Abstract
Experimental research was done on the heat transfer, entropy generation, and exergy efficiency of ethylene glycol (EG) based nanodiamond (ND) nanofluids flowing in a circular tube. The two-step approach was used to create ND nanofluids with volume concentrations ranging from 0.2 % to 1.0 %. To create stable nanofluids, the ND nanoparticles are ultrasonically agitated with EG for 4 h. At a constant heat flux of q = 9099 W/m2, ex-periments were carried out in a laminar flow with Reynolds numbers ranging from 264.4 to 2194.4. Results showed that ND nanofluids achieved higher heat transfer coefficients than the base fluid. At 1.0 vol% of nanofluid and a Reynolds number of 1454.4 in comparison to the base fluid, the Nusselt number and heat transfer coefficient are boosted by 29.43 %, 45.01 %, and a friction factor penalty of 27.59 %, respectively. The thermal entropy generation is decreased by 31.78 % and the frictional entropy generation is raised by 22.50 % over the basic fluid data at 1.0 % and Reynolds number of 1454.4. For 1.0 % vol. of nanofluid, the exergy ef-ficiency is 22.97 %, while for ethylene glycol, it is 6.78 %. For 1.0 % and a Reynolds number of 1454.4, the thermal performance factor is increased by 1.194-times above the basic fluid. New friction factor and Nusselt number equations were created.