Abstract
This work presents the experimental evaluation of energy consumption and refrigerant charge reduction when a commercial direct expansion refrigeration system is converted into an indirect system. The evaluation (with R-134a and R-507A) used a commercial cabinet with doors for medium temperature and a single-stage refrigeration cycle using a semi-hermetic compressor and electronic expansion valve; 24-h energy consumption tests were performed at laboratory conditions for each refrigerant and configuration at three heat rejection levels (23.3, 32.8 and 43.6 °C), maintaining an average product temperature inside the cabinet of 2 °C. The work analyses the impact of the conversion on temperature and pressure indicators, as well as, in the energy performance of each element. For R-134a the refrigerant charge was reduced in a 42.9%, but the energy consumption rose by 22.0%–22.8%; for R-507A the charge reduction was of 32.8% with an increase in energy consumption of between 27.7% and 38.7%.
Highlights
The 28th Meeting of the Parties to the Montreal Protocol adopted the Kigali Amendment on hydrofluorocarbons (HFC), included in the Montreal Protocol [1]
This agreement follows the same action line as the F-Gas Regulation adopted in Europe [2], which has limited the GWP value of the substances that could be used in different refrigeration applications according to different time lines
We focus on centralized commercial refrigeration systems with multiplexed direct expansion systems as they make the largest direct contribution to global warming because of their large refrigerant charge (300 to 3000 kg [5]) and high annual leakage rate
Summary
The 28th Meeting of the Parties to the Montreal Protocol adopted the Kigali Amendment on hydrofluorocarbons (HFC), included in the Montreal Protocol [1] This historic agreement aims to reduce the use and production of HFC worldwide, with the goal being to reduce HFC emissions by over 80 billion tonnes of carbon dioxide equivalent (CO2,e ) by 2050. The most important restrictions and limitations are: a GWP limit of 2500 for stationary equipment from 2020 on and the limit of GWP of 150 for multipack centralised refrigeration systems with rated capacity of more than 40 kW from 2022 on, except for the primary circuits of cascade systems, which GWP limit has been fixed in 1500 Another important aspect is the recharge limit with refrigerant of GWP higher than 2500, which has been fixed at 40 tonnes CO2,e (10.15 kg of R-404A, 10.03 kg of R-507A)
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