Fig. 11 shows the effect of EGR on the energy and availability
balances at the low load. It can be seen again that reduction in
the heat transfer loss is the dominant contributor to the increase
in the fraction of the brake work. The mechanical losses account
for more fractions in the total energy at the low load than those
at the medium and full loads. This is attributed mainly to the increased pumping work during the gas exchanging stroke at the
low load operation . Although approximately 60% of the total energy flow out with the heat transferred through the combustion
chamber walls and the exhaust gas, the availability when considering recovery of these heats is only about 40% of the total availability. The combustion-generated irreversibility accounts for about
21–22% in the total availability and with increasing EGR it increases firstly and then decreases slightly due to the increased
incomplete combustion.