Experimental Investigation on Heat Transfer of Al2O3-MWCNT/Water-Based Hybrid Nanofluids in Double-Pipe Mini Heat Exchanger: Design of Experiments Using RSM

Abstract

Heat exchangers are industrial equipment used to transfer energy from one medium to another at different temperatures. In the present study, the effects of using hybrid nanofluids in a double-pipe mini heat exchanger (DPMHE) on heat transfer and pressure drop performance were investigated using the response surface methodology (RSM). The DPMHE used in the present study differs from the minichannels widely applied in the literature in terms of heating mechanism and design. The Al2O3-MWCNT nanoparticles used in the experimental study were suspended into the deionized water used as the base fluid at three different volumetric ratios (0.1, 0.2, and 0.3) and three mixture ratios (75:25, 50:50, and 25:75) to prepare the hybrid nanofluids. The effects of volumetric concentration, the MWCNT percentage, and the Reynolds number Re, which were determined as input parameters in the response surface methodology, on the Nusselt number Nu and the friction factor f were analyzed statistically. The most effective parameters for the Nusselt number are Re, MWCNT percentage, and volumetric concentration, respectively, while the most effective parameters for f are Re and volumetric concentration, respectively. When the Nu number values calculated with experimental data and those calculated through the mathematical model obtained with RSM were compared, it was found that the error rate ranged between 0.37% and 1.84%, while this rate was in the range of 0.33% and 2.05% for the f values. In conclusion, the Nu and f values calculated using the mathematical model and the data from the verification experiments are very close to each other, and the error rate between them is at an acceptable level.