A MOZAFARI - DEPARTMENT OF MECHANICAL ENGINEERINGSHARIF UNIVERSITY OF TECHNOLOGYTEHRAN - IRAN

The heat transfer correlations, currently used to predict the heat transfer rates from the cylinder contents to the surrounding surfaces, have been developed using experimental data, obtained with normal hydro-carbon fuels and under normal running conditions.Some assumptions such as that employed by Annand [۱], may be in good agreement with some fuels under some running conditions. But the predictions with some other fuels, may well depart from the corresponding experimental values. This is believed to be due to actual Prandtl number deviating from the assumed value of ۰.۷.Non-hydro carbon fuels are probably the sole alternative for the future, and among them some like ammonia with a very high enthalpy of evaporation have shown acceptable potentials. A theoretical prediction of Prandtl number for iso-octane, methanol, propane and ammonia combustion in a spark ignition engine will show the validity of above-mentioned assumption by Annand for hydro carbon and non-hydro-carbon fuels.The heat transfer correlations applicable for future fuels may be developed if the important parameters affecting the heat transfer rates (such as Prandtl number) are studied. Using predicted and experimentally measured values of heat transfer rates, this paper discusses the variations of Prandtl number with crank-angle rotation, and evaluates the effects of high enthalpy of evaporation on Prandtl number and heat transfer rates.