Patent Description:
Subcooling can increase the difference in enthalpy between the condenser and the evaporator in a heating, ventilation, air conditioning, and refrigeration (HVACR) system. This can improve the capacity and efficiency of an HVACR system over the capacity and efficiency of an HVACR system having identical values for the suction and discharge pressure of a compressor included in that HVACR system.

This invention is directed to systems and methods for the control of superheat generated by a subcooler in a heating, ventilation, air conditioning, and refrigeration (HVACR) system.

Subcooling can be provided to an HVACR system using a suction line heat exchanger, where working fluid can release additional heat prior to entering an expansion device, and the heat can be absorbed by working fluid that is about to enter a suction of a compressor of the HVACR system. This subcooling can provide efficiency advantages.

Excessive subcooling may have detrimental effects on HVACR system performance. Depending on the operating mode of the HVACR system, excessive subcooling can result in issues including liquid slugging, or potentially freezing at one of the heat exchangers of the HVACR system, and thus may require defrost cycles which cost efficiency. An apparatus according to the preamble of claim <NUM> and a method according to the preamble of claim <NUM> are disclosed in <CIT>.

Providing controlled subcooling through a suction line heat exchanger may allow the advantages of subcooling with respect to capacity and efficiency to be realized while avoiding some of the associated risks or problems resulting from excessive subcooling. Control may be achieved by using a flow director to control a portion of the flow through a suction line heat exchanger, based on the superheat added to the suction line working fluid by the subcooled refrigerant. In some embodiments, the improvements to efficiency can be improvements to overall efficiency of heat pump operations, such as increase of heating capacity and reduction in power when at maximum heating capacity. In an embodiment, the controlled subcooling can provide an overall efficiency of heat pump operations of approximately <NUM>%, for example by increasing the heating capacity by approximately <NUM>% while also reducing energy consumption at maximum heating capacity by approximately <NUM>%.

The invention provides a heating, ventilation, air conditioning, and refrigeration (HVACR) circuit according to claim <NUM> and a method of operating a heating, ventilation, air conditioning, and refrigeration (HVACR) circuit according to claim <NUM>.

An HVACR circuit embodiment includes a compressor having a suction and a discharge, a first heat exchanger, an expander, a second heat exchanger, and a suction line heat exchanger. The suction line heat exchanger is configured to exchange heat between a first working fluid flow, where the first working fluid flow is a flow of working fluid from one of the first heat exchanger or the second heat exchanger to the suction of the compressor, and a second working fluid flow, where the second working fluid flow is a flow of working fluid from the other of the first heat exchanger or the second heat exchanger towards the expander. The HVACR circuit further includes a flow director configured to regulate an amount of the second working fluid flow entering the suction line heat exchanger. The HVACR circuit also includes a controller, configured to receive a first temperature of the first working fluid flow prior to entering the suction line heat exchanger, receive a second temperature of the first working fluid flow between the suction line heat exchanger and the suction of the compressor, determine a superheat generation at the suction line heat exchanger based on the first temperature and the second temperature; and control the flow director based on the superheat generation and a threshold superheat value.

In an embodiment, the HVACR circuit further includes a third temperature sensor configured to measure a temperature of the second working fluid flow prior to entering the flow director or at an inlet of the flow director, and the controller is configured to further control the flow director based on a reading from the third temperature sensor.

In an embodiment, in the HVACR circuit, the first heat exchanger is an outdoor heat exchanger receiving working fluid from the discharge of the compressor, the second heat exchanger is an evaporator, the first working fluid flow is from the second heat exchanger to the suction of the compressor, and the second working fluid flow is from the first heat exchanger to the expander.

In an embodiment, the HVACR circuit further includes a flow reverser configured to direct working fluid discharged from the discharge of the compressor to one of the first heat exchanger or the second heat exchanger. In an embodiment, the HVACR circuit is in a cooling mode when the flow reverser directs working fluid discharged from the discharge of the compressor to the first heat exchanger, and a heating mode when the flow reverser directs working fluid discharged from the discharge of the compressor to the second heat exchanger. In an embodiment, when the HVACR circuit is in the cooling mode, the first working fluid flow is from the second heat exchanger to the suction of the compressor, and the second working fluid flow is from the first heat exchanger to the expander. In an embodiment, when the HVACR circuit is in the heating mode, the first working fluid flow is from the first heat exchanger to the suction of the compressor, and the second working fluid flow is from the second heat exchanger to the expander.

In an embodiment, the suction line heat exchanger is a counter-flow heat exchanger.

In an embodiment, the flow director includes a stepped three-way valve and a bypass line.

In an embodiment, the flow director includes a plurality of controllable valves, and wherein the controller is configured to operate the plurality of controllable valves proportionally.

In an embodiment, controlling the flow director based on the superheat generation and a threshold superheat value comprises regulating the second working fluid flow such that the superheat generation is less than the threshold superheat value. In an embodiment, the threshold superheat value is at or about <NUM>° C.

The HVACR circuit according to the invention includes a first temperature sensor located upstream of the suction line heat exchanger with respect to the first working fluid flow, and wherein the controller receives the first temperature from the first temperature sensor.

The HVACR circuit according to the invention includes a second temperature sensor located between the suction line heat exchanger and the suction of the compressor, and wherein the controller receives the second temperature from the second temperature sensor.

In an embodiment, a method of operating an HVACR circuit includes providing a first working fluid flow through a suction line heat exchanger, wherein the first working fluid flow is a working fluid flow from a first heat exchanger to a suction of a compressor and providing a second working fluid flow through the suction line heat exchanger, separate from the first working fluid flow. The second working fluid flow is a working fluid flow from a second heat exchanger to an expander, and the first working fluid flow and the second working fluid flow exchange heat in the suction line heat exchanger. The method includes receiving a first temperature of the first working fluid flow at a position directly upstream of the suction line heat exchanger and receiving a second temperature of the first working fluid flow at a position directly downstream of the suction line heat exchanger. The method further includes determining a superheat generation based on the first temperature and the second temperature. The method also includes controlling a flow of the second working fluid flow through the suction line heat exchanger based on the superheat generation and a threshold superheat value. Controlling the flow of the second working fluid as disclosed herein may comprise controlling a quantity of the flow, for example a flow rate of the flow.

In an embodiment, the flow of the second working fluid flow is controlled such that the superheat generation does not exceed the threshold superheat value. In an embodiment, the threshold superheat value is at or about <NUM>° C.

In an embodiment, controlling the flow of the second working fluid flow includes directing a portion of the second working fluid flow to a bypass line via a stepped three-way valve.

In an embodiment, controlling the flow of the second working fluid flow includes operating a plurality of controllable valves proportionally to allocate flow between a bypass line and the suction line heat exchanger.

In an embodiment, the method further includes receiving a third temperature, wherein the third temperature is a temperature of the second working fluid flow, and controlling the flow of the second working fluid flow is further based on the third temperature.

In an embodiment, the suction line heat exchanger is a counter-flow heat exchanger wherein the first working fluid flow travels through the suction line heat exchanger in a first direction, and the second working fluid flow travels through the suction line heat exchanger in a second direction, wherein the second direction is opposite the first direction.

In an embodiment, the HVACR circuit is a heat pump circuit, the first heat exchanger is a heat exchanger receiving working fluid from the expander, and the second heat exchanger is a heat exchanger receiving working fluid from a discharge of the compressor.

This disclosure is directed to systems and methods for the control of superheat generated by a subcooler in a heating, ventilation, air conditioning, and refrigeration (HVACR) system.

<FIG> is a schematic of a heating, ventilation, air conditioning, and refrigeration (HVACR) circuit <NUM> according to an embodiment. HVACR circuit <NUM> includes compressor <NUM>, first heat exchanger <NUM>, expansion device <NUM>, second heat exchanger <NUM>, and suction line heat exchanger <NUM>. HVACR circuit further includes fluid line <NUM>, flow director <NUM>, bypass line <NUM>, and return line <NUM>. HVACR circuit <NUM> also includes first temperature sensor <NUM> and second temperature sensor <NUM>. HVACR circuit <NUM> further includes controller <NUM>. HVACR circuit <NUM> may optionally include a third temperature sensor <NUM>.

Compressor <NUM> is a compressor that compresses a working fluid of the HVACR circuit <NUM>. Compressor <NUM> may be any suitable type of compressor for an HVACR system such as, for example, a screw compressor or a scroll compressor. Compressor <NUM> includes suction <NUM>, where the working fluid enters the compressor <NUM>, and discharge <NUM>, where compressed working fluid exits the compressor <NUM>.

First heat exchanger <NUM> receives the compressed working fluid exiting from discharge <NUM> of compressor <NUM>. First heat exchanger <NUM> may be a condenser configured to allow the working fluid to release heat, for example to another fluid, condensing the working fluid. In an embodiment where HVACR circuit <NUM> is part of an air-cooled chiller, first heat exchanger <NUM> may be an outdoor condenser configured to exchange heat between the working fluid and ambient outdoor air to condense the compressed working fluid. In an embodiment, working fluid exits first heat exchanger <NUM> via fluid line <NUM>.

Expansion device <NUM> is a device configured to reduce the pressure of the working fluid. Expansion device <NUM> is an expander. As a result of reduction in the pressure in the working fluid at expansion device <NUM>, a portion of the working fluid is converted to a gaseous form. Expansion device <NUM> may be, for example, an expansion valve, orifice, or other suitable expander to reduce pressure of a working fluid such as the working fluid. In an embodiment, expansion device <NUM> includes multiple orifices. In an embodiment, the multiple orifices of expansion device <NUM> have different sizes. Expansion device <NUM> may be a controllable expansion device having a variable aperture. In an embodiment, expansion device <NUM> is an electronic expansion valve.

Second heat exchanger <NUM> is a heat exchanger receiving working fluid from expansion device <NUM>. In an embodiment where HVACR circuit <NUM> is part of a chiller, second heat exchanger may be an evaporator configured to exchange heat between the working fluid and a process fluid such as water or air to provide cooling to a building having climate control provided by a system including the HVACR circuit <NUM>. In this embodiment, the working fluid in second heat exchanger <NUM> may absorb heat from the process fluid to evaporate the working fluid. The working fluid exiting second heat exchanger <NUM> may pass to suction line heat exchanger <NUM>.

Suction line heat exchanger <NUM> is a heat exchanger allowing the exchange of heat between two working fluid flows through HVACR circuit <NUM>. Suction line heat exchanger <NUM> may receive a first flow of working fluid from second heat exchanger <NUM>, which then passes to suction <NUM> of compressor <NUM> following the exchange of heat within suction line heat exchanger <NUM>. Suction line heat exchanger <NUM> may receive a second flow of working fluid from flow director <NUM>, which then passes to return line <NUM> following the exchange of heat within suction line heat exchanger <NUM>. Suction line heat exchanger <NUM> may be any suitable form of heat exchanger for exchanging heat between the first and second flows of working fluid. In an embodiment, suction line heat exchanger <NUM> is constructed of one or more steel materials. In an embodiment, suction line heat exchanger <NUM> does not include copper. In an embodiment, suction line heat exchanger <NUM> includes a plurality of tubes conveying the first flow of working fluid, located within an outer pipe through which the second flow of working fluid travels. In an embodiment, suction line heat exchanger <NUM> is a counter-flow heat exchanger where the first flow of working fluid and the second flow of working fluid travel in opposite directions.

Fluid line <NUM> may direct the fluid exiting heat exchanger <NUM> to flow director <NUM>. Flow director <NUM> allocates the flow from fluid line <NUM> among the suction line heat exchanger <NUM> and a bypass line <NUM>. Flow director <NUM> may be any one or more flow controls that are configured to allow a variable amount of the flow exiting heat exchanger <NUM> to be directed to the suction line heat exchanger <NUM>. Flow director <NUM> may regulate the flow entering suction line heat exchanger <NUM> based on control by controller <NUM>. Bypass line <NUM> is a fluid line that conveys fluid from flow director <NUM> to return line <NUM> without passing through suction line heat exchanger <NUM>. Return line <NUM> is a line that conveys fluid received from suction line heat exchanger <NUM> and bypass line <NUM> to the expansion device <NUM>.

Flow director <NUM> may be, for example, a three-way valve. In an embodiment, flow director <NUM> is a motorized, stepped three-way valve. In an embodiment where flow director <NUM> is a three-way valve, the three-way valve has one input receiving flow from fluid line <NUM>, a first outlet from which fluid passes to suction line heat exchanger <NUM>, and a second outlet from which fluid passes to bypass line <NUM>.

In an embodiment, flow director <NUM> includes at least two variable-position valves. In this embodiment, the at least two variable-position valves may be controlled in a complementary fashion, where the extent of opening of each valve is controlled with respect to the others to allocate the flow among suction line heat exchanger <NUM> and bypass line <NUM>. This complementary control may be proportional, for example, having the aperture of the variable-position valve controlling flow to suction line heat exchanger <NUM> be set to a size proportional to the amount of flow to be directed to the suction line heat exchanger <NUM> while also having the variable-position valve controlling flow to bypass line <NUM> be set to a size proportional to the amount of flow to be directed to the bypass line <NUM>. Proportional control of valves in flow director <NUM> may be directed by controller <NUM>.

In an embodiment, flow director <NUM> includes multiple valves of varying aperture size for each of suction line heat exchanger <NUM> and bypass line <NUM> and the allocation of flow is achieved by opening or closing one or more of those multiple valves.

In an embodiment, first temperature sensor <NUM> is a temperature sensor located directly upstream of or at an inlet of the suction line heat exchanger <NUM> with respect to the flow of working fluid through the HVACR circuit <NUM>. First temperature sensor <NUM> is a sensor configured to obtain a temperature value, either directly or indirectly. First temperature sensor <NUM> obtains a first temperature reading that is a temperature of the first working fluid flow prior to the first working fluid flow exchanging heat in the suction line heat exchanger <NUM>. The first temperature sensor <NUM> may be any suitable temperature sensor for measuring a temperature of a working fluid flow prior to that working fluid flow entering the suction line heat exchanger <NUM>. First temperature sensor <NUM> is operatively coupled to controller <NUM> such that it can provide a first temperature reading to controller <NUM>. The operative coupling may be through any suitable connection to provide the first temperature reading, such as wired or wireless communications.

In an embodiment, second temperature sensor <NUM> is a temperature sensor located directly downstream of or at an outlet of the suction line heat exchanger <NUM> with respect to the flow of working fluid through the HVACR circuit <NUM>. Second temperature sensor <NUM> is a sensor configured to obtain a temperature value, either directly or indirectly. Second temperature sensor <NUM> obtains a second temperature reading that is the temperature of the first working fluid flow subsequent to that working fluid flow exchanging heat at suction line heat exchanger <NUM>. Second temperature sensor <NUM> is upstream of the compressor <NUM>. Second temperature sensor <NUM> is operatively coupled to controller <NUM> such that it can provide the second temperature reading to controller <NUM>. The operative coupling may be through any suitable connection to provide the second temperature reading, such as wired or wireless communications.

Controller <NUM> includes a processor. Controller <NUM> is operatively coupled to first temperature sensor <NUM> and second temperature sensor <NUM>. Controller <NUM> is further operatively coupled to flow director <NUM> such that the quantity of flow to suction line heat exchanger <NUM> can be controlled. Controller <NUM> may be configured to receive a first temperature from the first temperature sensor. Controller <NUM> may be configured to receive a second temperature from the second temperature sensor. Controller <NUM> may be configured to determine a superheat generation at the suction line heat exchanger based on the first temperature and the second temperature. In an embodiment, the superheat generation is determined by subtracting the first temperature from the second temperature. Controller <NUM> may further be configured to control the flow director <NUM> based on the superheat generation and a threshold superheat value. Controller <NUM> may include a memory, and the memory may be configured to store at least the threshold superheat value. The threshold superheat value may be a value of superheat that is permissible for HVACR circuit <NUM> during operations. The threshold superheat value may be based on parameters such as, for example, the design of the HVACR circuit <NUM>, and optionally the amount of working fluid that HVACR circuit <NUM> has been charged with. In an embodiment, the threshold superheat value is determined based on a superheat setpoint of the HVACR circuit <NUM>. In an embodiment, the threshold superheat value may be at or about <NUM>° C. The threshold superheat value may be a value selected based on one or more of, for example, avoiding liquid slugging or improving stability at the expansion device <NUM>. The threshold superheat value may further be dynamic with the variation in the threshold superheat value being based at least in part on, for example, ambient air temperature, saturated suction temperature, and/or compressor load of compressor <NUM>.

Optionally, third temperature sensor <NUM> may be included in HVACR circuit <NUM>. Third temperature sensor <NUM> may be located along fluid line <NUM>. Third temperature sensor <NUM> may be any suitable temperature sensor for measuring a temperature of the working fluid within fluid line <NUM>. Third temperature sensor <NUM>, when included, may measure a third temperature reading that is a temperature of the second working fluid flow that introduced into suction line heat exchanger <NUM>. Third temperature sensor <NUM>, when included, may be operatively coupled to controller <NUM> such that it can provide the third temperature reading to controller <NUM>. The operative coupling may be through any suitable connection to provide the second temperature reading, such as wired or wireless communications. In an embodiment where third temperature sensor <NUM> is included, the controller <NUM> may be further configured to determine the amount of flow for flow director <NUM> to allow into suction line heat exchanger <NUM> based on the third temperature reading.

<FIG> is a schematic of an HVACR circuit <NUM> according to an embodiment, wherein the HVACR circuit includes a heat pump in a cooling mode. HVACR circuit <NUM> includes compressor <NUM>, flow reverser <NUM>, first heat exchanger <NUM> and second heat exchanger <NUM>. HVACR circuit <NUM> optionally includes drier <NUM>. HVACR circuit <NUM> includes fluid line <NUM> which conveys fluid to flow director <NUM>. Flow director <NUM> allocates flow among bypass line <NUM> and suction line heat exchanger <NUM>. Suction line heat exchanger <NUM> and bypass line <NUM> convey fluid to return line <NUM>. HVACR circuit <NUM> further includes expansion device <NUM>. HVACR circuit <NUM> further includes first temperature sensor <NUM> and second temperature sensor <NUM>. HVACR circuit <NUM> also includes controller <NUM>. Optionally, third temperature sensor <NUM> may also be included in HVACR circuit <NUM>.

In the cooling mode shown in <FIG>, flow reverser <NUM> directs working fluid discharged from the discharge of compressor <NUM> to first heat exchanger <NUM>. In the cooling mode shown in <FIG>, check valves <NUM> permit the flow of the working fluid from the first heat exchanger <NUM> to optional drier <NUM> or fluid line <NUM>.

Compressor <NUM> includes suction <NUM> and discharge <NUM>. Compressor <NUM> is a compressor that compresses a working fluid of the HVACR circuit <NUM>. Compressor <NUM> may be, for example, any suitable type of compressor for an HVACR system, such as a screw compressor. Compressor <NUM> includes suction <NUM>, where the working fluid enters the compressor <NUM>, and discharge <NUM>, where compressed working fluid exits the compressor <NUM>.

Flow reverser <NUM> is a flow control configured to allow the direction of flow through HVACR circuit <NUM> to be switched between a first direction and a second direction, opposite the first. In an embodiment, flow reverser <NUM> is a four-way valve. In an embodiment where flow reverser <NUM> is a four-way valve, the four-way valve may have a first connection to the discharge <NUM> of compressor <NUM>, a second connection to first heat exchanger <NUM>, a third connection to the second heat exchanger <NUM>, and a fourth connection to the suction line heat exchanger <NUM>. In this embodiment, when HVACR circuit <NUM> is in a cooling mode, the first connection to discharge <NUM> is connected to the third connection to second heat exchanger <NUM>, and the second connection to first heat exchanger <NUM> is connected to the fourth connection to the suction line heat exchanger <NUM>.

First heat exchanger <NUM> is a heat exchanger allowing the working fluid to exchange heat as part of a heating or cooling operation of HVACR circuit <NUM>. In an embodiment, first heat exchanger <NUM> is an outdoor heat exchanger. In an embodiment, in the cooling mode, first heat exchanger <NUM> receives working fluid compressed by the compressor <NUM> from flow reverser <NUM>. In this embodiment, in the cooling mode, first heat exchanger <NUM> operates as a condenser allowing the compressed working fluid to reject heat to an ambient environment. In this embodiment, in the cooling mode, the working fluid leaving the first heat exchanger <NUM> then travels to one of optional drier <NUM> or to flow director <NUM> via fluid line <NUM>.

Second heat exchanger <NUM> is another heat exchanger separate from first heat exchanger <NUM>. In an embodiment, second heat exchanger <NUM> creates a heat exchange relationship between the working fluid and a process fluid such as water or air. In an embodiment, in the cooling mode, the second heat exchanger <NUM> receives working fluid from expansion device <NUM>. In this embodiment, in the cooling mode, the second heat exchanger functions as an evaporator where the working fluid absorbs heat from the process fluid to provide cooling to a space serviced by an HVACR system including HVACR circuit <NUM>. In this embodiment, in the cooling mode, the working fluid exiting the second heat exchanger <NUM> passes to flow reverser <NUM>.

HVACR circuit <NUM> may optionally include drier <NUM>. Drier <NUM> may receive working fluid from the first heat exchanger <NUM> when HVACR circuit <NUM> is in the cooling mode as shown in <FIG>.

Fluid line <NUM> conveys the working fluid in HVACR circuit <NUM> to flow director <NUM>. In an embodiment including optional drier <NUM>, the fluid line <NUM> may be from drier <NUM> to flow director <NUM>. In an embodiment, fluid line <NUM> may receive working fluid from the first heat exchanger <NUM> when the HVACR circuit <NUM> is in the cooling mode as shown in <FIG>.

Flow director <NUM> receives working fluid from fluid line <NUM>. Flow director <NUM> allocates the received working fluid among bypass line <NUM> and suction line heat exchanger <NUM>. By controlling the amount of working fluid allocated to suction line heat exchanger <NUM>, the superheat and subcooling occurring at suction line heat exchanger <NUM> can be controlled. The allocation of working fluid among bypass line <NUM> and suction line heat exchanger <NUM> may be determined by controller <NUM>, which may direct flow director <NUM> to allocate the flow according to a command.

Bypass line <NUM> allows fluid from flow director <NUM> to pass to return line <NUM> without passing through suction line heat exchanger <NUM>. Bypass line <NUM> may receive working fluid from flow director <NUM>, depending on the amount of fluid directed to suction line heat exchanger <NUM>.

Suction line heat exchanger <NUM> allows a first flow of working fluid from flow reverser <NUM> to suction <NUM> of compressor <NUM> to exchange heat with a second flow of working fluid from flow director <NUM>. In an embodiment, the first flow of working fluid is a suction gas. In an embodiment, the second flow of working fluid is a liquid at a relatively higher temperature than the first flow of working fluid. In an embodiment, heat exchange at suction line heat exchanger superheats the first flow of working fluid and subcools the second flow of working fluid. In an embodiment, a quantity of fluid included in the second flow of working fluid affects the extent of superheating and/or subcooling occurring as a result of the heat exchange at suction line heat exchanger <NUM>. In an embodiment, the first flow of working fluid travels through a plurality of tubes and the second flow of working fluid travels through an outer pipe surrounding the plurality of tubes. In an embodiment, the suction line heat exchanger <NUM> includes a steel material. In an embodiment, suction line heat exchanger <NUM> does not include copper. In an embodiment, suction line heat exchanger is a counter flow heat exchanger where the first working fluid flow and the second working fluid flow travel in opposite directions through suction line heat exchanger <NUM>.

Return line <NUM> receives the working fluid from the bypass line <NUM> and the second working fluid flow exiting the suction line heat exchanger <NUM>, and conveys the received working fluid to expansion device <NUM>.

Expansion device <NUM> is a device configured to reduce the pressure of the working fluid. As a result, a portion of the working fluid is converted to a gaseous form. Expansion device <NUM> may be, for example, an expansion valve, orifice, or other suitable expander to reduce pressure of a working fluid such as the working fluid. In an embodiment, expansion device <NUM> includes multiple orifices. In an embodiment, the multiple orifices of expansion device <NUM> have different sizes. Expansion device <NUM> may be a controllable expansion device having a variable aperture. In an embodiment, expansion device <NUM> is an electronic expansion valve.

First temperature sensor <NUM> is a temperature sensor located directly upstream of or at an inlet of the suction line heat exchanger <NUM> with respect to the flow of working fluid through the HVACR circuit <NUM>. First temperature sensor <NUM> may be located between the fourth connection of the flow reverser <NUM> and the suction line heat exchanger <NUM>. First temperature sensor <NUM> may obtain a first temperature reading that is a temperature of the first working fluid flow prior to the first working fluid flow exchanging heat in the suction line heat exchanger <NUM>. The first temperature sensor <NUM> may be any suitable temperature sensor for measuring a temperature of a working fluid flow prior to that working fluid flow entering the suction line heat exchanger <NUM>. First temperature sensor <NUM> may be operatively coupled to controller <NUM> such that it can provide a first temperature reading to controller <NUM>. The operative coupling may be through any suitable connection to provide the first temperature reading, such as wired or wireless communications.

Second temperature sensor <NUM> is a temperature sensor located directly downstream of or at an outlet of the suction line heat exchanger <NUM> with respect to the flow of working fluid through the HVACR circuit <NUM>. Second temperature sensor <NUM> may obtain a second temperature reading that is the temperature of the first working fluid flow subsequent to that working fluid flow exchanging heat at suction line heat exchanger <NUM>. Second temperature sensor <NUM> is upstream of the compressor <NUM>. Second temperature sensor <NUM> may be operatively coupled to controller <NUM> such that it can provide the second temperature reading to controller <NUM>. The operative coupling may be through any suitable connection to provide the second temperature reading, such as wired or wireless communications.

Optionally, third temperature sensor <NUM> may be included in HVACR circuit <NUM>. Third temperature sensor <NUM> may be located between flow director <NUM> and suction line heat exchanger <NUM>. Third temperature sensor <NUM> may be any suitable temperature sensor for measuring a temperature of the working fluid between flow director <NUM> and suction line heat exchanger <NUM>. Third temperature sensor <NUM>, when included, may measure a third temperature reading that is a temperature of the second working fluid flow that introduced into suction line heat exchanger <NUM>. Third temperature sensor <NUM>, when included, may be operatively coupled to controller <NUM> such that it can provide the third temperature reading to controller <NUM>. The operative coupling may be through any suitable connection to provide the third temperature reading, such as wired or wireless communications. In an embodiment where third temperature sensor <NUM> is included, the controller <NUM> may be further configured to determine the amount of flow for flow director <NUM> to allow into suction line heat exchanger <NUM> based on the third temperature reading.

<FIG> is a schematic of an HVACR circuit <NUM> according to an embodiment, wherein the HVACR circuit includes a heat pump in a heating mode. The HVACR circuit <NUM> includes the components discussed above in <FIG>. In the heating mode shown in <FIG>, flow reverser <NUM> directs working fluid discharged from the discharge of compressor <NUM> to second heat exchanger <NUM>. In the heating mode shown in <FIG>, check valves <NUM> permit the flow of the working fluid from the second heat exchanger <NUM> to optional drier <NUM> or fluid line <NUM>.

When HVACR circuit <NUM> is in a heating mode as shown in <FIG>, the first connection to discharge <NUM> is connected to the second connection to first heat exchanger <NUM> and the third connection to second heat exchanger <NUM> is connected to the fourth connection to the suction line heat exchanger <NUM>.

When HVACR circuit <NUM> is in a heating mode as shown in <FIG>, second heat exchanger <NUM> receives process fluid compressed by compressor <NUM> via the flow reverser <NUM>. In this embodiment, in the heating mode, the second heat exchanger <NUM> operates as a condenser allowing the compressed working fluid to reject heat to the process fluid to provide heating to the space served by the HVACR system including HVACR circuit <NUM>. In this embodiment, in the heating mode, the working fluid leaving the second heat exchanger then travels to one of optional drier <NUM> or to flow director <NUM> via fluid line <NUM>.

Drier <NUM> may receive working fluid from the heat exchanger <NUM> when the HVACR circuit <NUM> is in a heating mode as shown in <FIG>.

In an embodiment, fluid line <NUM> may receive working fluid from the second heat exchanger <NUM> when the HVACR circuit <NUM> is in a heating mode as shown in <FIG>.

When HVACR circuit <NUM> is in the heating mode as shown in <FIG>, first heat exchanger <NUM> receives working fluid from expansion device <NUM>. In an embodiment, in the heating mode, first heat exchanger <NUM> functions as an evaporator where the working fluid absorbs heat from the ambient environment. In this embodiment, in the heating mode, the working fluid exiting the first heat exchanger <NUM> passes to flow reverser <NUM>.

<FIG> is a sectional view of a suction line heat exchanger <NUM> according to an embodiment. Suction line heat exchanger <NUM> includes outer pipe <NUM> and a plurality of tubes <NUM>. Outer pipe <NUM> conveys a flow of liquid working fluid, from a heat exchanger of the HVACR circuit towards an expansion device of that HVACR circuit. Tubes <NUM> convey another flow of gaseous working fluid, from another heat exchanger of an HVACR circuit towards a suction of a compressor of that HVACR circuit. The flow of liquid working fluid enters through inlet <NUM> and exits through outlet <NUM>. In an embodiment, the working fluid in tubes <NUM> absorbs heat from the working fluid in outer pipe <NUM>, superheating the suction gas while subcooling the liquid working fluid. In an embodiment, the suction line heat exchanger <NUM> is a counter-flow heat exchanger, where a direction of the first flow of the working fluid in outer pipe <NUM> is opposite a direction of the second flow of the working fluid in tubes <NUM>, such as the flow within outer pipe <NUM> being out of the page, whereas the flow of the working fluid in tubes <NUM> being into of the page.

<FIG> is a schematic view of the suction line heat exchanger <NUM> according to an embodiment. In <FIG>, outer tube <NUM> is not shown so that tubes <NUM> and baffles <NUM> can be shown. Inlet <NUM> and outlet <NUM> are shown. Inlet <NUM> allows the first flow of the working fluid to enter outer pipe <NUM>. The flow of liquid working fluid is directed by baffles <NUM> as it passes through outer pipe <NUM> to outlet <NUM>. The flow of gaseous working fluid passes from gas inlet <NUM> to gas outlet <NUM> via the tubes <NUM>. In an embodiment, the direction of the flow of gaseous working fluid is opposite the direction of liquid working fluid, as shown in the arrangement of inlets and outlets shown in <FIG>.

<FIG> is a flowchart of a method <NUM> according to an embodiment. Method <NUM> includes providing a first working fluid flow to a suction line heat exchanger <NUM> and providing a second working fluid flow to the suction line heat exchanger <NUM>. Method <NUM> further includes receiving a first temperature of the first working fluid flow directly upstream of the suction line heat exchanger <NUM> and receiving a second temperature of the first working fluid flow directly downstream of the suction line heat exchanger <NUM>. Method <NUM> also includes determining a superheat generation <NUM> based on the first temperature and the second temperature, and controlling a quantity of flow of the second working fluid flow to the suction line heat exchanger <NUM> based on the superheat generation and a threshold superheat value. Optionally, a third temperature in the second working fluid flow can be received <NUM>.

Method <NUM> includes providing a first working fluid flow to a suction line heat exchanger <NUM>. The first working fluid flow may be a flow of a working fluid from a heat exchanger receiving the working fluid from an expansion device towards a suction of a compressor of an HVACR circuit in which method <NUM> is being performed. In an embodiment, the first working fluid flow is of a gas at a relatively low temperature. In an embodiment, the first working fluid flow is of suction gas in the HVACR circuit. In an embodiment where the HVACR circuit is incorporated into a chiller, the first working fluid flow may be from an evaporator used to absorb heat from a process fluid such as air or water. In an embodiment where the HVACR circuit is incorporated into a heat pump, the first working fluid flow may be from either an outdoor heat exchanger being used as an evaporator to absorb heat from an ambient environment when in a heating mode, or a heat exchanger being used as an evaporator to absorb heat from a process fluid such as air or water when the HVACR circuit is in a cooling mode.

Method <NUM> also includes providing a second working fluid flow to the suction line heat exchanger <NUM>. The second working fluid flow may be a flow of working fluid from a heat exchanger that receives working fluid from the discharge of a compressor of the HVACR circuit towards an expansion device of the HVACR circuit. In an embodiment, the second working fluid flow is from a liquid line in the HVACR circuit. In an embodiment, the second working fluid flow is a relatively warm liquid flow (i.e. at a temperature higher than that of the first working fluid flow provided at <NUM>). In an embodiment where the HVACR circuit is incorporated into a chiller, the second working fluid flow may be from a condenser used to reject heat to an ambient environment and upstream of an expansion device of the HVACR circuit. In an embodiment where the HVACR circuit is incorporated into a heat pump, the second working fluid flow may be from an indoor unit operating as a condenser to heat a process fluid such as air or water to provide heating in a heating mode, or a heat exchanger operating as a condenser to reject heat to an ambient environment when in a heating mode.

In an embodiment, the first working fluid flow provided at <NUM> and the second working fluid flow provided at <NUM> are kept separate within the suction line heat exchanger, exchanging heat with one another without any mixing occurring. In an embodiment, the suction line heat exchanger is a counter flow heat exchanger, where the first working fluid flow provided at <NUM> and the second working fluid flow provided at <NUM> respectively travel in directions opposite to one another in at least a portion of the suction line heat exchanger.

A first temperature of the first working fluid flow directly upstream of the suction line heat exchanger is received <NUM>. The first temperature may be obtained from, for example, a temperature sensor located directly upstream of the suction line heat exchanger. Directly upstream of the suction line heat exchanger is understood as being where no other component of the fluid circuit such as a heat exchanger, compressor, etc. are between the point of measurement and the suction line heat exchanger, aside from the fluid line conveying the working fluid to the suction line heat exchanger. The first temperature received at <NUM> may be measured at an inlet of the suction line heat exchanger. The first temperature received at <NUM> may be measured along a fluid line between the outlet of the heat exchanger receiving working fluid from the expansion device and the inlet of the suction line heat exchanger. The first temperature may be communicated to a controller via an operational coupling such as a wired or wireless connection between a temperature sensor taking the measurement and the controller.

A second temperature of the first working fluid flow directly downstream of the suction line heat exchanger is received at <NUM>. Directly downstream of the suction line heat exchanger is understood as being anywhere between the suction line heat exchanger and the next component of the fluid circuit other than a fluid line following the suction line heat exchanger, such as the suction of the compressor. The second temperature received at <NUM> may be obtained from, for example, a temperature sensor. The second temperature is a temperature of the first working fluid flow between the outlet of the suction line heat exchanger and a suction of the compressor of the HVACR circuit where method <NUM> is performed. In an embodiment, the second temperature is received <NUM> at the outlet of the suction line heat exchanger. In an embodiment, the second temperature is received <NUM> along a fluid line connecting the suction line heat exchanger to the suction of the compressor. The second temperature may be communicated to a controller via an operational coupling such as a wired or wireless connection between a temperature sensor taking the measurement and the controller.

A superheat generation is determined <NUM> based on the first temperature and the second temperature. The superheat generation <NUM> is a measure of the superheat added to the suction gas by the suction line heat exchanger. In an embodiment, the superheat generation is determined as the difference between the second temperature received at <NUM> and the first temperature received at <NUM>. In an embodiment, the superheat generation may be determined <NUM> by a controller receiving the first temperature at <NUM> and the second temperature received at <NUM>, for example by an operative coupling such as a wired or wireless connection between the controller and the sensors measuring the respective first and second temperatures.

A quantity of flow of the second working fluid flow to the suction line heat exchanger is controlled <NUM> based on the superheat generation determined at <NUM> and a threshold superheat value. The threshold superheat value may be a value of superheat that is permissible for HVACR circuit during method <NUM>. The threshold superheat value may be based on parameters such as, for example, the design of the HVACR circuit and optionally the amount of working fluid that HVACR circuit has been charged with. In an embodiment, the threshold superheat value is determined based on a superheat setpoint of the HVACR circuit <NUM>. In an embodiment, the threshold superheat value may be at or about <NUM>° C. The threshold superheat value may be a value selected based on one or more of, for example, avoiding liquid slugging or improving stability at an expansion device. The threshold superheat value may further be dynamic with the variation in the threshold superheat value being based at least in part on, for example, ambient air temperature, saturated suction temperature, and/or compressor load of a compressor of the HVACR system. In an embodiment, when the superheat generation determined at <NUM> exceeds the threshold superheat value, the quantity of flow of the second working fluid flow may be reduced at <NUM>. In an embodiment, when the superheat generation determined at <NUM> is less than the threshold superheat value, the quantity of flow of the second working fluid flow may be maintained or increased at <NUM>. In an embodiment, the quantity of flow of the second working fluid flow and the superheat generation may be used to determine a relationship between the quantity of flow of the second working fluid flow into the suction line heat exchanger and the superheat generation, and this relationship may be used to determine a value for the quantity of flow of the second working fluid flow to provide superheating at or near the threshold superheat value.

In an embodiment, control of the quantity of flow of the second working fluid flow may be achieved through the controller directing a flow director to operate. The flow director controlled by the controller to effect control of the quantity of flow of the second working fluid flow at <NUM> may be one or more flow controls that are configured to control the quantity of fluid allowed to flow into the suction line heat exchanger. The flow director may, for example, allocate the flow of fluid between the suction line heat exchanger and a bypass line that allows fluid to continue flow through the HVACR circuit without passing through the suction line heat exchanger. In an embodiment, the flow director is a three-way valve. In an embodiment, the flow director is a motorized, stepped three-way valve. In an embodiment, the flow director has one input, a first outlet from which fluid passes to suction line heat exchanger, and a second outlet from which fluid passes to bypass line. In an embodiment, the flow director includes at least two variable-position valves. In this embodiment, the at least two variable-position valves may be controlled in a complementary fashion, where the extent of opening of each valve is controlled with respect to the others to allocate the flow among the suction line heat exchanger and the bypass line. In an embodiment, the control of the at least two variable-position valves is proportional control. In an embodiment, the flow director includes multiple valves of varying aperture size for each of the suction line heat exchanger and bypass line and the allocation of flow is achieved by opening or closing one or more of those multiple valves.

Optionally, a third temperature in the second working fluid flow can be received <NUM>. The temperature can be measured upstream of the flow director used to control the quantity of flow of the second working fluid flow to the suction line heat exchanger at <NUM>. The third temperature may be used by the controller to further determine the quantity of flow of the second working fluid to be directed to the suction line heat exchanger at <NUM>. For example, the third temperature can be a parameter used to determine an expected superheating provided by a quantity of flow of the second working fluid flow into the suction line heat exchanger at <NUM>, and the expected superheating used to provide superheating in an amount below the threshold superheat value.

In an embodiment, the method <NUM> may be continuous. In an embodiment, the method <NUM> may iterate by returning from the control of the quantity of the flow of the second working fluid flow at <NUM> to the measurement of the first temperature at <NUM>, either continuously, at set intervals, or based on triggers such as changes in operating conditions.

Claim 1:
A heating, ventilation, air conditioning, and refrigeration (HVACR) circuit (<NUM>), comprising:
a compressor (<NUM>) having a suction (<NUM>) and a discharge (<NUM>);
a first heat exchanger (<NUM>);
an expander (<NUM>);
a second heat exchanger (<NUM>);
a suction line heat exchanger (<NUM>), configured to exchange heat between a first working fluid flow, wherein the first working fluid flow is a flow of working fluid from one of the first heat exchanger or the second heat exchanger to the suction of the compressor, and a second working fluid flow, wherein the second working fluid flow is a flow of working fluid from the other of the first heat exchanger or the second heat exchanger towards the expander;
characterized in that the HVACR circuit further comprises:
a flow director (<NUM>) configured to regulate an amount of the second working fluid flow entering the suction line heat exchanger;
a first temperature sensor (<NUM>) located upstream of the suction line heat exchanger with respect to the first working fluid flow;
a second temperature sensor (<NUM>) located between the suction line heat exchanger and the suction of the compressor; and
a controller (<NUM>), configured to:
receive a first temperature of the first working fluid flow from the first temperature sensor;
receive a second temperature of the first working fluid flow from the second temperature sensor;
determine a superheat generation at the suction line heat exchanger based on the first temperature and the second temperature; and
control the flow director based on the superheat generation and a threshold superheat value.