Abstract: It is confirmed that in internal combustion engines (ICEs), more than 30–40% of fuel energy wastes from the exhaust and just 12–25% of the fuel energy converts to useful work. On the other hand, statistics show that producing amounts of the internal combustion engines growth very fast and the concern of increasing the harmful greenhouse gases (GHG) will be appeared. So, researchers are motivated to search alternative solutions by using conservation ways, recover the heat from the waste sources in engines which not only reduces the demand of fossil fuels, but also reduce the GHG and help in energy saving. On the other hand, because exhaust gas heat recovery using heat exchanger may make a pressure drop and effects on the engine performance hence its design is very important and crucial. To select an appropriate heat exchanger design limitations for each heat exchanger type firstly should be considered. Though production cost is often the primary limitation, several other selection aspects such as temperature ranges, pressure limits, thermal performance, pressure drop, fluid flow capacity, cleanability, maintenance, materials, etc. are important. One of the most effective methods to increase heat transfer is using the fins which are widely used by the researchers across the heat recovery designers. Some of the special HEXs designs to recover the exhaust heat are introduced. This paper aims to model the heat transfer through exhaust gases to a cold fluid with modeling the fins with suitable viscous model to calculate the heat recovery amount. Two cases of previous experimental work are selected and numerical results are compared with experimental outcomes. Also, effect of fins size and engine load and speed on heat recovery is examined graphically.