Heat Transfer Enhancement Using Overlapped Dual Twisted Tape Inserts with Nanofluids

Abstract

The thermal performance of a heat exchanger can be improved by various techniques. It is a major concern when coming to industries as the heat losses play a major role in efficiency of the overall plant. The present work is carried out to enhance the heat transfer rate of a tubular heat exchanger by incorporating overlapped dual twisted tapes (ODTTs) or inserts into a tube and carrying out the numerical simulation for different twisting ratios of ODTTs. In addition to this, Al2O3 nanoparticles are used as additives to increase the value of heat transfer coefficient (h), thereby improving the Nusselt number (Nu) and overall thermal performance. The addition of ODTTs resulted in improved residence time, more contact surface area and improved fluid mixing and swirling for effective heat transfer to take place. The numerical simulation is repeated for nanofluid concentrations of 1% and 2% and also for varying twisting ratios of Yo/Y = 1.5, 2 and 2.5. The tube with 1% nanofluid concentration and twisting ratio Yo/Y = 2 yielded better results in comparison with all other combinations.