Abstract
An experimental method is used to investigate the performance of a small-scale organic Rankine cycle (ORC) system which is integrated with a radial flow turbine, using 90 °C hot water as a heat source. The considered working fluids are R245fa and R123. The relationship between cycle performance and the operation parameters is obtained. With constant condensing pressure (temperature), the outlet temperature of the hot water, the mass flow rate of the hot water and the evaporator heat transfer rate increase with increasing evaporating pressure. Turbine isentropic efficiency decreases and transmission-generation efficiency increases with rising evaporating pressure. In the considered conditions, the maximum specific energy is 1.28 kJ/kg, with optimal fluid of R245fa and an optimal evaporating temperature of 69.2 °C. When the evaporating pressure (temperature) is constant, the outlet temperature of the cooling water increases, and the mass flow rate of the cooling water decreases with increasing condensing pressure. Turbine isentropic efficiency increases and transmission-generation efficiency decreases with the rise of condensing pressure. In the considered conditions, the maximum specific energy is 0.89 kJ/kg, with optimal fluid of R245fa and an optimal condensing temperature of 29.1 °C. Turbine efficiency is impacted by the working fluid type, operation parameters and nozzle type.
Highlights
A great amount of researcher attention has been focused on exploiting or recovering low-grade heat energy using the organic Rankine cycle (ORC), which has potential in using low-grade heat energy
The mass flow rate of the hot water and the evaporator heat transfer rate increased with increasing evaporating pressure
In a small-scale ORC experimental system, this article studied the relationship between cycle performances and operation parameters, especially when achieved by varying the turbine performance performances and operation parameters, especially when achieved by varying the turbine and nozzle performance with evaporating pressure and condensing pressure
Summary
A great amount of researcher attention has been focused on exploiting or recovering low-grade heat energy using the organic Rankine cycle (ORC), which has potential in using low-grade heat energy (approximately 100–150 ◦ C). Tchanche et al [1] studied the theoretical cycle performance of a 2 kW micro ORC system using 90 ◦ C hot water as a heat source, produced by solar collectors. Several characteristics, such as efficiencies, volume flow rate, mass flow rate, pressure ratio, toxicity, flammability, ozone depression potential (ODP) and global warming potential (100 year) (GWP) were considered to screen an optimal fluid from as many as 20 fluids. The results showed that R134a was most suitable for small-scale solar
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