A working principle for charge air coolers:
A charge air cooler manufactured by Vestas aircoil will feature within it, a series of tube and fin elements. Fins are mechanically bonded to the outer surface of the tube. The principle is simple. By increasing the surface area, there is a consequent increase in the cooling surface, providing the bond between the tube and the fin is sufficiently strong to allow energy (heat) to pass. The same principle is used in reverse in a water heater (radiator).
The materials of construction are important: It’s all too easy to cut corners here. Of course, the prudent engineer wishes to purchase at the best possible price, but consider the lifetime you expect from the replacement and how an air cooler company achieves your requirement.
You should expect, first of all, that the materials of construction are of suitable quality and that the supplier can prove the case. Copies of material certificates should be available for inspection by you if you wish. 90/10 cooper nickel tubes are the optimum choice, but there are higher grades too if appropriate. As for the fins, copper is the correct material. If a company offers aluminum fins, you can expect a very short operational life.
The replacement cooler should be constructed in a way, which accounts for all the physical stresses that it will encounter. Of course, the cooler has no moving parts and is therefore often considered of less importance, but what happens if the cooler begins to fall apart in your engine?
Its design should allow for the stress of uneven expansion and contraction caused by a temperature difference in excess of 150 degrees C across it. It should also be rigid enough to withstand, sometimes, significant vibration.
A full tube support mechanism is therefore essential. Integral tube supports plates, positioned at intervals along the length of the air cooler are recommended. These plates are in effect intermediate tube plates and allow every tube to be mechanically bonded to every other tube, not just at either end of the cooler but throughout its entire length. If individual tubes or rows of tubes are allowed to float free or simply clamped with bars on the outside face of the cooler fins, then there is nothing to stop early mechanical failure caused by vibration. Our advice would be to question any potential supplier on this specific point in detail.
How are the fins attached to the tubes? There are two ways, and both are available from Vestas aircoil a/s. either by full immersion of the finished elements in to a bath of tin (Tin coated); thus effectively turning the fins and tubes into one solid component. Or: by expanding the diameter of the tube beyond its point of elasticity (Standard); thus gripping the fins to it. Both methods are effective but the coated versions have advantages in contaminated environments.
There is a significant advantage if the number of separate components is kept to a minimum. A “mono block” fin and tube element, encompassing as many tubes as possible is preferable. The lifetime of the product will be longer where the possibility of separate components interacting against each other is removed.
Vestas has extended its maximum fin width to 77 tubes wide, big enough for almost all size of coolers – we call it a “MonoBlock” element. A MonoBlock combined with a full integral support plate means there is effectively a one piece element. Fewer components means a more robust air cooler. Perfect where there is vibration.