Reduction of real gas losses with a DC flow in the practical regenerator of the refrigeration cycle

A working fluid behaves more like a real gas as the refrigeration temperature gets close to or below its critical temperature, and such real gas effects seriously degrade the refrigeration efficiency. Previous theoretical study has found that imposing a direct-current (DC) flow in an ideal regenerator improves the coefficient of performance (COP) significantly. However, factors in practical regenerators bring about profound influences on the DC flow, and its value deviates severely from that in ideal regenerators. In this paper, three factors are identified, and their effects are estimated based on specific simulations on regenerators. The expression of the DC flow and the COP are derived. Experimental measurements about the DC flow are carried out with a pulse tube refrigerator, and the COP at the temperature range of 4-7 K is found to be improved by a maximum value of 83%. It is the first time to provide a direct experimental evidence of reducing real gas losses with a DC flow in the regenerator. Further discussions on improvement potentials of the refrigeration performance and the liquefaction rate show that it should be a realistic way to utilize a DC flow in regenerative refrigeration systems.