My first posting, so apologies if this is in any way inappropriate to the forum/section. I am asking here for some scientific input to this question about a cooling system as, for example found in a classical motor vehicle; what is the likely relationship between coolant flow and heat transfer, given all other conditions being constant (heat input, air flow etc.). As an electrinics engineers, I have little knowledge of thermodynamics, so please keep answers fairly basic if possible. My suspicion is that there is a rate at which heat transfer peaks at some specific flow rate, ie faster flow rate does not necessarily result in greater heat transfer. In electronics, there is a maximum power transfer theorem that shows that maximum power is transferred from a generator when the load impedance matches the source impedance. I just wonder if something similar applies here?