en Numerical Investigation مقاله پژوهشي Research Paper <span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">This article investigates the effect of using three nanofluids as exhaust gas cooling fluid in an EGR cooler. Reducing the exhaust temperature of diesel engines can reduce environmental and thermal pollutants. In a conventional 3-liter engine in all kinds of vehicles, 20 to 40 kW of its 115 kW power is being wasted. The engine shell temperature rises to 600 degrees Celsius.&nbsp; Exhaust gas recirculation can recover a part of it. Exhaust gas recirculation can recover thermal energy by exhaust gas recirculation method by charging a thermal energy storage tank to feed a diesel engine in cold start.</span></span><span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">Many researchers have simulated natural convection in the nanofluids.</span></span><span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times=""> The innovation of the current research is the use of 61 tubes inside the small heat exchanger that is cooled by the discussed nanofluids in the exhaust gas recirculation system of the diesel engine that works with the paraffin phase changer and the exhaust gas recirculation rate is 60% to Reduce of environmental pollution and smoother operation of diesel engine. The inlet is steady state turbulent. The thickness of the inner tubes is considered close to zero. The shell is adiabatic.</span></span> <span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">Both of them exit the heat exchanger under pressure.</span></span> <span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">Three nanoparticles of diamond, silicon dioxide, and copper are considered. This numerical simulation has solved the continuity equations, energy, Navier-Stokes, the pressure drop along the pipe, flow, and rotation equation, kinetic energy disturbance, and energy loss rate equation</span></span><span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">.</span></span> <span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times="">The results showed a higher pressure drop</span></span><span style="font-size:11.0pt"><span new="" roman="" style="font-family:" times=""> for the silicon dioxide-ethylene glycol nanofluid. Silicon dioxide-ethylene glycol nanofluid has a higher Nusselt number, slightly different from other nanofluids. Also, Copper ethylene glycol has a lower Velocity among nanofluids</span></span> Numerical solution,Nanofluids,Cooling,Diesel engines,Shell and tube heat exchangers. 70 77 http://ijmt.ir/browse.php?a_code=A-10-8036-1&slc_lang=en&sid=1 Alireza Asadi alireza_asadi90@yahoo.com 10031947532846004253 10031947532846004253 No P.hd student, Campus faculty, University of Guilan Kourosh Javaherdeh javaherdeh@guilan.ac.ir 10031947532846004254 10031947532846004254 Yes Faculty of mechanical engineering, University of Guilan,Rasht,Iran. Mohammad Naghashzadegan naghash@guilan.ac.ir 10031947532846004255 10031947532846004255 No Faculty of Mechanical Engineering, University of Guilan, Iran.