Recent investigations in HFCs substitution with lower GWP synthetic alternatives: Focus on energetic performance and environmental impact

egulation (EU) No. 517/2014 (F-gas Regulation) controls the use of HFCs in several applications. This paper reviews the recent investigations performed because of F-gas Regulation, with focus on lower global warming potential (GWP) synthetic alternatives. The GWP limit and the date of prohibition have an influence on the studies found for each application. The major relevance of the studies has been observed on mobile air conditioners for pure hydrofluoroolefins (HFOs), possibly caused by the earlier control. Additionally, a great number of studies have been found for stationary refrigeration systems using several mixtures and residential air conditioners using R32. An important number of articles investigate synthetic alternatives for domestic refrigerators given the flammability barriers for hydrocarbons in some countries. Despite higher GWP allowance on cascade supermarket systems, few articles are available on this topic. Given the extent of the current studies and the rate of new refrigerant developments, an increase in studies using the new synthetic mixture is expected in the coming year

Experimental study of R450A drop-in performance in an R134a small capacity refrigeration unit

The Kigali amendment to the Montreal Protocol has highlighted the hydrofluorocarbons (HFCs) phase out as a priority to reduce the future global mean temperature increase. R134a is the most abundant HFC in the atmosphere and therefore it must be substituted using environmentally benign alternatives. In the short term, blends of HFCs and hydrofluoroolefins can replace R134a. This paper experimentally evaluates R450A (GWP of 547), a non-flammable mixture of R1234ze(E) and R134a, in an R134a small capacity refrigeration system. The controlled experimental conditions cover evaporating temperatures from −15 to 12.5 °C and condensing temperature of 25, 30 and 35 °C (36 tests in total for each refrigerant). The experimental results showed that with only a thermostatic expansion valve adjustment the average R450A cooling capacity and COP are 9.9% and 2.9% lower than those measured using R134a. Besides, the observed compressor discharge temperature values of R450A are not greater than that of R134a

Retrofit of lower GWP alternative R449A into an existing R404A indirect supermarket refrigeration system

R404A is going to be phased out from most of the commercial refrigeration systems due to its high GWP value of 3943. R449A (GWP of 1282) has been proposed to replace R404A with only minor system modifications in supermarkets. This paper presents the measurements of a light retrofit replacement of R404A using R449A in a medium temperature indirect refrigeration system (secondary fluid temperature at the evaporator outlet between −9 and −4 °C). It has been demonstrated that with a slight expansion device adjustment and 4% increase of refrigerant charge, R449A can be used in this refrigeration system designed for R404A because of its suitable thermodynamic properties and acceptable maximum discharge temperature. At a secondary fluid temperature at condenser inlet of 30 °C, the COP of R449A nearly matches that of R404A (both were between 1.9 and 2.2), despite having approximately 13% lower cooling capacity. As a conclusion, attending to the GWP reduction and similar energy performance, it was demonstrated using the TEWI methodology that the use of the recently developed refrigerant R449A in these applications can reduce the total CO2 equivalent emissions of an indirect supermarket refrigeration system designed for R404A refrigerant.This research is funded by the Swedish Refrigeration Cooperation Foundation, KYS (project “Utvärdering av en potentiell R404A-ersättare – fältprov med R449A”) and Swedish Energy Agency (EFFSYS Expand P08) with the support of Bosch Thermoteknik AB, Danfoss Värmepumpar AB, Nibe AB, Nowab, Energi & Kylanalys AB and Svenska Kyltekniska Föreningen

R450A and R513A as lower GWP mixtures for high ambient temperature countries: Experimental comparison with R134a

In recognition of the impact of the refrigeration sector on climate change, global commitments are achieved to replace hydrofluorocarbon substances with more planet-friendly alternatives. In this regard, countries with high ambient temperatures (HAT) face additional problems in identifying suitable alternatives due to the impact of such temperatures on energy performance in vapor compression systems. This paper presents an experimental analysis using R134a and two lower global warming potential (GWP) mixtures in a small capacity vapor compression refrigeration system for HAT environments. The range of evaporating and condensing conditions was selected to simulate a refrigeration system working at HAT conditions. The experimental operating results show that although R450A values are acceptable, R513A shows better adaptation to the refrigeration system in terms of pressure ratio, discharge temperature, and mass flow rate. Then, attending to experimental energetic results, R450A energy performance (quantified by COP) and cooling capacity are lower than R513A and R134a. TEWI analysis of a small refrigeration unit shows CO2 equivalent emission saving when using R450A in the different condensation conditions. However, taking into account the variation of cooling capacity, R513A system results in the lowest TEWI when normalizing per unit of delivered cooling capacity

Experimental assessment of R134a and its lower GWP alternative R513A

Lower GWP refrigerants are essential to mitigate the impact of refrigeration systems on climate change. HFO/HFC mixtures are currently considered to replace HFCs in refrigeration and air conditioning systems. The aim of this paper is to present the main operating and performance differences between R513A (GWP of 573) and R134a (GWP of 1300), the most used refrigerants for medium evaporation temperature refrigeration systems and mobile air conditioners. To perform the experimental comparison, 36 tests are carried out with each refrigerant at evaporating temperatures between −15 and 12.5°C and condensing temperatures between 25 and 35°C. The conclusion of the experimental comparison is that R513A can substitute R134a with only a thermostatic expansion valve adjustment, achieving better performance and higher cooling capacity. The discharge temperature of R513A is always lower than that of R134a.The authors thankfully acknowledge the Ministry of Education, Culture and Sports, Spain for supporting this work through “Becas y Contratos de Formación de Profesorado Universitario del Programa Nacional de Formación de Recursos Humanos de Investigación del ejercicio 2012 (Grant number FPU12/02841)” and “Ayudas complementarias para beneficiarios de ayudas (FPU): Estancias Breves. Convocatoria 2015 (Grant number EST15/00154)”. This research is also done within the Effsys Expand P08 project that is funded by the Swedish Refrigeration Cooperation Foundation, KYS and Swedish Energy Agency with the support of Bosch Thermoteknik AB, Danfoss Värmepumpar AB, Nibe AB, Nowab, Svensk Energi & Kylanalys AB and Svenska Kyltekniska Föreningen

Energy, Exergy, and Environmental (3E) Analysis of Hydrocarbons as Low GWP Alternatives to R134a in Vapor Compression Refrigeration Configurations

The phase-down of hydrofluorocarbons and substitution with low global warming potential values are consequences of the awareness about the environmental impacts of greenhouse gases. This theoretical study evaluated the energy and exergy performances and the environmental impact of three vapor compression system configurations operating with the hydrocarbons R290, R600a, and R1270 as alternatives to R134a. The refrigeration cycle configurations investigated in this study include a single-stage cycle, a cycle equipped with an internal heat exchanger, and a two-stage cycle with vapor injection. According to the results, the alternative hydrocarbon refrigerants could provide comparable system performance to R134a. The analysis results also revealed that using an internal heat exchanger or a flash tank vapor injection could improve the system’s efficiency while decreasing the heating capacity. The most efficient configuration was the two-stage refrigeration cycle with vapor injection, as revealed by the exergy analysis. The environmental impact analysis indicated that the utilization of environmentally-friendly refrigerants and improving the refrigeration system’s efficiency could mitigate equivalent CO2 emissions significantly. The utilization of hydrocarbons reduced the carbon footprint by 50%, while a 1% to 8% reduction could be achieved using the internal heat exchanger and flash tank vapor injection

Design of an environmentally friendly refrigeration laboratory based on cooling capacity calculation for graduate students

Lower global warming potential (GWP) refrigerants must be used in refrigeration education to integrate the environmentally responsible engineering principles in class. However, most of the refrigeration educational laboratories are still using hydrofluorocarbons (HFCs) as working fluids, which are considered as greenhouse gases. This paper shows the procedure to adapt the new refrigerant R513A in a refrigeration system used for a cooling capacity educational laboratory. First, the paper describes the organization of the laboratory session, and the characteristics of the different methods of cooling capacity calculation taught to the master’s degree students. Then, the benefits of including new sensors in the experimental setup to obtain more accurate results are explained. Later, accurate new graphics and an equation to calculate the R513A cooling capacity are provided. Finally, the educational aspects worked with the students in this session, and each cooling capacity method are assessed. The procedure explained in this paper can be used as a guide for introducing lower GWP refrigerants in similar educational refrigeration laboratories

ANN Modeling to Analyze the R404A Replacement with the Low GWP Alternative R449A in an Indirect Supermarket Refrigeration System

Artificial neural networks (ANNs) have been considered for assessing the potential of low GWP refrigerants in experimental setups. In this study, the capability of using R449A as a lower GWP replacement of R404A in different temperature levels of a supermarket refrigeration system is investigated through an ANN model trained using field measurements as input. The supermarket refrigeration was composed of two indirect expansion circuits operated at low and medium temperatures and external subcooling. The results predicted that R449A provides, on average, a higher 10% and 5% COP than R404A at low and medium temperatures, respectively. Moreover, the cooling capacity was almost similar with both refrigerants in both circuits. This study also revealed that the ANN model could be employed to accurately predict the energy performance of a commercial refrigeration system and provide a reasonable judgment about the capability of the alternative refrigerant to be retrofitted in the system. This is very important, especially when the measurement data comes from field measurements, in which values are obtained under variable operating conditions. Finally, the ANN results were used to compare the carbon footprint for both refrigerants. It was confirmed that this refrigerant replacement could reduce the emissions of supermarket refrigeration systems