Suitability of magnetic nanofluid in heat transfer loops

Abstract

The objective of this paper is to provide a simple procedure to find the suitability of magnetic nanofluid (MNF) for the purpose of using it as working fluid in different cooling loops. Fe3O4/water nanofluid which is one type of MNF is chosen for the study. Heat can be transferred from one place to other place by using (i) Natural Circulation Loops (in which flow is driven due to the density difference generated within the loop) (ii) Forced Circulation Loop (in which flow is driven by the external aid). Effect of using Fe3O4/water nanofluid in these two different loops is evaluated quantitatively. Analytical expressions are derived for both flow configurations (FCL and NCL). The results are presented in terms of non-dimensional diameters ratio and non-dimensional temperature gradients ratio. Comparison is made between water and Fe3O4/water nanofluid. It is found that Fe3O4/water nanofluid based Natural Circulation Loop size is reduced by 4% at 1% nanofluid concentration and the size reduction is more at higher concentrations. In case of Forced Circulation Loop, the results are presented in terms of newly defined term called as 'figure of merit' as well as diameters ratio. Effect of external magnetic field strength on thermal conductivity is measured and empirical correlation is proposed. A separate analytical expression is derived to predict the change in the size of the heat transfer loop due to the applied magnetic field. It is to be note that, the procedure laid down in this paper is adoptable to any fluid. It is found that, by applied external magnetic field, size of loop is reduced considerably.