Refrigerator and method of operating refrigeration system

Abstract

A refrigeration system 4 controlled by a control system 26 , wherein the refrigeration system 4 comprises: an evaporator 8 , a compressor 10 , a condenser 12 , and an expansion arrangement 15 . The control system 26 is adapted: to establish a momentary cooling requirement based on the differential between a set-point temperature and an actual temperature averaged over time, to form a requirement variable relating to the momentary cooling requirement, to fix a first duration during which the compressor is switched on and a second duration during which the compressor is switched off, and to switch on and to switch off the compressor according to the first and second durations. The refrigeration system 4 comprises a first shut-off valve 20 . The control system 4 is adapted: to close the first shut-off valve 20 in connection with switching off the compressor 10 , and to open the first shut-off valve 20 in connection with switching on the compressor 10.

1 . A method of operating a refrigeration system ( 4 ), wherein the refrigeration system ( 4 ) comprises:
 an evaporator ( 8 ) adapted to be arranged in thermal communication with a compartment ( 6 ) to be cooled, a compressor ( 10 ), a condenser ( 12 ), an expansion arrangement ( 15 ), and conduits interconnecting the evaporator ( 8 ), the compressor ( 10 ), the condenser ( 12 ) and the expansion arrangement ( 15 ), wherein the method comprises:
 establishing ( 100 ) a momentary cooling requirement of the compartment ( 6 ) based on the differential between a set-point temperature and an actual temperature averaged over time 
 forming ( 102 ) a requirement variable relating to the momentary cooling requirement, the requirement variable being a ratio between a switch-on duration of the compressor ( 10 ) and a switch-off duration of the compressor ( 10 ), 
 fixing ( 104 ) a first duration during which the compressor ( 10 ) is switched on and a second duration during which the compressor ( 10 ) is switched off on the basis of the requirement variable, and 
 switching on ( 106 ) and switching off ( 108 ) the compressor ( 10 ) according to the first and second durations, 
   characterized in that   the refrigeration system ( 4 ) comprises a first shut-off valve ( 20 ) arranged in a conduit extending between the condenser ( 12 ) and the evaporator ( 8 ), and in that the method comprises:
 closing ( 110 ) the first shut-off valve ( 20 ) in connection with switching off ( 108 ) the compressor ( 10 ), and 
 opening ( 112 ) the first shut-off valve ( 20 ) in connection with switching on ( 106 ) the compressor ( 10 ). 
   
     
     
         2 . The method according to  claim 1 , wherein the refrigeration system ( 4 ) comprises the compartment ( 6 ) and the compartment ( 6 ) is adapted for domestic foodstuff storing. 
     
     
         3 . The method according to  claim 1 , wherein the compressor ( 10 ) is a single speed compressor controlled by a control system to run at a constant speed during the first duration. 
     
     
         4 . The method according to  claim 3 , wherein the refrigeration system ( 4 ) further comprises a valve arrangement ( 32 ) in a conduit between the compressor ( 10 ) and the condenser ( 12 ), and
 a by-pass conduit ( 36 ) extending between an outlet side of the compressor ( 10 ) and an inlet side of the compressor ( 10 ), and wherein the method further comprises:
 equalizing ( 114 ) a pressure difference between the outlet side and the inlet side of the compressor ( 10 ) during the second duration. 
   
     
     
         5 . The method according to  claim 4 , wherein the valve arrangement ( 32 ) comprises a check valve ( 38 ) and wherein the refrigeration system ( 4 ) further comprises a second shut-off valve ( 40 ) arranged in the by-pass conduit ( 36 ), and wherein the method further comprises:
 maintaining ( 118 ) the second shut-off valve ( 40 ) closed during the first duration, and   opening ( 116 ) the second shut-off valve ( 40 ) during the second duration to achieve said equalizing ( 114 ) the pressure difference.   
     
     
         6 . The method according to  claim 4 , wherein the valve arrangement ( 32 ) comprises a 3-way valve ( 42 ), the 3-way valve ( 42 ) being connected to the by-pass conduit ( 36 ), and wherein said equalizing ( 114 ) the pressure difference includes:
 opening ( 120 ) a connection between the outlet side of the compressor ( 10 ) and the by-pass conduit ( 36 ) and closing ( 122 ) a connection between the compressor ( 10 ) and the condenser ( 12 ) by means of the 3-way valve ( 42 ), and wherein the method further comprises:   closing ( 124 ) the connection between the outlet side of the compressor ( 10 ) and the by-pass conduit ( 36 ) and opening ( 126 ) the connection between the compressor ( 10 ) and the condenser ( 12 ) by means of the 3-way valve ( 42 ) during the first duration.   
     
     
         7 . The method according to any one of the preceding  claim 1 , wherein the expansion arrangement ( 15 ) comprises a capillary tube ( 16 ). 
     
     
         8 . The method according to  claim 1 , wherein the first shut-off valve ( 20 ) forms part of the expansion arrangement ( 15 ). 
     
     
         9 . The method according to  claim 1 , wherein the first duration and the second duration collectively have a length of between 1-100 minutes. 
     
     
         10 . The method according to  claim 1 , wherein the compressor ( 10 ) is adapted to provide a cooling capacity of between 10-500 W according to ASHRAE LBP or HMBP standard. 
     
     
         11 . A refrigerator comprising a compartment ( 6 ) cooled by a refrigeration system ( 4 ) controlled by a control system ( 26 ), wherein the refrigeration system ( 4 ) comprises: an evaporator ( 8 ) arranged in thermal communication with the compartment ( 6 ), a compressor ( 10 ), a condenser ( 12 ), an expansion arrangement ( 15 ), and conduits interconnecting the evaporator ( 8 ), the compressor ( 10 ), the condenser ( 12 ) and the expansion arrangement ( 15 ), and wherein the control system ( 26 ) is adapted:
 to establish a momentary cooling requirement of the compartment ( 6 ) based on the differential between a set-point temperature and an actual temperature averaged over time,   to form a requirement variable relating to the momentary cooling requirement, the requirement variable being a ratio between a switch-on duration of the compressor ( 10 ) and a switch-off duration of the compressor ( 10 ),   to fix a first duration during which the compressor ( 10 ) is switched on and a second duration during which the compressor ( 10 ) is switched off on the basis of the requirement variable, and   to switch on and to switch off the compressor ( 10 ) according to the first and second durations,   characterized in that   the refrigeration system ( 4 ) comprises a first shut-off valve ( 20 ) arranged in a conduit extending between the condenser ( 12 ) and the evaporator ( 8 ), and in that the control system ( 26 ) is further adapted:
 to close the first shut-off valve ( 20 ) in connection with switching off the compressor ( 10 ), and 
 to open the first shut-off valve ( 20 ) in connection with switching on the compressor ( 10 ). 
   
     
     
         12 . The refrigerator according to  claim 11 , wherein the compartment ( 6 ) is adapted for domestic foodstuff storing. 
     
     
         13 . The refrigerator according to  claim 11  wherein the compressor ( 10 ) is a single speed compressor controlled by the control system ( 26 ) to run at a constant speed during the first duration. 
     
     
         14 . The refrigerator according to  claim 13 , wherein the refrigeration system ( 4 ) further comprises a valve arrangement ( 32 ) in a conduit between the compressor ( 10 ) and the condenser ( 12 ), and a by-pass conduit ( 36 ) extending between an outlet side of the compressor ( 10 ) and an inlet side of the compressor ( 10 ). 
     
     
         15 . The refrigerator according to  claim 14 , wherein the valve arrangement ( 32 )
 comprises a check valve ( 38 ) and the refrigeration system ( 4 ) further comprises a second shut-off valve ( 40 ) arranged in the by-pass conduit ( 36 ), and wherein the control system ( 26 ) is adapted:
 to maintain the second shut-off valve ( 40 ) closed during the first duration, and 
 to open the second shut-off valve ( 40 ) during the second duration to equalize a pressure difference between the outlet side and the inlet side of the compressor ( 10 ) during the second duration. 
   
     
     
         16 . The refrigerator according to  claim 14 , wherein the valve arrangement ( 32 ) comprises a 3-way valve ( 42 ), the 3-way valve ( 42 ) being connected to the by-pass conduit ( 36 ), and wherein the control system ( 26 ) is adapted:
 to open a connection between the outlet side of the compressor ( 10 ) and the bypass conduit ( 36 ) and to close a connection between the compressor ( 10 ) and the condenser ( 12 ), by means of the 3-way valve ( 42 ) during the second duration, and   to close the connection between the outlet side of the compressor ( 10 ) and the bypass conduit ( 36 ) and to open the connection between the compressor ( 10 ) and the condenser ( 12 ), by means of the 3-way valve ( 42 ) during the first duration.   
     
     
         17 . The refrigerator according to  claim 11  wherein the compressor ( 10 ) is a variable speed compressor controlled by the control system ( 26 ) to run at variable speed during the first duration. 
     
     
         18 . The refrigerator according to  claim 11 , wherein the expansion arrangement ( 15 ) comprises a capillary tube ( 16 ). 
     
     
         19 . The refrigerator according to  claim 11 , wherein the first shut-off valve ( 20 ) forms part of the expansion arrangement ( 15 ). 
     
     
         20 . The refrigerator according to  claim 11 , where the refrigeration system ( 4 ) comprises a filter ( 14 ) arranged in a conduit between the condenser ( 12 ) and the expansion arrangement ( 15 ). 
     
     
         21 . The refrigerator according to  claim 20 , wherein the first shut-off valve ( 20 ) is arranged in a conduit between the filter ( 14 ) and the expansion arrangement ( 15 ).