Doubts in the calculation of HTRI heat exchanger processes
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In the calculations using the HTRI heat exchanger methodology, water is used as the fluid in both the tube side and the shell side; there is no phase change, and forced convection heat transfer occurs, with the equipment arranged in a vertical configuration. In the pipe train, there is a significant difference in the heat transfer coefficient on the pipe train side when water flows from below to above or from above to below. Why is this? According to available literature, in the case of forced convection without phase change, the orientation of the flow—whether vertical or horizontal—should not have any effect on the heat transfer coefficient. Are any experts interested in researching this? What are the considerations behind HTRI?
In my opinion, vertical and horizontal arrangements result in different flow velocities and flow patterns of the fluid within the heat exchanger; the heat transfer efficiency varies depending on these flow conditions, with laminar flow yielding the lowest heat transfer efficiency.
I personally think it has an impact, but the difference should be significant, so it’s unlikely. Let’s see if it’s a problem with your software settings
There is conversion between forms of energy, such as conversion between gravitational potential energy and kinetic energy. When the speed changes, it naturally has an impact on the heat transfer coefficient. You can increase the length of the heat exchanger, and this difference will become more apparent.
This post was last edited by lupg on 2016-3-5 13:35. 1. If the flow directions in both the shell side and the tube side change simultaneously, there is a greater likelihood of being affected by pressure drop. 2. In the design approach, once an allowable pressure drop is set, if the actual pressure drop exceeds this value during the calculation process, the number of pipes or even the number of devices will be adjusted. The fluid resistance in a vertical arrangement is relatively high, making it easy for the pressure drop to exceed the set limit. 3. After making these adjustments, the flow velocities for the two different arrangements will differ, and the K values will also change. 4. It might be worth trying again: when using a bottom-in/top-out arrangement, increase the allowable pressure drop to a sufficiently high level so that there is no need to rearrange the pipes; in other words, keep the same number of pipes in both arrangements, and then see how much the difference in K values is.
Thank you all for your responses. I tried it again: the fluid Reynolds number remained unchanged, the flow velocity stayed the same, the pressure drop was unchanged, only the heat transfer coefficient changed. Everyone is interested in giving it a try by simulating it.