An Experimental Study of Nanofluids Operated Shell and Tube Heat Exchanger with Air Bubble Injection Article in Press

Shell and Tube heat exchangers are the heat exchangers that are most widely used in industries and for other commercial purposes. There are many techniques that have been utilized to enhance the heat transfer performance of the shell and tube heat exchangers. Air bubble injection is one of the promising and inexpensive techniques that can create turbulence in the fluids resulting in to enhancement of heat transfer characteristics of the shell and tube heat exchangers. In this paper, experimental study of heat transfer characteristics have been done by injecting air bubbles at tube inlet and throughout the tube for 0.1%v/v and 0.2%v/v Al2O3 nanoparticle concentration. Results obtained at two different injection points for both concentrations are compared with the case when no air bubble injection is done. The results showed the enhancement in the heat transfer characteristics with air bubble injection and volumetric concentration of nanoparticles. The maximum enhancement was found to be in the case where air bubbles are injected throughout the tube which is followed by the air bubble injection at the tube inlet and without air bubble injection. As the bubbles were injected throughout the tube, approximately 22-33% enhancement was observed. The overall heat transfer coefficient with injecting air bubbles throughout the tube showed an enhancement of about 12-23% and 14-25% for 0.1% and 0.2% of nanofluids.