Quote Originally Posted by relttem View Post
This can be answered by that balance I posted:

h*A*(T2-T1) this is the air side heat transfer. IF, the air flow rate is the same, then h is constant, A and (T2-T1) are both constant as you mentioned.

This has to be balanced by

mdot*Cp*(T2-T1), which is the water side heat transfer.

mdot is your mass flow rate. Cp is going to be pretty constant at these small temperature changes. So, as mdot slows (T2-T1) (larger temperature difference) has to go up to balance the equation..or the other way around...as mdot gets higher your (T2-T1) (smaller temp difference) gets smaller..
Which is exactly what I am getting at. The situation as described by rosco has the low speed fans saturated from a certain flowrate onwards. This means that the airflow half of the equation is constant. The problem here is that the chart shows the water half of the equation going down .... how?