Abstract:
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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 61/930,205 titled “HEAT PUMP TEMPERATURE CONTROL” filed on Jan. 22, 2014 and the entire contents of which is expressly incorporated herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    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. 
         [0003]    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 
       [0004]    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. 
         [0005]    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. 
         [0006]    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. 
         [0007]    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. 
         [0008]    These and other aspects, advantages, and features of the present invention will be better understood and appreciated from the drawings and the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         [0009]    The drawings are for illustrative purposes only and the invention is not to be limited to the exemplary embodiment shown therein. In the drawings: 
           [0010]      FIG. 1  shows a heat pump system according to one embodiment of the invention; 
           [0011]      FIG. 2  shows a heat pump system according to another embodiment of the invention; and 
           [0012]      FIG. 3  shows an operational control sequence associated with the heat pump systems shown in  FIGS. 1 and 2 . 
       
    
    
       [0013]    In describing the preferred embodiments of the invention, which are illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents, which operate in a similar manner to accomplish a similar purpose. For example, the word connected or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized, as being equivalent by those skilled in the art. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]      FIG. 1  shows a heat pump system  40  according to one embodiment of the present invention. System  40  includes a working fluid path or fluid path  42  associated with a compressor  44 , a first heat exchanger such as a condenser  46 , and the second heat exchanger such as an evaporator  48 . One or both of condenser  46  and evaporator  48  can fluidly communicate with an airflow  49  associated with an environment whose temperature is intended to be manipulated. Evaporator  48  is located upstream of compressor  44  whereas condenser  46  is oriented generally downstream from compressor  44  and upstream relative to evaporator  48  with respect to the direction of the fluid flow associated with fluid path  42 . 
         [0015]    System  40  includes a bypass passage  50  that fluidly connects a portion of fluid path  42  that is downstream of compressor  44  but upstream of condenser  46  to a portion of fluid path  42  that is upstream of evaporator  48  and compressor  44 . Bypass passage  50  includes an unloading modulating valve assembly or simply valve assembly  54 . Valve assembly  54  is operable to allow a portion of the fluid output from compressor  44  directed toward condenser  46  to bypass condenser  46  and be reintroduced to fluid stream  42  at a location upstream of evaporator  48  and/or compressor  44 . Another valve assembly  55  can be disposed in fluid path  42  between condenser  46  and evaporator  48 . The operation of one or more of valve assemblies  54 ,  55  is described further below with respect  FIG. 3  with 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 system  40 . 
         [0016]      FIG. 2  shows a heat pump assembly or system.  60  according to another embodiment of the invention. System  60  includes a compressor  62  that is disposed in a fluid path  64  generally between a heat exchanger such as a condenser  66  and another heat exchanger such as an evaporator  68 . Compressor  62  is preferably a multi-stage compressor. Like system  40 , heat exchanger  66  and evaporator  68  can each or both be disposed to an airstream  69  whose temperature is intended to be manipulated via operation of heat pump system  60 . 
         [0017]    Due to the thermal demands associated with operation and utilization of system  60 , system  60  can include a fluid, such as water, that is communicated to a refrigerant heat exchanger  70  that includes a first fluid path  72  and the second fluid path  74  that are isolated from one another but in thermal interaction with one another. It should be appreciated that second fluid path  74  of heat exchanger  70  forms a respective portion of fluid path  64 , and the fluid associated therewith. System  60  can include one or more valves  76 ,  78 ,  80 ,  82 ,  84 ,  86 ,  89 ,  91  and one or more directional flow devices, such as backflow preventers  90 ,  92 , associated with achieving a desired flow associated with flow path  64  through system  60  to achieve the desired thermal exchange associated with the airflow  69  whose temperature is being manipulated via interaction with one or both of heat exchanger  66 , evaporator  68 , and/or heat exchanger  70 . 
         [0018]    System  60  includes an unloading modulation valve  96  that is fluidly associated with a bypass passage  98 . Bypass passage  98  is fluidly connected downstream of compressor  62  and upstream relative to heat exchanger  66 . System  60  can include one or more pressure signal passages or connections and/or supplemental bypass passages  100 ,  102 ,  104 ,  106 ,  108  that are operable to communicate fluid condition signals or allow respective portions of the fluid flow associated with fluid path  64  to bypass one or more of heat exchanger  66 , evaporator  68 , and/or heat exchanger  70 , to achieve the desired operational and thermal exchange associated with the communication of the treated air flow  69  through heat exchanger  66  and/or evaporator  68 . For example, connection  104  communicates a pressure signal to valve  82  but does not accommodate a flow of fluid whereas bypass passage  108  accommodates a flow of fluid toward compressor  62  along a passage that bypasses evaporator  68 . It is further appreciated that although unloading modulation valve  96  is shown as being disposed in bypass passage  98 , other configurations are envisioned to achieve the objectives described below with respect to  FIG. 3  and the corresponding operation of systems  40  and/or  60 . 
         [0019]      FIG. 3  is a graphical representation associated with the operation of systems  40  and/or  60 . It is appreciated that the operational logic shown in  FIG. 3  can 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 system  40 ,  60  to achieve the desired operation thereof. Referring to  FIG. 3 , during a heating mode of operation  112  of systems  40 ,  60 , a determination is made with respect to the component compressor modulation loop  114  as to whether the required capacity is greater than an actual capacity  116  associated with a current operating condition of compressor  44 ,  62 . If the required capacity is not greater than the actual capacity  118 , compressor modulation loop  114  assesses whether a required capacity or demand is less than an actual capacity  120  and, if not  122 , current operating conditions  124  are maintained and modulation loop  114  returns  126  to the capacity assessment  116 . 
         [0020]    If a required capacity or demand is greater than an actual current capacity  118 , compressor modulation loop  114  assesses whether compressor  44 ,  62  is operating at maximum capacity  128  associated with a respective stage of operation and, if not  130 , increases the compressor capacity  132  prior to reassessing the capacity  134 ,  116 . If the required capacity is greater than the actual capacity  118 , and the compressor is currently at maximum capacity  136 , system  40 ,  60  maintains current operating conditions  138  associated with compressor modulation loop  114  prior to returning to assess required versus actual capacity  116 . If the required capacity is not greater than the actual capacity  118 , and the required capacity is less than an actual capacity  144 , compressor modulation loop  114  determines if the compressor  44 ,  62  is at a minimum capacity  146  and, if not  148 , decreases the compressor capacity  149 , and system  40 ,  60  returns to the assessment of capacity being greater than actual capacity  116 . 
         [0021]    If compressor modulation loop  114  determines that the compressor is at a relative minimum capacity  150  associated with any given stage of operation associated with the compressor relative to the demand placed upon system  40 ,  60 , the control of systems  40 ,  60  proceed to an unloading valve operation loop  160  associated with manipulating the operation of the respective unloading valve  54 ,  96 . The respective unloading valve incrementally opens  162  such that unloading valve loop  160  can assess whether required capacity is less than an actual capacity  164 . If the required capacity is less than the actual capacity  166 , unloading valve loop  160  assesses an open condition of the valve  168  and, if the valve is not at a maximum open position  170 , loop  160  returns to increment opening of the unloading valve  162 . 
         [0022]    If the respective unloading valve is in fact all the way open  172 , indicating a full bypass condition, the operating conditions associated with modulation loop  114  and control valve loop  160  are maintained  174  and loop  160  returns to the assessment of the required capacity versus actual capacity  164  associated with operation of the respective system. If the required capacity is not less than the actual capacity  178 , loop  160  determines whether the required capacity is greater than the actual capacity  180  and, if not  182 , maintains the instantaneous operating conditions  184  prior to returning  185  to the assessments associated with compressor modulation loop  114 . If the required capacity is greater than the actual capacity  186 , unloading valve loop  160  assesses whether the unloading modulation valve  54 ,  96  is at a minimum open condition  188  and if not  190 , increments closing of the valve  192  prior to returning to the assessment of capacity  176 . If the required capacity is greater than the actual capacity  186 , and the unloading modulation valve is at a minimum open condition  190 , unloading valve loop  160  returns  194  to compressor modulation loop  114  to repeat the assessment associated with the operation of compressor modulation loop  114 . 
         [0023]    The operation of systems  40 ,  60  provides 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. 
         [0024]    During operation of systems  40 ,  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 systems  40 ,  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 systems  40 ,  60  or the discrete components or devices associated therewith. 
         [0025]    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. 
         [0026]    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. 
         [0027]    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. 
         [0028]    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.