Laminar convective heat transfer, entropy generation, and exergy efficiency studies on ethylene glycol based nanofluid containing nanodiamond nanoparticles

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.