Assessment of single rotor expander-compressor device in combined organic Rankine cycle (ORC) and vapor compression refrigeration cycle (VCR)

Abstract

An environmental degradation due to consumption of fossil fuel based high grade energy releasing greenhouse gases is a pressing issue around the world. The use of low-grade heat from renewable energy sources using organic Rankine cycle is an attractive solution to reduce of emission of greenhouse gases and protect the environment. This paper investigates the potential of a new single rotor expander-compressor device in a combined Vapor Compression Refrigeration (VCR) cycle and an organic Rankine cycle (ORC). The numerical model of combined ORC-VCR is developed and validated. The thermal performance of combined cycle has been evaluated under the influence of evaporation temperature of ORC (62.75 °C–89.7 °C) and VCR (−20 °C–5 °C), condensation temperature of ORC (20 °C–45 °C) and rotor speed (500–3000 rpm) at a constant hot source (water) temperature of 95 °C. The maximum cooling effect, heat-to-cooling efficiency, and exergy efficiency achieved are found to be 5.38 kW, 56% and 63% when the evaporation temperature of ORC and VCR is 62.75 °C and −5 °C, and condensation temperature of ORC is 20.5 °C. Moreover, cooling effect increases linearly with the rotor speed, however, the heat-to-cooling efficiency and exergy efficiency are not affected by the rotor speed.