Regulation of the interaction of heat exchange and throttling effect for a Joule-Thomson cooler with rectangular microchannels.

• A J–T cooler fabricated using PCB technology serves as a prototype. • Experiments are conducted with two fluids, and the mathematical model is proved. • Strategies are proposed to regulate the thermodynamic state before throttling. • The analysis surpasses the concept of neglecting heat exchange during throttling. Applying microchannels in Joule-Thomson (J-T) coolers can enhance precooling. The regulation of heat transfer and throttling is crucial to lower the cold terminal temperature T cold.The present cooler with rectangular microchannels served as the prototype. The experiments were carried out under 4, 5 and 6 MPa, with Ar and N 2 as the refrigerants. The cooler can achieve the lowest cold terminal temperature (T cold , 194.9 K) at 6 MPa. Then, the mathematical model was verified. The analysis showed that under the premise of constant total length and working condition, the precooled temperature before throttling could be reduced, and finally, the T cold could be reduced. There are two ways to regulate. On the one hand, extending the recuperative structure (CFHX)'s length and reducing the length and cross-sectional flow area of the throttling structure (THR). This regulation increased the heat exchange per unit mass q m and the integral throttling effect ΔT jt in each section and finally reduced the T cold. When the length of THR was decreased to 15 mm, and the end of THR reached the chocked flow, the T cold reached the lowest value of 166.3 K. On the other hand, when fins were added in CFHX, THR became shorter. This method enhanced the precooling at the expense of pressure drop in CFHX. When the fins' number raised from 0 to 6, T cold declined. When the number is 6, the T cold decreased by 7.7 K. As the number went on rising, the performance eventually deteriorated. [ABSTRACT FROM AUTHOR]