Mitigation of effects of pulsed heat load from fusion devices on helium refrigerator: A novel technique using vapor compression cycle

• Helium refrigerators operate in pulsed heat load from fusion devices.
• Immediate effect is high fluctuation in mass flow rate of stream returning to cold-box.
• Use of vapor compression cycle may mitigate flow fluctuations.
• Maximum mitigation of 70% and 96% during high and low heat load conditions may be achieved.
• Applicability of the scheme and feasibility of cold compressor and parallel heat exchanger are presented.

Helium refrigerators used in fusion devices are subjected to pulsed heat load. Immediate effect of such load is high fluctuation of mass flow rate at the return stream. A novel technique using vapor compression cycle at the cold end of helium refrigerators has been proposed to mitigate this flow fluctuation. The concept behind the proposed scheme is to re-liquefy excess return stream during high heat load condition and store. During low heat load condition, mitigation is obtained by increasing vapor fraction after expansion in JT valves by increasing inlet temperature of these valves. Dynamic simulation of a plant modified with vapor compression cycle has been performed and it has been found that approximately 70% and 96% mitigation of flow fluctuation during high and low heat load respectively, can be achieved. Criteria of selection and technical feasibility of critical equipment for implementation of the concept have also been discussed.