A point that is very confusing in the process calculations for heat exchangers
Thread Content
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 information, 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?
Different pressure drops should be the main reason for the differences in heat transfer coefficients.
This post was last edited by lupg on 2016-3-5 13:37. 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 layout is more sensitive, making it easier for the pressure drop to exceed the set limit. 3. After making these adjustments, the flow velocities for the two different layouts will differ, and the K values will also change. 4. It might be worth trying again: when using a bottom-in/top-out layout, increase the allowable pressure drop sufficiently so that there is no need to rearrange the pipes; in other words, keep the same number of pipes in both layouts, and then see how much the difference in K values is.
The poster is referring to flow in the same direction and flow in the opposite direction, right? Definitely, heat transfer with flow in the opposite direction is much better than that with flow in the same direction