Experimental characterization of the refrigerant distribution along a finned tubes heat exchanger

Abstract

[EN] According to the European Commission, heating, cooling and domestic hot water (DHW) production imply 79% of the total energy consumed in households. Moreover, as 84% of this energy is still generated from fossil fuels, it is required taking measures in order to improve the current situation. Following this intention, the path of the European Union is the reduction of the energy consumption and increasing the percentage of energy produced by renewable sources. One way to achieve the objectives set by the European Union is by the use of the heat pump powered by renewable sources, while the directive 2009/28/CE consider that heat pumps use renewable sources under certain conditions. Nowadays, refrigerants used by heat pumps are mainly hydrofluorocarbons (HFCs) which have a high global warming potential (GWP) and have a clear deadline defined at F-Gas EU Regulation 517/2014. For this reason, natural refrigerants, will play an important role within heating, cooling and DHW production at household sector. However, most of the natural refrigerants with acceptable thermodynamic properties are at least slightly flammable, and this attempt against the safety. For this reason, the amount of refrigerant charge must satisfy the maximum refrigerant charge limited by regulations, and the prediction of this maximum charge has become an important matter within the design process of a heat pump. Nevertheless, calculating the amount of refrigerant for a given heat pump is a difficult process with many uncertainties, like refrigerant mal-distribution in heat exchangers. In this work, an experimental characterization of the amount of refrigerant along the finned tubes heat exchanger (FTHE) of a heat pump working with R290 has been done. This qualitative and quantitative study has been carried out by measuring and comparing the temporary temperatures pattern distribution of the refrigerant in the FTHE, using thermocouples and thermographies