Air-side resistance of plate-fin heat exchangers
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I need help from all the teachers! When designing the cooling system, plate-fin heat exchangers (water-air heat exchangers) are used, with an overall thickness of 100–120 mm. However, the parameters provided by the heat exchanger manufacturers are rather vague; the air-side wind resistance is sometimes given as 120 Pa and at other times as over 300 Pa. This makes it difficult to choose the appropriate fan. When using EBM axial flow fans, there are basically no airflow specifications available when the wind resistance exceeds 250 Pa. I would like to ask the experienced experts here: when using plate-fin heat exchangers as water-air heat exchangers, in the absence of phase change heat transfer, how should one consider the air resistance of the heat exchanger and the selection of fans? (As far as I know, the air resistance of plate-fin heat exchangers is indeed very high.)
I have no experience with plate-fin heat exchangers. Based on my experience with air-cooled units of the finned-tube type, the wind resistance depends on the length and width of the heat exchanger as well as its thickness. At a static pressure of 120 Pa, the wind speed should be quite low. It is recommended to achieve a static pressure of over 200 Pa upon marriage
The greater this wind pressure, the lower shouldn’t the air volume of fans of the same model be? The air volume of the fan I use regularly is around 17,000 m3 at 120 Pa; it drops significantly when the pressure reaches 200 or 300 Pa
Since I am not familiar with your design structure, based on our experience with plate-fin heat exchangers, I suggest considering this aspect: for the same equipment size, if the fins are thicker, or for the same fan but with a smaller equipment size, then increase the static pressure
It can be considered to ensure that the air volume at 200 Pa meets the air requirement of the heat exchanger. At this time, the resistance on the air side of the heat exchanger is 120 Pa, and the fan has sufficient airflow capacity.
You should agree on the resistance value with the manufacturer in advance; choose the fan based on this resistance value, so that the manufacturer’s heat exchanger will not exceed the resistance level you specified. Of course, any subsequent adjustments also need to be carried out simultaneously.