Process analysis and sizing of heat exchangers for an LN₂ cooled external helium purifier

Horizontal Testing Stand (HTS) and Vertical Test Stand (VTS) facilities are operational at RRCAT, Indore for testing of the Super Conducting Radio Frequency (SCRF) cavity at 2 K temperature. An external helium purifier is required to ensure the continuous and efficient operation of these testing facilities for longer durations. This system purifies the impure helium from these testing facilities and supplies it to the cryogenic liquid helium (LHe) plant for liquefaction. The purifier consists of helium dryer, three heat exchangers and Liquid Nitrogen (LN₂) cooled charcoal adsorber. Impure helium is initially cooled to LN₂ temperature using series of heat exchangers, and then it passes through a charcoal adsorber for further purification. This complete heat exchanger assembly is housed inside the vacuum vessel. The present work describes the design of these heat exchangers, system analysis for different process conditions, and parametric study to identify the relative importance of each heat exchanger of a helium purifier. A computer program has been developed for the parametric study and for sizing of heat exchangers considering the fluid properties variations.