CO
A refrigeration system having a primary receiver, a secondary receiver, a first gas bypass valve, and second gas bypass valve, a feed control valve, and a controller. The primary receiver has a primary receiver operating pressure and is configured to collect a refrigerant circulated by the refrigeration system. The secondary receiver includes a liquid refrigerant inlet fluidly coupled to a primary receiver liquid refrigerant outlet. The feed control valve is coupled between the primary receiver liquid outlet and the secondary receiver liquid refrigerant inlet. The controller operates the feed control valve to control a flow of a liquid refrigerant from the primary receiver to the secondary receiver.
1 . A refrigeration system, comprising:
a primary receiver having a primary receiver operating pressure and configured to collect a refrigerant circulated by the refrigeration system and comprising:
a primary receiver inlet through which the refrigerant enters the primary receiver;
a primary receiver gas outlet through which a gas refrigerant exits the primary receiver to a first suction line of one or more first compressors in a first set of compressors;
a first primary receiver liquid refrigerant outlet through which at least part of a liquid refrigerant exits the primary receiver; and
a second primary receiver liquid refrigerant outlet;
a secondary receiver having a secondary receiver operating pressure that is less than the primary receiver operating pressure, the secondary receiver comprising:
a liquid refrigerant inlet fluidly coupled to the primary receiver and configured to receive the at least part of the liquid refrigerant from the primary receiver; and
a secondary receiver gas outlet through which a second gas refrigerant exits the secondary receiver to a second suction line fluidly coupled to one or more second compressors in the first set of compressors and fluidly decoupled from the first suction line, the one or more second compressors of the first set of compressors operating in parallel with the one or more first compressors of the first set of compressors;
a first gas bypass valve fluidly coupled to the primary receiver gas outlet and operable to control a flow of the gas refrigerant from the primary receiver through the first gas bypass valve and to the one or more first compressors in the first set of compressors through the first suction line;
a second gas bypass valve fluidly coupled to the secondary receiver gas outlet and operable to control a flow of the second gas refrigerant from the secondary receiver through the second gas bypass valve and to the one or more second compressors of the first set of compressors through the second suction line;
one or more first evaporators comprising a first group of evaporators and a second group of evaporators, the second group of evaporators comprising a group of low temperature (LT) evaporators, and the primary receiver is configured to direct another part of the liquid refrigerant to the first group of evaporators, and the secondary receiver is configured to direct at least a portion of the at least part of the liquid refrigerant to the second group of evaporators;
one or more second evaporators configured to operate at a different pressure than the one or more first evaporators, the one or more second evaporators fluidly coupled with and configured to direct part of the refrigerant to the one or more second compressors operating in parallel, the one or more second compressors configured to operate in a transcritical state, the secondary receiver comprising a secondary receiver liquid refrigerant outlet through which a part of the liquid refrigerant exits to the one or more second evaporators;
a feed control valve coupled between the primary receiver liquid outlet and the liquid refrigerant inlet of the secondary receiver; and
a controller configured to operate the feed control valve to control a flow of the at least part of the liquid refrigerant from the primary receiver to the secondary receiver.
2 . The refrigeration system of claim 1 , wherein:
the receiver operating pressure in the primary receiver is between 60 bar and about 90 bar; and
the receiver operating pressure in the secondary receiver is less than 60 bar.
3 . The refrigeration system of claim 1 , wherein the controller is configured to operate the feed control valve to maintain a level of the liquid refrigerant in the secondary receiver at a setpoint.
4 . The refrigeration system of claim 1 , wherein the controller is configured to operate the feed control valve to maintain a level of the liquid refrigerant in the secondary receiver within a predetermined range.
5 . The refrigeration system of claim 1 , wherein the controller is configured to maintain a level of the liquid refrigerant in the primary receiver at or above a minimum level.
6 . The refrigeration system of claim 1 , wherein the controller is configured to maintain a level of the liquid refrigerant in the primary receiver at or above a minimum level and a level of the liquid refrigerant in the secondary receiver at or above a minimum level.
7 . The refrigeration system of claim 1 , wherein the feed control valve comprises a pressure regulator valve.
8 . The refrigeration system of claim 1 , wherein the feed control valve comprises a solenoid valve.
9 . The refrigeration system of claim 1 , wherein the one or more first compressors comprise a first group of transcritical compressors fluidly coupled to the primary receiver gas outlet, and the one or more second compressors comprise a second group of transcritical compressors fluidly coupled to the secondary receiver gas outlet.
10 . The refrigeration system of claim 1 , wherein the refrigeration system comprises a first subsystem and a second subsystem, wherein the first subsystem receives the liquid refrigerant from the primary receiver, wherein the second subsystem receives the liquid refrigerant from the secondary receiver.
11 . The refrigeration system of claim 1 , wherein:
the refrigeration system further comprises a medium temperature (MT) subsystem configured to receive the liquid refrigerant from the secondary receiver, the first set of compressors is a set of MT compressors configured to operate in a transcritical state, and
the MT subsystem comprises the set of MT compressors, the one or more second evaporators, and one or more MT expansion valves.
12 . The refrigeration system of claim 1 , wherein:
the refrigeration system further comprises a low temperature (LT) subsystem configured to receive the liquid refrigerant from the secondary receiver; and
the LT subsystem comprises one or more LT compressors configured to operate in a subcritical state, the group of LT evaporators, and one or more LT expansion valves.
13 . The refrigeration system of claim 1 , wherein the refrigeration system further comprises:
an LT subsystem and an MT subsystem each configured to receive the liquid refrigerant from the secondary receiver; and
a primary subsystem configured to receive the liquid refrigerant from the primary receiver.
14 . The refrigeration system of claim 1 , further comprising an ejector fluidly coupled between a gas cooler of the refrigeration system and the primary receiver.
15 . The refrigeration system of claim 1 , further comprising one or more subcritical compressors operating in series with the first set of compressors that operate in parallel.
16 . The refrigeration system of claim 1 , further comprising an additional receiver configured to receive the liquid refrigerant from the secondary receiver.
17 . The refrigeration system of claim 1 , wherein the refrigerant is carbon dioxide.
18 . The refrigeration system of claim 1 , wherein the first set of compressors comprises medium temperature (MT) compressors configured to operate in a transcritical state, the refrigeration system further comprises one or more low temperature (LT) compressors configured to operate in a subcritical state, the primary receiver gas outlet of the primary receiver is fluidly coupled with the MT compressors, and the second primary receiver liquid refrigerant outlet of the primary receiver is fluidly coupled with the first group of evaporators.
19 . The refrigeration system of claim 13 , wherein the primary subsystem comprises an air-conditioning system.
20 . The refrigeration system of claim 13 , wherein the primary subsystem comprises a process cooling loop.
21 . The refrigeration system of claim 18 , wherein the LT compressors are fluidly coupled with and configured to direct gas refrigerant to the one or more second compressors operating in parallel.
22 . The refrigeration system of claim 18 , wherein the secondary receiver is fluidly coupled with and configured to direct refrigerant to the MT compressors, MT evaporators, and the LT evaporators.
23 . A refrigeration system, comprising:
two or more receivers configured to collect refrigerant circulated by the refrigeration system, a first one of the receivers comprising a first gas outlet through which a gas refrigerant exits the first one of the receivers to a first suction line of one or more first compressors in a first set of compressors, and a second one of the receivers comprising a second gas outlet through which the gas refrigerant exits the second one of the receivers to a second suction line of one or more second compressors in the first set of compressors, the one or more second compressors of the first set of compressors operating in parallel with the one or more first compressors of the first set of compressors;
a liquid refrigerant feed line between a first liquid refrigerant outlet of the first one of the receivers and a liquid refrigerant inlet of the second one of the receivers having a receiver operating pressure lower than a receiver operating pressure of the first one of the receivers;
one or more first evaporators comprising a first group of evaporators and a second group of evaporators, the second group of evaporators comprising a group of low temperature (LT) evaporators, and the first one of the receivers is configured to direct a first liquid refrigerant to the first group of evaporators, and the second one of the receivers is configured to direct a second liquid refrigerant to the second group of evaporators;
a fluid conduit fluidly connecting a second liquid refrigerant outlet of the first one of the receivers with the first group of evaporators of the one or more first evaporators;
one or more second evaporators configured to operate at a different pressure than the one or more first evaporators, the one or more second evaporators fluidly coupled with and configured to direct part of the gas refrigerant to the one or more second compressors operating in parallel, the one or more second compressors configured to operate in a transcritical state, the second one of the receivers comprising a secondary receiver liquid refrigerant outlet through which a part of the second liquid refrigerant exits to the one or more second evaporators;
one or more feed control valves in the liquid refrigerant feed line; and
a controller configured to operate the feed control valves to control a level of the liquid refrigerant in at least the second one of the receivers.
24 . The refrigeration system of claim 23 , wherein:
the two or more receivers comprise a primary receiver, a secondary receiver, and a tertiary receiver,
the secondary receiver receives a flow of the liquid refrigerant from the primary receiver and has a secondary receiver operating pressure that is lower than the primary receiver operating pressure,
the tertiary receiver receives a flow of the liquid refrigerant from the secondary receiver and has a tertiary receiver operating pressure that is lower than the secondary receiver operating pressure.
25 . The refrigeration system of claim 23 , wherein the refrigerant is carbon dioxide.
26 . A method for operating a refrigeration system, the method comprising:
collecting a refrigerant circulated by the refrigeration system within a primary receiver having a primary receiver operating pressure, the primary receiver comprising a primary receiver gas outlet through which a gas refrigerant exits the primary receiver to a first suction line of one or more first compressors in a first set of compressors, the primary receiver comprising a first liquid refrigerant outlet through which at least part of a liquid refrigerant exits the primary receiver, and a second liquid refrigerant outlet through which another part of the liquid refrigerant exits the primary receiver to one or more first evaporators;
providing the at least part of the liquid refrigerant from the primary receiver to a secondary receiver having a secondary receiver operating pressure that is lower than the primary operating pressure;
operating a first gas bypass valve fluidly coupled to the primary receiver gas outlet to control a flow of the gas refrigerant from the primary receiver through the first gas bypass valve and to the first suction line;
operating a second gas bypass valve fluidly coupled to a secondary receiver gas outlet to control a flow of the gas refrigerant from the secondary receiver through the second gas bypass valve and to a second suction line of one or more second compressors in the first set of compressors;
operating a feed control valve to control a flow of the at least part of the liquid refrigerant from the primary receiver to the secondary receiver; and
operating the one or more first compressors in parallel with the one or more second compressors;
wherein the refrigeration system further comprises one or more expansion valves and one or more second evaporators configured to operate at a different pressure than the one or more first evaporators, the one or more second evaporators fluidly coupled with the one or more expansion valves and the one or more second compressors operating in parallel, the secondary receiver comprising a secondary receiver liquid refrigerant outlet through which at least a second part of the liquid refrigerant exits to the one or more expansion valves, and the method further comprises operating the one or more expansion valves to expand the second part of the liquid refrigerant received from the secondary receiver liquid refrigerant outlet, and direct the expanded refrigerant to the one or more second evaporators, and the method further comprises providing the another part of the liquid refrigerant from the primary receiver to a first group of evaporators of the one or more first evaporators, and providing a third part of the liquid refrigerant from the secondary receiver to a second group of evaporators of the one or more first evaporators, the second group of evaporators comprising a group of low temperature (LT) evaporators.
27 . The method of claim 26 , wherein operating the feed control valve to control a flow of the at least part of the liquid refrigerant from the primary receiver to the secondary receiver comprises maintaining a liquid level in the secondary receiver within a particular operating range.
28 . The method of claim 26 , further comprising:
monitoring a liquid refrigerant level in the primary receiver, and
maintaining the liquid refrigerant level in the primary receiver at or above a predetermined minimum level.
29 . A method for operating a refrigeration system, the method comprising:
collecting a gas refrigerant circulated by the refrigeration system within a primary receiver having a primary operating pressure, the primary receiver comprising a primary receiver gas outlet through which a gas refrigerant exits the primary receiver to a first suction line of one or more first compressors in a first set of compressors, the primary receiver comprising a first liquid refrigerant outlet through which at least part of a liquid refrigerant exits the primary receiver, and a second liquid refrigerant outlet through which another part of the liquid refrigerant exits the primary receiver to one or more first evaporators;
providing the at least part of the liquid refrigerant from the primary receiver to a secondary receiver having a secondary receiver operating pressure that is less than the primary receiver operating pressure, the secondary receiver comprising a secondary receiver gas outlet to which the gas refrigerant exits the secondary receiver to a second suction line of one or more second compressors in the first set of compressors;
operating a feed control valve to control a flow of the at least part of the liquid refrigerant from the primary receiver to the secondary receiver to maintain a level of the liquid refrigerant in the secondary receiver within a particular operating range; and
operating the one or more first compressors in parallel with the one or more second compressors;
wherein the refrigeration system further comprises one or more expansion valves and one or more second evaporators configured to operate at a different pressure than the one or more first evaporators, the one or more second evaporators fluidly coupled with the one or more expansion valves and the one or more second compressors operating in parallel, the secondary receiver comprising a secondary receiver liquid refrigerant outlet through which a second part of the liquid refrigerant exits to the one or more expansion valves, the method further comprising operating the one or more expansion valves to expand the second part of the liquid refrigerant received from the secondary receiver liquid refrigerant outlet, and direct the expanded refrigerant to the one or more second evaporators, and the method further comprises providing the another part of the liquid refrigerant from the primary receiver to a first group of evaporators of the one or more first evaporators, and providing a third part of the liquid refrigerant from the secondary receiver to a second group of evaporators of the one or more first evaporators, the second group of evaporators comprising a group of low temperature (LT) evaporators.
30 . The method of claim 29 , further comprising:
monitoring a liquid refrigerant level in the primary receiver, and
maintaining the liquid refrigerant level in the primary receiver at or above a predetermined minimum level.
31 . The method of claim 29 , further comprising:
receiving a portion of the liquid refrigerant from the secondary receiver into a tertiary receiver; and
operating a feed control valve to control a flow of the portion of the liquid refrigerant from the secondary receiver to the tertiary receiver to maintain a level of the portion of the liquid refrigerant in the tertiary receiver within a particular operating range.