Air cooler
Thread Content
If the heat transfer coefficient on the inner surface of the tubes of the air cooler is high, why is it still necessary to use large fins? Why choose low wings or even bare tubes when the coefficient is low?
Because the fins used have an outer diameter of 25 mm; those with a height of 12.5 mm are low fins while those with a height of 16 mm are high fins, in order to accommodate the thermal expansion of the tube bundle.
The heat transfer coefficients vary depending on the material inside the tube and the heat exchange medium; however, cooling by air outside the tube results in the lowest heat transfer coefficient. Thus, the bottleneck for heat exchange lies outside the tube, which is why it is necessary to increase the heat transfer coefficient inside the tube； If the heat transfer coefficient inside the tube is lower than that outside, adding fins will not improve the situation; therefore, using a plain tube is also sufficient
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