Experimental analysis of heat transfer behavior of silver, MWCNT and hybrid (silver plus MWCNT) nanofluids in a laminar tubular flow

Experimental investigations were carried out in order to study the heat transfer performance of silver (Ag), multiwalled carbon nanotubes (MWCNT) and silver (Ag) + multiwalled carbon nanotubes (Ag + MWCNTs) dispersed in distilled water. Nanofluids were synthesized and characterized using different techniques. Experimental facility was fabricated to validate the heat transfer performance of nanofluids in the laminar flow. The nanofluids were tested at mass concentrations of 0.02%, 0.05%, 0.1%, 0.2% and 0.5% for all the three nanofluids. Experimental average heat transfer coefficient was evaluated as a function of Reynolds number. The highest heat transfer augmentation of 67.5% was observed for 0.5 mass% MWCNT/distilled water nanofluids followed by 59.8% for hybrid Ag-MWCNT/distilled water nanofluids, and the least enhancement of 52.1% was observed with Ag/distilled water nanofluids for Reynolds number 2200. The hybrid nanofluids showed better enhancement compared to silver nanofluids. The heat transfer showed an increase with Reynolds number and particle loading. New correlations were developed for the nanofluids for heat transfer enhancement.