RU2159912C1 - Self-contained system of nitrogen refrigeration for thermostatting and long-term keeping of food-stuffs - Google Patents

Abstract

FIELD: cryogenic engineering and cryogenic refrigerating machines operating on the Stirling reverse cycle principle, applicable for thermostatting of various objects and long-term keeping of food-stuffs. SUBSTANCE: the self-contained system represents a closed circuit of nitrogen liquefier. Liquid nitrogen is fed to the object being cold by the natural draft method with the use of evaporator. For supercondensation of nitrogen vapors use is made of the Stirling cryogenic machine. For removal of heat load from the Stirling machine use is made of a refrigeration circuit with two heat exchangers. EFFECT: prevented loss of nitrogen, thermostatic temperature control of objects at a high level of explosion- and fireproofness, enhanced safekeeping of food- stuffs in nitrogen medium. 1 dwg

Description

 The invention relates to the field of cryogenic technology and cryogenic refrigeration machines operating on the reverse Stirling cycle, can be used for thermostating of various objects and long-term storage of food products.

 Known technical solutions for the gasification of liquefied gases before distributing them to the consumer using high pressure pumps (Questions of deep cooling. / Sat articles edited by prof. MPMalkov /. M., Foreign literature, 1961, p. 287- 288).

 Known technical solutions for emptying cryogenic containers by self-pressurization, in which part of the liquid is supplied to the evaporator for heat exchange with atmospheric air and the transition to a gaseous state with increased pressure, and returns to the tank in the free space above the liquid (R.F. Barron. Cryogenic systems. 2nd ed., Edited by A.K. Gorodov, Moscow: Energoatomizdat, 1989, p. 323).

 A device of the Dewar vessel for liquid nitrogen with vacuum-powder insulation is known (Sokolov E.Ya., Brodyanky V.M. Energy principles of heat transformation and cooling processes. Textbook for universities. 2nd ed. -M.: Energoizdat, 1981 , p. 202).

 It is known that in the region of cryogenic temperatures (60–160 K), the reverse Stirling cycle is the most highly efficient cycle. The effectiveness of cryogenic Stirling machines is almost 2 times higher compared to other plants used for gas liquefaction (IP Usyukin Installations, machines and apparatuses of cryogenic technology. M: Light and food industry, 1982, cf. 185-186).

 A device of the gas refrigerating machine Philips, operating on the reverse Stirling cycle, designed to liquefy the air and includes a block of heat exchangers: a condenser, a regenerator and a refrigerator. Helium is used as a working fluid in the refrigeration machine (Questions of deep cooling. // Collection of articles edited by prof. MPMalkov /. M., Foreign Literature, 1961, p. 35). However, liquid air has an increased fire hazard.

 It is known that nitrogen is a chemically inactive substance, it is not toxic and can be used to create an inert environment, due to its explosion and fire safety (Glinka N.L. General chemistry. Textbook for universities. 22nd ed., Rev. L .: Chemistry, 1982 g., pp. 398-399). However, nitrogen production is an expensive process.

 A known system of nitrogen cooling in a heat-insulated car body, designed to transport products and allows you to quickly cool the internal volume of the body. The system includes a container with liquid nitrogen, a submersible centrifugal pump for supplying liquid nitrogen, while the nitrogen medium has a beneficial effect on the stored products (Akulov L.A., Borzenko E.I., Soloviev V.A. Nitrogen cooling system in thermally insulated car body. // Abstracts of reports of the international scientific and technical conference "Refrigeration equipment of Russia. Status and prospects on the eve of the XXI century" //, St. Petersburg, 1998, p. 32). However, this system involves the release of used nitrogen into the atmosphere, which leads to the irretrievable loss of an expensive gas - nitrogen.

 The technical result that can be obtained by carrying out the invention is to exclude an irretrievable loss of nitrogen, the possibility of using the system for thermostating of any objects, for example, infrared radiation sensors, with a high level of explosion and fire safety, as well as quick freezing and long-term storage of food in a nitrogen atmosphere.

 To achieve this technical result, an autonomous nitrogen cooling system for thermostating and long-term storage of products, including a tank with liquid nitrogen, a cooled insulated volume, is equipped with a closed nitrogen circuit containing a control valve for supplying liquid nitrogen, a nitrogen evaporator, a coil in the gas-containing part of the tank with liquid nitrogen, nitrogen distribution and collection systems located in a cooled insulated volume, throttle valve, expansion tank, cryogenic refrigeration a Stirling machine, a Dewar vessel, a high-pressure pump supplying liquid nitrogen from a Dewar vessel to a container with liquid nitrogen, and a check valve, as well as a cooling circuit of the Stirling cryogenic machine, which includes a pump, a primary heat exchanger, a secondary heat exchanger, and a cooling ambient supply system medium, for example atmospheric air, consisting of a line of heating liquid nitrogen with a control valve passing through a nitrogen evaporator and a secondary heat exchanger of the cooling circuit, and a line passing through the primary ploobmennik cooling circuit, wherein the drive cryogenic Stirling machine by an electric motor, or a separate thermal engine of the vehicle engine.

 Introduction to the composition of an autonomous nitrogen cooling system for temperature control and long-term storage of products, a closed nitrogen circuit with a liquid nitrogen evaporator and a cryogenic Stirling machine, a cooling circuit of a cryogenic machine with two heat exchangers and an atmosphere air supply system consisting of separate lines, each of which passes through one from heat exchangers of the cooling circuit, allows you to get a new property, which consists in eliminating the release of evaporated nitrogen into the environment due to its conversion compensation in the cryogenic Stirling machine and in reducing the power consumption for driving the cryogenic Stirling machine by lowering the upper temperature of the machine cycle.

 The drawing shows an autonomous nitrogen cooling system for thermostating and long-term storage of products.

 The autonomous system consists of a closed nitrogen circuit, which includes a tank with liquid nitrogen 1, a control valve for supplying liquid nitrogen 2, a nitrogen evaporator 2, a coil 4 located in the gaseous part of the tank 1, an insulated cooled volume 5, a nitrogen distribution and collection system 6, a throttle valve 7, expansion vessel 8, cryogenic Stirling refrigeration machine 9, including a condenser 10 and a refrigerator 11, a Dewar vessel 12, a high pressure pump 13, a check valve 14, and a cooling circuit of a cryogenic machine 8, consisting about from the pump 15, the first heat exchanger 16 and the second heat exchanger 17, and a cooling medium supply system, for example, atmospheric air, including a liquid nitrogen heating line 18 with a control valve 19, passing sequentially through the evaporator 3 and the secondary heat exchanger 17 and the line 20 s control valve 21 passing through the primary heat exchanger 16.

 Autonomous nitrogen cooling system for thermostating and long-term storage of products works as follows.

 Due to heat inflows from the ambient air supply system in the evaporator 3, liquid nitrogen is heated and goes into a gaseous state with increased pressure, and then enters the coil 4 located in the gas-containing part of the tank 1, where the gaseous nitrogen is cooled by heat exchange with liquid nitrogen vapors. The temperature and vapor pressure of liquid nitrogen in the tank 1 rises, which ensures the supply of liquid nitrogen to the evaporator 3. The supply of liquid nitrogen to the evaporator 3 is controlled by valve 2. From the coil 4, gaseous nitrogen of increased pressure with a cryogenic temperature enters the nitrogen distribution and collection system 6, located in a thermally insulated cooled volume 5, it cools the internal environment of volume 5 to the desired temperature, while he heats up. The supply of nitrogen gas of cryogenic temperature inside the volume 5 allows, on the one hand, to efficiently, for example, without vibration, thermostat various objects, for example infrared radiation sensors, on the other hand, in the case of food storage, quickly freeze and create a favorable nitrogen atmosphere. In order to pre-cool and reduce pressure, nitrogen from volume 5 is throttled through valve 7 to expansion vessel 8. From expansion vessel 8, gaseous nitrogen is sucked into the condenser 10 of Stirling's cryogenic refrigeration machine 9, where it condenses, passing into the liquid phase, and drains by gravity into a vessel Dewar 12, where, using a high-pressure pump 13 through the check valve 14 is fed back into the tank with liquid nitrogen 1.

 To drive the cryogenic Stirling machine 8, a vehicle engine, an electric motor, or a special heat engine (not shown) can be used. In order to cool the cryogenic machine 9, a contour of the cooling system is provided. On this circuit, the cooling fluid heated from the working fluid of machine 9 from the refrigerator 11 of machine 9 is first pumped to the first heat exchanger 16, where the liquid is cooled to ambient temperature, and then to the second heat exchanger 17, where it is cooled to a temperature below ambient temperature Wednesday.

 To remove the heat load from the cryogenic Stirling machine 9, an ambient air supply system is provided, consisting of a line 20 with a control valve 21 providing air to the heat exchanger 16 to cool the cooling liquid of the cooling circuit of the Stirling machine 9 to the ambient temperature, and line 18 with a control a valve 19, which supplies air first to the evaporator 3 to cool it to a low temperature, and then to the heat exchanger 17 to cool the coolant s Stirling 9 to a temperature below the ambient temperature. Due to heat transfer between the coolant with a low temperature and the working fluid of the machine 9, the upper temperature of the cycle of the machine 9 decreases, which leads to an increase in the refrigeration coefficient of the machine 9 and a decrease in the power consumption for its drive.

Sources of information
1. Issues of deep cooling. / Sat. articles edited by prof. M.P. Malkova /. Publishing House: "Foreign Literature", Moscow, 1961, p. 287-288.

 2. R. F. Barron. Cryogenic systems. 2nd ed. under the editorship of A.K. Gorodova M .: "Energoatomizdat", 1989, p. 323.

 3. Sokolov E. Ya., Brodyansky V. M. Energy fundamentals of heat transformation and cooling processes: Textbook for universities. -2nd ed., -M.: Energoizdat, 1981, p. 202.

 4. Usyukin I.P. Installations, machines and apparatuses of cryogenic equipment. M .: Light and food industry, 1982, pp. 185-186.

 5. Issues of deep cooling. /Sb.Articles under the editorship of prof. M.P. Malkova /. Publisher: "Foreign Literature", Moscow, 1961, p. 35.

 6. Glinka N. L. General chemistry: Textbook for universities. - 22nd ed., Rev. L .: "Chemistry", 1982, pp. 398-399.

 7. Akulov L.A., Borzenko E.I., Soloviev V.A. Nitrogen cooling system in a thermally insulated car body. // Abstract. reports of international scientific - tech. conf. "Refrigeration equipment in Russia. Status and prospects on the eve of the XXI century" // St. Petersburg, 1998, p. 32. - prototype.

Claims (1)

 Autonomous nitrogen cooling system for thermostating and long-term storage of products, including a container with liquid nitrogen, a cooled insulated volume, characterized in that it is equipped with a closed nitrogen circuit containing a control valve for supplying liquid nitrogen, a nitrogen evaporator, a coil in the gas-containing part of the container with liquid nitrogen , nitrogen distribution and collection system located in a cooled insulated volume, throttle valve, expansion tank, Stirling cryogenic refrigeration machine , a Dewar vessel, a high pressure pump supplying liquid nitrogen from a Dewar vessel to a vessel with liquid nitrogen, and a check valve, as well as a cooling circuit of a cryogenic Stirling machine, including a pump, first and second heat exchangers, and a supply system for a cooling environment, such as atmospheric air, consisting of a line of heating liquid nitrogen with a control valve passing through the nitrogen evaporator and the second heat exchanger of the cooling circuit, and a line passing through the first heat exchanger of the cooling circuit, The Riogenic Stirling machine is carried out from an electric motor, a separate heat engine, or from a vehicle engine.