Barnard
Heat lost by a surface = temp diferential between surface and air X heat transfer coeficcient x area.
If you drop heat transfer coefficent by a factor of 4 it has the same effect as reducing the temperature differential by the same factor when you look at heat transfer from the surface.
With a moving fluid at the heat transfer surface it gets more complicated, but the basics are still the same.
Anything technical written by Max Torque is fact. I wish he posted a lot more so that we hobby tuners could poach/apply more of his (and his employers)insider knowledge, thats come from r&d budgets we can only dream of.
If you think it makes no difference, ceramic coat your intercooler core.
The heat transfer coefficient of the coating has very little to do with it.
Firstly, the heat transfered by convection is dependent on the
overall heat transfer coefficient between the media (air and the ceramic or metal surfaces). Not by just one of them. The heat lost to air by natural convection is mainly determined by the heat transfer coefficient of air which is about 2000 times worse than steel and about 130 times worse than Zirconia (the coating)
The overall transfer coefficient is determined by
adding the reciprocal of the individual heat transfer coefficients together. So even if you reduce the heat transfer coefficient of one component by a factor of 4 it only reduces the overall coefficient by 7%
Secondly, the heat lost by radiation is not affected by the heat transfer coefficient at all, only by the temperature of the surface and its colour.
I agree that ceramic coating an intercooler would be a dumb thing to do, but only because:
a) the heat is transferred by
forced convection which in this case would be 30-50 times more effective than natural.
b) there is no heat lost by radiation.
I agree fully with you about Max_Torque (and Bill for that matter) and normally their knowledge is far greater than mine, but having experience in this field I felt I should comment rather than let somebody waste their money.
If Max (or anybody) has any under bonnet ambient air and surface temperatures that show surface coatings do the job then please share them.
Bernard