Heat pump unit and the control method thereof

Abstract

A heat pump unit and methods for operating the heat pump unit are provided. The heat pump unit includes a compressor ( 101 ), a throttling device ( 107 ), a first heat exchanger ( 104 ), a second heat exchanger ( 102 ), a third heat exchanger ( 103 ) and a mid-pressure tank ( 110 ). The heat pump unit operates in multiple run modes and switches between the run modes without shutdown. The first heat exchanger or the second heat exchanger is capable of acting as a condenser in the multiple run modes. When switching from a pre-switching run mode to a post-switching run mode, a control device determines whether to perform a pressure release operation to the first heat exchanger or the second heat exchanger.

1 . A heat pump unit, comprising:
 a compressor having a suction end and an exhaust end;   a throttling device having an inlet end and an outlet end;   a first heat exchanger, a second heat exchanger and a third heat exchanger, the first heat exchanger having a first port and a second port, the second heat exchanger having a first port and a second port, and the third heat exchanger having a first port and a second port; and   a mid-pressure tank being provided with a mid-pressure tank first inlet;   wherein the first port of the first heat exchanger and the first port of the second heat exchanger are controllably fluidly connected to the suction end of the compressor, and controllably fluidly connected to the exhaust end of the compressor, and wherein the first port of the third heat exchanger is fluidly connected to the suction end of the compressor; and   wherein the second port of the first heat exchanger and the second port of the second heat exchanger are controllably fluidly connected to the inlet end of the throttling device, controllably fluidly connected to the outlet end of the throttling device, and controllably fluidly connected to the mid-pressure tank first inlet, and wherein the second port of the third heat exchanger is controllably fluidly connected to the outlet end of the throttling device.   
     
     
         2 . The heat pump unit of  claim 1 , further comprising:
 a four-way valve having a first interface, a second interface, a third interface, and a fourth interface;   wherein the first port of the first heat exchanger is connected to the second interface of the four-way valve, the first port of the second heat exchanger is connected to the fourth interface of the four-way valve, the suction end of the compressor is connected to the first interface of the four-way valve and the exhaust end of the compressor is connected to the third interface of the four-way valve.   
     
     
         3 . The heat pump unit of  claim 2 , further comprising:
 a throttling-device-inlet-side control valve group including a first valve and a second valve, wherein the second port of the first heat exchanger and the second port of the second heat exchanger are controllably fluidly connected to the inlet end of the throttling device via the first valve and the second valve of the throttling-device-inlet-side control valve group, respectively; and   a throttling-device-outlet-side control valve group including a first valve, a second valve and a third valve, wherein the second port of the first heat exchanger and the second port of the second heat exchanger are controllably fluidly connected to the outlet end of the throttling device via the first valve and the second valve of the throttling-device-outlet-side control valve group, respectively, and wherein the second port of the third heat exchanger is controllably fluidly connected to the outlet end of the throttling device via the third valve of the throttling-device-outlet-side control valve group.   
     
     
         4 . The heat pump unit of  claim 3 , wherein:
 the mid-pressure tank is provided with a mid-pressure tank first outlet, the mid-pressure tank first outlet is controllably fluidly connected to the outlet end of the throttling device; and   the heat pump unit further comprises:
 a mid-pressure tank first inlet control valve group comprising a first valve and a second valve, wherein the second port of the first heat exchanger and the second port of the second heat exchanger are controllably fluidly connected to the mid-pressure tank first inlet via the first valve and the second valve of the mid-pressure tank first inlet control valve group, respectively; and 
 a mid-pressure tank first outlet control valve wherein the mid-pressure tank first outlet is controllably fluidly connected to the outlet end of the throttling device via the mid-pressure tank first outlet control valve. 
   
     
     
         5 . The heat pump unit of  claim 4 , further comprising:
 a mid-pressure tank pressure-increasing control valve and a mid-pressure tank pressure-reducing control valve;   wherein the mid-pressure tank is provided with a mid-pressure tank second inlet and a mid-pressure tank second outlet; and   wherein the mid-pressure tank second inlet is connected to the fluid path between the exhaust end of the compressor and the four-way valve via the mid-pressure tank pressure-increasing control valve, and the mid-pressure tank second outlet is connected to the suction end of the compressor via the mid-pressure tank pressure-reducing control valve.   
     
     
         6 . The heat pump unit of  claim 4 , wherein the mid-pressure tank first inlet control valve group further comprises a first one-way valve and a second one-way valve, wherein the first one-way valve is connected between the first valve of the mid-pressure tank first inlet control valve group and the mid-pressure tank first inlet, and the second one-way valve is connected between the second valve of the mid-pressure tank first inlet control valve group and the mid-pressure tank first inlet. 
     
     
         7 . The heat pump unit of  claim 5 , wherein the first valve and the second valve of the throttling-device-inlet-side control valve group are one-way valves. 
     
     
         8 . The heat pump unit of  claim 7 , further comprising a control device wherein the four-way valve the throttling-device-outlet-side control valve group, the mid-pressure tank first inlet control valve group, the mid-pressure tank first outlet control valve, the mid-pressure tank pressure-increasing control valve and the mid-pressure tank pressure-reducing control valve are connected to and controlled by the control device. 
     
     
         9 . The heat pump unit of  claim 1 , wherein the first heat exchanger and the third heat exchanger are connected to a first water supply and return pipe and a second water supply and return pipe, respectively. 
     
     
         10 . The heat pump unit of  claim 1 , wherein:
 the heat pump unit is configured such that said heat pump unit is capable of running in multiple modes and being switched between the multiple modes by controlling the flow path of the refrigerant through the compressor, the throttling device, the first heat exchanger, the second heat exchanger and the third heat exchanger; and   the high-pressure refrigerant from any of the first heat exchanger and the second heat exchanger which needs pressure release at the time of mode switching can be received by the mid-pressure tank.   
     
     
         11 . A method for controlling a heat pump unit, the heat pump unit comprising a compressor, a throttling device, a first heat exchanger, a second heat exchanger, a third heat exchanger, and a mid-pressure tank wherein the heat pump unit is capable of running in multiple modes and the first heat exchanger or the second heat exchanger is capable of acting as a condenser in the multiple modes, the method comprising:
 determining whether it is desired to perform a pressure release operation to the first heat exchanger or the second heat exchanger when it is desired to switch the run mode of the heat pump unit from a pre-switching run mode to a post-switching run mode; and   maintaining the pre-switching run mode and performing a first operation responsive to a determination that it is desired to perform the pressure release operation to the first heat exchanger, wherein the first operation comprises fluidly connecting the first heat exchanger to a first inlet of the mid-pressure tank so as to discharge the refrigerant from the first heat exchanger to the mid-pressure tank; or   maintaining the pre-switching run mode and performing a second operation responsive to a determination that it is desired to perform the pressure release operation to the second heat exchanger, wherein the second operation comprises fluidly connecting the second heat exchanger to the first inlet of the mid-pressure tank so as to discharge the refrigerant from the second heat exchanger to the mid-pressure tank.   
     
     
         12 . The method of  claim 11 , further comprising:
 performing a third operation, wherein the third operation comprises disconnecting the first heat exchanger from the first inlet of the mid-pressure tank after a first predetermined amount of time has elapsed since the first operation is performed; or   performing a fourth operation, wherein the fourth operation comprises disconnecting the second heat exchanger from the first inlet of the mid-pressure tank after a second predetermined amount of time has elapsed since the second operation is performed.   
     
     
         13 . The method of  claim 12 , further comprising starting the post-switching run mode and ending the pre-switching run mode after the third operation or the fourth operation is performed. 
     
     
         14 . The method of  claim 11 , further comprising:
 Performing a fifth operation responsive to a determination that it is desired to supplement refrigerant to the refrigerant circulation loop of the post-switching run mode after the post-switching run mode is started, wherein the fifth operation comprises fluidly connecting a first outlet of the mid-pressure tank to an outlet end of the throttling device.   
     
     
         15 . The method of  claim 14 , further comprising:
 fluidly connecting a second inlet of the mid-pressure tank to an exhaust end of the compressor so as to increase the pressure in the mid-pressure tank responsive to a determination that the pressure in the mid-pressure tank is below a first predetermined pressure value during the fifth operation.   
     
     
         16 . The method of  claim 11 , further comprising:
 fluidly connecting a second outlet of the mid-pressure tank to a suction end of the compressor so as to reduce the pressure in the mid-pressure tank responsive to a determination that the pressure in the mid-pressure tank is above a second predetermined pressure value during the first operation or the second operation.   
     
     
         17 . The method of  claim 11 , wherein the step of determining whether it is desired to perform a pressure release operation to the first heat exchanger or the second heat exchanger comprises:
 determining that it is desired to perform the pressure release operation to the first heat exchanger or the second heat exchanger when the first heat exchanger or the second heat exchanger acting as a condenser in the pre-switching run mode does not act as a condenser in the post-switching run mode.   
     
     
         18 . The method of  claim 17 , wherein:
 the multiple modes comprise a cooling only mode, a heating only mode, a cooling plus heating mode, and a defrosting mode; and   the first heat exchanger and the third heat exchanger are connected to a first water supply and return pipe and a second water supply and return pipe, respectively.   
     
     
         19 . The method of  claim 18 , wherein:
 the compressor, the throttling device, the second heat exchanger and the third heat exchanger are in a refrigerant circulation loop when the heat pump unit runs in the cooling only mode, wherein the second heat exchanger acts as a condenser in the cooling only mode;   the compressor, the throttling device, the first heat exchanger and the second heat exchanger are in a refrigerant circulation loop when the heat pump unit runs in the heating only mode, wherein the first heat exchanger acts as a condenser in the heating only mode;   the compressor, the throttling device, the first heat exchanger and the third heat exchanger are in a refrigerant circulation loop when the heat pump unit runs in the cooling plus heating mode, wherein the first heat exchanger acts as a condenser in the cooling plus heating mode; and   the compressor, the throttling device, the first heat exchanger and the second heat exchanger are in a refrigerant circulation loop when the heat pump unit runs in the defrosting mode, wherein the second heat exchanger acts as a condenser in the defrosting mode.   
     
     
         20 . The method of  claim 19 , wherein determining whether it is desired to perform a pressure release operation to the first heat exchanger or the second heat exchanger comprises:
 determining that it is desired to perform the pressure release operation to the second heat exchanger when the pre-switching run mode is the cooling only mode while the post-switching run mode is the heating only mode or the cooling plus heating mode;   determining that it is desired to perform the pressure release operation to the first heat exchanger when the pre-switching run mode is the heating only mode while the post-switching run mode is the cooling only mode or the defrosting mode;   determining that it is desired to perform the pressure release operation to the first heat exchanger when the pre-switching run mode is the cooling plus heating mode while the post-switching run mode is the cooling only mode; or   determining that it is desired to perform the pressure release operation to the second heat exchanger when the pre-switching run mode is the defrosting mode while the post-switching run mode is the heating only mode.