Our lab designs a heat exchangers for hydrogen gas. Coolant is water, thus it is very difficult to determine heat transfer parameters in this gas-liquid system. Repeated experiments gives overdesign value 6.06%, overall heat transfer coefficient 36.32 ($kcal/m^2-hr-^{circ}C$) for Hydrogen. Theoretically determined overall heat transfer coefficient is 38.44 ($kcal/m^2-hr-^{circ}C$). Our lab simulated this system and overdesign 30.4% shows good match with this experiment by HTRI. These parameters are in same range with literature.