Abstract: Liquid hydrogen has the advantages of high density and being able to be stored at atmospheric pressure, making it more suitable for storage and transportation than high-pressure gaseous hydrogen. In current liquid storage gas refueling hydrogen refueling stations, the stored liquid hydrogen needs to be pressurized and gasified, and can only be used for fueling after being transformed into high-pressure gaseous supercritical hydrogen in an Air Ambient Vaporizer（AAV）. For the design of AAV, currently only basic heat transfer calculation formulas are used as guidance, and there is a lack of exploration of the heat transfer characteristics of specialized vaporizer used for high-pressure （45 MPa） supercritical fluids. The numerical simulation methods and Fluent software were used to calculate the overall coupled heat transfer model, including the internal and external flow fields and the solid domain of the pipe wall. Using the obtained overall heat transfer coefficient as a reference, the special structure of the vaporizer, the temperature and flow state of the air domain, and the inlet temperature and flow rate of the supercritical hydrogen were discussed. The results are helpful for the design and calculation of similar vaporizers, and also provide reference for the overall layout of vaporizers during actual operation.