The influence of the number of shell sides in a heat exchanger on the flow direction of the fluid
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I have always thought that hot fluids move from top to bottom, while cold fluids move from bottom to top. But when he reviewed my diagrams, he said it’s not absolute and depends on the number of shell sides of the heat exchanger. If it is a double-pass type, then both the cold and hot fluids flow in from the top and out from the bottom. But I don’t quite understand; please give me some guidance.
The flow direction of hot and cold fluids is not fixed; it depends on the equipment and the actual production conditions. Whether the flow is from top to bottom or from bottom to top depends on the specific process medium and production conditions, and cannot be determined simply by looking at the number of tubes in the heat transfer circuit
The two-way, six-way, eight-way, etc., design of heat exchangers has nothing to do with the inlet and outlet positions of the hot and cold fluids; it’s not true that a two-way heat exchanger necessarily has fluid entering from above and exiting from below. The inlet and outlet arrangement in a heat exchanger is primarily determined by the properties of the medium, the heat exchange requirements, and the structure of the heat exchanger itself. Except in cases where gases such as steam are used for heating, conventional designs with one-way or two-way flow usually involve fluid entering from below and exiting from above. This arrangement allows the gas to be expelled after the medium enters the heat exchanger, ensuring that the heat exchange medium can fill the entire heat exchanger. Since the heat transfer efficiency of liquids is much higher than that of gases, this approach helps to maximize the heat exchange performance of the heat exchanger.
The flow direction of hot and cold fluids must take into account the structure of the heat exchanger and its heat transfer efficiency, as well as whether phase changes occur.
It’s not fixed; what was said on the second floor makes a lot of sense. Sometimes, for example, it’s necessary to take into account the temperature difference for heat exchange, in order to avoid a situation where that temperature difference is 0.
I found that one of the heat exchangers in our factory works in the same way: the hot fluid enters at the lower level and exits at the higher level, while the cold fluid enters at the higher level and exits at the lower level! I can’t figure it out!