With the same process conditions, why is there such a large difference in the overall heat transfer coefficients of the shell-and-tube and tube-shell exchangers designed?
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The process conditions are the same; why is there such a large difference in the overall heat transfer coefficient between a shell-and-tube heat exchanger and a double-pipe heat exchanger? ? I calculated using TASC, and the overall heat transfer coefficient of a shell-and-tube heat exchanger is 2.5 times that of a tubular heat exchanger. Why is this? ? I did some research on it myself, and the main difference is that the flow velocity of the fluid in the heat exchanger inside the sleeve is about 10 times that in a shell-and-tube heat exchanger. Could this be the reason?
You’ve done the right research – the convective heat transfer coefficient is related to the Reynolds number; it is approximately proportional to the 0.3–0.4 power of the Reynolds number. Since the Reynolds number is proportional to the square of the velocity, this means that a higher velocity results in a higher convective heat transfer coefficient. This effect is particularly significant for liquids such as water~~
In other words, if the flow rates of the fluids on both sides are relatively low, resulting in extremely low flow velocities within the shell-and-tube heat exchanger and thus a very low overall heat transfer coefficient, it would be advisable to consider changing the conventional shell-and-tube heat exchanger, for example by replacing it with a coiled-tube heat exchanger? ?
Right! In a typical shell-and-tube heat exchanger, if the fluid in the shell side is a liquid, the flow rate should be around 0.7 m/s; for the tube side, it should be 1.0 m/s. If these flow rates are not met, the heat exchange efficiency will be poor, and another type of heat exchanger may need to be used. Of course, sometimes a comprehensive consideration is needed; when the total heat exchange area is less than 30 m2, the multiple-tube and double-tube hairpin type can also be used. Therefore, the type must be selected after obtaining the process data.
Those who are looking for tube-and-shell heat exchanger designers and want to change their work environment can get in touch with me~~~~~:lol
This post was last edited by wanlirn on 2022-8-8 at 15:36. Another factor is that the sleeve operates in pure counterflow mode. The temperature difference correction factor for shell-and-tube exchangers… Let me tell you another secret: the calculation formula for shell-and-tube heat exchangers is derived by using experiments conducted with coiled tube exchangers, and then adding a series of coefficients to obtain an approximate formula. Do you see that the calculation of the heat transfer coefficient in the shell side includes an equivalent diameter? It was switched to a shell-and-tube heat exchanger
Yes, this answer is very standard