Understanding the physical phenomena that occur inside heat exchanger for liquefactin of hydrogen

Abstract

Liquid hydrogen is an attractive solution for long-range distribution. The largest barriers for implementing large-scale hydrogen liquefaction plants are currently their high energy consumption and cost. The heat exchangers are among the most important equipment in these plants. It has been shown that it may be beneficial to use a mixture of helium-neon ("Nelium") as refrigerant in the cryogenic cooling cycle, because this gives the possibility to utilize highly efficient turbocompressor equipment. In this work, we discuss the physical phenomena that are expected to occur inside cryogenic heat exchangers if Nelium is used as refrigerant for low temperature cooling and liquefaction of hydrogen. We present a detailed heat exchanger model for a simple heat exchanger geometry and study phenomena such as nonequilibrium ortho-para conversion, possible solid-formation of neon and boiling/condensation of Nelium at the lowest temperatures. We elaborate how the physical phenomena can be exploited in the design of more energy- and spaceefficient heat exchanger equipment for hydrogen liquefaction processes.