Forum for competition engine enthusiasts. RIP Guy Croft 09/11/2020 - This forum will continue both as a source of information and as a memorial to Guy.
Guy Croft wrote:Remember it's not being constantly pumped - the rad is still working when the hot engine is turned off. That cooling phase - heat soak is critical. That's why electric fans run on. The hottest point is the top of the engine, so quite naturally one puts the entry at the highest point of the radiator.
Yes for the engine radiator, you are quite right, but this is a water to air intercooler application. The water should never be anywhere near boiling temperature, and when the heat exchanger is really donig significant work the pump should always be working.
I agree if doing the entire heat exchanger design, tube sizes, fin thickness and reynold numbers etc. etc. should be calculated to find the optimum design. But this is a road car and choice of heat exchangers is probably somewhat limited so that might be a bit overkill.
Well, first thing to say I've never thought about it before, but the truth is is that both unions do not have to be at the top. I buy from Mocal and reading their catalogue - you can specify wherever you want them!
But with the small size of most car coolers and the high oil flow velocity I do know that great emphasis is placed on the efficiency of the fluid heat transfer by forced convection - between the end tanks, oil plates and air louvres than any effects from pure convection. And, notwithstanding the validity of the question, they work pretty well, don't they?!