Improving the Energy Performances of the Refrigeration Systems with Subcooling Using the Eco-Friendly Refrigerant R600a: Initial Experimental Results Edison Gundabattini 1 , Claudia Masselli 2* , Darius S. Gnanaraj 3 , Sohith Tadikonda 4 , Vikram Karnati 4 , Vamsi Krishna Vemireddy 4 1 Department of Thermal & Energy Engineering, Vellore Institute of Technology (VIT), Vellore, Tamil Nadu 632014, India 2 Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II 132, 84084, Fisciano (SA), Italy 3 Department of Design & Automation, Vellore Institute of Technology (VIT), Vellore, Tamil Nadu 632014, India 4 School of Mechanical Engineering, Vellore Institute of Technology (VIT), Vellore, Tamil Nadu 632014, India Corresponding Author Email: cmasselli@unisa.it https://doi.org/10.18280/i2m.190201 ABSTRACT Received: 9 November 2019 Accepted: 10 February 2020 In this paper the attention is focused on introducing the initial experimental results of a comparative experimental investigation on the energy performances of R600a tested as drop-in of R134a in a test-bench refrigeration system developed at the School of Mechanical Engineering of VIT University located in Vellore (India). Moreover, a comparison of the energy performances was pursued also with the system working with and without sub-cooling. The initial experimental investigation is performed respecting the requirement that the two fluids occupy the same volume. The initial energy performances are carried out in terms of evaporator temperature, coefficient of performance and refrigeration effect. The effect of drop-in with R600 a system previously working with R134a, carries an enhancement of the energy performances in terms of COP and refrigeration effect. Moreover, subcooling carries to an additional benefit on the refrigeration effect. The introduced initial experimental results constitute just the first step of a bigger investigation to be conducted in India, focused on analyzing the impact of the drop-in of HFC with new eco-friendly refrigerants. Keywords: refrigeration, R134a, R600a, hydrocarbons, subcooling, drop-in, cooling systems, GWP 1. INTRODUCTION Nowadays, global warming is a shared worldwide problem: the human end contributed significantly in the last half century to its intensification, since the energy consumption is considered among the main reasons to temperature increment in our world. The warning signals launched by our planet are already worrying and all the world is called to responsibility to avoid the catastrophic consequences that could occur. All the most critical sectors for energy consumption are called to adopt countermeasures to counteract the progress of global warming. Among them, more than 20% of the worldwide energy consumption originates from the sector identified by refrigeration, air conditioning and heat pumping. Almost the totality of the cooling systems is based on Vapor Compression (VC) and therefore on fluid refrigerants. Since the beginning of the utilization of VC-based systems and up to a couple of decades ago, the benchmark refrigerants were ChloroFluoroCarbons (CFCs) and HydroChloroFluoro- Carbons (HCFCs) due of high Ozone Depletion Potential (ODP) and Global Warming Potential (GWP) [1]. They were the cause of the CFCs and HCFCs banning by the Montreal Protocol [2] that took place in 1987 to the purpose of protecting the stratospheric ozone layer. Over the years subsequent measures were taken in 1997 with Kyoto Protocol [3], an international agreement linked to the United Nations Framework Convention on Climate Change. Because of their significant Ozone Depletion Potential (ODP), the usage of HCFC has been forbidden since 2000 and the only fluorinated class of allowed refrigerant was the HydroFluoroCarbons (HFCs), characterized by no ODP but consistent GWP [4-7]. Since then, periodical meetings among the Parties agreeing to the Montreal Protocol have been succeeding over the year modifying and adapting the measures approved to counteract the global warming and, more generally, preserve the ecosystem. From 2009, a progressive phasing out of HFCs has been established, in order to reduce greenhouse gases emissions. The 28th Meeting of the Parties (MOP28) [8] to the Montreal Protocol which was held in Kigali, Rwanda, from October 10 to 14, 2016, led to an international agreement on the phase-down of the production and consumption of HFCs. Specifically, the Kigali amendment identifies the countries composing the Article 5 as the 136 primarily developing countries as specified by Montreal Protocol, except for ten countries: Bahrain, India, Iran, Kuwait, Oman, Pakistan, Qatar, Saudi Arabia and the United Arab Emirates. These ten countries constitute a separate group of Article 5 countries (group II), because they are characterized by elevate ambient air temperature and therefore, they are particularly dependent by air conditioning. All the other countries (the “developed” countries) are classified are non-Article 5 parties [9]. The Kigali amendment represents a milestone agreement that prescribes a gradual 80% to 85% phase-out of HFC at the end of 2040s with a staggered execution of consumption freezers from: 2019 for non-Article 5 countries (the “developed” countries); 2024 for most of the “developing” countries (Article-5 group I); 2028 for the other ten “developing” countries (Article-5 group II). Basing on above prescriptions, Instrumentation Mesure Métrologie Vol. 19, No. 2, April, 2020, pp. 73-81 Journal homepage: http://iieta.org/journals/i2m 73