The present analysis is essentially a theoretical approach to establish the performance characteristics of engine oil cross flow heat exchanger with cold air as the unmixed coolant at different altitudes of the flight. The present configuration of the heat exchanger is a specific case being used by Vehicle Research Development Establishment (VRDE). The study takes into account the thermo- physical property variation of engine oil with respect to temperature in the oil ducts. The predictions from theoretical considerations are compared with the conventional empirical equations available in heat transfer handbooks. It is observed that the theoretical results related to effectiveness of heat exchanger deviate markedly from results of computational procedures found in the heat transfer data books. Further, the present analytical approach is rendered into a dimensionless correlation .The outlet temperature estimates from the analytical study for the engine oil and cold air at different altitudes agree very satisfactorily with the corresponding values from the proposed correlation equation.
Mixed cross flow heat exchanger, property variation, altitude effects on effectiveness
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