Cascade refrigeration system

Abstract

A cascade refrigeration system is provided. The cascade refrigeration system includes a low stage having a first refrigerant flowing therethrough and a high stage having a second refrigerant flowing therethrough. The low stage includes a compressor and evaporator coils. The input of the evaporator coils is operatively connected to the output of the compressor by an input conduit and the output of the operator unit is operatively connected to the input of the compressor by an output conduit. A bypass line has an input in communication with the input conduit and an output in combination with the output conduit. A bypass heat exchanger effectuates the heat exchange relationship between the first refrigerant flowing through the bypass line and the first refrigerant flowing through the input conduit.

1. A two-stage cascade refrigeration system, comprising:
 a low stage having a first refrigerant flowing therethrough, the low stage including a compressor having an input and an output, and an evaporator unit having an input operatively connected to the output of the compressor through a stage heat exchanger by an input conduit and an output operatively connected to the input of the compressor by an output conduit, the stage heat exchanger having an upstream side and a downstream side; 
 a bypass line having an input in communication with the input conduit of the low stage and connected to the low stage input conduit downstream of the stage heat exchanger, an output in communication with the connected to the low stage output conduit of the low stage; and 
 a bypass heat exchanger for effectuating a heat exchange relationship between the first refrigerant in the bypass line and the first refrigerant in the input conduit of the low stage, the bypass line passing through a bypass heat exchanger in heat exchange relationship with the first refrigerant in the low stage input conduit upstream of the stage heat exchanger. 
 
     
     
       2. The system of  claim 1  further comprising:
 a high stage having a second refrigerant flowing therethrough, the high stage including a high stage input conduit and a high stage output conduit, a compressor having an input and an output, and a condenser unit having an input operatively connected to the output of the high stage compressor and an output operatively connected to the input of the high stage compressor by output conduit; and 
 a second heat exchanger for effectuating a heat exchange relationship between the first refrigerant within the input conduit of the low stage and the second refrigerant within the output conduit of the high stage, the second refrigerant flowing between the high stage compressor and the high stage condenser unit through the high stage input and output conduits, the high stage refrigerant in each exchange relationship with the low stage refrigerant in the stage heat exchanger. 
 
     
     
       3. The system of  claim 2  wherein the input of the bypass line communicates with the input conduit of the low stage downstream of the second heat exchanger. 
     
     
       4. The system of  claim 2  wherein the condenser unit of the high stage effectuates a heat exchange between the second refrigerant therein and a fluid from a fluid source. 
     
     
       5. The system of  claim 2  wherein the high stage further includes a first bypass line having an input in communication with the input conduit of the high stage and output in communication with the output conduit of the high stage downstream of the heat exchanger. 
     
     
       6. The system of  claim 5  further comprising a bypass solenoid in the first bypass line of the high stage for controlling the flow of the second refrigerant therethrough. 
     
     
       7. The system of  claim 1  further comprising a bypass valve interconnecting the bypass line to the input conduit of the low stage, the bypass valve controlling the flow of the first refrigerant therebetween in the first bypass line upstream of the stage heat exchanger, the low stage bypass valve controlling the flow of low stage refrigerant based on an amount of pressure in the low stage output conduit. 
     
     
       8. The system of  claim 1  wherein the input conduit of the low stage includes a condenser unit upstream of the bypass heat exchanger for effectuating a heat exchange between the first refrigerant therein and a fluid from a fluid source. 
     
     
       9. A two-stage cascade refrigeration system, comprising:
 a low stage compressor having an input and an output; 
 a low stage evaporator unit having an input and an output;  
 a low stage input conduit for operatively connecting the output of the low stage compressor to the input of the low stage evaporator unit through a stage heat exchanger, the stage heat exchanger having an upstream side and a downstream side; 
 a low stage output conduit for operatively connecting the output of the low stage evaporator unit to the input of the low stage compressor; 
 a low stage refrigerant flowing between the low stage compressor and the low stage evaporator unit through the low stage input and output conduits; 
 a first bypass line having an input in communication with connected to the low stage input conduit and downstream of the stage heat exchanger, an output in communication with the connected to the low stage output conduit, the first bypass line passing through a bypass heat exchanger in heat exchange relationship with the low stage refrigerant in the low stage input conduit upstream of the stage heat exchanger; and 
 a bypass heat exchanger for effectuating a heat exchange relationship between the first refrigerant in the first bypass line and the low stage refrigerant in the low stage input conduit 
 wherein the low stage input conduit further includes a condenser unit upstream of the bypass heat exchanger for effectuating heat exchange between the low stage refrigerant therein and a fluid from a fluid source. 
 
     
     
       10. The system of  claim 9  further comprising:
 a high stage compressor having an input and an output; 
 a high stage condenser unit having an input and an output; 
 a high stage input conduit for operatively connecting the output of the high stage compressor to the input of the high stage condenser unit; 
 a high stage output conduit for operatively connecting the output of the high stage condenser unit to the input of the high stage compressor through the stage heat exchanger; and 
 a high stage refrigerant flowing between the high stage compressor and the second stage condenser unit through the high stage input and output conduits, the high stage refrigerant in heat exchange relationship with the low stage refrigerant in the stage heat exchanger. 
 
     
     
       11. The system of  claim 10  wherein the high stage condenser unit effectuates a heat exchange between the high stage refrigerant therein and a fluid from a fluid source. 
     
     
       12. The system of  claim 10  further comprising a second heat exchanger for effectuating a heat exchange between the low stage refrigerant within the low stage input conduit and the high stage refrigerant within the high stage output conduit. 
     
     
       13. The system of  claim 12  wherein the input of the first bypass line communicates with the low stage input conduit downstream of the second heat exchanger. 
     
     
       14. The system of claim  12  9 further comprising a second bypass line having an input in communication with the high stage input conduit and output in communication with the high stage output conduit downstream of the second heat exchanger connected to the downstream side of the stage heat exchanger and an output connected to the low stage output conduit. 
     
     
       15. The system of  claim 14  further comprising a second bypass solenoid in the second bypass line for controlling the flow of the high stage refrigerant therethrough wherein the second bypass line includes an expansion valve. 
     
     
       16. The system of  claim 9  further comprising a low stage bypass valve interconnecting the first bypass line to the low stage input conduit in the first bypass line upstream the stage heat exchanger, the low stage bypass valve controlling the flow of the low stage refrigerant therebetween therethrough based on an amount of pressure in the low stage output conduit. 
     
     
       17. The system of  claim 9  wherein the low stage input conduit includes a condenser unit upstream of the bypass heat exchanger for effectuating a heat exchanger between the low stage refrigerant therein and a fluid from a fluid source. 
     
     
       18. A two-stage cascade refrigeration system, comprising:
 low stage having a first refrigerant flowing therethrough, the low stage including a compressor having an input and an output, and an evaporator unit having an input operatively connected to the output of the compressor through a stage heat exchanger by an input conduit and an output operatively connected to the input of the compressor by an output conduit; 
 a high stage having a second refrigerant flowing therethrough, the high stage including a compressor having an input and an output, and a heat exchanger having an input operatively connected to the output of the high stage compressor by an input conduit and an output operatively connected to the input of the high stage compressor by output conduit, the heat exchanger effectuating a heat exchange between the first refrigerant within the input conduit of the low stage and the second refrigerant within the output conduit of the high stage; 
 a bypass line having an input in communication with the input conduit of the low stage downstream of the stage heat exchanger and an output in communication with the output conduit of the low stage; and 
 a bypass heat exchanger for effectuating a heat exchange relationship between the first refrigerant in the bypass line and the first refrigerant in the input conduit of the low stage with first refrigerant in the low stage input conduit upstream of the stage heat exchanger. 
 
     
     
       19. The system of  claim 18  wherein the high stage includes a condenser unit for effectuating a heat exchange between the second refrigerant flowing through the input conduit and a fluid from a fluid source. 
     
     
       20. The system of  claim 18  wherein the input of the bypass line communicates with the input conduit of the low stage downstream of the heat exchanger. 
     
     
       21. The system of  claim 19  wherein the high stage further includes a first bypass line having an input in communication with the input conduit of the high stage and output in communication with the output conduit of the high stage downstream of the heat exchanger. 
     
     
       22. The system of  claim 21  further comprising a bypass solenoid in the first bypass line of the high stage for controlling the flow of the second refrigerant therethrough wherein the second bypass line includes an expansion valve. 
     
     
       23. The system of  claim 19  further comprising a bypass valve for interconnecting the bypass line to the input conduit of the low stage, the bypass valve controlling the flow of the first refrigerant therebetween. 
     
     
       24. The system of  claim 19  wherein the input conduit of the low stage includes a condenser unit upstream of the bypass heat exchanger for effectuating a heat exchange between the first refrigerant therein and a fluid from a fluid source. 
     
     
       25. The system of claim 15 wherein the bypass heat exchanger has an upstream input conduit side and a downstream input conduit side, the system further including a third bypass line having an input connected to the upstream input conduit side of the bypass heat exchanger and an output connected to the low stage output conduit.