Thermal design of liquid cooled charge air cooler: A computational approach

Abstract

Successive advent of vehicle emissions norms & strong emphasis on fuel efficiency have enforced vehicle manufactures to deploy turbo charging of intake air prior to intake manifold. However introduction of turbochargers also signify need of a heat exchanger called charge air cooler or intercooler to reduce the temperature of turbocharged air to optimum limit prior to intake manifold of engine. The major limitation of conventional air to air charge air coolers is that they yield low heat transfer rate to weight ratio & low heat transfer rate to frontal area ratio characteristics. Beside this at higher boost pressure and higher temperature conditions there are metallurgical challenges for conventional air to air charge air coolers. Therefore; design optimization aimed at improved heat transfer from charge air is the need of strict environmental norms (Euro V onward). Rapid growth of automobile sector coupled with cutting edge technology development is also leading demand for highly efficient as well as compact solutions for charge air cooler. This provide motivation and challenge to design highly optimized new technology based system, which can provide increased rate of heat transfer with lesser pressure drop & overall compact size. To overcome discussed limitations of conventional air to air charge air cooler; the present research explores thermal design of liquid cooled charge air cooling device with unique charge air flow mechanism. The new design of liquid cooled charge air cooler provides multiple flow passes in order to achieve advantages of both cross flow as well as counter flow type heat exchangers. Multiple flow passes basically ensure maximum interaction of two heat exchanging fluids; hence heat exchanger effectiveness gets improved. Charge air is introduced to the heat exchanger with the help of an inlet tank header. The flow of charge air around the heat exchanger is precisely controlled by a casing, which ensures a uniform guided flow to successive passes of heat exchanger. An outlet tank header serves the purpose of supplying charge air to the engine intake manifold. A Computational Fluid Dynamics (CFD) methodology is used to optimize flow dynamics of two working fluids, namely liquid water and charged air coming out of turbocharger.