HOT UNDER THE COLLAR

Every few months I see something in Car Mechanics which is so completely wrong that I feel compelled to contact you about it. This time it’s in the Cool It! feature on page 62 of the October issue:

Q: Is a shiny alloy radiator less efficient at absorbing heat than a standard black plastic and steel radiator?

A: Black absorbs the heat, so a black radiator retains more of the heat than a shiny radiator, which reflects and emits it.

A radiator is not used to absorb heat, it is there to dissipate heat from the coolant, thus cooling the engine (this is correctly stated in ‘Radiator Upgrades’ on p63). Being black does not mean the radiator retains more heat, rather it makes it more efficient than a shiny one at transferring the heat from the coolant into the air.

The suggestion that a shiny radiator reflects heat is irrelevant in a normal car radiator – the fact that a radiator is shiny will mean it doesn’t emit heat as well as a black one, all other things being equal.

Given that there was no restriction in what questions to put in the FAQ, it was a pity that one that showed a lack of clarity in both the question and the answer could not have been substituted with one that was more informative. To have selected that particular question and answer made me doubt the validity of the whole article.

John Mcnally

Rob Hawkins responds:

You’re quite right, John, and thanks for pointing this out. I was trying to further explain heat absorption and upon reflection (no pun intended), I should have tackled it differently in the FAQ section.