This paper compares amount of thermal energy lost through exhaust gases when an engine was operated on diesel and biodiesel. The study used a 4.7 hp (3.5 kW) single cylinder, four-stroke, multi-fuel engine which was operated on diesel and biodiesel fuels. Experiments were conducted for the two fuels at engine speeds of 1000, 1250 and 1500 rpm in accordance with the manufacturer's recommendations. The engine was tested for torque loads of 6 to 22 Nm at intervals of 4 Nm for speeds and fuels

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... ed. The instrumentation of the engine was mainly equipped with data acquisition system and software for analysis. Exhaust gas mass flow rate and temperature measurements were used to determine lost thermal energy. Lost heat energy depended on the temperature of the waste heat gases and mass flow rate of exhaust gas. The energy lost in exhaust gases increased substantially with increased exhaust gas temperature. The results showed that more energy was lost through exhaust when the engine used biodiesel as compared to when it was fueled on diesel. Maximum heat loss through exhaust was 18.7% of fuel energy when the engine used biodiesel at a speed of 1500 rpm and a torque load of 14 Nm.