Abstract: An endless conveyor carries articles being cooled through a freezing tunnel. Spray nozzles at longitudinally spaced locations along the tunnel expand high pressure liquid nitrogen to substantially atmospheric pressure to create a central flow of cold fluid in association with a surrounding inducer. The nozzles are arranged in an array with a first group being directed downward and toward the entrance and with a second group being directed downward and toward the exit end. A fan disposed in the intermediate region between the two groups creates an upward flow of cryogen vapor into the region that maintains a head of higher pressure vapor at the entrance to each of the inducers. Downwardly directed blowers are located between the array and both the entrance and exit ends in order to assure there is efficient extraction of heat from articles being carried along the conveyor from end to end.

Abstract: A cabinet cooler or freezer which efficiently utilizes cryogenic refrigeration either with or without mechanical refrigeration. The freezer intermittently freezes relatively large batches of food by efficiently utilizing the natural expansion effect of a liquid cryogen, in combination with mechanical circulation by blowers, to create an overall circulation that efficiently removes heat from the food. A secondary circulation effect is induced, in a manner similar to the operation of a jet pump, which amplifies the circulation and allows CO.sub.2 to be employed with modulating valve control to achieve uniformly low temperature throughout the cabinet without snow build-up on the cabinet bottom. Some cabinet versions create a cyclonic circulation pattern about a vertical axis that is particularly effective.

Abstract: A CO.sub.2 food freezer has an elongated enclosure through which material to be cooled is carried on an endless porous belt conveyor with an upper operating belt run vertically spaced from the lower return run to provide an intermediate region therebetween. Liquid CO.sub.2 injection means is located in an upper region to direct CO.sub.2 snow plus cold CO.sub.2 vapor downward onto material being conveyed. Blowers aimed at an angle of between about 5.degree. and about 35.degree. upward from the horizontal are located in the intermediate region, and fans in the upper region direct CO.sub.2 vapor downward onto material on the belt. The belt includes a plurality of longitudinally spaced transverse rods and a plurality of wire sections that respectively interconnect adjacent rods in pairs. The wire sections are bent so that all segments of wire extending generally between said rods lie in substantially the same plane which constitutes the upper surface of the upper run. The rods effectively deflect cold CO.sub.

Abstract: A holding chamber may be supplied from a storage vessel system with a cryogen, such as liquid CO.sub.2, or it may itself be large enough to take the place of a separate storage vessel. The temperature within the holding chamber is reduced to the triple point or below to form a refrigeration reservoir of solid cryogen, as by removing vapor from the chamber to cause evaporation or by employing mechanical refrigeration. The stored cooling power of the reservoir is later employed to meet a large or a periodic refrigeration demand and is thereafter replenished over a number of hours, preferably during a period of non-peak electric demand. This storage principle can be incorporated into a variety of different refrigeration systems. For example, a CO.sub.2 storage system may be used to produce and store solid CO.sub.2 during a period of low demand upon a coupled mechanical refrigeration system; thereafter, the solid CO.sub.

Abstract: A system for filling transportable tanks with a cryogen, such as low pressure liquid carbon dioxide. A holding chamber is supplied with liquid CO.sub.2 from a storage vessel system, and the pressure of liquid CO.sub.2 is reduced to the triple point to create CO.sub.2 snow and form a low-temperature coolant reservoir. CO.sub.2 vapor from the chamber is compressed and returned to the storage vessel system. Liquid CO.sub.2 can be supplied simultaneously to the tanks of several vehicles at below about 125 psig, and vapor from these tanks is promptly condensed by melting CO.sub.2 snow in the holding chamber. Standby cooling of vehicle cargo compartments can also be effected with recovery of the CO.sub.2 vapor using an auxiliary compressor.

Abstract: Material is cooled by direct contact with CO.sub.2, and the CO.sub.2 vapor is recovered. A coolant reservoir is created in a holding tank wherein CO.sub.2 vapor, CO.sub.2 liquid and solid CO.sub.2 exist in equilibrium in the form of slush plus vapor. Liquid CO.sub.2 is supplied to a cooling chamber to cool the material by direct contact, creating contaminated CO.sub.2 vapor. The contaminated CO.sub.2 vapor is removed and directed to the coolant reservoir to condense the CO.sub.2 vapor and any contaminants which liquefy at temperatures above -69.degree. F. by melting solid CO.sub.2. Clean CO.sub.2 vapor and any noncondensables are withdrawn from the holding tank and the withdrawn CO.sub.2 vapor is reliquefied and returned to the CO.sub.2 storage vesssel. Condensable contaminants are periodically removed from the holding tank by heating to a temperature where they can be blown out the bottom.

Abstract: A cargo compartment of a refrigerated vehicle is cooled by a cryogen, such as carbon dioxide. A storage tank carried by the vehicle is filled with CO.sub.2 slush. Liquid CO.sub.2 is separated from solid CO.sub.2 and supplied to a heat-exchanger where it is vaporized and the vapor is warmed by heat transfer from the cargo compartment atmosphere. A minimum vapor pressure of at least about 75 psia is maintained in the heat-exchanger, and a portion of the vapor is returned to the vehicle tank, melting solid CO.sub.2 therein. The major portion of the vapor stream is expanded through one or more gas motors, passed through one or more additional heat-exchangers to cool the cargo compartment and then vented. The pressure of the returning vapor is preferably increased by a compressor attached to a gas motor and injected into the vehicle tank.

Abstract: A product, such as tobacco, is introduced into a processing chamber that is coupled with a holding chamber. A cryogen vapor pressure is established in the processing chamber, and a compressor is operated to transfer liquid cryogen near equilibrium conditions by differential pressure flow from the holding chamber to the processing chamber and, after treatment, and for returning liquid cryogen by differential pressure flow back to the holding chamber. Pressure in both chambers is maintained above the saturation pressure whenever differential pressure transfer occurs. Vapor from the processing chamber is recovered in first, second and third gas receivers which are respectively interconnected by a low-pressure compressor and a high-pressure compressor. After treatment, a processing chamber is sequentially interconnected with the first receiver, then with the second gas receiver and subsequently with the third gas receiver.

Abstract: Material is cooled by direct contact with CO.sub.2, and the CO.sub.2 vapor is recovered. A coolant reservoir is created in a holding tank wherein CO.sub.2 vapor, CO.sub.2 liquid and solid CO.sub.2 exist in equilibrium in the form of slush plus vapor. Liquid CO.sub.2 is supplied to a cooling chamber to cool the material by direct contact, creating contaminated CO.sub.2 vapor. The contaminated CO.sub.2 vapor is removed and directed to the coolant reservoir to condense the CO.sub.2 vapor and any contaminants which liquefy at temperatures above -69.degree. F. by melting solid CO.sub.2. Clean CO.sub.2 vapor and any noncondensables are withdrawn from the holding tank and the withdrawn CO.sub.2 vapor is reliquefied and returned to the CO.sub.2 storage vessel. Condensable contaminants are periodically removed from the holding tank by heating to a temperature where they can be blown out the bottom.

Abstract: Apparatus for supplying a refrigeration system with a low-temperature liquid CO.sub.2. High pressure liquid CO.sub.2 is supplied from a storage vessel system to a holding chamber where the pressure is reduced to create vapor and CO.sub.2 snow, forming a low-temperature coolant reservoir. Vapor is removed from the chamber to maintain the pressure therein at about 75 p.s.i.a. or below by a compressor and returned to the storage vessel. The stored cooling power of the reservoir is then employed to meet refrigeration demand and is thereafter replenished over a period of hours. The storage principle can be incorporated into a variety of different systems. For example, additional liquid CO.sub.2 may be supplied from the storage vessel to a refrigeration system wherein vapor is created that is transferred to the holding chamber for condensation by melting the snow.

Abstract: A system for filling vehicle tanks with low pressure liquid carbon dioxide. A holding chamber is supplied with high pressure liquid CO.sub.2 from a storage vessel system, and the pressure of liquid CO.sub.2 is reduced to about 60 psig or below to create CO.sub.2 vapor and CO.sub.2 snow and form a low-temperature coolant reservoir in the holding chamber. CO.sub.2 vapor from the chamber is compressed and returned to the storage vessel system. Liquid CO.sub.2 from the storage vessel system can be supplied simultaneously to several vehicle tanks at below about 125 psig, and vapor created as a result thereof is condensed by melting CO.sub.2 snow in the holding chamber. Standby cooling of vehicle compartments is provided by vaporizing liquid CO.sub.2 from a vehicle tank in a heat exchanger for vaporization therein, expanding the vapor to cool it and then passing the expanded vapor through a second heat exchanger.

Abstract: A system for CO.sub.2 cooling of the cargo compartment of a refrigerated vehicle. A vessel carried by the vehicle holds liquid CO.sub.2 at pressure preferably not greater than about 125 psia. Liquid CO.sub.2 is supplied to first heat-exchanger where it is vaporized and warmed a predetermined amount while the pressure is maintained at at least about 80 psia. The pressure of the warmed CO.sub.2 is lowered to about atmospheric pressure without the creation of solid CO.sub.2, while simultaneously cooling the CO.sub.2 vapor, using a gas-driven motor through which the CO.sub.2 vapor is passed. The cooled CO.sub.2 vapor from the motor is passed through a second heat-exchanger, and a fan connected to the motor circulates the atmosphere in the cargo compartment in association with both heat-exchangers. The CO.sub.2 vapor from the second heat-exchanger is vented to the atmosphere exterior of cargo compartment.

Abstract: A method of controlling a CO.sub.2 snow-making operation which is promptly self-correcting should an upset occur that results in incomplete separation of CO.sub.2 snow from the cold CO.sub.2 vapor. The separated snow is fed to a generally closed chamber, while a major portion of the cold CO.sub.2 vapor is passed in heat-exchange relationship with warmer liquid CO.sub.2 flowing toward the expansion nozzle. The temperature and/or pressure of the CO.sub.2 vapor exiting the heat-exchanger is monitored, and upon detecting a condition indicative of incomplete separation of snow from vapor, the flow of vapor through the heat-exchanger is temporarily reduced while flow of a minor portion of CO.sub.2 vapor is permitted to exit from the generally closed chamber. Prompt correction of the situation causing the incomplete separation automatically results.