Design and Optimization of Heat Exchanger for Cooling of Supercritical Helium Using Boiling Liquid Helium

Abstract

The indigenous Helium Refrigeration and Liquefaction plant (mixed mode operation) at IPR has an equivalent capacity of 1 kW refrigeration at 4.5 K. The vacuum chamber of the cold box in the He plant contains a liquid Helium container. This container will hold a heat exchanger to cool the supercritical Helium(SHe) from about ~5 K to 4.6 K. This project will involve the design and optimization of this heat exchanger. This vacuum chamber of the cold box will be a horizontal cylinder with a tentative diameter of 2.5 m and length ~8 m. It consists of many cold components for the production of liquid He (LHe). A part of high-pressure cold He will be taken to the LHe chamber through a J-T valve to produce liquid Helium and cool the supercritical Helium coming out the cold circulator (CC) using this heat exchanger. This cold circulator can circulate Helium in a closed loop through a by-pass valve within the cold box. Besides this, cold Helium (or SHe) required for applications outside this cold box are also circulated using the CC. This CC is a pump which will provide ~300 g/s supercritical Helium flow at ~4bar pressure and ~6 K temperature. The heat energy going into supercritical He due to pumping work and external heat load of the CC need to be removed by the heat exchanger contained in the liquid He container. The vapor from this container will return to the low-pressure cold return line passing through the heat exchangers of the main cycle of the He plant. As this chamber will be within the vacuum vessel, its size has to be minimized considering the size of the heat exchanger and the heat duty of it in different operational situations. There will be a requirement of operation of this He plant when external Dewar is not available, in which this internal LHe chamber will be used to produce liquid He for the performance test of He plant. This project will involve design and analysis taking into account of manufacturing, assembly and maintenance aspects and different off-normal operational conditions. It will also require the study of capabilities and deficiencies of Indian industries to manufacture this heat exchanger and try to find ways to remove these shortcomings towards realizing such heat exchanger.