Heat pump temperature control

A heat pump system that can be selectively utilized to discharge excessive heating and cooling capacity toward secondary devices of the system to maintain operation of the heat pump system to better manage the respective temperatures associated with the fluid flows in a manner that reduces the need for cycling the heat pump system ON and OFF to attain desired fluid output temperature manipulations.

BACKGROUND OF THE INVENTION

The present invention relates generally to heat pump systems and more particularly to a heating and cooling system constructed to generate a desired output flow temperature in a manner that maintains operation of the underlying heat pump system so as to mitigate cycling of the system between ON and OFF operating states.

Many standard heat pumps utilize fixed speed compressors and multiple condensers to discharge only a required or desired amount of heat into an air flow. Using multiple condensers results in configurations wherein one or more condensers are not in the airstream associated with the fluid flow whose temperature is being manipulated such that such condensers discharge excess heat to a thermal dump. The thermal discharge associated with such condensers is considered wasted energy in as much as the energy associated with the thermal dump is never recaptured by the system and thereby detracts from the overall efficiency associated with operation of the underlying heat pump system. Although using only one condenser decreases the amount of waste heat generated, such systems require that the compressor be repeatedly cycled between ON and OFF operating states to prevent overheating of a respective air stream and thereby the space whose environmental temperature is to be manipulated. Cycling the compressor between and ON and OFF operating conditions results in inefficient utilization of the compressor and can increase wear associated with operation of the compressor which promotes premature failure of the compressor. Accordingly, there is a need for a heat pump system that can more efficiently transfer or communicate system energy to an intended environment and in a manner that mitigates undesired overshoot associated with call for heat instructions.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is directed to a heat pump system and method of controlling heat pump systems that solves one of more of the shortcomings disclosed above. The heat pump system according to one aspect of the present invention provides heating and cooling functionality in a manner that mitigates overshoot associated with manipulation of the fluid whose temperature is to be controlled. The system can utilize the functionality of a second heater during both heating, and cooling operations to improve the control and efficiency associated with operation of the heat pump system.

Another aspect of the invention discloses a heat pump system having a variable stage compressor that is fluidly connected to a fluid flow. An evaporator is connected to the fluid flow and disposed upstream relative to the direction of the fluid flow toward the variable stage compressor. A condenser is connected to the fluid flow and associated with an air stream and disposed downstream of the variable stage compressor. A valve assembly is disposed in the fluid flow associated with a bypass passage between an upstream side of the evaporator and an upstream side of the condenser. The valve assembly is operable to allow a portion of the fluid flow directed from the variable stage compressor toward the condenser to be directed upstream of the evaporator to reduce a thermal exchange between the fluid flow and the air stream directed through the condenser.

Another aspect of the invention discloses a method of forming a heat pump system that includes manipulating a pressure of a fluid with a variable stage compressor. Operation of the variable stage compressor is controlled in response to a temperature demand from a heat exchanger and a fluid conducting condition of a bypass passage that allows a portion of the fluid output from the variable stage compressor to bypass the heat exchanger and to be directed upstream of the variable stage compressor.

Another aspect of the invention discloses a heat pump system that includes a variable stage compressor, a first heat exchanger and a second heat exchanger. The first heat exchanger is fluidly disposed upstream of the variable stage compressor and the second heat exchanger is disposed downstream of the variable stage compressor such that an air flow can be disposed in thermal communication with at least one of the first heat exchanger and the second heat exchanger. A bypass passage extends between upstream sides of the first heat exchanger and the second heat exchanger and a valve arrangement is associated with a bypass passage. The valve arrangement is operable to direct a fluid flow directed from the variable stage compressor toward the second heat exchanger to be directed upstream of the first heat exchanger to reduce a thermal exchange between the fluid flow and the air flow directed through the second heat exchanger.

These and other aspects, advantages, and features of the present invention will be better understood and appreciated from the drawings and the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a heat pump system40according to one embodiment of the present invention. System40includes a working fluid path or fluid path42associated with a compressor44, a first heat exchanger such as a condenser46, and the second heat exchanger such as an evaporator48. One or both of condenser46and evaporator48can fluidly communicate with an airflow49associated with an environment whose temperature is intended to be manipulated. Evaporator48is located upstream of compressor44whereas condenser46is oriented generally downstream from compressor44and upstream relative to evaporator48with respect to the direction of the fluid flow associated with fluid path42.

System40includes a bypass passage50that fluidly connects a portion of fluid path42that is downstream of compressor44but upstream of condenser46to a portion of fluid path42that is upstream of evaporator48and compressor44. Bypass passage50includes an unloading modulating valve assembly or simply valve assembly54. Valve assembly54is operable to allow a portion of the fluid output from compressor44directed toward condenser46to bypass condenser46and be reintroduced to fluid stream42at a location upstream of evaporator48and/or compressor44. Another valve assembly55can be disposed in fluid path42between condenser46and evaporator48. The operation of one or more of valve assemblies54,55is described further below with respectFIG. 3with respect to manipulating the capacity of the heat pump system to exchange thermal energy with the air system to which it is associated and in a manner that improves the efficiency associated with operation and utilization of system40.

FIG. 2shows a heat pump assembly or system.60according to another embodiment of the invention. System60includes a compressor62that is disposed in a fluid path64generally between a heat exchanger such as a condenser66and another heat exchanger such as an evaporator68. Compressor62is preferably a multi-stage compressor. Like system40, heat exchanger66and evaporator68can each or both be disposed to an airstream69whose temperature is intended to be manipulated via operation of heat pump system60.

Due to the thermal demands associated with operation and utilization of system60, system60can include a fluid, such as water, that is communicated to a refrigerant heat exchanger70that includes a first fluid path72and the second fluid path74that are isolated from one another but in thermal interaction with one another. It should be appreciated that second fluid path74of heat exchanger70forms a respective portion of fluid path64, and the fluid associated therewith. System60can include one or more valves76,78,80,82,84,86,89,91and one or more directional flow devices, such as backflow preventers90,92, associated with achieving a desired flow associated with flow path64through system60to achieve the desired thermal exchange associated with the airflow69whose temperature is being manipulated via interaction with one or both of heat exchanger66, evaporator68, and/or heat exchanger70.

System60includes an unloading modulation valve96that is fluidly associated with a bypass passage98. Bypass passage98is fluidly connected downstream of compressor62and upstream relative to heat exchanger66. System60can include one or more pressure signal passages or connections and/or supplemental bypass passages100,102,104,106,108that are operable to communicate fluid condition signals or allow respective portions of the fluid flow associated with fluid path64to bypass one or more of heat exchanger66, evaporator68, and/or heat exchanger70, to achieve the desired operational and thermal exchange associated with the communication of the treated air flow69through heat exchanger66and/or evaporator68. For example, connection104communicates a pressure signal to valve82but does not accommodate a flow of fluid whereas bypass passage108accommodates a flow of fluid toward compressor62along a passage that bypasses evaporator68. It is further appreciated that although unloading modulation valve96is shown as being disposed in bypass passage98, other configurations are envisioned to achieve the objectives described below with respect toFIG. 3and the corresponding operation of systems40and/or60.

FIG. 3is a graphical representation associated with the operation of systems40and/or60. It is appreciated that the operational logic shown inFIG. 3can be disposed on various types of electronic devices or one or more controllers associated with providing the variable control associated with operation of a respective system40,60to achieve the desired operation thereof. Referring toFIG. 3, during a heating mode of operation112of systems40,60, a determination is made with respect to the component compressor modulation loop114as to whether the required capacity is greater than an actual capacity116associated with a current operating condition of compressor44,62. If the required capacity is not greater than the actual capacity118, compressor modulation loop114assesses whether a required capacity or demand is less than an actual capacity120and, if not122, current operating conditions124are maintained and modulation loop114returns126to the capacity assessment116.

If a required capacity or demand is greater than an actual current capacity118, compressor modulation loop114assesses whether compressor44,62is operating at maximum capacity128associated with a respective stage of operation and, if not130, increases the compressor capacity132prior to reassessing the capacity134,116. If the required capacity is greater than the actual capacity118, and the compressor is currently at maximum capacity136, system40,60maintains current operating conditions138associated with compressor modulation loop114prior to returning to assess required versus actual capacity116. If the required capacity is not greater than the actual capacity118, and the required capacity is less than an actual capacity144, compressor modulation loop114determines if the compressor44,62is at a minimum capacity146and, if not148, decreases the compressor capacity149, and system40,60returns to the assessment of capacity being greater than actual capacity116.

If compressor modulation loop114determines that the compressor is at a relative minimum capacity150associated with any given stage of operation associated with the compressor relative to the demand placed upon system40,60, the control of systems40,60proceed to an unloading valve operation loop160associated with manipulating the operation of the respective unloading valve54,96. The respective unloading valve incrementally opens162such that unloading valve loop160can assess whether required capacity is less than an actual capacity164. If the required capacity is less than the actual capacity166, unloading valve loop160assesses an open condition of the valve168and, if the valve is not at a maximum open position170, loop160returns to increment opening of the unloading valve162.

If the respective unloading valve is in fact all the way open172, indicating a full bypass condition, the operating conditions associated with modulation loop114and control valve loop160are maintained174and loop160returns to the assessment of the required capacity versus actual capacity164associated with operation of the respective system. If the required capacity is not less than the actual capacity178, loop160determines whether the required capacity is greater than the actual capacity180and, if not182, maintains the instantaneous operating conditions184prior to returning185to the assessments associated with compressor modulation loop114. If the required capacity is greater than the actual capacity186, unloading valve loop160assesses whether the unloading modulation valve54,96is at a minimum open condition188and if not190, increments closing of the valve192prior to returning to the assessment of capacity176. If the required capacity is greater than the actual capacity186, and the unloading modulation valve is at a minimum open condition190, unloading valve loop160returns194to compressor modulation loop114to repeat the assessment associated with the operation of compressor modulation loop114.

The operation of systems40,60provides a precision temperature control heat pump that utilizes a variable capacity compressor to limit the amount of heat that needs to be rejected at any given stage of operation of the respective system and/or compressor. When the compressor is at its minimum capacity, the operation of the unloading valve assemblies allows a portion of the output of the respective compressor to bypass the respective condenser and toward the respective evaporator which further decreases the thermal transfer capacity associated with the system and, in turn, results in very accurate temperature control associated with operation of the heat pump and with only negligible wasted heat. Such a construction allows operation of the respective system compressor at minimum capacities associated with satisfying respective system demands at each stage of operation of the respective compressor.

During operation of systems40,60, if the air-side condenser is overheating the treated air flow, such that the capacity produced is greater than the capacity required, the respective unloading modulation valve opens slightly to bypass the respective condenser and send hot gas to the evaporator associated with the system. The hot gas passing through the respective bypass valve assembly decreases the amount of gas directed into the air-side condenser which reduces the thermal exchange capacity. The gas also increases suction temperature associated with the upstream compressor flow thereby decreasing evaporator and system thermal exchange capacity in a manner that controls operation of the system to maintain the system parameters at conditions that accommodate target temperature conditions with smaller deviations relative thereto. The bypass modulating valve assemblies associated with the respective systems modulate to achieve desired supply air temperature conditions until the mode of operation changes from cooling, the thermal exchange capacity increases such that the unloading valve assembly completely closes and the compressor may increase capacity, and/or the maximum allowable valve open condition is reached thereby indicating a change to the compressor stage is required if available. Preferably, in order to maintain some cooling capacity associated with operation of systems40,60, the control associated with the operation of the respective bypass unloading valve assembly includes an upper threshold associated with allowing the precise temperature control described above in a manner that does not jeopardize the longevity associated with operation of systems40,60or the discrete components or devices associated therewith.

Therefore, one embodiment of the invention includes a heat pump system having a variable stage compressor that is fluidly connected to a fluid flow. An evaporator is connected to the fluid flow and disposed upstream relative to the direction of the fluid flow toward the variable stage compressor. A condenser is connected to the fluid flow and associated with an air stream and disposed downstream of the variable stage compressor. A valve assembly is disposed in the fluid flow associated with a bypass passage between an upstream side of the evaporator and an upstream side of the condenser. The valve assembly is operable to allow a portion of the fluid flow directed from the variable stage compressor toward the condenser to be directed upstream of the evaporator to reduce a thermal exchange between the fluid flow and the air stream directed through the condenser.

Another embodiment of the invention includes a method of forming a heat pump system that includes manipulating a pressure of a fluid with a variable stage compressor. Operation of the variable stage compressor is controlled in response to a temperature demand from a heat exchanger and a fluid conducting condition of a bypass passage that allows a portion of the fluid output from the variable stage compressor to bypass the heat exchanger and to be directed upstream of the variable stage compressor.

Another embodiment of the invention includes a heat pump system having a variable stage compressor, a first heat exchanger, and a second heat exchanger. The first heat exchanger is fluidly disposed upstream of the variable stage compressor and the second heat exchanger is disposed downstream of the variable stage compressor such that an air flow can be disposed in thermal communication with at least one of the first heat exchanger and the second heat exchanger. A bypass passage extends between upstream sides of the first heat exchanger and the second heat exchanger and a valve arrangement is associated with a bypass passage. The valve arrangement is operable to direct a fluid flow directed from the variable stage compressor toward the second heat exchanger to be directed upstream of the first heat exchanger to reduce a thermal exchange between the fluid flow and the air flow directed through the second heat exchanger.

The present invention has been described in terms of the preferred embodiments, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims. It is further appreciated that although various embodiments of the proposed systems are disclosed herein, that various features and/or aspects of the various embodiments are combinable and/or usable together.