Experiment Research And Numerrical Simulation Of A Novel Absorber Using Liquid-Gas Ejector

Energy conservation and environmental protection have become a growing concern. Lithium bromide absorption chillers can be driven by low-grade heat source. It has two major significant features:energy saving and environmental refrigerant, and it has received considerable attention in recent years. Absorber, the main component of the lithium bromide absorption chiller, plays an important role on the system performance, size and cost. The key to improve system efficiency and reduce exchange area is to improve the absorption rate.In this paper, a new ejector absorber is described. The conventional falling film absorber is replaced by liquid-gas ejector and heat exchanger. The mass transfer is enhanced in the liquid-gas ejector and the heat transfer enhanced in the heat exchanger. The main work of this paper is given as follows:Based on the theory of computational fluid dynamics and dependent on the schnerr-sauer model, the numerical simulations about cavitation, occurring in nozzle, have been performed. The results show that cavitation takes place more easily under higher injection pressure and the outlet pressure of nozzle restrains the phenomenon of cavitation. The more straight length can make the flow rate of outlet less. The large divergent angle can make the flow detach easily from the wall, which is conducive to the occurrence of cavitation. Cavitation, occurring in convergent nozzle, is less than the convergent-divergent nozzle. The straight length plays an important role on cavitation occurring in convergent nozzle. The volume fraction of vapor increases firstly and decreases with the increase of the straight length.The solution flow pattern in the ejector is studied by a high-speed camera. At the nozzle throat, cavitation phenomenon easily occurs, which impacts on the flow pattern of aqueous lithium bromide solution. Using smaller throat diameter of nozzle, cavitation intensity increases, which make larger surface disturbance and more droplets.Liquid-gas ejector is studied in an experimental absorption refrigeration setup. The results show that:the absorption rate increases with the throat diameter of diffuser and the diameter of the suction chamber. Compared with the convergent nozzle, the divergent-convergent nozzle is with a higher absorption rate. The absorption rate increases with the mass flow rate and the evaporator temperature. And the absorption rate increases as the inlet solution temperature and back pressure deceases.Simulation study of liquid-gas ejector with the convergent nozzle is done using Eular-Eular model. The simulation results well agree with the experimental results. Liquid-gas ejector’s performance under different conditions is predicted. There is no disturbance on the surface of jet, which is not beneficial to absorb the vapor. The more flow rate of solution and driving force for mass transfer can make the performance of ejector higher.