Refrigerated counterflow

In this section, we will describe the various types of mechanical coolers with reference to their working cycles. We shall start with a brief description of counterflow heat exchangers. This subject will be further dealt in Chapter 6 when treating dilution refrigerators. 

Fig. 6.6. Scheme of a counterflow heat exchanger for dilution refrigerator. 

The J-T circuit consists of a series of counterflow heat exchangers connected between each of the adjacent temperature, levels a final exchanger is located between the last stage of refrigeration (14 K) and a liquid-helium stage. The... 

The work of Kapitza [7] and the exceptionally notable developments of Collins [8] had in common the utilization of expansion engines in combination with counterflow heat exchangers, and both were successful in liquefying helium. The Collins system was the first to use multiple engines operating at intermediate temperatures and thereby eliminate the need for any auxiliary refrigeration. This feature, combined with certain constructional advantages [9], has led to a wide acceptance of the Collins system for helium liquefaction. 

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