Cyclic Simulation of Stirling Cryogenerator with Two-Component Two-Phase Fluid

Abstract

A Stirling cycle cryogenerator operates on a closed regenerative thermodynamic cycle with compression and expansion of the working fluid occurring at different temperature levels. Generally, hydrogen or helium is used as a single-component working fluid in the cryogenerators used for liquefaction of nitrogen. The use of a two-component working fluid, one condensing at the required refrigerating temperature, can improve the performance of the cryogenerator.

If maximum cycle pressure in the cryogenerator is kept the same as when using a single- component working fluid, the pressure varies over a larger range. This provides an increase in the available refrigerating effect, but at a correspondingly higher input power.

Thus, a particular cryogenerator can provide a larger liquefaction capacity when working with a two-component two-phase working fluid. Alternately, for a fixed liquefaction capacity, the maximum cycle pressure can be kept lower than the maximum cycle pressure with a single- component working fluid. The change over to a two-component fluid does not involve any change in the cryogenerator configuration.

In this paper a computer simulation using second order cyclic analysis has been carried out for a PLN-106 cryogenerator used for the liquefaction of nitrogen at a capacity of 6–6.5 dm³ h⁻¹. The results using a single-component working fluid are compared with those for a two-component working fluid with the same maximum cycle pressure.