Optimized modeling and experimental investigation on the thermal/electrical characteristics of MWCNT nanofluid for effective solar thermal applications

Abstract

In this study, a multi-objective optimization tool, response surface methodology (RSM) was utilized to determine the optimum thermal and electrical conductivity characteristics of a nanofluid consisting of solar glycol (SG)-water (H2O) (50:50) blend with multiwall carbon nanotube (MWCNT) for efficient solar thermal applications. A three-level factorial optimization design involved evaluating the effects of volumetric concentration and operating temperature on the electrical and thermal conductivities of MWCNT-SG/H2O nanofluid. Further several experiments were carried out to establish a second-order polynomial correlation for evaluating of electrical and thermal conductivity properties of the nanofluid. Optimization results indicated that higher operating temperature and volume concentration of MWCNT contributed to higher thermal and electrical conductivities in the MWCNT-SG/H2O nanofluid, respectively, demonstrating that the inherent physical and operational properties predominantly influence the behavior of the nanofluid. Further experimental results substantiated the optimization results with good agreement, indicating the direct effect of temperature and volume concentration on the performance of the nanofluid. Thus, the optimum conditions for achieving competent thermal and electric characteristics in MWCNT-SG/H2O nanofluid were identified to be the operational temperature of 66.2°C and MWCNT volume concentration of 0.125% in SG/H2O base fluid, respectively.