Modelisation de machines frigorifiques entrainées par énergie solaire thermique; application à la climatisation
Tutor / director / evaluatorFrère, Marc
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - confidentiality agreement
It is well known that the global warming consciousness is nowadays largely widespread. A strong increase of the electricity dependence, the time proximity of the peak fossil fuels and protocols imposing a substantial reduction of the greenhouse gases emissions in industrialised countries will lead to important use of renewable energies. According to the International Energy Agency (IEA), the cooling production in developed countries is responsible for 10 to 30% of the electrical consumption. This fact is due to the need of using electricity to run out the typical vapour compression machines. This thesis is focused on this problem and it will try to find a renewable solution of air conditioning for domestic buildings, i.e. the cooling power included in the 5-15 kW range. The fact that peak cooling demand in summer is associated with high solar radiation offers an excellent opportunity to exploit solar thermal technologies that can match heat-driven cooling technologies. It is in this context where this thesis is emplaced. The technology which will be studied in this thesis is the absorption cycle with solar energy as hot source in this work. The absorbent-refrigerant couple is water – LiBr. The target of this report is, firstly, to search LiBr solution properties by comparing different values appearing in literature sources. Secondly, by applying these properties, the thermodynamically cycle calculation (by imposing absorber and generator temperatures, low and high pressures) is required to estimate the mass flow rates and concentrations to characterise the system. Thirdly, a selection and a design of the absorber are made: a multi-tube absorber with wetted walls and vertical concurrent flow from up to bottom. Finally, a modelling of three kinds of absorption conditions, from the least to the more realistic one, is carried out with the aim of studying mass transfer in an isothermal and adiabatic model, heat and mass transfers in an adiabatic model and also heat and mass transfers in an absorber with heat transfer with outside air model (finned tubes). In all the cases, the variations of parameters (LiBr concentrations, solution temperature or heat duties) are calculated all along the tubes.
SubjectsRefrigeration and refrigerating machinery, Solar thermal energy, Refrigeració i màquines frigorífiques, Energia tèrmica solar
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