Thermal Engines (TE), either Diesel Engines (DE) or Internal Combustion Engines (IEC) are the most important industrial prime movers used in automobile, manufacturing, aerospace sectors etc. TE’s operate by chemical combustion of fuels and 60 – 70% unused thermal energy carried out by the exhaust gases. In this paper, methodology for recovering waste heat energy of exhaust gas of diesel engine is presented by placing a heat exchanger in the exhaust manifold so that energy from the exhaust gases can be used for preheating the fuel. Effectiveness of heat exchanger depends on the convection heat transfer coefficient of the fluid. Maximum fuel temperature achieved for counter flow arrangements at 50% of full load at 1440 rpm. Waste heat recovered at 50% full load condition is found to be 72%. Internal Spleen Pipes structured Turbulence promoters are used in enhancing the heat transfer and mass flow rates in the given section. Variable liquid flow rate in the range of 50 lph to 200 lph is used and air velocity in the range of 14.0 m/s to 20.0 m/s. The fluid inlet temperature was varying from 40°C to 135°C to find the optimum inlet condition. Ultrahigh performance cooling is one of the important needs of many industries. However, low thermal conductivity is a primary limitation in developing energy-efficient heat transfer fluids that are required for cooling purposes. Nanofluids are engineered by suspending nano particles with average sizes below 100 nm in heat transfer fluids such as water, oil, diesel, ethylene glycol, etc. Convective heat transfer coefficient of water, Alum - Water, Ag+ NP-water of 2% nanoparticle concentration has been calculated for counter flow heat exchanger. These suspended nanoparticles can change the transport and thermal properties of the base fluid. It is found that convective heat transfer coefficient of Ag+ - DI water, Alum- DI water nanofluids are 81 % and 66% higher compared to pure water respectively. It is found that overall heat transfer coefficient of Ag+ NP – Di water, Alum-DI water nanofluids are 23%, and 20% higher compared to pure water respectively. Results demonstrate that increasing coolant flow rate an improve the heat transfer performance. Also increasing the air flow rate improves the heat transfer rate. The rate of heat transfer enhancement was found 19% to 42% in comparison with pure water.
