Improved thermal performance of annular fin-shell tube storage system using magnetic fluid

Abstract

The main contribution of this paper is achieving a significant thermal performance improvement of annular fins-shell-tube heat exchanger energy storage system using magnetic fluid. The fin efficiency is increased by 20% with annular fin-magnetic fluid geometry as compared to without magnetic fluid. This improvement in thermal characteristics of annular fin system can be attributed to the formation of nano-channels in the field directions and effective increase in overall heat transfer coefficient due to the replacement of solid-gas interface with the liquid-gas interface. This replacement leads to improved convective heat transfer rate and overall thermal characteristics, which is the new knowledge contribution for various energy storage systems. In the present work, a simple and novel method for improving the thermal performance of natural convection energy storage system is reported. This novel method can improve the overall performance of the systems with natural convection extended surfaces and makes it suitable for numerous heat transfer applications. A magnetic fluid thin layer association with annular fin geometry has been proposed to improve the shell-tube heat exchangers performance, and an in-house experimental setup is used to study its dimensional and non-dimensional heat transfer characteristics. Kerosene and water-based MF were prepared by chemical co-precipitation method and employed on the top surface of the fin to maximise the heat transfer rate and to increase the effectiveness (ε) of the fin system. This thin layer of MF was maintained on the top surface of the fins using the magnetic ring of small NdFeB magnet of 1 mm thickness and 2.5 mm diameter. It is observed that a significant increase in relative heat transfer rate (∼35%) taking place using a thin MF layer over the top surface of the fin which leads to enhancement in fin performance. Also, the temperature distribution along the length of the fin shows a sharp decrease in temperature near the top surface which corroborates our observations that the magnetic ring over the surface works as a chill block which provides a directional cooling through magnetic nano-channels. These new findings can be valuable in the design of an efficient annular fin-shell tube latent heat exchanger storage system.