Numerical Simulation of Direct Solar Vapor Generation of Acetone for an Organic Rankine Cycle Using an Evacuated Tube Collector

This paper analyzes the direct solar vapor generation of acetone by solar radiation falling on the heat pipes of an evacuated tube collector (ETC) that can activate a domestic scale organic Rankine cycle (ORC). The irradiance from the sun determines the mass flow of acetone along the horizontal manifold of the ETC to produce vapor at the collector outlet. A scilab code is developed to simulate the flow of acetone inside the manifold where subcooled acetone undergoes heating and evaporation process. Simulation is run from 60 °C to a saturation temperature of 120 °C at a pressure of 604 kPa, vapor qualities from 1% to 100%, and solar radiation from 300 to 1100 W/m2. The Kattan–Thome–Favrat flow boiling model is used to obtain the two-phase local heat transfer coefficients along the horizontal manifold, and it is validated with the numerical and experimental values of ammonia. The ORC system can generate 218 kWh/year of electrical energy, a thermal power capacity of 1616 kWh/year and achieve an ORC efficiency of 84.4%. The solar-ORC has a thermal efficiency of 3.25% and an exergy efficiency of 21.3% with a solar collector of 2.84 m2.