Transient cooling and operational performance of the cryogenic part in reverse Brayton air refrigerator

Accurate calculation of the transient cooling performance is crucial for the operation and control of a reverse Brayton refrigerator. Components of the refrigerator have complex working characteristics individually and interact each other mutually. To solve the problem easily, the turboexpander matching characteristics were usually ignored and relations among components were simplified. In this study, a cryogenic reverse Brayton air refrigerator equipped with gas bearing turboexpander and plate-fin heat regenerator was presented. The ultimate refrigerating temperature was proposed through analysis. The transient cooling characteristics of the cryogenic part in refrigerator were resolved into the turboexpander matching performance and the regenerator transient cooling characteristics. The regenerator was simulated through numerical heat transfer and computational fluid dynamics by considering the axial conduction and cold loss. The matching model was improved by adopting a significant method of constant rotating speed. Using the dual non-steady time steps, a transient cooling model of the cryogenic part was explored via C++ code, and verified by experiment. Through the model, the refrigerator cooling performances were evaluated under different operation modes, and the energy utilization efficiency was determined. It can be used to evaluate the operation strategy of refrigerators and help to promote energy efficiency.