An intercooler is used to remove waste heat from the first stage two stage air compressor. Due to its inherent efficiency, a two-stage air compressor was manufactured. The cooling effect of the intercooler is mainly to increase the efficiency and bring it closer to the Carnot efficiency. The removal of the heat of compression from the effluent of the first stage has the effect of densifying the charge of the air. This in turn allows the second phase to generate more work from its fixed compression ratio. Adding an intercooler to the setup requires an additional investment.
Two-stage compressor pump showing the location of the intercooler.
Internal combustion engines
Intercoolers increase the efficiency of induction systems by reducing the amount of induced air heat generated by the supercharger or turbocharger and promoting more thorough combustion. This eliminates the heat of compression (i.e., temperature rise) that occurs in any gas as the pressure rises (i.e., its unit mass per unit volume - density - increases).
Due to the forced induction, the reduction in the intake air temperature maintains the use of more dense intake air into the engine. The reduction in intake air charge air temperature also eliminates the risk of pre-explosion (knocking) of fuel/air charge prior to timed spark ignition. This preserves the benefit of more fuel/air combustion per engine cycle, increasing the output of the engine.
The intercooler also eliminates the need to use a wasteted method of reducing the charge charge temperature by injecting excess fuel into the intake chamber of the cylinder to cool the intake charge before the intake air stream enters the cylinder. This wasteful approach (before using the intercooler) almost eliminates the increase in engine efficiency caused by forced induction, but it does not require any cost to prevent engine damage caused by engine knock before detonation.
The inter prefix in the device name originates from its use as a cooler in between compression cycles. Typically in automobiles the intercooler is placed between the turbocharger (or supercharger) and the engine (the piston compression produces the next compression cycle). Aircraft engines are sometimes built with charge air coolers that were installed between multiple stages of forced induction, thus the designation of inter. In a vehicle fitted with two-stage turbocharging, it is possible to have both an intercooler (between the two turbocharger units) and an aftercooler (between the second-stage turbo and the engine). The JCB Dieselmax land speed record-holding car is an example of such a system. In general, an intercooler or aftercooler is said to be a charge-air cooler.
Intercoolers can vary dramatically in size, shape and design, depending on the performance and space requirements of the entire supercharger system. Common spatial designs are front mounted intercoolers (FMIC), top mounted intercoolers (TMIC) and hybrid mount intercoolers (HMIC). Each type can be cooled with an air-to-air system, air-to-liquid system, or a combination of both.