Hasan Mousa

Water film cooling over the glass cover of a solar still including evaporation effects

The effect of water film cooling of the glass cover on the efficiency of a single-basin still has been investigated numerically. Proper use of the film-cooling parameters may increase the still efficiency by up to 20%. On the other hand, a poor combination of these parameters leads to a significant reduction in efficiency. The presence of the cooling film neutralizes the effect of wind speed on still efficiency. Only a small fraction of the cooling film evaporates as it passes over the glass cover.

Desalination and hot water production using solar still enhanced by external solar collector

Abstract A unit consisting of a solar still enhanced by an external solar collector to desalinate and produce hot water was designed and tested. The unit consists of three main parts: water basin, external solar collector, and heat exchanger. The water in the basin is heated by direct solar irradiation and by hot water flowing in the heat exchanger heated by the external collector. This enhances water evaporation from the basin. The produced vapor condenses on the lower part of the double glass cover through which cooling water flows. The condensate is withdrawn as desalinated (fresh) water. The effect of cooling water flow rate, ambient temperature, solar intensity, and hot water production rate on the amount of desalinated water produced was investigated. The results showed that the production rate is proportional to the solar irradiation, ambient temperature, and cooling water flow rate. On average the unit was capable of producing 0.4 l/h desalinated water of low salinity (2–6 ppm) and hot water of te...

Determination of the Orthokinetic Coalescence Efficiency of Droplets in Simple Shear Flow Using Mobile, Partially Mobile and Immobile Drainage Models and Trajectory Analysis

The orthokinetic coalescence efficiency, of two Newtonian droplets submerged in a Newtonian fluid in simple shear flow, was theoretically investigated. The investigation considered three drainage models: immobile, partially mobile and mobile interfaces. The coalescence efficiency was also determined by solving the trajectory equations of the simple shear flow. The analysis showed that a critical approach angle, αcrit exists, below which the colliding droplets separate. Above this critical angle the collision leads to coalescence. The coalescence efficiency, , is related to αcrit by = cos(αcrit). Dimensional analysis showed that the coalescence efficiency depends on several dimensionless groups namely the flow number, the capillary number, the viscosity ratio and the radii ratio of the colliding droplets. The dependence of the coalescence efflciency on the flow number, the capillary number and the viscosity ratio was studied. It was found that the coalescence efficiency decreases as the capillary number and the flow number increase. For immobile interfaces the coalescence efficiency is independent of the capillary number until deformation sets in where it drops sharply. It was also found that the coalescence efficiency increases as the viscosity ratio increases. The coalescence efficiency calculated from the trajectory analysis decreases as the flow number increases. The dependence is strong for small values of the flow number and weak for large values. The relative position of one droplet with respect to the other in space strongly influences the coalescence efficiency. The maximum efficiency is achieved when the two droplets are in the same shear plane, i.e., when θ = 90°. As the angle θ decreases the coalescence effiiency also decreases. Below a certain value of the angle θ the collision is inefficient and no coalescence takes place. The minimum distance between two colliding droplets as a function of θ was determined. The results revealed that the minimum distance is smallest when θ = 90°. An equation to calculate the average coalescence efficiency is presented.

Experimental Investigation of the De-inking of Recycled Newspaper Using Plastic Particles

The effect of the type of plastic particles, its average diameter, and its total surface area on the de-inking of recycled newspaper was investigated. It was found that plastics vary in their ability to remove ink. Among the various types of plastics examined, low density polyethylene (QAPCO) was found to have the largest capacity of ink removal. Ink removal versus plastic particle size was found to go through a maximum. Studying the effect of the total surface area of plastic particles on de-inking shows that a limiting surface area exists above which no more ink can be separated.

Kinetics of deposition of carbon particles on plastic spheres

The kinetics of particle deposition onto the surface of spherical collector particles suspended in a stirred batch vessel was investigated. The study considered monodisperse particle and monodisperse spherical collector particles. The Langmuir model for the deposition process was presented with model parametric study as well as model limiting cases of Smoluchowski analysis and equilibrium state. A method for obtaining the model parameters from model limiting cases was demonstrated. The model was experimentally tested by studying the deposition of small carbon particles onto plastic spheres. This is useful in the de-inking process of waste paper using plastic spheres. The obtained deposition curves are fitted to the model. The estimated parameters from model limiting cases are in agreement with those, obtained from the full deposition curves fitted to Langmuir kinetics. The maximum number of carbon particles that can deposit on plastic particles is estimated theoretically from geometrical analysis. The estimated value is very close to that determined from the model.

Microemulsions of Potassium Oleate, Tween-20, Propylene Carbonate, and Ethylene Glycol as Drug Vehicles for Mefenamic Acid

Different microemulsions were prepared with and without mefenamic acid (MFA). The base microemulsion was mainly composed of distilled water; the aqueous phase, propylene carbonate; the oil phase, potassium oleate; the surfactant, and finally di-ethylene glycol; the cosurfactant. The effect of mixing ionic (potassium oleate) with nonionic (Tween-20) surfactant was investigated via constructing the phase diagrams of such systems. Changes in conductivity and viscosity of the freshly prepared microemulsion over time were monitored as an indication for the stability of the microemulsion. Measurements were carried out at room temperature, after a freeze-thaw cycle and also after storage for 3 days at 60°C, where the latter is treated as an accelerated test for the time-temperature effects on the stability of a microemulsion. It was found that a set of surfactants, instead of a single surfactant, and inclusion of cosurfactant resulted in a broader region where a stable microemulsion is predominant. At a mass ratio of 1:2 of potassium oleate to Tween-20, O/W microemulsions were found to have maximum stability among all examined systems, under the accelerated test, such that they have a minimum portion of combined surfactants and cosurfactant of 60 wt% and maximum of 80 wt%. With the aforementioned specifications, no phase separation and neither significant change in the conductivity nor in the viscosity was observed in any of the examined systems after subjecting them both to the accelerated and freeze-thaw cycle test, indicating that such systems were thermodynamically stable. Samples of micro emulsions passing previous tests were further subjected to an acidic medium by dispersing 1 g of MFA-containing microemulsion in 10 g HCl solution (pH 1) in a shaking water bath at 37°C, for a 6 hour period. The maximum solubility of MFA in a stable microemulsion was approximately 5 wt%, evaluated at room temperature.

Characterization of adsorption of aqueous arsenite and arsenate onto charred dolomite in microcolumn systems

In this work, the removal of arsenite, As(III), and arsenate, As(V), from aqueous solutions onto thermally processed dolomite (charred dolomite) via microcolumn was evaluated. The effects of mass of adsorbent (0.5–2 g), initial arsenic concentration (50–2000 ppb) and particle size (<0.355–2 mm) on the adsorption capacity of charred dolomite in a microcolumn were investigated. It was found that the adsorption of As(V) and As(III) onto charred dolomite exhibited a characteristic ‘S’ shape. The adsorption capacity increased as the initial arsenic concentration increased. A slow decrease in the column adsorption capacity was noted as the particle size increased from>0.335 to 0.710–2.00 mm. For the binary system, the experimental data show that the adsorption of As(V) and As(III) was independent of both ions in solution. The experimental data obtained from the adsorption process were successfully correlated with the Thomas Model and Bed Depth Service Time Model.

Modeling the deposition of colloidal particles on solid spheres

Abstract A theory describing the deposition of monodisperse and polydisperse carbon particles onto the surface of monodisperse and polydisperse plastic spheres in simple shear flow was developed. The polydispersity of the plastic and the carbon particles was described by log normal distributions. Smoluchowskis equation for the collision frequency between the carbon and the plastic spheres was used. The theory involves few assumptions, the most important one being that the carbon particle occupies an area on the plastic surface equal to its projected area. Expressions were derived to calculate the orthokinetic deposition efficiency and hence the deposition rate at the early stages of the deposition phenomenon. Comparing theoretically calculated with experimentally measured values of the number of carbon particles enables calculation of the orthokinetic deposition efficiency.

Improving the productivity of a falling film solar desalination unit

AbstractThis study aimed at improving the productivity of a falling film solar desalination unit by cooling the glass cover and by improving the hot surface wettability. The glass cover was made of double layers through which cooling water passes. The advantage of this design is that the latent heat of evaporation is absorbed by the cooling water and returned to the system. The effect of the various parameters such as feed water flow rate, cooling water flow rate, weather conditions, solar irradiation intensity, and collector’s surface area was investigated. The results showed that increasing the cooling water flow rate enhanced fresh water production. The productivity of the unit decreased with increasing feed water flow rate. Recycling the hot water to the feed water tank improved the productivity of the unit from 0.13 to 0.18 L/h (~34%). Fog formation on the double glass cover was found to reduce the productivity of the unit. Modifying the surface of the black plate with cotton cloth or with plastic st...

Semicontinuous solar drying of sludge from a waste water treatment plant

This study presents a newly developed system to utilize solar energy to dewater the sludge in a semicontinuous mode. The semicontinuous dryer mainly consists of a moving belt on which aluminum bars are fixed to hold the sludge and a fan is used to drive the air at the required speed. The effects of operating conditions, such as air velocity, belt speed, and mode of contact between the sludge and air, on the drying rate of water were investigated. The drying rate of water was measured under the effects of different operating conditions, including air velocity, belt speed, and mode of contact between the sludge and air. The experimental results proved the technical feasibility of the developed solar drying system to efficiently evaporate water. The achieved drying rates were 2.02 kg water/m2 h and 0.49 kg water/m2 h in September and February, respectively. Under a given insolation rate, a high evaporation rate is achieved at large air velocity and slow motor speed. An empirical relationship to predict the m...