Effect of Design Parameter Variation on Flat Plate Solar Collector Efficiency Using Nano Working Fluids

Abstract

Flat plate solar collectors have relatively low efficiencies compared to other types of collectors. Water, which is the most commonly used working fluid limits the efficiency of flat plate solar collectors due to its poor heat transfer properties. Also, proper sizing of collector design parameters is a major factor for enhanced efficiency. In this study, the efficiency of a flat plate solar collector was simulated using water and three different nano working fluids: graphene, aluminium oxide and copper oxide nano fluids. Three different mass fractions of nano particles: 0.025, 0.05 and 0.075 weight percent (wt. %) were used for each of the nano fluids. Collector performance equations were programmed and simulated in MATLAB, using collector area of 1.2 m², average solar radiation of 750 W/m² and inlet working fluid temperature of 40^oC. The collector design parameters: tube spacing, fluid mass flow rate, and tube diameter were varied and the effect on efficiency determined. The values of these parameters which gave maximum efficiencies for each of the working fluids were obtained. Maximum collector efficiencies attained were 0.78, 0.7 and 0.68 for graphene, aluminium oxide and copper oxide nano fluids respectively, at mass fraction of 0.075 wt. %, 0.1 kg/s mass flow rate, 0.1 m tube diameter and tube spacing between 0.1 to 0.12 m.  At zero loss efficiency point and mass fraction 0.075 wt. %, increase in collector efficiency attained by the nano fluids over water as working fluid were 28%, 22.8% and 19.2% for graphene, aluminium oxide and copper oxide nano fluids respectively.