Parametric study on thermal shield cool-down: Effect of various flow conditions

Thermal performance criterion of the TACB (Test Auxiliary Cold Box) dictates the need for an effective thermal shield between the ambient temperature at 300 K and the cold mass at 4 K, in line with the maximum heat load limitation of the cryoplant at 4 K temperature level. This thermal shield, to be forced flow cooled and maintained at 80 K temperature level will screen direct thermal conduction and radiation heat loads from the ambient to the cold mass. The design objective is to attain cool-down of the shield within a desired time frame with least possible cryogen mass flow rate and pressure drop across the thermalization channel while adhering to the allowable heat load limit at 80 K temperature level. In the present paper, a transient thermal analysis is carried out by varying the process conditions, i.e. pressure and mass flow rate of the cooling fluid to compare time dependent thermal characteristics of the shield during cool-down and decide the optimum flow parameters from the available range.