Thermodynamic, Economic, and Environmental Comparison Between the Direct and Indirect CO2 Refrigeration Cycle With Conventional Indirect NH3 Cycle With Considering a Heat Recovery System in an Ice Rink: A Case Study

Abstract

In industrial refrigeration systems, such as ice rinks, because of consumption of a lot of energy, the selection of a refrigeration system is very important. At this work, environmental considerations are combined with thermodynamics and economics for the comparison of three different refrigeration systems in an ice rink, including the NH3/brine, CO2/brine, and full CO2. The first law of thermodynamics is used to calculate the system's coefficient of performance (COP) and the second law of thermodynamics is applied to quantify the exergy destructions in each component of a refrigeration system. With regard to the above, the exergy efficiency and energy consumption of the systems are determined by taking into account the heat recovery process that has been performed in the above-mentioned cycles. The results indicate that if a heat recovery system has been used in the refrigeration system, coefficient of performance of full CO2 refrigeration system is 33% higher than the CO2/brine and 66% greater than the NH3/brine system. The results also show that, whatever the refrigeration evaporating temperature in the NH3/brine system reaches lower than −12.4 °C, the total cost of this system will be greater than the full CO2 system.