The number of these baffles and the ratio of arch gaps have been set too high
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This post was last edited by wpw121 on 2010-6-26 at 17:01. It deals with a heat exchanger in which the tubes are arranged in a regular hexagonal pattern. The inner diameter of the tubes is 15 mm, the outer diameter is 19 mm, the length of the exchanger is 6 m, there are 56 tubes in total, the shell diameter is 270 mm, the distance between the baffles is 200 mm, and there are 29 baffles. The effective cross-sectional area through which the fluid in the shell side passes through the tube bundle is 0.0131 m2. To make the effective cross-sectional area through the gaps similar to 0.0131 m2, it is necessary to choose a bow-shaped gap ratio of 45% for the shell diameter; in this case, the effective cross-sectional area through the gaps becomes 0.0121 m2. It seems that the number of baffles and the chosen bow-shaped gap ratio are too high. (The pressure drop in the shell side is 1 kPa, which is within the allowable range.) ； Please discuss it.
It is mainly a problem related to the flow rate in the shell side; too low a flow rate can result in an insufficient overall heat transfer coefficient. It is also necessary to compare this with the heat transfer coefficient on the tube side. If the heat transfer coefficient on the tube side is higher than that on the shell side, then it is important to consider increasing the flow rate, as this will yield better results. As a consequence, the pressure drop of the fluid in the shell side will increase. For small heat exchangers like these, this is not an insurmountable problem.
Since other process conditions are not provided, it’s really impossible to proceed, and there’s no direction for the discussion.
Is the gap between the baffles of 200 mm determined through process calculations or is it set arbitrarily? Is it too large?