Seeking help in selecting a heat exchanger
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Dear sea friends, if you are facing urgent challenges in selecting heat exchangers at work, could you please help? The specific known data are as follows: Air is preheated using flue gas from a heat treatment furnace. The flue gas inlet temperature is around 500 degrees, with a flow rate of 11,000 cubic feet per hour. The inlet air is at room temperature, the outlet temperature is 300 degrees, and the flow rate is 5900 cubic feet per hour. I wonder if these given parameters are sufficient? I choose a shell-and-tube heat exchanger; please calculate the heat exchange area. Thank you. I hope the calculation steps can be more detailed
In this case, a finned tube heat exchanger is more suitable.
Finned-tube types won’t work; a plain tube air preheater is what’s needed – just place the tube bundle directly inside the flue. It’s sufficient to increase the wind pressure of the exhaust fan a bit. I can’t do the calculations, so I’ll ask someone from my company to handle it
Why can’t finned tubes be used?
Go back to the 4th floor; too high a temperature will create thermal resistance due to gaps, which affects the heat exchange efficiency.
Thank you all, waiting for your calculation results
Fin shapes can be used, but it is not suitable for high-temperature materials to flow outside the tubes; moreover, the issue mentioned by the friend on the 5th floor also exists, so external fins are not appropriate. Internal fins are still suitable; I have worked on many projects involving heat recovery from high-temperature gases using heat exchangers with internal fins, and the results have been good (such as heat recovery from engine exhaust gases, etc.).
If external finned tubes are used, medium and low fins in an integrally fabricated form can be employed. It’s possible to do it.
OP, the unit of your traffic seems a bit unclear. 11,000 cubic meters per hour – shouldn’t there be a length unit after cubic as well?
If I were to do this, first of all, this operation involves gas-to-gas heat exchange; therefore, based on my past experience and achievements, I would design it as a finned heat exchanger with inner and outer fins. What needs to be considered next is the level of solid dust in the flue gas. If the dust content is low, hot flue gas can be routed through the inner fins while cold air can be routed through the outer fins. . . . . The parameters provided by the poster currently need to be clarified: the flow rate must be specified, as well as the volumetric flow rate under specific operating conditions; in addition, the exact pressure is required (it is usually slightly positive, but it’s best to provide it anyway) ； The allowable pressure drop also needs to be provided; furthermore, if cold air is introduced using conventional fans, it is advisable to provide the humidity parameter. To facilitate connection with other equipment on-site, it is advisable to provide the pipe sizes for the hot and cold gas inlets and outlets as well. . . . . .
That’s the basic unit of measurement that’s commonly used; for example, if your height is 1.80, it’s understood that the unit is meters