The issue of temperature difference between the primary and secondary sides of the heat exchanger
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Must the temperature difference between the primary and secondary sides of a heat exchanger be the same? For example, the primary side is 70℃/48℃, and the secondary side is 65℃/43℃. The end difference is 5°C. Can the temperature on the secondary side be 65°C/40°C? The end differences are 5°C and 8°C respectively.
The temperature differences between the primary and secondary sides of the heat exchanger can be different; the specific magnitude of these differences depends on the actual design of the heat exchanger and the conditions under which it is used. In the example you provided, the temperature on the secondary side can be 65°C/40°C, with terminal differences of 5°C and 8°C respectively. It should be noted, however, that either an excessively large or small end difference will affect the heat transfer efficiency and performance of the heat exchanger; therefore, a reasonable choice should be made based on the actual conditions. .
The temperature difference can be arbitrary, but thermal equilibrium must be maintained
Sure, it’s possible to reduce the amount of water on the secondary side
First of all, avoid using vague terms like “primary side, secondary side”; instead, use standard terms such as “shell side, tube side”； Secondly, as long as the temperatures on both sides do not cross each other, it is acceptable; if the temperature difference is fixed, what use is there for a heat exchanger?
:dizzy: Are heat exchangers only shell-and-tube types?
The terminal temperature difference on the primary and secondary sides depends on the process requirements, and it is determined by the process engineers, not by the designers. The smaller the end difference, the larger the heat exchange area required.
It seems to have relatively strict requirements regarding temperature; with co-current heat exchange, the efficiency would be low, I guess.
The plate type can achieve an end difference of 1 degree, while the shell and tube type can achieve 5 degrees. It becomes uneconomical at smaller sizes
Firstly, a heat exchanger is a tool for heat transfer; thermal equilibrium is sufficient within it, and the temperatures do not need to be identical. Of course, this is under the condition that the amount of heat transferred remains constant; if the temperatures differ, then the flow rate of the fluid will also vary. This is what enables thermal equilibrium, and it requires the use of calculation software as well as the expertise of designers to manage it. From your question, it seems that the person asking is referring to plate heat exchangers – in the case of plate heat exchangers, terms like \"primary side\" and \"secondary side\" are used, and these terms are intended for those who are not familiar with this field.:lol