Channel geometry and throttling regulation effects on printed circuit Joule-Thomson cryocooler performance

Abstract

To solve the shortcomings of the current microchannel Joule-Thomson (J-T) cryocooler, such as monotonous channel configurations and limited parallelization, this study integrates printed circuit heat exchanger fabrication technology with distributed throttling refrigeration theory. A distributed J-T effect cryocooler featuring a multi-rectangular microchannel parallel structure was successfully developed. Performance investigations were conducted with the cryocooler as the prototype. By analyzing the thermodynamic parameter evolution of Ar at critical nodes, the weak link of the prototype was identified: the low J-T coefficient ${\mu }_{\mathrm{jt}}$ at the throttling inlet limits overall efficiency. To resolve this, a dual optimization strategy was proposed. First, topology optimization of the channel form of the counterflow heat exchanger was implemented to enhance precooling. The results show that the airfoil fin channels exhibit superior performance compared to other configurations. When the inlet parameters are 6.0 MPa and 285.0 K, compared with the prototype, the cold-end temperature decreases from 194.9 K to 167.8 K, the J-T efficiency is increased from 49.1 % to 56.1 %. the airfoil geometry intensifies heat transfer, thereby promoting more significant distributed J-T effect and heat transfer coupling in the throttling section, which is the key to improving refrigeration performance. In addition, length ratio optimization between counterflow heat exchanger and throttle was explored. The results show that increasing the length ratio of the throttling channel can effectively suppress the limit velocity of the fluid, thus delaying the occurrence of choked flow. Conversely, reducing this proportion lowers the cold-end temperature. constrained by choked flow limits, the minimum throttling length under the conditions described in this study is 12 mm, achieving a further temperature drop to 136.4 K, with peak J-T efficiency (74.1 %) and heat flux (2.77 W/mm). The established dual optimization framework, structural refinement and zonal proportioning, provides theoretical and technical guidance for for designing high-performance microchannel J-T cryocoolers.