Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Performance analysis and exergoeconomic evaluation of a TRC system enhanced by a dedicated mechanical subcooling Ali Zahedi Miran a , Arash Nemati b , Mortaza Yari b, ⁎ a Department of Mechanical Engineering, University College of Nabi Akram, Tabriz, Iran b Faculty of Mechanical Engineering, University of Tabriz, 29th Bahman Blvd., Tabriz, Iran ARTICLEINFO Keywords: Exergy Exergoeconomic Mechanical subcooling Transcritical refrigeration ABSTRACT Inthepresentstudy,atranscriticalrefrigerationcycle’sperformancewithdedicatedmechanicalsubcooling(MS) is investigated from the energy, exergy and exergoeconomic viewpoints. Three diferent refrigerants containing CO 2 (R744), N 2 O (R744A) and ethane (R170) are considered as the transcritical cycle’s refrigerant. A thorough parametric study is carried out on the system and fnally, the efect of dedicated subcooling system is checked out on the energy, exergy and exergoeconomic perimeters. Based on the results, value of the COP and exergy performanceforN 2 O,unliketheCO2,isthehighest.Inotherwords,theCO 2 refrigerantshowsthebesteconomic performance. By comparing the system with and without subcooling cycle, it can be concluded that utilizing subcooler improves performance of the system and increases the unit product cost. However, the unit product cost increment is much lower than COP improvement which makes the subcooling an efective and economical way to improve the refrigeration system’s performance. Application of subcooler leads to an enhancement of 30.74%,26.48%and36.1%inCOPforCO 2 ,N 2 O,andethane,respectivelywhiletheunitproductcostincrement is 9.04%, 8.37% and 10.63% for the mentioned refrigerants, respectively. 1. Introduction Extensive use of synthetic refrigerants in the feld of air-con- ditioningandrefrigerationinrecentdecades,suchasCFCs,HCFCs,and HFCs, is one of the main causes of average global temperature rise [1]. Hence,naturalfuidssuchasCO 2 ,N 2 O,andethanehavereceivedgreat attention as refrigerants [2]. Carbon dioxide (R744) as a natural re- frigerant has many advantages [3] such as no toxicity, no combust- ibility, and high volume capacity with the compact system, better heat transfer specifcations, low pressure ratio, full adaptability with con- ventional lubricants, easy access and low price [4].TheuseofCO 2 asa refrigerant has been discussed in automotive air-conditioning [5], heat pump,andenvironmentalcontrolunit [6].Inaddition,CO 2 canbeused as a refrigerant in low-temperature applications such as quick-freezing systems and frozen food storage. Due to the low critical temperature of R744 (31.1°C) which is usually less than air-conditioning and heat pump systems usual temperature, the supercritical vapor compression cycle (VCC) can be used instead of conventional vapor compression cycle for this refrigerant [7]. Nitrous oxide (N 2 O) and ethane has si- milarthermodynamicpropertiestothoseofCO 2 andalsoarepromising natural refrigerant [8]. Therefore, many researchers have worked on the analysis of CO 2 transcritical cycles (TRCs). However, N 2 O and ethane systems have not been well studied. An ejector-expansion refrigeration cycle using nitrous oxide (N 2 O) was examined by Aghazadeh Dokandari et al [9].Theresultsshowthat their proposed cycle has a maximum coefcient of performance and exergy efciency of 12% and 15% relative to the internal heat ex- changercycle,respectively.Theyfoundthattotalexergydestructionfor the N 2 O ejector-expansion cycle was 63% and 53% lower than the in- ternal heat exchanger cycle and vapor compression cycle, respectively. Also, it was concluded that the highest COP for the three types of carbon dioxide refrigeration system was equal to the pressure side of 8.4MPa. A vortex tube can be used instead of an expansion valve to improve the performance of the refrigeration cycle for useful energy losses. Jain et al. [10] studied a used vortex tube in a vapor compres- sion cycle as an expansion device, with using nitrous oxide (N 2 O) to improve the COP, also the results of the transcritical cycle with ex- pansion valve were compared. They found that the coefcient of per- formance of the transcritical cycle with the vortex tube improved from 1.72% to 27.01% relative to the transcritical cycle with the expansion valve. Comparison of the performance of N 2 O and CO2 in the tran- scritical cycle with the vortex tube shows that, as the optimal pressure required for N 2 OislessthanCO 2 , also its maximum cooling coefcient of performance is higher than that of CO 2 . In another study, Jain et al. https://doi.org/10.1016/j.enconman.2019.111890 Received 29 May 2019; Received in revised form 29 July 2019; Accepted 30 July 2019 ⁎ Corresponding author. E-mail address: myari@tabrizu.ac.ir (M. Yari). Energy Conversion and Management 197 (2019) 111890 0196-8904/ © 2019 Elsevier Ltd. All rights reserved. T