Numerical Investigation on Nanofluid based High Temperature Direct Absorption Solar Collector

Abstract

The advance and efficient solar thermal systems are necessary to remove the burden on fossil fuel energy generation technology. In present work, analysis of nanofluid based volumetric receiver, has been done to evaluate the efficiency of nanofluid based high temperature direct absorption solar collector in which nanoparticles absorb incident solar radiation directly within the fluid. The concept of harvesting solar radiation by direct absorbing nanofluid recently been shown numerically and experimentally to be an efficient method. Dispersing small amount of nanoparticles in heat transfer fluid (HTF) significantly alters the optical as well as thermophysical properties of HTF. This study is to contribute towards the development of volumetric flow receiver design and to quantify the effect of different parameter over the thermal efficiency of the receiver. Furthermore, to quantify the absorption capability, solar weighted absorptivity of copper nanoparticles dispersed in water/ silicon oil have been computed by using DDSCAT Fortran-90 open package software. For Numerical investigation of receiver, it has been mathematically modeled (two dimensional), and the governing equations, convection-diffusion (C-D) equation and radiative transfer equation (RTE), have been numerically solved using finite difference technique. In order to evaluate the temperature profile inside the receiver and convective and radiative losses from the collector, the energy balance equation, RTE and heat transport equation were solved by using MATLAB software. It was observed that by changing the concentration ratio and bottom wall optical properties, the overall system performance such as thermal efficiency, average outlet temperature and radiative losses alter significantly. Furthermore, Optical properties of nanoparticles closely related to shape, size and the dielectric medium in which the nanoparticles dispersed. As the aspect ratio of nanoparticles and effective diameter varies the absorption and scattering peaks of changes significantly, also solar weighted absorption coefficient increases with volume fraction of the nanoparticles.