Heat Exchanger Theory and Intercoolers
by John Estill
Theory
An intercooler is a heat exchanger. That means there are two or more fluids that don't physically touch each other but a transfer heat or energy takes place between them. Turbo Regals made in 1986/87, Turbo TAs, GMC Syclones and Typhoons all came with intercoolers to cool down the hot compressed air coming from the turbocharger. Turbo Regals and Turbo TAs use outside air as the cooling media; Syclones and Typhoons use water. Turbo Regals made in 1985 and before did not have intercoolers as original equipment.
At wide open throttle and full boost the hot compressed air coming from a turbocharger is probably between 250 and 350 deg F depending on the particular turbo, boost pressure, outside air temperature, etc.. We want to cool it down, which reduces its volume so we can pack more air molecules into the cylinders and reduce the engine's likelihood of detonation.
How does an intercooler work? Hot air from the turbo flows through tubes inside the intercooler. The turbo air transfers heat to the tubes, warming the tubes and cooling the turbo air. Outside air (or water) passes over the tubes and between fins that are attached to the tubes. Heat is transferred from the hot tubes and fins to the cool outside air. This heats the outside air while cooling the tubes. This is how the turbo air is cooled down. Heat goes from the turbo air to the tubes to the outside air.
There are some useful equations which will help us understand the factors involved in transfering heat. These equations are good for any heat transfer problem, such as radiators and a/c condensers, not just intercoolers. After we look at these equations and see what's important and what's not, we can talk about what all this means.
The info is quoted at: http://www.gnttype.org/techarea/turbo/intercooler.html
