Experimental Investigation of Helical Coil Tube in Tube Heat Exchanger with Microfins Using Al2O3/Water Nano Fluid

Abstract

In this work, three passive heat transfer augmentation techniques are used in counterflow tube in tube heat exchanger. First is transforming the straight heat exchanger tubes into helical coil heat exchanger tubes, second is to make use of nanofluid in heat exchanger and third is to make micro fins over the outer surface of inner tube. The experimentation was done on plane tube as well as micro fined tubes by varying the concentration of Al2O3 nanoparticle in deionized water. 500 micro fins created within 1 m length of heat exchanger tubes. Height and thickness of micro fins are 0.4 mm and 1 mm, respectively. Heat transfer rate, overall heat transfer coefficient, pressure drop, effectiveness, Nusselt number, and entropy generation of helically coiled tube in tube heat exchanger were experimented by varying the volume concentration of Al2O3 nanoparticle as 0%, 0.25% and 0.3% [1]. Mass flow rate through inner tube as well as annulus were kept constant for observing the variation of various quantities, e.g., heat transfer rate, effectiveness, etc. Results obtained from micro finned helical coil heat exchanger have compared with the plane helical coil heat exchanger. Heat transfer performances increased in helically coiled heat exchanger using nanofluid with different concentrations of nanoparticle. Also, the effectiveness of heat exchanger increases and entropy generation decreases as the concentration of nanoparticle increases.