Optimization of heat exchangers for throttled microcryogenic systems

Grezin, A. K.; Zakharov, N. D.; Морозов, В. П.

doi:10.1007/bf01144865

Chem Petrol Eng

1978

DOI: 10.1007/bf01144865

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Optimization of heat exchangers for throttled microcryogenic systems

A. K. Grezin¹,

N. D. Zakharov²,

В. П. Морозов³

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“…2). The descried liquid oxygen and nitrogen production method can be applied for production of less than 15 kg/h (less than about 300 cm 3 /min of nitrogen and about 200 cm 3 /min of oxygen), including for solving problems of microcryogenic engineering, for example, for developing batch-operated refrigerating system [6].…”

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Production of Liquid Oxygen and Nitrogen Using Adsorptive Air-Fractionating Plant and Cryogenic Gas Machine

2015

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A method of producing liquid oxygen and nitrogen employing an adsorptive air-fractionating plant and a cryogenic gas machine is described. The method is of practical interest for producing less than 15 kg/h of liquid oxygen and nitrogen.Methods of producing liquid nitrogen in small quantities (50-60 kg/h) employing Azh-0.05 type of air-fractionating plant that includes a cryogenic gas machine (CGM) and a fractionating column are well known [1]. The possibility of using CGM for liquefaction of natural gas has also been discussed [2].A variant of liquid nitrogen production employing an adsorptive air-fractionating plant for getting gaseous nitrogen (AAFP-N) and a Phillips CGM was described earlier [3] (Fig. 1).In this process flow diagram, the cold for cooling and liquefaction of gaseous nitrogen stream is supplied at a low temperature level T c(l) . In this case, the specific quantity of cold supplied for 1 kg of liquid is about 400 kJ/kg. In [4], the ratio of the real refrigerating machine performance coefficient ε r to the Carnot cycle refrigeration coefficient ε Car is given as a function of minimum temperature on the Phillips CGM head (single-stage helium machine).According to [5], this function can be approximated in the temperature range 70 K < T c < 120 K by the equation

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Production of Liquid Oxygen and Nitrogen Using Adsorptive Air-Fractionating Plant and Cryogenic Gas Machine

2015

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“…The number of cycles in unit time influences the basic parameters [1][2][3][4]: the time to reach the steady state, the working resource, and the cold production.…”

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Effects of drive rotation speed on cold production and startup period in a Gifford-McMahon cryorefrigerator with slide valve gas distribution

Lyapin¹,

Yalovnarov²,

Rubtsov³

2006

Chem Petrol Eng

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Studies have been done on a one-stage microcooler in a Gifford-McMahon cryorefrigerator with a gas distribution mechanism including a rotating slide valve.The following relationships have been determined: heat flow in relation to cryostatic temperature with various motor speeds, temperature on the time to reach the steady state, and slide rotation frequency as a function of temperature.Some types of cryogenic vacuum pump use single-stage Gifford-McMahon (GM) cryorefrigerators for cooling the radiation screens as well as cryopanels (in condensation cryopumps). These coolers are also used in air microliquefiers (AML). The performance of a cryovacuum pump or MO AML is dependent on the working parameters of the microcoolers (MC) of the GM, and in that connection it is necessary to raise the cold output.Theoretical studies have been performed on the physics of the processes in gas cryogenic machines that influence the cold production as the cycle frequency varies at several temperature levels. With a small temperature difference, the losses of performance are relatively small, i.e., with an infinitely small temperature difference between the warm and cold sources, the thermodynamic process tends to ideal, and therefore the losses are minimal at the higher working temperature level of the cryorefrigerator.If one assumes that the thermodynamic processes are ideal, one can say that the cold production increases with the cycle frequency. However, actual processes differ considerably from ideal, and the losses associated with increase in hydraulic resistance and the frictional heat increase with the cycle frequency, gas flow speeds, and displacer speed. Also, as the periods of blowing through the regenerator are shortened, there is an increase in the loss of heat recuperation in the exchange of the gas with the packing elements in the regenerative heat exchanger.It has therefore been suggested that the losses dependent on the temperature difference persist at a higher temperature level, and therefore there is scope for increasing the cycle frequency, which would raise the MC cold production. Correspondingly, at the lower temperature, it is necessary to reduce the basic losses as the temperature difference increases, which are due to the hydraulic resistance, frictional heat, and loss of recuperation in the heat exchange.The cycle frequency change is not unambiguous, and there should be a turning point in the dependence of the cold production on the rotation frequency. It is therefore desirable to determine the best cycle frequency at various temperature levels.

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Optimization of heat exchangers for throttled microcryogenic systems

Cited by 2 publications

References 0 publications

Production of Liquid Oxygen and Nitrogen Using Adsorptive Air-Fractionating Plant and Cryogenic Gas Machine

Production of Liquid Oxygen and Nitrogen Using Adsorptive Air-Fractionating Plant and Cryogenic Gas Machine

Effects of drive rotation speed on cold production and startup period in a Gifford-McMahon cryorefrigerator with slide valve gas distribution

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