How to Design a Cryogenic JouleThomson Cooling System: Case Study of Small Hydrogen Liquefier

Heat exchangers are the critical components of refrigeration and liquefaction processes. Selection of appropriate operational conditions for cryogenic recuperative heat exchanger and expansion valve operating in JouleThomson cooling system results in improving the performance and efficiency. In the current study, a straightforward procedure is introduced to design an efficient JouleThomson cooling system. Determining the appropriate operational conditions and configuration of streams within the recuperative heat exchanger are discussed comprehensively. A JouleThomson cooling system including helically coiled tube in tube heat exchanger and expansion valve was considered as a case study. Simulation was performed by procedure different from conventional finite element method and the results were validated versus data obtained from small laboratory hydrogen liquefier. In accordance with mathematical modeling performed on the recuperative heat exchanger, it is better to flow low pressure hydrogen inside the inner tube and high pressure hydrogen within the annulus. This arrangement results in needing shorter length for heat exchanger tubes compared with reverse arrangement..