Quote:
Originally Posted by Drake
How can two passing air flows do more than reach equilibrium? The same with relative humidity of the air flows. Without a HP extracting it.
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If the angle between the two airflows is perpendicular or less (ie they are going in the same direction) then you are correct. But in a countercurrent HX it is possible extract much more heat: Imagine air (or any other gas or liquid) in the cold intake - when it enters the HX it starts to collect heat from the 'hot' side (which at this point is barely 'warm', since it is already leaving the HX having given up most of its heat). As the 'cold' air makes its way through the HX the 'hot' side is getting warmer, so it still has heat to give up. The 'cold' air exits the HX where the 'hot' air enters, ie where the 'hot' side's temperature is highest.