Evaluation of the Heat Recovery Potential by Using an Exergy Analysis Approach to Improve Energy Efficiency of Industrial Refrigeration Systems

Abstract

Abstract-This work applies an exergy analysis approach to investigate the performance and waste heat recovery potential of an industrial air-cooled screw chiller. To reduce the factory overall primary energy demand, a 410 kW chiller with 274 kW heat reclaim capability for generation of 70˚C hot water, was analyzed. The evaluation was established based on system irreversibility and Total Recovery Potential (TRP) or exergy efficiency of the recovered heat.For evaluation of the total recovery potential, exergy efficiency of the refrigeration system with heat recovery was expressed in terms of recovery efficiency and effectiveness to identify the importance and contribution of each term to improve the exergy efficiency. The analysis was conducted for various cooling capacity for the analysis boundary including the refrigeration system and the suitable used point e.g. water or space heating.It was concluded that due to the low quality of the waste heat from the refrigeration system, total recovery potential or exergy efficiency of the recovered heat was more a question of effectiveness rather than merely an efficiency-based evaluation. Therefore TRP was low, approximately 6-12%, even though the recovery efficiency reached up to 94% for the half load capacity. Also it was observed that due to the higher compressor power demand for the system with heat recovery, COP and COP Ex were 3.43 and 3 respectively which were quite lower than of the values for conventional refrigeration system. Index Terms-Exergy efficiency, air-cooled chiller, total recovery potential, waste heat recovery.