A parametric study on the cooling characteristics of an infrared detector cryochamber

This work investigates the steady and transient cooling characteristics of an infrared (IR) detector cryochamber, which has a critical effect on the c ooling load that a refrigeration system should carry away. The current ther mal modeling considers the conduction heat transfer through a cold well, th e gaseous conduction due to outgassing, and the radiation heat transfer. Th e steady cooling load is obtained by using a fin equation. The transient co oling performance, i.e., the cool-down time, is determined using a finite d ifference method. It is shown that the gaseous conduction plays an importan t role in determining the steady cooling load, whereas it has a negligible effect on the cool-down time due to a short thermal penetration depth. The steady cooling load increases lineally with the bore conductivity when it i s high. However, when the bore conductivity is low and the eas pressure is high, the cooling load becomes more sensitive to the bore conductivity. The steady cooling load increases linearly with the difference between the amb ient temperature and the detector operation temperature, but rather the coo l-down time is proportional to the square of the temperature difference. Th e results of this work can be used to determine the thermally optimal desig n and operation conditions of the cryochamber. (C) 2001 Elsevier Science Lt d. All rights reserved.