Heat pump system

Abstract

A heat pump system includes a heat pump circuit, a heat load circuit, first and second heat exchangers, a flow rate adjustment element, and a controller. The heat pump circuit circulates primary refrigerant through a low and high stage-side compression elements, an expansion element and an evaporator. The heat load circuit circulates a first fluid and has a first and second branching portions, first and second branching channels, and a heat-load-processing section. The first and second heat exchangers perform heat exchange between the primary refrigerant and the first fluid. Flow rate of the first fluid in the first and/or second branching channel is adjustable. The controller performs flow rate adjustment control so as to maintain a state in which a predetermined temperature condition is satisfied, or to reduce a difference between the temperature of the first fluid flowing through portions of the first and second branching channels.

1 . A heat pump system comprising:
 a heat pump circuit configured to have a primary refrigerant circulated therethrough, the heat pump circuit including at least a low-stage-side compression element, a high-stage-side compression element, an expansion element, and an evaporator;   a first heat load circuit configured to have a first fluid circulated therethrough, the first heat load circuit having
 a first branching portion, 
 a second branching portion, 
 a first branching channel arranged to connect the first branching portion and the second branching portion, 
 a second branching channel arranged to connect the first branching portion and the second branching portion without merging with the first branching channel, and 
 a first heat-load-processing section; 
   a first heat exchanger arranged and configured to perform heat exchange between
 the primary refrigerant flowing from a discharge side of the low-stage-side compression element toward an intake side of the high-stage-side compression element and 
 the first fluid flowing through the first branching channel; 
   a second heat exchanger arranged and configured to perform heat exchange between
 the primary refrigerant flowing from the high-stage-side compression element toward the expansion element and 
 the first fluid flowing through the second branching channel; 
   a first flow rate adjustment element arranged and configured to adjust at least one of
 a flow rate of the first fluid in the first branching channel and the 
 a flow rate of the first fluid in the second branching channel; and 
   a controller configured to perform flow rate adjustment control of the first flow rate adjustment element so as to
 maintain a state in which a predetermined temperature condition is satisfied, including a case in which a ratio between temperature of the first fluid flowing through a portion of the first branching channel that has passed through the first heat exchanger and temperature of the first fluid flowing through a portion of the second branching channel that has passed through the second heat exchanger is 1, or 
 reduce a difference between the temperature of the first fluid flowing through a portion of the first branching channel that has passed through the first heat exchanger and the temperature of the first fluid flowing through a portion of the second branching channel that has passed through the second heat exchanger, 
   the heat pump circuit, the first heat load circuit, the first heat exchanger, the second heat exchanger, the first flow rate adjustment element and the controller being configured and arranged such that the first fluid cooled in the first heat load circuit and not yet warmed can be fed to the first heat exchanger and the second heat exchanger.   
     
     
         2 . The heat pump system according to  claim 1 , wherein
 the controller is further configured to control output of the low-stage-side compression element and the high-stage-side compression element so that   temperature of the primary refrigerant that flows into the first heat exchanger and temperature of the primary refrigerant that flows into the second heat exchanger both become a temperature equal to or greater than a first heat-load-corresponding temperature requested in the first heat-load-processing section, while causing
   the temperature of the primary refrigerant flowing to the first heat exchanger to become a temperature equal to or greater than the first fluid flowing to the first heat exchanger, and   the temperature of the primary refrigerant flowing to the second heat exchanger to become a temperature equal to or greater than the first fluid flowing to the second heat exchanger.   
   
     
     
         3 . The heat pump system according to  claim 2 , wherein
 the first heat load circuit further includes
 a first heat load bypass circuit arranged to connect a portion between the first heat-load-processing section and the first branching portion, and a portion between the first heat-load-processing section and the second branching portion; and 
 a first heat-load-bypass flow-rate-adjustment element arranged and configured to adjust a flow rate of the first fluid that passes through the first heat load bypass circuit; 
   the controller is further configured to perform a control in the flow rate adjustment control so that a target value of the temperature of the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger and a target value of the temperature of the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger become a temperature that exceeds the first heat-load-corresponding temperature; and   the controller is further configured to operate the first heat-load-bypass flow-rate-adjustment element and adjust the flow rate of the first fluid flowing through the first heat load bypass circuit so that the temperature of the first fluid fed to the first heat-load-processing section becomes the first heat-load-corresponding temperature.   
     
     
         4 . The heat pump system according to  claim 2 , wherein
 the controller is further configured to perform a control in the flow rate adjustment control so that a target value of the temperature of the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger and a target value of the temperature of the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger become the first heat-load-corresponding temperature.   
     
     
         5 . The heat pump system according to  claim 2 , wherein
 the controller is further configured to control at least one of the low-stage-side compression element, the high-stage-side compression element, and the expansion element in the flow rate adjustment control so as to:
 maintain a state in which a predetermined compression ratio condition is satisfied, including a case in which a ratio between compression ratio in the low-stage-side compression element and compression ratio in the high-stage-side compression element is 1, or 
 reduce a difference between the compression ratio in the low-stage-side compression element and the compression ratio in the high-stage-side compression element. 
   
     
     
         6 . The heat pump system according to  claim 5 , wherein
 the controller is further configured to perform a low-stage intake degree-of-superheat control in order to increase a degree of superheat of the primary refrigerant taken in by the low-stage-side compression element in a case where the discharge temperature of the primary refrigerant of the low-stage-side compression element increases when the flow rate adjustment control is performed.   
     
     
         7 . The heat pump system according to  claim 6 , wherein
 the heat pump circuit further includes a primary-refrigerant-to-primary-refrigerant heat exchanger arranged and configured to cause heat exchange to be performed between the primary refrigerant taken in by the low-stage-side compression element and the primary refrigerant that has passed through the second heat exchanger and then flows toward the expansion element; and   the controller is further configured to perform a the low-stage intake degree-of-superheat control using the primary-refrigerant-to-primary-refrigerant heat exchanger.   
     
     
         8 . The heat pump system according to  claim 5 , wherein the controller is further configured to perform a control during load reduction in order to reduce a degree of superheat of the primary refrigerant taken in by the low-stage-side compression element while reducing a target value of the discharge temperature of the primary refrigerant of the low-stage-side compression element in a case where the temperature of the first fluid flowing from the first heat-load-processing section toward the first heat exchanger and the second heat exchanger has increased when the flow rate adjustment control is performed. 
     
     
         9 . The heat pump system according to  claim 8 , further comprising:
 a second heat load circuit configured to have a second fluid circulated therethrough, the second heat load circuit having a second heat load section; and   a third heat exchanger arranged and configured to cause heat exchange to be performed between the second fluid circulating through the second heat load circuit and the primary refrigerant flowing from the high-stage-side compression element toward the second heat exchanger.   
     
     
         10 . The heat pump system according to  claim 9 , further comprising
 a fourth heat exchanger arranged and configured to cause heat exchange to be performed between
 the second fluid flowing from the second heat-load-processing section toward the third heat exchanger, among the second fluid that passes through the second heat load circuit, and 
 the primary refrigerant which has passed through the second heat exchanger and is thereafter flowing toward the expansion element. 
   
     
     
         11 . The heat pump system according to  claim 9 , wherein
 the controller is further configured to adjust a circulation amount of the second fluid circulating through the second heat load circuit so that the temperature of the primary refrigerant that passes through the third heat exchanger approximates a target value of the temperature of the primary refrigerant discharged by the low-stage-side compression element in a case where the target value of the temperature of the primary refrigerant discharged by the low-stage-side compression element is less than the target value of the temperature of the primary refrigerant discharged by the high-stage-side compression element.   
     
     
         12 . The heat pump system according to  claim 9 , wherein
 the second heat load processing section is a hot-water-supply tank; and   the second fluid is water used for hot-water supply.   
     
     
         13 . The heat pump system according to  claim 2 , wherein
 the controller is further configured to operate the first flow rate adjustment element in the flow rate adjustment control in order to reduce flow rate of the first fluid having a lower temperature of
 the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger; and 
 the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger. 
   
     
     
         14 . The heat pump system according to  claim 13 , wherein
 the first flow rate adjustment element arranged and configure to adjust a ratio between a flow rate of the first fluid flowing through the first branching channel and a flow rate of the first fluid flowing through the second branching channel; and   the controller is further configured to operate the first flow rate adjustment element in the flow rate adjustment control in order to reduce the flow rate ratio of the first fluid having a lower temperature of
 the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger; and 
 the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger, 
   while keeping constant a flow rate of the first fluid fed to the first heat-load-processing section.   
     
     
         15 . The heat pump system according to  claim 13 , wherein
 the first flow rate adjustment element is further arranged and configured to adjust a flow rate of the first fluid fed to the first heat-load-processing section; and   the controller is further configured, in the flow rate adjustment control, to reduce the flow rate of the first fluid fed to the first heat-load-processing section by operating the first flow rate adjustment element in a case where a flow rate ratio is low for the first fluid having a lower temperature of
 the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger; and 
 the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger. 
   
     
     
         16 . The heat pump system according to  claim 13 , wherein
 the first flow rate adjustment element includes
 a ratio adjustment section configured to adjust a ratio between a flow rate of the first fluid flowing through the first branching channel and a flow rate of the first fluid flowing through the second branching channel, and 
 a flow rate adjustment section configured to adjust a flow rate of the first fluid fed to the first heat-load-processing section; 
   the controller is further configured to operate the first flow rate adjustment element in the flow rate adjustment control in order to
 increase the flow rate of the first fluid having a temperature that exceeds the first heat-load-corresponding temperature and/or 
 reduce the flow rate of the first fluid having a temperature that is less than the first heat-load-corresponding temperature, 
   as determined from among the temperature of the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger and the temperature of the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger; and   the controller is further configured to reduce the flow rate of the first fluid fed to the first heat-load-processing section in proportion to the increase of the temperature of the first fluid fed to the first heat-load-processing section in a case where the temperature of the first fluid fed to the first heat-load-processing section has exceeded the first heat-load-corresponding temperature.   
     
     
         17 . The heat pump system according to  claim 1 , further comprising:
 a first branching channel temperature detector arranged and configured to ascertain temperature of the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger; and   a second branching channel temperature detector arranged and configured to ascertain temperature of the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger.   
     
     
         18 . The heat pump system according to  claim 1 , further comprising:
 a branching portion temperature detector arranged and configured to ascertain at least one of
 a temperature of the first fluid flowing through the portion of the first branching channel that has passed through the first heat exchanger and 
 a temperature of the first fluid flowing through the portion of the second branching channel that has passed through the second heat exchanger; and 
   a merging portion temperature detector arranged and configured to ascertain a temperature of the first fluid flowing toward the first heat-load-processing section after the first fluid which has passed through the first branching channel has merged with the first fluid which has passed through the second branching channel.   
     
     
         19 . The heat pump system according to  claim 1 , further comprising:
 a first branching channel flow rate detector arranged and configured to ascertain a flow rate of the first fluid flowing through the first branching channel; and   a second branching channel flow rate detector arranged and configured to ascertain a flow rate of the first fluid flowing through the second branching channel.   
     
     
         20 . The heat pump system according to  claim 1 , further comprising:
 a branching portion flow rate detector arranged and configured to ascertain at least one of a flow rate of the first fluid flowing through the first branching channel and a flow rate of the first fluid flowing through the second branching channel; and   a merging portion flow rate detector arranged and configured to ascertain a flow rate of the first fluid flowing toward the first heat-load-processing section after the first fluid flowing through the first branching channel and the first fluid flowing through the second branching channel have merged.   
     
     
         21 . The heat pump system according to  claim 1 , wherein
 the primary refrigerant flowing from the discharge side of the low-stage-side compression element toward the intake side of the high-stage-side compression element and the first fluid flowing through the first branching channel are in an opposing-flow relationship in the first heat exchanger; and   the primary refrigerant flowing from the high-stage-side compression element toward the expansion element and the first fluid flowing through the second branching channel are in an opposing-flow relationship in the second heat exchanger.   
     
     
         22 . The heat pump system according to  claim 1 , wherein
 the first heat-load-processing section is an air-warming heat exchanger used to warm air in a disposed target space; and   the first fluid is a secondary refrigerant.   
     
     
         23 . The heat pump system according to  claim 1 , wherein
 the low-stage-side compression element and the high-stage-side compression element utilize have a shared rotating shaft, which is rotatably driven such that compression work is performed.   
     
     
         24 . The heat pump system according to  claim 1 , wherein
 the controller is further configured to keep a discharge pressure of the high-stage-side compression element at a pressure that is equal to or greater than a critical pressure of the primary refrigerant in the flow rate adjustment control; and   the heat pump system is configured to be used in an environment in which ambient temperature of the first heat-load-processing section is a temperature equal to or less than a critical temperature of the primary refrigerant.   
     
     
         25 . The heat pump system according to  claim 1 , wherein
 the primary refrigerant is carbon dioxide.