How does everyone calculate the overall heat transfer coefficient when designing heat exchangers?
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This post was last edited by a senior beginner in design on 2016-3-11 at 09:35. I am currently working on the design of a shell-and-tube heat exchanger; saturated steam flows in the shell side, while wastewater with a certain concentration flows in the tube side. It is necessary for the fluid in the tube side to evaporate to produce steam, with an evaporation mass ratio of less than 10%. Based on preliminary calculations using the EDR and HTRI software, the values for the overall heat transfer coefficient obtained by these software tools are all in the range of 1100–1200 (W/m2·K). The property data used in the software are all those of water. Since it is a forced circulation, the overall heat transfer coefficient seems to be a bit low. Additionally, the fouling caused by dirty water must also be a significant factor; it doesn’t seem like it could be that substantial. So I’m quite unsure about this overall heat transfer coefficient. I previously calculated it manually using the formulas from the chemical process design manual, and the assumed values and the actual calculated values turned out to differ significantly. I would like to ask everyone: how can we estimate the overall heat transfer coefficient appropriately during design?
I think the impact of dirt thermal resistance is quite significant.
It’s all based on experimental empirical values; I don’t know either
I think it’s not low; one factor is the flow rate within your system, and the other is the choice of scaling, as these have a significant impact on the overall heat transfer coefficient.
Isn’t the dirt thermal resistance being ignored for now? I’m optimistic about many cleaning coefficients