Enthalpy control for CO2 refrigeration system
First Claim
1. A method of refrigerating air in a compartment comprising the steps of:
- delivering liquid carbon dioxide through a first heat exchanger such that sufficient heat is absorbed to evaporate the liquid carbon dioxide to form pressurized vapor;
heating the vapor to a temperature to prevent solidification of the carbon dioxide when it becomes depressurized;
depressurizing the vapor to provide isentropic expansion of the vapor into a second heat exchanger;
delivering vapor from the second heat exchanger to maintain surfaces in a dehumidifier at a temperature below the dewpoint of air in the compartment; and
circulating air in the compartment in heat exchange relation with the surfaces in the dehumidifier and subsequently in heat exchange relation with carbon dioxide in the first and second heat exchangers such that moisture in the circulating air condenses on surfaces in the dehumidifier enroute to the first and second heat exchangers.
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Accused Products
Abstract
A method and apparatus to refrigerate air in a compartment wherein liquid CO2 is delivered through a first primary heat exchanger such that sufficient heat is absorbed to evaporate the liquid carbon dioxide to form pressurized vapor. The pressurized vapor is heated in a gas fired heater to prevent solidification of the pressurized carbon dioxide when it is depressurized to provide isentropic expansion of the vapor through pneumatically driven fan motors into a secondary heat exchanger. Orifices in inlets to the fan motors and solenoid valves in flow lines to the fan motors keep the vapor pressurized while the heater supplies sufficient heat to prevent solidification when the CO2 vapor expands through the motors. CO2 vapor is routed from the second heat exchanger to chill surface in a dehumidifer to condense moisture from a stream of air before it flows to the heat exchangers.
74 Citations
22 Claims
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1. A method of refrigerating air in a compartment comprising the steps of:
- delivering liquid carbon dioxide through a first heat exchanger such that sufficient heat is absorbed to evaporate the liquid carbon dioxide to form pressurized vapor;
heating the vapor to a temperature to prevent solidification of the carbon dioxide when it becomes depressurized;
depressurizing the vapor to provide isentropic expansion of the vapor into a second heat exchanger;
delivering vapor from the second heat exchanger to maintain surfaces in a dehumidifier at a temperature below the dewpoint of air in the compartment; and
circulating air in the compartment in heat exchange relation with the surfaces in the dehumidifier and subsequently in heat exchange relation with carbon dioxide in the first and second heat exchangers such that moisture in the circulating air condenses on surfaces in the dehumidifier enroute to the first and second heat exchangers. - View Dependent Claims (2, 3, 4, 5)
- delivering liquid carbon dioxide through a first heat exchanger such that sufficient heat is absorbed to evaporate the liquid carbon dioxide to form pressurized vapor;
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6. A method of controlling the heat transfer rate through a wall of a tube in a compartment comprising the steps of:
- delivering liquid carbon dioxide into the tube;
moving fluid in the compartment in heat exchange relation with the tube such that heat is absorbed by the carbon dioxide to form pressurized carbon dioxide vapor in the tube;
heating the pressurized carbon dioxide vapor;
delivering the heated carbon dioxide vapor to drive a motor driven fan to move fluid in the compartment in heat exchange relation with the tube; and
controlling the flow of heated vapor to the motor to prevent solidification of the carbon dioxide as it depressurizes upon reaching the pneumatic motor chambers. - View Dependent Claims (7, 8, 9, 10)
- delivering liquid carbon dioxide into the tube;
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11. A method of controlling temperature in a compartment comprising the steps of:
- circulating liquid carbon dioxide through a primary coil such that heat is absorbed by the carbon dioxide;
changing the enthalpy of carbon dioxide exhausted from the primary coil to assure that it is in a vapor phase;
delivering the carbon dioxide vapor through a pneumatic motor arranged to drive a fan; and
circulating carbon dioxide from the pneumatic motor through a secondary coil, the primary and secondary coils being positioned such that the fan driven by the pneumatic motor moves air in heat exchange relation with the coils. - View Dependent Claims (12)
- circulating liquid carbon dioxide through a primary coil such that heat is absorbed by the carbon dioxide;
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13. Temperature control apparatus comprising, a coil;
- means to deliver fluid through said coil;
means to move air across the coil;
first sensor means to sense temperature of carbon dioxide exhausted from the coil;
second sensor means to sense the temperature of the surface of the coil;
means to generate a signal when the temperature of carbon dioxide exhausted from the coil is less than a predetermined temperature;
means energized by said signal to heat surfaces of the coil to melt ice thereon; and
means energized by said second sensor to terminate heating of the surfaces of the coil. - View Dependent Claims (14, 15, 16, 17, 18)
- means to deliver fluid through said coil;
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19. Apparatus to control temperature in a cargo compartment of a trailer comprising:
- a source of liquefied carbon dioxide carried by the trailer;
evaporator means positioned in heat exchange relation with air in the compartment;
first conduit means connecting said evaporator means and the source of liquid carbon dioxide;
heat exchanger means;
second conduit means connecting the heat exchanger means with said evaporator means;
a pneumatically operated motor;
fan means driven by said motor arranged to cause air in the compartment to circulate over surfaces of the evaporator means, said heat exchanger means being adapted to deliver carbon dioxide from said evaporator means to said motor in a temperature range to prevent solidification of carbon dioxide as it becomes depressurized in said motor. - View Dependent Claims (20, 21, 22)
- a source of liquefied carbon dioxide carried by the trailer;
Specification