Identificador: TDX:283
Autors: Nogués Aymamí, Miquel
Resum:
The electrical demand in Catalonia has raised around 70% between 1986 and 1999, and the foreseen demand in 2010 is around 43% higher than the present one. Similar increases in other parts of the country may produce a collapse in the Spanish Electrical Network. Moreover, around 12% of the present electrical consumption in Spain is just for air conditioning.Considering this situation and the enormous favourable perspectives in the Spanish air conditioning market, the development of an absorption unit for residential and light commercial applications is proposed in this thesis. In the target conditions, the unit should to provide a heating capacity of 24.5 kW in winter, while in summer the cooling capacity is targeted to 20 kW. In both cases, the expected electrical demand is below 2 kW, because the driving energy required is from a thermal source at temperatures between 120 and 150ºC. Most of the commercial absorption units have some limitations related to working pair (corrosion, crystallisation, operating pressure or rectification). In order to overcome these limitations, in this study an organic pair has been selected, being the refrigerant Methanol and the absorbent Dimethylether tetraethylenglycol. The advantages of this mixture are its full miscibility, the good chemical and thermal stability in the expected operating temperatures and its compatibility with most of materials commonly used in the air conditioning units.The developed unit operates in summer under an absorption-compression double effect cycle with a COP>1.2, while in winter the unit is shifted to a single effect absorption-compression cycle with a COP>1.4. In both cases, the compression step provides a higher temperature lift between the evaporator and the absorber, which makes feasible to reject the heat through a dry system instead of a cooling tower.The unit has been built using plate heat exchangers in order to have high heat transfer surfaces in a low volume, accomplishing a compact unit with low thermal inertia.The first results obtained in a test facility confirm both the suitable control strategy and the promising perspectives for the unit.
Repositori URV