Mathematical Modeling of the Heat Generated through an Evaporator-Absorber Accompanied by Thermal Storage for the Solar Energy Applications

Abstract

An evaporator-absorber geometry allows the absorption of incident solar radiation andconverts it into thermal energy useful for the evaporation of a working fluid. The evaporator-absorberworks with two fluids: a heat transfer fluid transmitting heat to a working fluid, which, circulatesalong the thermal circuit composed of an evaporator, a turbine, a condenser and a pump. The aim ofthis research work is to analyze the heat transfer through the evaporator-absorber and to extract themathematical equations model the heat exchange process between the component elements of theevaporator-absorber: a serpentine tube, a working fluid and a cylindrical tube. In this case, theworking fluid is water, and the heat transfer fluid is air, which is heated by the thermal energyconverted from solar energy. The mathematical equations describing the heat transfer are extractedby using the nodal method and discretized by the finite difference method. Afterwards, the presentwork estimates the outlet temperature of each element of the evaporator-absorber and studies thestorage capacity of the cylindrical tube. Then, the water temperature distribution on the geometry ofthe evaporator and the required quantity of water and the number of spires to have a high outlettemperature of the water vapor are determined. As a result, the mathematical modeling estimated thatthe outlet temperature of the serpentine tube is higher than the outlet temperature of the water.Additionally, the temperature of the storage tube maintains its increase throughout the day. Thequality of the heat transfer in the serpentine tube is improved by placing the tube in a vertical positionand by adopting a lower volume of water compared to the maximum volume, which is supported bythis tube.