Evaluation of a technique to mitigate effects of pulsed heat load of fusion devices on helium refrigerator

Abstract

Pulsed heat load in helium refrigerators used in fusion devices causes high fluctuation at return stream to cold-box. Therefore, inlet temperatures and volumetric flow rates to turbines and temperature profiles of heat exchangers varies unacceptably resulting tripping of the plant. Therefore, there is a need to reduce the fluctuation in return stream to an acceptable level. The simplest mitigation scheme is to bypass excess flow rate during high heat load. However, this technique leads to thermodynamic losses. The purpose of the paper is to present the losses associated with this technique and to demonstrate use of heating systems during low heat load together with this method for mitigation of fluctuating flow throughout the pulsed load. The competing parameters of thermodynamic losses vis-a-vis level of fluctuation of vital parameters have been presented in this paper to design and operate the plant at an optimum level.