Numerical-Experimental Analysis of Solar Liquid Flat-Plate Collector with Different HTF and Internal Grooves Profiles in the Absorber Duct

Abstract

Solar Liquid Flat Plate Collector (LFPC) system used for low-temperature domestic water heating has wide applications. However, the conversion efficiency is observed to be poor since losses from collector surface is higher. Mostly heat transfer augmentation in solar collectors is one of the key issues in energy saving, compact designs and different operational temperatures. The present work focusses on coining an appropriate Heat Transfer Fluid (HTF) and internal grooves to the Heat Transfer Fluid (HTF) ducts to enhance the performance of LFPC, taking Mumbai as site for analysis. Experimental feasibility study at Mumbai city for four months unrolled maximum global radiation of 800 W/m² and 32.5°C of ambient temperature. Thermophysical analysis of three distinct base fluids namely Molten Salt, Dowtherm A and Therminol VP-1 showcased significant performance of therminol VP-1 with specific heat, density and thermal conductivity of about 1688.8 J/kg-K, 1351.6 kg/m³ and 20.99 W/mK respectively at 50°C. Similarly, three different internal groove profiles (plain, rectangular and trapezoidal) where analysed, of which trapezoidal profile showed improved system performance with maximum of 51.6°C as outlet temperature and 1478 W useful heat gain. The efficiency of trapezoidal profile (77.3%) was found to be 1.01 and 1.003% upfront of plain and rectangular groove profiles. Experimental values for LFPC system with water and plain duct was recorded to compare with other combinations. The enhancement achieved is helpful for addressing various green-house gas emissions and clean energy sustainability.