Retrofitting of R404a Commercial Refrigeration Systems with R410a and R407f HFCs Refrigerants

Retrofitting of R404a Commercial Refrigeration Systems with R410a and R407f HFCs Refrigerants

Mauro Gamberi (University of Padua, Italy), Marco Bortolini (University of Bologna, Italy), Alessandro Graziani (University of Padua, Italy) and Riccardo Manzini (University of Bologna, Italy)
DOI: 10.4018/978-1-4666-8398-3.ch007
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This chapter presents an experimental analysis about the retrofitting of two commercial stationary refrigeration systems marketed by an Italian leading company of the sector. Such systems operate both at medium temperature (MT) and low temperature (LT) and they are originally designed to work with the high global warming potential (GWP) hydrofluorocarbon (HFC) R404a fluid (GWP = 3922). The purpose is to investigate the performances of HFCs R410a (GWP = 2088) and R407f (GWP = 1825) chosen as effective alternatives to HFC R404a, due to their compatibility, non-flammability and market availability. Furthermore, such fluids meet the EU restrictions in force in the next future for high GWP HFCs. The experimental analysis compares the performances, in terms of COP and cooling capacity, of R404a and the two identified alternatives under different operating conditions, i.e. chamber and condenser inlet air temperatures. In case of comparable performances, significant environmental benefits are introduced by the adoption of R407f and R410a in the MT and LT refrigeration systems.
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According to the fifth assessment report (AR5) of the International Panel on Climate Change (IPCC), the global emissions of greenhouse gases (GHGs) are at unprecedented level despite the rising attention to policies limiting the climate change. As in Figure 1, the total GHG emissions reach 49(±4.5) GtCO2eq/year in 2010, while the average annual GHG emission growth from 2000 to 2010 is of about 1.0 GtCO2eq/year (+2.2%), compared to the 0.4 GtCO2eq/year (+1.3%) measured from 1970 to 2000, showing an exponential trend. However, the climate change scenarios assessed in the AR5 of the IPCC show that to have a likely chance of limiting the increase in global mean temperature to 2°C, and thus prevent undesirable climate effects, means lowering GHG emissions by 40 to 70 percent compared with 2010 by mid-century, and to near-zero by the end of this century (IPCC, 2014).

Figure 1.

Global annual anthropogenic GHG emissions by group of gases 1970-2010

(IPCC, 2014)

In accordance with the international agreements on the global warming and climate change, e.g. Kyoto Protocol in the 1997, the European Union (EU) establishes and continuously updates a roadmap to progressive reduce GHG emissions in different sectoral areas. The growing concern on climate change reported on the forth assessment (AR4) of the IPCC (IPCC, 2007) accelerates this process and the European Directive (29/2009/EC), known as ''20/20/20 climate and energy package”, sets ambitious targets by 2020:

  • 20% reduction in EU GHG emissions from 1990 levels;

  • 20% increase of the share of EU energy consumption produced from renewable sources;

  • 20% improvement of the EU energy efficiency.

Refrigeration and air conditioning systems contribute to GHG emissions due to the energy consumption, which is identified as indirect emission, and the adoption of working fluids with significant GWP, which represents a direct emission due to the risk of accidental gas leakage into the atmosphere (Bovea, Cabello, & Querol, 2007). Following the Montreal Protocol (1987), fluorinated gases (F-Gases), mostly the hydrofluorocarbons (HFCs), replace the chlorofluorocarbons (CFC) and hydrochlorofluorocarbons (HCFC) ozone-depleting refrigerants. They have no ozone depletion potential because chlorine is eliminated from their chemical structure, low toxicity, non-flammability and thermally stability. However, HFCs are a family of powerful GHG, listed into the basket of seven GHGs (Kyoto Protocol, 1997), with a warming effect on the atmosphere up to 23'000 times greater than that of CO2 and responsible of the 2% of EU overall GHG emissions.

The EU defines measures to control their emissions (842/2006/EC), while the EU Directive (40/2006/EC) sets significant limits, i.e. 100yr GWP<150, to the emissions from air-conditioning systems in motor vehicles. In the other sectors, after several discussed proposals (EU Legislative Resolution, 2014), the EU Regulation No 517 of the European Parliament and of the council of 16 April 2014 on F-gases for the most common refrigeration and air-conditioning systems defines a program to reduce F-Gas emissions and reach IPCC targets. Particularly, non-CO2 emissions, including F-gases, should be reduced by 72% to 73% by 2030 and by 70-78% by 2050, compared to the 1990 levels. To achieve such purpose, a two-third reduction in F-gas emissions by 2030 is mandatory. A phase-down program to decrease F-gas sold in the EU and to ban F-gases in some of new equipment is set. Such a program is cost-effective because proven and tested alternatives are available in many sectors (517/2014/EU).

Key Terms in this Chapter

Cooling Capacity: The ability of a cooling system to remove heat from a low temperature ambient.

Vapor Compression Cycle: It is the most widely adopted cycle for refrigeration systems. It uses a refrigerant as a medium which absorbs heat from the volume to be cooled flowing it elsewhere.

Global Warming Potential: Index expressing the climatic warming potential of a GHG relative to that of carbon dioxide. Global warming potential is used to measure the GHG effect of a gas based on its radiative properties over a given time frame.

Hydrofluorocarbon: Organic compound that contain fluorine and hydrogen atoms. Hydrofluorocarbons are widely adopted refrigerants in cooling systems.

Coefficient of Performance: Index to assess the performance of a refrigeration system or a heat pump. It is defined as the ratio between the useful effect (refrigeration effect or heating effect) and the the work input.

Retrofitting: Process to add new technologies or features to existent systems.

Refrigerant: Primary working fluid used to produce a cooling effect in a refrigeration system. All refrigerants extract heat at low temperature and low pressure during evaporation and reject heat at high temperature and pressure during condensation.

Greenhouse Gas: Gas in the atmosphere that absorbs and emits radiations within the thermal infrared range. This process is the fundamental cause of the GHG effect.

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