About safety valve calculations

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Dear seniors, I have just entered the design industry for two years and have not been exposed to many projects. This time the company sent me to another place and asked me to calculate the safety valve. There was no one around to guide me, and I almost fainted. After reading API520 for two days, I have some questions that I don’t understand. Please help experts to answer them. (I hope to get help as soon as possible, because I will finish the calculation in the near future. . . . . . ), any help would be greatly appreciated. 1 Regarding the discharge amount under thermal expansion conditions, gpm=BH/500GC. This formula refers to hydraulic expansion. If the temperature rises and the gas expands, can this formula still be used? H is the total heat transfer, and the one I am calculating now is a reactor with cooling water flowing outside. In fact, the whole is equivalent to a heat exchanger, but how to calculate this heat transfer? (Q=K * A * T? ) 2 In API520 of the discharge amount under fire conditions, there is Q=21000FA^0.82, which is said to be the heat absorption of the wetted surface and the heat absorption of the unwetted surface A=F'A'/(P^1/2). If there is liquid in the tank and it absorbs heat and vaporizes, choose the first one. But if so, does this part of the heat make the original gas above the tank absorb heat or the liquid in the tank absorb heat and vaporize? As for the second formula, does it mean that only the gas absorbs heat? How is it different from that under thermal expansion conditions? 3. The problem of discharge temperature. How do you determine the discharge temperature under discharge pressure? For example, the discharge temperature under thermal expansion conditions and the discharge temperature under fire conditions is the saturated vapor pressure temperature under the discharge pressure? ? Please help me seniors, thank you. . . . . . . . . . . . .