The role of nanofluids and fins in a heat exchanger on waste energy recovery from a diesel engine: An experimental and numerical study

Abstract

A 3.7 kW diesel engine and a shell-and-tube heat exchanger were used in this study to decrease the temperature of exhaust gases and reduce the effects of greenhouse gases, respectively. The innovations utilized in this paper include the use of four novel non-linear arrangements of fins on the heat exchanger body, two different types of nanofluids (Ag, Fe3O4) in single and hybrid forms, and using the nanoparticles shape factor. The embedded simulation in the ANSYS-FLUENT commercial software was evaluated under the K-epsilon (κ−ɛ) turbulence modeling. The study results showed that the exhaust gases’ temperature drops by an average of 7.0% by increasing the curvature of the fins, while this value was obtained as 5.80% by enhancing the height of the fins from 8 mm to 24 mm. Examining the effect of the shape of the used nanoparticles revealed that changing the shape factor from Spherical to Lamina led to the increase of heat transfer rate by 4.33%. Also, at a constant shape factor, increasing the number of fins caused a 47.12% growth in the heat transfer rate. Therefore, one can say that the arrangement and number of fins have a larger influence on increasing the heat transfer rate than the nanoparticles shape factor. Moreover, increasing the concentration of nanofluids from 1% to 5% led to a 0.67% drop in the temperature of the exhaust gases. According to the research results, we can recognize the parameters of the number, shape, and arrangement of the fins, the type of nanofluid, and the nanoparticles shape factor as factors effective in reducing the temperature of exhaust gases from a diesel engine.