Methods and systems for compressor operation

Abstract

There is provided a refrigeration system ( 10 ) comprising a compressor ( 12 ) having a suction ( 11 ) and a discharge ( 13 ), a heat rejecting heat exchanger. ( 14 ), an expansion valve ( 16 ), and a heat accepting heat exchanger ( 18 ). Preferably the system ( 10 ) comprises any one or more of: a pressure equalisation valve ( 4 O 3 42 ) for equalising the pressure differential between the compressor suction ( 11 ) and compressor discharge ( 13 ); a liquid valve ( 44 ), preferably a liquid solenoid valve or an electronic expansion valve, the liquid. valve ( 44 ) arranged in a flow line ( 24 ) between the heat rejecting heat exchanger ( 14 ) and the expansion valve ( 16 ); and a check valve ( 46 ), preferably a solenoid valve or an electronic expansion valve, arranged in a flow line ( 22 ) between the heat rejecting heat exchanger ( 14 ) and the compressor ( 12 ). The valves ( 40, 42, 44, 46 ) are operated in a variety of manners upon compressor shutdown and startup to avoid damage to the components of the compressor ( 12 ). Preferably the system further comprises means for heating at least one component of the compressor ( 12 ) and preferably also control means for activating the heating means when appropriate, such as when compressor startup is required, and starting the compressor after heating.

1 . A refrigeration system comprising:
 a compressor having a suction and a discharge;   a heat rejecting heat exchanger;   an expansion valve;   a heat accepting heat exchanger; and   a pressure equalisation valve for equalising the pressure differential between the compressor suction and compressor discharge.   
     
     
         2 . A refrigeration system as recited in  claim 1 , wherein the pressure equalization valve comprises a bypass passage connecting the compressor, suction to the compressor discharge to enable the compressor to be bypassed and a valve to control flow of refrigerant therethrough. 
     
     
         3 . A refrigeration system as recited in  claim 1 , further comprising: a liquid valve, preferably a liquid solenoid valve, arranged in a flow line between the heat rejecting heat exchanger and the expansion valve. 
     
     
         4 . A refrigeration system as recited in  claim 1 , further comprising:
 control for operating the system in at least one of a plurality of predetermined sequences; and   at least one sensor, wherein the control operates the system in a particular one of the plurality of predetermined sequences based on at least one parameter of the system measured by the sensor.   
     
     
         5 . (canceled) 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . (canceled) 
     
     
         9 . (canceled) 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . (canceled) 
     
     
         13 . A method of optimizing startup of a compressor of a refrigeration system comprising the steps of:
 providing a refrigeration system comprising a compressor, a heat rejecting heat exchanger, an expansion valve, a heat accepting heat exchanger, and a pressure equalisation valve that connects a suction and a discharge of the compressor for equalising the pressure differential between the compressor suction and compressor discharge;   preheating at least one component of the compressor;   opening the pressure equalisation valve to thereby reduce the pressure differential between the compressor suction and discharge; and   starting the compressor, preferably at substantially the same time as opening the pressure equalisation valve.   
     
     
         14 . A method as recited in  claim 13 , wherein the step of starting the compressor comprises operating the compressor at a predetermined frequency f 1  that is less than the operating frequency f n  of the compressor during normal operating conditions of the system. 
     
     
         15 . A method as recited in  claim 14 , further comprising the steps of:
 providing a liquid valve in a refrigerant flow path between the heat rejecting heat exchanger and the expansion valve;   opening the liquid valve in response to a first event;   closing the pressure equalization valve in response to a second event; and increasing the operating frequency of the compressor.   
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . A method as recited in  claim 13  further comprising the steps of:
 providing at least one system sensor and measuring at least one parameter of the system with the sensor; and 
 operating the system in at least one of a plurality of predetermined sequences based on the at least one parameter measured by the sensor. 
 
     
     
         19 . A method as recited in  claim 13 , wherein the compressor has a compressor body, a compressor motor and oil in the compressor and the step of preheating at least one component of the compressor comprises the step of:
 heating at least one of the compressor body, the oil in the compressor, and the compressor motor when it is determined that compressor startup is required.   
     
     
         20 . (canceled) 
     
     
         21 . A method as recited in  claim 19 , further comprising the steps of:
 providing at least one sensor;   measuring at least one parameter of the system with the sensor; and   heating the at least one component of the compressor for a predetermined period of time based on the at least one parameter.   
     
     
         22 . A method as recited in  claim 21 , wherein the predetermined period is based on at least one of a temperature of the oil in the compressor, a compressor shell temperature, a compressor discharge temperature, an ambient temperature and a length of time for which the compressor has been inactive. 
     
     
         23 . A method as recited in  claim 13 , further comprising the step of:
 measuring the temperature of oil in the compressor;   determining the saturated discharge temperature of refrigerant in the compressor; and   heating at least one component of the compressor such that the oil is maintained at a temperature above the saturated discharge temperature.   
     
     
         24 . A refrigeration system comprising:
 a compressor;   a heat rejecting heat exchanger;   an expansion valve;   a heat accepting heat exchanger;   a liquid valve, preferably a liquid solenoid valve or an electronic expansion valve, the liquid valve arranged in a flow line between the heat rejecting heat exchanger and the expansion valve; and   a check valve, preferably a solenoid valve or an electronic expansion valve, arranged in a flow line between the heat rejecting heat exchanger and the compressor.   
     
     
         25 . A system as recited in  claim 24 , wherein the check valve is configured such that a pressure differential between an inlet of the valve and an outlet of the valve opens the check valve. 
     
     
         26 . (canceled) 
     
     
         27 . A system as recited in  claim 25 , wherein the check valve comprises resilient means, preferably a spring or the like, that biases the valve into a closed position when the pressure at the inlet and the outlet of the check valve is balanced. 
     
     
         28 . (canceled) 
     
     
         29 . A method of controlling a refrigeration system comprising the steps of: providing a refrigeration system comprising a compressor, a heat rejecting heat exchanger, an expansion valve, a heat accepting heat exchanger, a liquid valve between the heat rejecting heat exchanger and the expansion valve, and a check valve between the heat rejecting heat exchanger and the compressor;
 initiating shutdown of the compressor;   closing the check valve and the liquid valve, preferably substantially simultaneously with shutdown of the compressor.   
     
     
         30 . (canceled) 
     
     
         31 . A method as recited in  claim 29 , wherein the liquid valve and the check valve comprise solenoid valves and the step of closing the check valve and the liquid valve comprises activating the solenoid valve(s). 
     
     
         32 . A method as recited in  claim 29   31 , further comprising the steps of:
 starting the compressor thereby causing a pressure differential between the condenser and the compressor and opening the check valve provided in the flow line therebetween; and   opening the liquid valve.   
     
     
         33 . (canceled) 
     
     
         34 . (canceled) 
     
     
         35 . A method of controlling a refrigeration system comprising the steps of:
 providing a refrigeration system comprising a compressor, a heat rejecting heat exchanger, an expansion valve, a heat accepting heat exchanger, and a pressure equalization valve that connects a suction and a discharge of the compressor for equalizing the pressure differential between the compressor suction and compressor discharge;   initiating shutdown of the compressor; and   opening the pressure equalization valve for equalizing the pressure differential between the compressor suction and discharge.   
     
     
         36 . A method as recited in  claim 35 , wherein the step of opening the pressure equalization valve comprises opening the valve as or substantially immediately after compressor shutdown is effected.