Heat transfer and exergy efficiency analysis of 60% water and 40% ethylene glycol mixture diamond nanofluids flow through a shell and helical coil heat exchanger

The thermodynamic, heat transfer and thermal performance factor were analyzed experimentally at different particle volume loadings of water + ethylene glycol mixture based nanodiamond (ND) nanofluids flow in a shell and helical coiled tube heat exchanger. Chemical treatment was used to make ND nanoparticles with an average size of 5.42 nm. The stable ND nanofluids were prepared by considering 60:40% water + ethylene glycol (weight percentage) mixture as base fluid and the experiments were performed at particle loadings ranging from 0.2% to 1.0% and the Reynolds number ranging from 900 to 4800, respectively. In the heat exchanger, the hot fluid passes through the shell side and the cold fluid (nanofluid) passes through the helical coil side. The Wilson plot method is used to analyze the helical coil side heat transfer coefficients. The hot fluid volume flow rate was fixed to 1 lit/min, whereas, the cold fluid (nanofluid) volume flow rate was varied from 2 to 6 lit/min. Results show, at 1.0 vol% and the Reynolds number of 2702, the heat transfer coefficient and Nusselt number is increased by 36.05%, and 27.47%, respectively, over the base fluid. However, the penalty in friction factor and pressure drop is 17.28% and 14.24% under the same Reynolds number and 1.0 vol% nanofluid over the base fluid. Similarly, at 1.0 vol% and Reynolds number of 2702, the thermal entropy generation is dropped by 38.12%, frictional entropy generation is raised by 12.86%, exergy efficiency is enhanced by 36.48% and thermal performance factor is augmented by 1.2094 times over the base fluid.