Vehicle refrigerator having a liquid line subcooled vapor cycle system
A vapor cycle refrigeration system includes a thermoelectric device (TED) as a sub-cooler to sub-cool liquid refrigerant exiting a condenser to increase cooling capacity of an evaporator and pull down temperature within a refrigerated compartment quickly. The TED sub-cooler is turned off after initial temperature pull down and is not operated during steady state operation for maintenance of the compartment temperature.
1. A refrigeration system that cools a compartment, the refrigeration system comprising:
a compressor,
a condenser,
a thermoelectric device (TED) sub-cooler including at least one TED, the TED sub-cooler including a hot side heat sink integrated with and in thermal communication with the condenser on a same hot side of the at least one TED, the hot side heat sink sharing a cooling mechanism integrated with the condenser by which the hot side heat sink is to be cooled together with the condenser, and the TED sub-cooler including on an opposite side of the at least one TED a cold side fluid heat exchanger to sub-cool refrigerant that has passed through the condenser,
an expansion valve,
an evaporator, and
tubing adapted to transport the refrigerant through the refrigeration system in a circulation order from the compressor to the condenser to the TED sub-cooler to the expansion valve to the evaporator and back to the compressor again.
2. The refrigeration system of claim 1 , wherein the TED sub-cooler sub-cools the refrigerant exiting the condenser by at least approximately ten degrees Fahrenheit.
3. The refrigeration system of claim 1 , wherein the TED sub-cooler operates when a difference between a measured temperature in the compartment and a temperature set point is greater than or equal to a preset threshold, and does not operate when the difference is less than the preset threshold.
4. The refrigeration system of claim 3 , wherein the preset threshold is between approximately two and ten degrees Fahrenheit.
5. The refrigeration system of claim 1 , further comprising a condenser fan that circulates air to cool both the condenser and the hot side heat sink of the TED sub-cooler.
6. The refrigeration system of claim 1 , wherein the TED sub-cooler is powered by direct electrical current.
7. The refrigeration system of claim 1 , wherein the TED sub-cooler is controlled using a Pulse Width Modulation control signal.
8. The refrigeration system of claim 1 , further comprising an enclosure that encloses the compartment and the refrigeration system, the enclosure having a door that provides closeable access to the compartment and vents through which a condenser fan outputs condenser exhaust and inputs ambient air for cooling the condenser and the TED sub-cooler.
9. The refrigeration system of claim 1 , further comprising a controller that controls the refrigeration system according to sensor data from temperature and pressure sensors in the refrigeration system.
10. The refrigeration system of claim 9 , wherein the controller is remotely controlled using a computer system which communicates with the controller over a data communications network.
11. The refrigeration system of claim 1 , further comprising a refrigerant heat exchanger that superheats refrigerant entering the compressor using refrigerant upstream of the expansion valve.
12. A method of controlling a refrigeration system comprising a compressor, a condenser, a thermoelectric device (TED) sub-cooler including at least one TED, the TED sub-cooler including a hot side heat sink integrated with and in thermal communication with the condenser on a same hot side of the at least one TED, the hot side heat sink sharing a cooling mechanism integrated with the condenser by which the hot side heat sink is to be cooled together with the condenser, and the TED sub-cooler including on an opposite side of the at least one TED a cold side fluid heat exchanger to sub-cool refrigerant after passing through the condenser, an expansion valve, an evaporator, and tubing adapted to transport the refrigerant through the refrigeration system in a circulation order from the compressor to the condenser to the TED sub-cooler to the expansion valve to the evaporator and back to the compressor again, the method comprising:
inputting sensor data;
determining whether a measured temperature of the compartment is greater than or equal to a preset threshold;
controlling the TED sub-cooler when the temperature is greater than or equal to the preset threshold;
not operating the TED sub-cooler when the temperature is less than the preset threshold;
when operating the TED sub-cooler, cooling the hot side heat sink together with the condenser, and sub-cooling the refrigerant after passing through the condenser; and
controlling motors and valves of the refrigeration system according to the sensor data to maintain a set temperature of the compartment within a predetermined maintenance range.
13. The method of claim 12 , wherein the TED sub-cooler sub-cools the refrigerant exiting the condenser by at least approximately ten degrees Fahrenheit (F).
14. The method of claim 12 , wherein the preset threshold is between approximately two and ten degrees F.
15. The method of claim 12 , further comprising circulating air to cool both the condenser and a hot side heat sink of the TED sub-cooler using a fan.
16. The method of claim 12 , wherein the TED sub-cooler is powered by direct electrical current.
17. The method of claim 12 , wherein the TED sub-cooler is controlled using a Pulse Width Modulation control signal.
18. The method of claim 12 , wherein the sensor data is received from temperature and pressure sensors in the refrigeration system.
19. The method of claim 12 , further comprising remotely controlling the refrigeration system using a computer system which communicates with the controller over a data communications network.
20. The method of claim 12 , further comprising superheating the refrigerant upstream of the compressor by a refrigerant heat exchanger using refrigerant upstream of the expansion valve.