Cryogenic cold energy recovery in liquid hydrogen refueling station with double-pipe heat exchanger

Abstract

Recovering the cryogenic cold energy of liquid hydrogen (LH2) for precooling high-pressure hydrogen gas before refueling can significantly reduce the electricity and energy consumption of liquid hydrogen refueling stations. Existing methods, such as blending, require continuous cryogenic pump operation and are not suitable for various operating conditions. This work proposes a novel method to recover LH2 cryogenic cold energy using a double-pipe heat exchanger, which can decouple the compression and refueling process and meet the fluctuating demand for the cryogenic cold energy required by the hydrogen dispenser. The lumped parameter method and temperature partition method were adopted to design the heat exchanger structure. Numerical simulations of a 2D axisymmetric swirl model were done to verify the accuracy of the temperature partition method applied to high-pressure cryogenic hydrogen. Due to the low temperature of LH2, the secondary refrigerant dichloromethane (CH2Cl2) risks freezing. Comparing the outer wall surface temperature of the inner pipe with the CH2Cl2 freezing point temperature, the optimal anti-freezing condition is that the outer pipe nominal diameter should be selected as 0.032 m and CH2Cl2 mass flow rate should be at least 1.72 kg s−1. Recovery efficiency can reach over 75.39% without freezing.