# Calculating the effectiveness of a Radiator and Fan Combination

 P: 50 There are a couple of different approaches this. I'll explain one possible method. Firstly, I would say that it is essential to establish the flow rate of air through the radiator. You said that you have the pressure-flow characteristics of your fan. However, you don't know the operating point on the fan curve. You need to determine the resistance curve (pressure-drop curve) of the radiator. You could do this experimentally but I'm not sure what kind of equipment you have to do this? It would probably be better to find some friction factor correlation in literature and calculate the pressure drop from this. This friction factor is a strong function of the geometry so be carefull when selecting an appropriate correlation. This will enable you to calculate the pressure drop for a range of arbitrary flow rates. This curve can then be plotted against the fan curve and the intersection between them is your operating point! At this stage you can calculate your heat transfer. One possible way is by using the equation $\dot{Q}$=$\dot{m}$Cp(Tfluid - Tair) where mdot is the mass flow of air established from your operating point. An alternative approach would be to calulate the Nusselt number, which will give you the heat transfer coefficient and you could then use the equation Q=hAdeltaT. But this is probably more complicated.