Forced Convective Heat Transfer of MWCNT/Water Nanofluid Under Constant Heat Flux: An Experimental Investigation

This research article investigates the effect of multi-walled carbon nanotubes (MWCNT)/water nanofluid on convective heat transfer in a uniformly heated copper tube under laminar flow regime. The MWCNT were synthesized using chemical vapor deposition method and characterized using transmission electron microscope. These nanoparticles were dispersed (with 0.05, 0.1, 0.3 and 0.5 % weight concentrations) in distilled water to form stable suspensions of nanofluids. The heat transfer coefficients (HTC) of nanofluids and distilled water (base fluid) were evaluated and compared using constant velocity basis. The thermophysical properties of nanofluids change with the addition of nanoparticles; thus, we have considered the constant velocity criteria which provide the true comparison in contrast to constant Reynolds number used by earlier researchers. The effect of flow velocity (0.166-0.232 m/s) and nanoparticles weight concentration on the HTC considering constant heat flux boundary conditions was studied. It is observed that with the increase in the weight concentration of nanoparticles or flow velocity, the HTC increases. Nanofluids show higher HTC with respect to distilled water at all the concentrations of nanoparticles. At 0.5 wt.% weight concentration and flow velocity of 0.232 m/s, the maximum HTC obtained is 77.60 % in comparison with distilled water.