A new optimization concept of the recuperator based on Hampson-type miniature cryocoolers

The novel concept of "low pressure drop instead of the low temperature difference to obtain high heat flux" is proposed to improve the performance of recuperator for Hampson cryocoolers. The equivalent temperature T-eqva is introduced to repaint the T-Q diagram for intuitively observing the variation of the total exergy destruction in different structures in this study. By substituting the total exergy destruction for the heat transfer exergy destruction, the flow resistance is also considered in the recuperator optimization. It is discovered that the recuperator with first-dense-then-sparse type structure reduces the average equivalent temperature greatly, leading to lower exergy destruction. Otherwise, the non-isometric structure offers the possibility to gain both larger heat flux and decreased flow resistance at the same time. With the pressure-enthalpy diagram analysis, the favourable temperature behaviour is explained. The supercritical fluids in the recuperator of Hampson cryocoolers can obtain lower enthalpy when higher temperatures and pressure are obtained at the same time. Therefore, the optimization of the recuperator should not only concentrate on improving the temperature difference but also on reducing the pressure difference. And the average equivalent temperature will be an effective parameter to evaluate the performance of the recuperator in the future study. (c) 2021 Elsevier Ltd. All rights reserved.