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14 Modelling of RACHP systems 14.1 Overview There are a number of models used to calculate data for refrigeration and air conditioning applications: 1. Thermodynamics based models that, in a straightforward manner, calculate energy efficiency and energy consumption for an RACHP application under certain well determined ambient (i.e., running) conditions; 2. Combined thermodynamic, flow and heat transfer models used in R&D studies to investigate the impact of refrigerant heat transfer, refrigerant properties, flow patterns (either steady state or dynamic simulation) and to investigate component, cycle and equipment design. In principle the focus is on the refrigerant and the consequences of its properties for the design. Important articles have been published by McLinden et al. (2017); 3. Models that focus on total (climate relevant) emission reductions from the application of RACHP equipment. They depart from assumptions or data on the number of pieces of equipment of certain types in the RAC(HP) subsector and from test data regarding energy efficiency improvements possible by changing refrigerants; they can therefore calculate climate benefits expressed in CO2-eq. These models often combine both the climate benefit from the impacts of energy efficiency increase and the heat-cooling load reduction, which makes the whole “climate relevant reduction” not very transparent; this also because the fuel mix in power generation (the power factor) also plays an important role here; 4. Inventory (“bottom-up”) models that calculate the amounts of refrigerant charged into RACHP equipment, where the equipment numbers are based on sales data of various types of equipment for a country or region, which can then also be defined as the (total, regional) bank of refrigerants. Together with assumptions regarding leakage and recovery during the equipment operation and at end of life, and most importantly, during servicing and maintenance, the refrigerant demand and the refrigerant emissions can be determined for a given year. Also the fluctuations in the size of the bank over a certain period can be calculated. Once a period is studied, it is evident that, in a first instance, economic data on growth and shrinking have to be taken into account as the dominant parameter for the time dependent demand and resulting bank and emissions behaviour. A description of the model is given in the Annex to the RTOC 2010 Assessment Report (RTOC, 2010). This type of model has been applied for scenario calculations up to the year 2050 in various TEAP Task Force reports that investigated possible future high GWP HFC as well as low GWP refrigerant demand. These reports were particularly published in the period 2012-2016, e.g., see (TEAP, 2016a). During the last assessment period, 2014-2018, and even before, the focus for modelling has been on “bottom-up” models used to predict the regional or global refrigerant demand for RACHP equipment. This is clearly reflected in this 2018 Assessment Report. As mentioned above, it requires the determination of the number of pieces of equipment charged with refrigerants (which then forms the total inventory or “bank”), and knowledge related to the average lifetime and the emission rates of equipment, plus assumptions on recycling, disposal, and other parameters. Important parameters are the number of pieces of equipment (per sub-sector) manufactured in certain countries or certain regions per year, where the changes are very much dependent on economic growth (GDP) parameters, the types of refrigerants used, the ongoing development in equipment design, and, last but not least, the required refrigerant demand for servicing. A very sensitive issue here is the growth in the sales of pieces of equipment, which is, particularly at present and particularly for the AC subsector, completely disconnected from the overall economic 2018 TOC Refrigeration, A/C and Heat Pumps Assessment Report 271PDF Image | Heat Pumps Technical Options
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