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