Diesel engines are fuel efficient and have better part load characteristics than their
counterpart petrol engines. Approximately thirty percent of heat is rejected in the
exhaust gases of diesel engine. Many research works have been carried out to
recover this waste heat for the utilization of power generation and other
applications. The most notable one is the turbocharger, with others being various
types of heat exchangers. All these devices have worked well in recovering heat.
They also have their drawbacks. The present work is about recovering waste heat
using thermoelectric devices to generate power directly. But the problem was
how effectively this waste heat could be recovered. In this present work an
exhaust passage has been designed to extracts maximum amount of heat from the
exhaust and supplies it to the thermoelectric module. The passage has two main
components. The central passage which extracts heat from exhaust and supplies it
to the thermoelectric generator. The heat sink ensures the continuous absorption
of heat from the thermoelectric module. Two types of designs were developed.
One passage uses air for cooling the heat sink. The other passage uses water for
cooling the heat sink. Then testing was carried out by connecting the passage to
the exhaust pipe of the single cylinder diesel engine. Testing was carried out
separately for air cooling and water cooling. A comparison was made on
theoretical heat transfer, actual heat transfer, module power in both air- and
water-cooled setups. Efficiencies based on heat transfer and module power were
also calculated. It showed around 9% of heat had been converted to electricity by
the module.
Keywords: Diesel engine, TEG Module, waste heat recovery, seebeck effect