tailieunhanh - Thermodynamics Systems in Equilibrium and Non Equilibrium Part 6

Tham khảo tài liệu 'thermodynamics systems in equilibrium and non equilibrium part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 Conception of an Absorption Refrigerating System Operating at Low Enthalpy Sources Nahla Bouaziz Ridha BenIffa Ezzedine Nehdi and Lakdar Kairouani Engineering National School of Tunis Tunisia 1. Introduction Since the work of Duhem in 1899 relating to binary mixtures that the absorption chillers have been growing significantly. In 1930 Borzig had developed a machine using the couple water-ammonia. This system is interesting in that it works by supplying heat energy regardless of its origin waste heat geothermal water solar energy. . 2. Operating principle The operating principle of such a machine is briefly describe below Figure 1 . The absorption system differs from the vapor compression machine by providing a third heat source which is the generator Qg . The absorption machine uses a binary mixture one fluid is more volatile than the other and constitutes the refrigerant. Couples most commonly used are Water-Ammonia H2O NH3 Ammonia is the refrigerant. Lithium Bromide-Water LiBr H2O water is the refrigerant. The elements of an absorption machine are shown in Figure 1. They are Boiler or generator the refrigerant rich solution is heated to the temperature Tg which is higher than the temperature of vaporization of refrigerant to the pressure considered. Condenser similar to that of a vapor compression machine. Evaporator similar to that of a vapor compression machine. - Absorber steam from the evaporator is absorbed by the existing solution which will be enriched in refrigerant. The absorber is also connected to the generator. The weak solution coming from the boiler enters to the absorber. - Inter-exchange solution all current machines include a heat exchanger sometimes called internal transmitter between the rich solution leaving the absorber to Tab and the weak solution leaving the boiler at Tg. This exchanger is used to preheat the rich solution before entering at the generator. A pump is used to lead the rich solution to the generator and an expander is used