Help with calculating heat transfer area
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I need to design a heat exchanger, which can also be considered a heater. Coils are installed inside a tank, with saturated steam (0.8 MPa, 170°C) flowing through these coils; the output fluid is cooled water at 50°C. The diameter of the tubes and the flow rate are known, but it is not clear how many tubes are used to convey the steam. In this process, condensation and cooling take place, resulting in heat release； At the same time, the Freon liquid in the tank absorbs heat and evaporates to become saturated Freon vapor. Once the Freon liquid has absorbed enough heat to reach stability, I believe the temperature remains constant, just like when water boils; this temperature is known (the temperature of saturated Freon vapor may be slightly higher than that of the Freon liquid, with the liquid temperature being 38 degrees). The Freon liquid inside the tank does not flow, but the evaporated Freon vapor condenses and returns to the tank. It can be assumed for now that this has little effect on the unevaporated Freon liquid in the tank. Experts, how can one calculate the overall heat transfer coefficient, the heat transfer area, given that the amount of heat transferred is already known? I’m begging experts for help! It would be great if anyone could send me similar examples. Thank you all in advance! ! ! !
Q = M*CP*ΔT = UA(LMTD). With the specific heat known, the temperature difference known, and the mass known, the total amount of heat can be determined. It depends on what type of heat exchanger you are using; the theoretical U value and area can be found, and then the calculation can be carried out. One thing to note is that when using saturated steam for heating, the outlet temperature becomes 50°C. In other words, the steam undergoes a phase change before its temperature drops inside the heat exchanger... Therefore, for steam, the energy calculation needs to take into account both the phase change and the temperature drop. That’s how it works
Q = M*CP*ΔT = UA(LMTD). With the specific heat known, the temperature difference known, and the mass known, the total amount of heat can be determined. It depends on what type of heat exchanger you are using; the theoretical U value and area can be found, and then the calculation can be carried out. One thing to note is that when using saturated steam for heating, the outlet temperature becomes 50°C. In other words, the steam undergoes a phase change before its temperature drops inside the heat exchanger... Therefore, for steam, the energy calculation needs to take into account both the phase change and the temperature drop. That’s how it works
The last edit to this post was made by wiseboy on 2019-6-11 at 14:38: “But the fluorocarbon vapor that evaporates condenses and returns to the tank.” The only key figure you didn’t mention is the amount of vapor that evaporates. If you tell me the evaporation rate, my coil heat exchange simulation software is designed specifically to calculate this issue. Such problems are common, which is why we developed the Coiled Tube Heat Exchange Doctor software.