A numerical cool-down analysis for Dewar-detector assemblies cooled with Joule–Thomson cryocoolers

• Finite-elements modeling procedure of a DDA cooled by a JT cryocooler is presented.
• Pre-calculated properties are used to overcome the analysis limitations.
• The analysis is verified and validated against 12 experimental results.
• The analysis enables the prediction of the cool-down performances of JT cryocoolers.

Joule–Thomson (J–T) cryocoolers are commonly in use for rapid cool-down of Infra-Red (IR) detectors. The cool-down time is governed both by the J–T cryocooler performances and the Dewar structure, which is usually geometrically complicated. A finite-element model of the complete Dewar-Detector-Cooler Assembly (DDCA) is developed. The analysis calculates the heat transfer in the Dewar and the J–T cryocooler, the coolant flow rate, the pressure drop in the vessel that supplies the coolant to the J–T cryocooler, and the pressure drop in the low pressure stream of the heat exchanger that determines the pressure in the evaporator. A verification of the analysis is conducted against experimental results with a single cryocooler at a single scenario and the model is further validated against eleven other experimental results. A satisfactory agreement is obtained between the analysis and the experimental results.