Abstract： Based on the dimensional formula h(,i)=C()d－0.2p0.8w0.8T－0.8μ－0.47eλ0.67ec0.33p, a local heat transfer model was developed and characteristic parameters were proposed as transient flow and heat transfer parameters. The total quantity of heat transfer was calculated using Woschni correlation. By ensuring that the total quantity of heat transfer from local heat transfer model is always equal to Woschni correlation at every crankangle, the undetermined coefficient C() was obtained. The improved model was applied to a singlecylinder watercooled natural aspirated fourstroke direct injection diesel engine. The simulation results are satisfactorily in agreement with the experiment.
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