236.

In some embodiments, the economizer liquid solenoid valve232, the economizer expansion device234can be replaced with an electronic expansion valve with, for example, a stepper motor, a fast pulsing valve, etc. Similarly, the optional downstream economizer liquid solenoid valve232′ and the optional downstream expansion device234′ can be replaced with an electronic expansion valve with, for example, a stepper motor, a fast pulsing valve, etc. In these embodiments, the electronic expansion valve can be run with liquid working fluid over-feed thereby potentially rendering the liquid injection line275and the liquid injection valve238unnecessary.

The circuit200can also include one or more sensors to monitor, for example, a temperature or pressure at various points within the circuit200. For example, the circuit200can include a pressure sensor that is configured to monitor a suction pressure of working fluid at the main suction port206of the compressor205.

It will also be appreciated that one or more fans (not shown) may be associated with each of the condenser210and the evaporator220. The condenser fan(s) can be configured to provide a heat exchange between the working fluid passing through the condenser210and ambient air from outside of the transport unit. The evaporator fan(s) can be configured to provide a heat exchange between the working fluid passing through the evaporator220and air within the climate controlled space. Operation of the circuit200is discussed below with respect toFIG. 3.

FIG. 3illustrates a flowchart of a method300for providing supplemental flow control of working fluid through the transport climate control circuit200during a start-stop cooling operation mode, according to a first embodiment.

The method300begins at305prior to initial startup of the compressor205whereby a controller (e.g., the climate controllers107,114,130,145shown inFIGS. 1A-1D) closes the main liquid suction solenoid valve236. The method300then proceeds to310.

At310, the controller monitors a space temperature TCwithin the climate controlled space (e.g., the climate controlled space106,116,122,132shown inFIGS. 1A-1D). In some embodiments, the controller receives space temperature data from one or more temperature sensors provided within the climate controlled space. The method300then proceeds to315.

At315, the controller determines whether the monitored space temperature TCis greater than or equal to a desired setpoint temperature TSfor the climate controlled space plus a tolerance value tol. The desired setpoint temperature TScan be a predetermined temperature value that is inputted into the climate control system to maintain the cargo being stored within the climate controlled space. The tolerance value tol can be set to a value that provides stability during constant minor fluctuations in the space temperature TC. In some embodiments, the tolerance value can be, for example, a value between 0.0 to 0.9° C. When the monitored space temperature TCis greater than or equal to the desired setpoint temperature TSplus the tolerance value tol, the method300proceeds to320. When the monitored space temperature TCis not greater than or equal to the desired setpoint temperature TSplus the tolerance value tol, the method300proceeds to340.

At320, the controller instructs the compressor205to turn ON or remain ON depending on how the compressor205is operating. The method300then proceeds to325. Optionally, in some embodiments, where the economizer bypass valve240is being used to assist in supplemental flow control, the method300can proceed to365.

At325, the controller monitors a suction pressure PSUCTat the main suction port206of the compressor205. In some embodiments, the controller receives suction pressure data from a pressure sensor configured to monitor pressure data at the main suction port206. The method300then proceeds to330.

At330, the controller determines whether the monitored suction pressure PSUCTis less than or equal to a pressure threshold PThresh. The pressure threshold PThreshis set to a value that determines whether the circuit200is close to a vacuum condition at the main suction port206of the compressor205. In some embodiments, the pressure threshold PThreshcan be set to a value of 0 psig. When the monitored suction pressure PSUCTis less than or equal to a pressure threshold PThresh, the method300proceeds to335. When the monitored suction pressure PSUCTis not less than or equal to a pressure threshold PThresh, the method300proceeds back to325.

At335, the controller opens the main liquid suction solenoid valve236to allow working fluid exiting the receiver225to be directed to the main expansion device215. The method300then proceeds back to310.

At340, the controller determines whether the monitored space temperature TCis less than or equal to the desired setpoint temperature TSfor the climate controlled space minus the tolerance value tol. In some embodiments, the tolerance value tol can be different from the tolerance value tol used at315. When the monitored space temperature TCis less than or equal to the desired setpoint temperature TSminus the tolerance value tol, the method300proceeds to345. When the monitored space temperature TCis not less than or equal to the desired setpoint temperature TSminus the tolerance value tol, the method300proceeds to360.

At345, the controller determines whether the main liquid suction solenoid valve236is closed. When the controller determines that the main liquid suction solenoid valve236is closed, the method300proceeds to350. When the controller determines that the main liquid suction solenoid valve236is open, the method300proceeds to355. Optionally, in some embodiments, where the economizer bypass valve240is being used to assist in supplemental flow control, the method300can proceed to370.

At350, the controller ensures that the compressor is OFF or stops operation of (e.g., turns OFF) the compressor205. The method300then proceeds back to310. At355, the controller closes the main liquid suction solenoid valve236and then proceeds to350.

At360, the controller maintains the current operation of the compressor205. For example, if the compressor205is currently operating (e.g., the compressor205is ON), the controller maintains operation of the compressor205. On the other hand, if the compressor205is currently not operating (e.g., the compressor205is OFF), the controller maintains the compressor from operating. The method300then proceeds to310.

At optional365, the controller opens the economizer bypass valve240. In some embodiments, the controller also closes the economizer liquid solenoid valve232(or the optional downstream economizer liquid solenoid valve232′). Accordingly, the gaseous working fluid can escape the auxiliary port207and can be directed through the economizer bypass line285back to the main suction port206. In some embodiments, the economizer bypass valve240can be opened and closed based on how close the climate controlled space temperature TCis to the desired setpoint temperature TS. That is, the economizer bypass valve240can be closed to increase the capacity of the compressor to bring the climate controlled space temperature TCcloser to the desired setpoint temperature TS. In some embodiments, the controller can pulse the economizer bypass valve240instead of simply opening the economizer bypass valve at optional365. For example, the controller can pulse the economizer bypass valve240to approach a step-less climate control. In some embodiments, the amount of time that the economizer bypass valve240is closed during a pulse cycle can be proportional to the difference between the climate controlled space temperature TCand the desired setpoint temperature TS. The method300then proceeds to325.

At optional370, the controller determines whether the economizer bypass valve240is closed. When the controller determines that the economizer bypass valve240is closed, the method300can proceed to350. When the controller determines that the economizer bypass valve240is open, the method300can proceed to optional375. At375, the controller closes the economizer bypass valve240and then can proceed to350.

The method300allows for a delayed startup of the circuit200by starting the compressor205for a period of time before the main liquid suction solenoid valve236is opened. This can cause condensation buildup in the receiver225and the condenser210and cause liquid refrigerant to be emptied from the evaporator220. The circuit200can continue to buildup condensation in the receiver225and the condenser210and empty liquid refrigerant from the evaporator220until the main suction port206reaches a near vacuum condition. At that point, the main liquid suction solenoid valve236can be opened such that working fluid can be directed through the expansion device215and the evaporator220.

Accordingly, the method300can increase the amount of time the compressor205is ON and the amount of time that the compressor205is OFF during a start-stop cooling cycle relative to a conventional start-stop cooling operation mode. It will be appreciated that a conventional start-stop cooling operation mode merely provides that the compressor205be turned ON and OFF based on a monitored space temperature within the climate controlled space with the circuit200and either does not include the main liquid suction solenoid valve236or keeps the main liquid suction solenoid valve236open at all times during start-stop cooling operation. By increasing the amount of time the compressor205is ON and the amount of time that the compressor205is OFF during a start-stop cooling cycle, the number of cycles that the compressor205is turned ON and OFF during a set period of time can be reduced and the amount of time for a single cycle in which the compressor205is turned ON and then OFF can be increased.

When the method300also includes the optional economizer bypass option via365,370and375, the amount of time that the compressor205is ON can be further increased, thereby further reducing the number of cycles that the compressor is turned ON and OFF during a set period of time and further increasing the amount of time for a single cycle in which the compressor205is turned ON and then OFF.

FIG. 4illustrates a flowchart of a method400for providing supplemental flow control of working fluid through the transport climate control circuit200during a start-stop cooling operation mode, according to a second embodiment.

The method400begins at405prior to initial startup of the compressor205whereby a controller (e.g., the climate controllers107,114,130,145shown inFIGS. 1A-1D) instructs the compressor205to turn ON. The method400then proceeds to410.

At410, the controller monitors a space temperature TCwithin the climate controlled space (e.g., the climate controlled space106,116,122,132shown inFIGS. 1A-1D). In some embodiments, the controller receives space temperature data from one or more temperature sensors provided within the climate controlled space. The method400then proceeds to415.

At415, the controller determines whether the monitored space temperature TCis less than or equal to the desired setpoint temperature TSfor the climate controlled space minus the tolerance value tol. The desired setpoint temperature TScan be a predetermined temperature value that is inputted into the climate control system to maintain the cargo being stored within the climate controlled space. The tolerance value tol can be set to a value that provides stability during constant minor fluctuations in the space temperature TC. In some embodiments, the tolerance value can be, for example, a value between 0.0 to 0.9° C. When the monitored space temperature TCis less than or equal to the desired setpoint temperature TSminus the tolerance value tol, the method400proceeds to420. When the monitored space temperature TCis not less than or equal to the desired setpoint temperature TSminus the tolerance value tol, the method400returns to410.

At420, the controller closes the main liquid suction solenoid valve236. The method400then proceeds to425. At425, the controller monitors a suction pressure PSUCTat the main suction port206of the compressor205. In some embodiments, the controller receives suction pressure data from a pressure sensor configured to monitor pressure data at the main suction port206. The method400then proceeds to430.

At430, the controller determines whether the monitored suction pressure PSUCTis less than or equal to a pressure threshold PThresh. The pressure threshold PThreshis set to a value that determines whether the circuit200is close to a vacuum condition at the main suction port206of the compressor205. In some embodiments, the pressure threshold PThreshcan be set to a value of 0 psig. When the monitored suction pressure PSUCTis less than or equal to a pressure threshold PThresh, the method400proceeds to435. When the monitored suction pressure PSUCTis not less than or equal to a pressure threshold PThresh, the method400proceeds back to425.

At435, the controller stops operation of (e.g., turns OFF) the compressor205. The method400then proceeds to440.

At440, the controller monitors the space temperature TCwithin the climate controlled space. In some embodiments, the controller receives space temperature data from one or more temperature sensors provided within the climate controlled space. The method400then proceeds to445.

At445, the controller determines whether the monitored space temperature TCis greater than or equal to the desired setpoint temperature TSfor the climate controlled space plus a tolerance value tol. In some embodiments, the tolerance value tol can be different from the tolerance value tol used at415. When the monitored space temperature TCis greater than or equal to the desired setpoint temperature TSplus the tolerance value tol, the method400proceeds to450. When the monitored space temperature TCis not greater than or equal to the desired setpoint temperature TSplus the tolerance value tol, the method400proceeds back to440.

At450, the controller opens the main liquid suction solenoid valve236to allow working fluid exiting the receiver225to be directed to the main expansion device215. The method400then proceeds back to405.

The method400allows for a delayed shutdown of the circuit200by keeping the compressor205ON for a period of time with the main liquid suction solenoid valve236closed before the compressor205is turned OFF. This can cause condensation buildup in the receiver225and the condenser210and cause liquid refrigerant to be emptied from the evaporator220. The circuit200can continue to buildup condensation in the receiver225and the condenser210and empty liquid refrigerant from the evaporator220until the main suction port206reaches a near vacuum condition. At that point, the compressor205can be turned OFF.

Accordingly, the method400can increase the amount of time the compressor205is ON during a start-stop cooling cycle relative to a conventional start-stop cooling operation mode. A conventional start-stop cooling operation mode, as referred to herein, merely provides that the compressor205be turned ON and OFF based on a monitored space temperature within the climate controlled space with the circuit200either not including the main liquid suction solenoid valve236or keeping the main liquid suction solenoid valve236open at all times during a start-stop cooling operation.

FIG. 5illustrates a flowchart of a method500for providing supplemental flow control of working fluid through the transport climate control circuit200during a start-stop cooling operation mode, according to a third embodiment.

The method500begins at505prior to initial startup of the compressor205whereby a controller (e.g., the climate controllers107,114,130,145shown inFIGS. 1A-1D) monitors a space temperature TCwithin the climate controlled space (e.g., the climate controlled space106,116,122,132shown inFIGS. 1A-1D). In some embodiments, the controller receives space temperature data from one or more temperature sensors provided within the climate controlled space. The method500then proceeds to510.

At510, the controller determines whether the monitored space temperature TCis greater than or equal to a desired setpoint temperature TSfor the climate controlled space plus a tolerance value tol. The desired setpoint temperature TScan be a predetermined temperature value that is inputted into the climate control system to maintain the cargo being stored within the climate controlled space. The tolerance value tol can be set to a value that provides stability during constant minor fluctuations in the space temperature TC. In some embodiments, the tolerance value can be, for example, a value between 0.0 to 0.9° C. When the monitored space temperature TCis greater than or equal to the desired setpoint temperature TSplus the tolerance value tol, the method500proceeds to515. When the monitored space temperature TCis not greater than or equal to the desired setpoint temperature TSplus the tolerance value tol, the method500proceeds back to505.

At515, the controller instructs the compressor205to turn ON. The method500then proceeds to520. At520, the controller closes the expansion device bypass valve244. This prevents the working fluid from bypassing the expansion device215when being directed from the economizer heat exchanger230to the evaporator220. It will be appreciated that in some embodiments the controller can instruct the compressor205to turn ON and close the expansion device215at the same time.

In some embodiments, instead of the controller closing the expansion device bypass valve244at520, the controller can instruct the valve244to pulse open and closed. The method500then proceeds to525.

At525, the controller monitors the space temperature TCwithin the climate controlled space. The method then proceeds to530. At530, the controller determines whether the monitored space temperature TCis less than or equal to the desired setpoint temperature TSfor the climate controlled space minus the tolerance value tol. In some embodiments, the tolerance value tol can be different from the tolerance value tol used at510. When the monitored space temperature TCis less than or equal to the desired setpoint temperature TSminus the tolerance value tol, the method500proceeds to535. When the monitored space temperature TCis not less than or equal to the desired setpoint temperature TSminus the tolerance value tol, the method500proceeds back to525.

At535, the controller stops operation of (e.g., turns OFF) the compressor205. The method500then proceeds to540. At540, the controller opens the expansion device bypass valve244. This allows working fluid to bypass the expansion device214when being directed from the economizer heat exchanger230to the evaporator220. The method500then proceeds to545.

At545, the controller instructs one or more evaporator fan(s) and/or one or more condenser fan(s) to continue operation while the compressor205is OFF.

The method500allows for working fluid in the form of hot liquid that is not throttled by the bypass the expansion device215to enter the evaporator215. This can supply heat to the evaporator220. Accordingly, the method500can increase the amount of time the compressor205is ON and decrease the amount of time the compressor is OFF during a start-stop cooling cycle relative to a conventional start-stop cooling operation mode. A conventional start-stop cooling operation mode merely provides that the compressor205be turned ON and OFF based on a monitored space temperature within the climate controlled space with the circuit200not including the expansion device bypass valve244or keeping the expansion device bypass valve244open at all times during start-stop cooling operation.

It will be appreciated that the features of the methods300,400,500can be combined to provide improved flow control of working fluid during a start-stop cooling operation mode of the transport climate control circuit200. That is, in some embodiments, delayed startup of the of the circuit200as provided in the method300can be combined with the delayed shutdown of the circuit200as provided in the method400and/or with expansion device bypass as provided in the method500. Also in some embodiments, the delayed shutdown of the circuit200as provided in the method400can be combined with expansion device bypass as provided in the method500. Further, in some embodiments, the delayed shutdown of the circuit200as provided in the method400and/or the expansion device bypass as provided in the method500can include an economizer bypass as provided at365in the method300.

It is to be appreciated that any of aspects 1-8 can be combined with any of aspects 9-16.

Aspect 1. A method for providing supplemental flow control of working fluid through a transport climate control circuit during a start-stop cooling operation mode, the climate control circuit being part of a climate control system providing climate control within a climate controlled space of a transport unit, the transport climate control circuit including a condenser, an expansion device, an evaporator, and a compressor with a main suction port, an auxiliary port and a discharge port, the method comprising:closing a main liquid suction solenoid valve disposed between a condenser and an evaporator of the transport climate control circuit when the compressor is OFF;monitoring a climate controlled space temperature within the climate controlled space;when the monitored climate controlled space temperature is greater than or equal to a predetermined setpoint temperature:turning the compressor ON, andopening the main liquid suction solenoid valve when a suction pressure at the suction port of the compressor is less than or equal to a predetermined suction pressure threshold; andwhen the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:turning the compressor OFF, andclosing the main liquid suction solenoid valve.
Aspect 2. The method of aspect 1, further comprising directing the working fluid from the condenser to the auxiliary port of the compressor via an economizer suction line when the compressor is ON and the main liquid suction solenoid valve is closed.
Aspect 3. The method of any of aspects 1 and 2, further comprising opening an economizer bypass valve and directing the working fluid exiting the auxiliary port of the compressor directly to the main suction port of the compressor when the monitored climate controlled space temperature is greater than or equal to the predetermined setpoint temperature.
Aspect 4. The method of any of aspects 1-3, further comprising pulsing an economizer bypass valve to open and close for directing the working fluid exiting the auxiliary port of the compressor directly to the main suction port of the compressor when the monitored climate controlled space temperature is greater than or equal to the predetermined setpoint temperature.
Aspect 5. The method of any of aspects 1-4, wherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:closing the main liquid suction solenoid valve, and then turning the compressor OFF.
Aspect 6. The method of any of aspects 1-5, wherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:turning the compressor OFF and then closing the main liquid suction solenoid valve when a suction pressure at a suction port of the compressor is less than or equal to a predetermined suction pressure threshold.
Aspect 7. The method of any of aspects 1-6, wherein when the monitored climate controlled space temperature is greater than or equal to a predetermined setpoint temperature:closing an expansion device bypass valve to allow the working fluid from the condenser to pass through the main expansion device; andwherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:opening the expansion device bypass valve to allow the working fluid from the condenser to bypass the main expansion device and travel directly to the evaporator.
Aspect 8. The method of aspect 7, wherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:operating at least one of a condenser fan and an evaporator fan while the compressor is OFF and the expansion device bypass valve is open.
Aspect 9. A climate control system for providing climate control within a climate controlled space of a transport unit comprising:a controller; anda transport climate control circuit, the transport climate control circuit including a condenser, an expansion device, an evaporator, and a compressor that includes a main suction port, an auxiliary port, and a discharge port,wherein the controller is configured to:close a main liquid suction solenoid valve disposed between the condenser and the evaporator of the transport climate control circuit when the compressor is OFF,monitor a climate controlled space temperature within the climate controlled space,when the monitored climate controlled space temperature is greater than or equal to a predetermined setpoint temperature:turn the compressor ON, andopen the main liquid suction solenoid valve when a suction pressure at the suction port of the compressor is less than or equal to a predetermined suction pressure threshold, andwhen the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:turn the compressor OFF, andclose the main liquid suction solenoid valve.
Aspect 10. The climate control system of aspect 9, wherein the controller is configured to direct the working fluid from the condenser to the auxiliary port of the compressor via an economizer suction line when the compressor is ON and the main liquid suction solenoid valve is closed.
Aspect 11. The climate control system of any of aspects 9 and 10, wherein the controller opens an economizer bypass valve to direct the working fluid exiting the auxiliary port of the compressor directly to the main suction port of the compressor when the monitored climate controlled space temperature is greater than or equal to the predetermined setpoint temperature.
Aspect 12. The climate control system of any of aspects 9-11, wherein the controller pulses an economizer bypass valve to open and close to direct the working fluid exiting the auxiliary port of the compressor directly to the main suction port of the compressor when the monitored climate controlled space temperature is greater than or equal to the predetermined setpoint temperature.
Aspect 13. The climate control system of any of aspects 9-12, wherein the controller closes the main liquid suction solenoid valve, and then turns the compressor OFF when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature.
Aspect 14. The climate control system of any of aspects 9-13, wherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:the controller turns the compressor OFF and then closes the main liquid suction solenoid valve when a suction pressure at a suction port of the compressor is less than or equal to a predetermined suction pressure threshold.
Aspect 15. The climate control system of any of aspects 9-14, wherein when the monitored climate controlled space temperature is greater than or equal to a predetermined setpoint temperature:the controller closes an expansion device bypass valve to allow the working fluid from the condenser to pass through the main expansion device; andwherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:the controller opens the expansion device bypass valve to allow the working fluid from the condenser to bypass the main expansion device and travel directly to the evaporator.
Aspect 16. The climate control system of aspect 15, wherein when the monitored climate controlled space temperature is less than or equal to the predetermined setpoint temperature:the controller operates at least one of a condenser fan and an evaporator fan while the compressor is OFF and the expansion device bypass valve is open.

With regard to the preceding description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size, and arrangement of parts, without departing from the scope of the present disclosure. The word “embodiment” as used within this specification may, but does not necessarily, refer to the same embodiment. This specification and the embodiments described are examples only. Other and further embodiments may be devised without departing from the basic scope thereof, with the true scope and spirit of the disclosure being indicated by the claims that follow.