Efficient cooling system designs are required for the modern diesel truck engine to meet new standards of increased efficiency and reduced emissions. Often, emissions reduction requires substantial cooled exhaust gas recirculation (EGR) to decrease peak combustion temperatures. This extra heat rejection imposes additional costs on the cooling system, and may not comply with application space constraints. Space and cost constraints require minimization of EGR cooler size and the risks from coolant boiling and exhaust condensation, while restraining growth in radiator frontal area, pumping power, and fan power. These objectives are usually contradictory, and a careful optimization is needed. This paper examines the effect of a coolant flow rate and peak temperature on these objectives, in parallel-flow and counter-flow arrangements of EGR cooler systems. It is concluded that these systems are likely to be inadequate, and alternative configurations may be necessary.

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