An Optimized Design of Heat Pipe Based Evacuated Tube Solar Water Heater with Thermal Storage (Case Study : - Wonji-Shoa Sugar Factory)

Abstract

Solar energy is one of the promising renewable sources in a direct and indirect methods of en ergy conversion. Solar water heating is simplest and most direct application of solar radiation into heat. The study aims to investigate design of solar water heating system for the case of Wonji-Shoa sugar factory milling plant section and heat transfer enhancement of Heat Pipe Evacuated Tube Solar collector(Hp-ETSc) using nanofluids numerically. Nanofluids are nanotechnology-based heat transfer fluids that are derived by stably suspend ing nanometer-sized particles in conventional heat transfer fluid. Heat pipes are effective heat transfer devices in which the nanofluid operates in the two phases,evaporation and conden sation; also known as nanofludic heat pipe. ANSYS/FLUENT powerful CFD package used to compute the complex evaporation and condensation phenomena inside the thermosyphon heat pipe. Transient numerical simulation was used for prediction of heat transfer coefficients and thermal resistance of water, Al and Cu nanofluids in Two Phase Closed Thermosyphon-Heat Pipe (TPCT-HP) with 50% filling ratio of evaporator section at 4kP a initial pressure. The syn thesized water nanofluid characterized 0.5 and 4.41vol% of Cu and Al with 25nm and 18nm particle size respectively. The various design parameters are gathered from solar water heater collector manufacturers official site, National Meteorology Agency and case site. The analytical design parameters of the proposed system gives total number of 10 HP-ETSc modules with 1.15MW h annual sensible thermal energy storage. Annual contribution of solar system to heating load is 2.112MW h. The system save 40, 356kg bagasse fuel for alternative use and 28, 957.5kgCO2 emissions to atmosphere is avoided. The economic analysis of the system was done with an initial total investment of 96, 761ET Birr with 3.6years payback pe riod. Numerical simulation result showed heat transfer coefficient increases by about 25.2% and 37.9% for Cu and Al nanofluid respectively as compared to water at evaporator section; on the other hand, Cu-water nanofluid is about 30.95% and 78.55% greater than those of Al nanofluid and water respectively. The overall thermal resistance for TPCT-HP is decreased by about 51.86% for Cu nanofluid, whereas it is reduced by 42.75% for Al nanofluid compared with water