Search

This article presents a theoretical study and experimental validation of a new solar bubbler basin using as a humidifier in humidification–dehumidification desalination system. The prototype consists mainly of a simple solar basin, filled with water, through which air is forced to travel upwards in form of bubbles. A detailed mass and heat transfer analysis was elaborated to model the dynamic behavior of the new humidifier. It is through a comparison with the experimental data that the validity of the proposed model was tested. The simulation results have revealed that the humidification efficiency and the amount of evaporated water can reach 98% and 6 kg m−2 day−1, during the spring equinox. The effects of some operational parameters (water depth, inlet air temperature, and flow rate) were investigated. It was found that the inlet air temperature and flow rate have a significant effect on the water content difference in the humidifier. © 2018 American Institute of Chemical Engineers Environ Prog, 38: 518–526, 2019 [ABSTRACT FROM AUTHOR]

The mathematical model will be able to predict the operated condition (required tube diameters, heat input. and submergence ratio&hellip). That will result in a successful bubble pump design and hence a refrigeration unit In the present work a one dimensional two fluid model of boiling mixing ammonia water under constant heat flux is developed. The present model is used to predict the outlet liquid and vapor velocities and pumping ratio for different heat flux input to pump. The influence of operated conditions such as: ammonia fraction in inlet solution and tube diameter on the functioning of the bubble pump is presented and discussed. It was found that, the liquid velocity and pumping ratio increase with increasing heat flux, and then it decreases. Optimal heat flux depends namely on tube diameter variations. Vapor velocity increases linearly with increasing heat flux under designed conditions. [ABSTRACT FROM AUTHOR]

In the present study, the ammonia-water mixing flow in a bubble pump is numerically simulated. The flow patterns of a two-phase flow in a bubble pump were studied under different conditions of heat flux and tube diameter. A one-dimensional two-fluid model was developed under constant heat flux. This model was used to predict the variations in void fraction and liquid and vapor velocities throughout the tube. Then, the void fraction profile and the curve of liquid velocity versus vapor velocity were used to predict the flow patterns along the tube length. It was found that at heat fluxes below 15 kW m-2, bubbly, slug, and churn flows are the dominating regimes, and the length of these flow regimes depends on the tube diameter. For heat fluxes higher than 15 kW m-2, the bubble pump operates under the chum and annular regimes, and the bubble pump performance is improved when the tube diameter increases. [ABSTRACT FROM AUTHOR]

In arid coastal regions, the lack of potable water coincides often with high solar insolation. In this case, coupling of the desalination systems with solar energy is of great importance. Among the desalination systems, the membrane distillation technique holds numerous advantages. The present work focuses on the vacuum membrane distillation coupled with solar energy. The aim is to simulate a novel membrane configuration in order to enhance the permeate product. This novel membrane is composed of hollow fiber wound in helically coiled shape. Two-dimensional Navier-Stokes equations are written and then solved using the finite element method. For a pitch of 32.2mm and a coil radius of 95.7mm, the simulation results of the permeate product are 0.2685 kg/h and 7.688 10-3 kg/sm² for the permeate flux. These values present an enhancement when compared to the linear hollow fiber configuration at the same operating conditions. This enhancement is about 28% for the permeate flow rate. [ABSTRACT FROM AUTHOR]

Abstract: The thermal conversion of solar energy by means of solar concentrators makes it possible to reach high temperatures able to boil the salted water with pressures higher or equal to the atmospheric one. In order to test these concentrators in the brackish water desalination field, we have designed, dimensioned and built in our laboratory a small solar desalination unit equipped with a paraboloid concentrator. To evaluate the performance of this unit, we developed a theoretical model to calculate the absorber average temperature as well as the distillate flow rate as a function of solar flux. The experimental results were compared with those calculated theoretically. A small difference in the absorber average temperature was found between both results. On the other hand, distillate flow rate reached an average relative error of 42%. These results indicate that the design of our unit needs to be improved with special emphasis on the absorber. [Copyright &y& Elsevier]