HEAT TRANSFER ENHANCEMENT IN A HELICALLY COILED CONVERGENT AND DIVERGENT TUBE HEAT EXCHANGER WITH Al2O3 NANOFLUID

In this investigation, the analysis of the heat transfer coefficient of a shell, helically coiled convergent-divergent tube heat exchanger has been carried out by utilizing Al2O3 -water nanofluid. The nanofluid was prepared using a two-stage technique with proportions of 0.1 vol.%, 0.3 vol.%, and 0.5 vol.%. The inner heat transfer coefficient, overall heat transfer coefficient, and Nusselt number were analyzed and it found that the heat transfer coefficient is increased, with increase of inner dean number and particle volume concentration. The experimental tests were carried out in the range of Dean number, 1100 < De < 4200. When compared to base fluid, the overall heat transfer coefficient improved by 27%, 55%, and 78% at 0.1%, 0.3% and 0.5% with Al2O3 -water nanofluid, respectively. When compared to base fluid at a fixed dean number, the increase in Nusselt number was viewed as 27%, 51%, and 72% at 0.1%, 0.3%, and 0.5% of Al2O3 - water nanofluid, respectively. The investigations of enhancement were increased due to increased nanofluid thermal conductivity while increasing the vol.% concentration and Brownian movement of the nanoparticles. The viscosity of nanofluid is increased with increase of particle volume which increase the pressure drop. It is concluded the convergent-divergent helically coiled tube heat exchangers along with nanofluid is able to enhance the heat transfer with considerable pressure drop. There is no adverse effect on the development of optional streams or the blending of liquids.