Waste Heat Availability from a High Temperature Diesel Engine

JONAS ADLER

Manufacturers continue to make incremental gains in internal combustion engine efficiency, but as much as 60% of the fuel energy may still be rejected to the environment as waste heat. Research on recovering this waste heat has produced disappointing results due to the low heat capacity rate of the exhaust gases and the low temperature of the coolant (~90°), which limit the average relative efficiency gains to less than 10%. Increasing the engine coolant temperature would greatly increase the availability of waste heat and could result in efficiency gains of over 20%. Therefore, I am building an experiment using a small diesel engine to measure the availability of waste heat as the engine coolant temperature is incrementally increased. An energy balance will be performed on the modified Daihatsu three-cylinder diesel engine, which uses a copper head gasket, upgraded engine oil seals, and custom oil and cooling systems. The results from the experiment will then be used to model the output of a waste heat recovery system and demonstrate the possible efficiency gains.