Experimental investigations on the performance of a thermo-mechanical refrigeration system utilizing ultra-low temperature waste heat sources

Experimental studies that investigate the utilization of ultra-low temperature (between 48 degrees C and 120 degrees C) waste heat, which forms 25 % of the global unrecovered waste heat, to drive thermal cooling systems are rare. Thus, this study fills a significant gap in the literature by (i) exper-imentally evaluating the performance of a new full-scale thermo-mechanical refrigeration (TMR) system at ultra-low temperatures ranging from 50 degrees C to 85 degrees C, (ii) characterizing its operation with different commercial refrigerants, and (iii) identifying optimal operating conditions and working fluids for the investigated TMR system. An organic Rankine cycle (ORC), vapor compression cycle (VCC), and expander-compressor unit (ECU) make up the TMR system. To ensure its efficient operation, flexibility, and reliability, a full-scale ECU-based TMR system with a design capacity of 1 kW at a heat source temperature of 85 degrees C is built and put through a series of tests. Further-more, the TMR system is tested with different commercial refrigerants (R134a, R410A, R407C) over a wide range of operating conditions of the power loop. The results reveal that the ECU -based TMR system can work with ultra-low temperatures of 65 degrees C with an energy efficiency of 5.92 % and COP of 2.36, for the ORC and VCC, respectively. At a heat source temperature of 85 degrees C, a condenser water temperature of 15 degrees C, and an evaporator water temperature of 33 degrees C, the energy efficiency of the ORC and COP of the VCC are increased to 9.85 % and 3.99, respec-tively. For the cooling quality, the TMR system shows a minimum evaporator temperature of -10 degrees C using R134a in both the power and cooling loop, which is improved to lower than -20 degrees C by using R407C in the cooling loop. The results presented herein will be beneficial to the development, design, and optimization of refrigeration and power systems that utilize low -temperature waste heat.(c) 2023 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/ 4.0/).

Automated summary

Experimental study on utilization of ultra-low temperature waste heat for thermal cooling system is rare, and this study aims to fill this gap by evaluating the performance of a new full-scale TMR system, characterizing operation with different refrigerants, and identifying optimal operating conditions. The study shows that the TMR system achieves energy efficiency of 5.92% and COP of 2.36 at ultra-low temperature of 65℃, and higher values of 9.85% and 3.99 at heat source temperature of 85℃ with different refrigerants. These findings are valuable for the development and optimization of refrigeration and power systems utilizing low-temperature waste heat.