Energy Analysis of a Novel Ejector-Compressor Cooling Cycle Driven by Electricity and Heat (Waste Heat or Solar Energy)

Fahid Riaz, Kah Hoe Tan, Muhammad Farooq, Muhammad Imran and Poh Seng Lee
Additional contact information
Fahid Riaz: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
Kah Hoe Tan: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore
Muhammad Farooq: Department of Mechanical Engineering, University of Engineering and Technology, GT Road, Lahore 54000, Pakistan
Muhammad Imran: School of Mechanical, Biomedical and Design Engineering, College of Engineering and Applied Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
Poh Seng Lee: Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117575, Singapore

Sustainability, 2020, vol. 12, issue 19, 1-21

Abstract: Low-grade heat is abundantly available as solar thermal energy and as industrial waste heat. Non concentrating solar collectors can provide heat with temperatures 75–100 °C. In this paper, a new system is proposed and analyzed which enhances the electrical coefficient of performance (COP) of vapour compression cycle (VCC) by incorporating low-temperature heat-driven ejectors. This novel system, ejector enhanced vapour compression refrigeration cycle (EEVCRC), significantly increases the electrical COP of the system while utilizing abundantly available low-temperature solar or waste heat (below 100 °C). This system uses two ejectors in an innovative way such that the higher-pressure ejector is used at the downstream of the electrically driven compressor to help reduce the delivery pressure for the electrical compressor. The lower pressure ejector is used to reduce the quality of wet vapour at the entrance of the evaporator. This system has been modelled in Engineering Equation Solver (EES) and its performance is theoretically compared with conventional VCC, enhanced ejector refrigeration system (EERS), and ejection-compression system (ECS). The proposed EEVCRC gives better electrical COP as compared to all the three systems. The parametric study has been conducted and it is found that the COP of the proposed system increases exponentially at lower condensation temperature and higher evaporator temperature. At 50 °C condenser temperature, the electrical COP of EEVCRC is 50% higher than conventional VCC while at 35 °C, the electrical COP of EEVCRC is 90% higher than conventional VCC. For the higher temperature heat source, and hence the higher generator temperatures, the electrical COP of EEVCRC increases linearly while there is no increase in the electrical COP for ECS. The better global COP indicates that a small solar collector will be needed if this system is driven by solar thermal energy. It is found that by using the second ejector at the upstream of the electrical compressor, the electrical COP is increased by 49.2% as compared to a single ejector system.

Keywords: ejector; low-grade heat; CCP; vapour compression; VCC; refrigeration; efficiency; energy (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (6)

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