Ali A. Badran

Performance of cool towers under various climates in Jordan

The concept of cool towers, which is a modern version of the historical wind catchers was re-visited. In contrast with the expression of cooling towers, which usually refers to equipment used to cool the water in power stations, air conditioning plants etc., cool towers are used to cool the air to provide comfort conditions for occupants. The main driving force for air in cool towers is the difference in density of air between the inside and outside of the tower. Since the inside air is cooler than the outside, its density is higher and the resulting density difference creates a reversed chimney effect. This effect translates into the flow of cold air down the tower to the conditioned space. A new set of criteria for Amman, Jordan was used in this work, which resulted in a realistic performance of the tower. In addition, the performance of the tower was studied for other climatic regions of Jordan, such as the desert areas, Jordan valley (Ghor) and Aqaba, where air conditioning is needed most. It was found that under those climates, the height of the tower necessary to create proper air flow is less than 9 m. This is in contrast to the traditional design which may reach up to 15 m in height. A tower of 4 m height can produce the equivalent of 1 t of refrigeration.

Comparative study for under-floor heating using solar collectors or solar ponds

A theoretical and experimental study is made for underfloor heating system using solar collectors. Also a study for a similar system using solar ponds is made under the same local conditions. Results obtained show that the solar collector system is 7% more efficient than the solar pond system. Economic analysis show that the Solar Collector System (SCS) will break even earlier than the Solar Pond System (SPS). Practical considerations show that the SCS requires less operation and maintenance work.

Simulation and experimental study for an inverted trickle solar still

Abstract An experimental study for an inverted trickle solar still was performed. The still was basically composed of an inclined absorber plate painted black on the top. Saline water flowed at the backside of the plate and was kept attached to the plate. The water flow rate was kept low so that its temperature was raised to produce vapor. Condensation took place in another compartment where a heat exchanger was placed to provide heat recovery. The still was tested using brackish water of 6000 ppm salinity during the month of November at 47° and 32° tilt angles. The condensate obtained was 2.8 and 2 L/d at the above angles, respectively. This represents an 18% increase in this kind of output over previous work, which is due to reduction in the salinity of feed water. However, the intermediate header production, which is saline water of reduced salinity (3600 ppm), was also reduced by 13%. A computer simulation program was developed to predict the performance of the still.

Inverted trickle solar still: effect of heat recovery

Abstract The inverted trickle solar still, which has been recently developed, is improved mainly by adding a heat exchanger inside the condenser. The exchanger recovers part of the heat released in the condensation process and utilizes it in heating the saline water feed. This improvement, in addition to insulating the sides of the still and increasing the flow rate of the saline water feed, resulted in increasing the productivity from about 2.5 l/d to 2.8 l/d during the month of May. This improvement, which amounts to about 12%, is related mainly to the condensate production. This productivity was also increased by about 42% for a flow rate increase of 50%. A mixture of condensate and intermediate product at a rate of 8.2 l/d and a salinity of 7130 ppm may be obtained, which is suitable in some types of agriculture.

INVERTED TRICKLE SOLAR STILL

The concept of inverted water trickle, which has been recently developed for use in flat plate collectors. is utilized for solar distillation. The concept is based on the flow of a thin layer (trickle) of water on the back of the absorber plate. This layer is maintained attached to the plate by means of a wire screen welded to it, together with the effect of surface tension force. As the water moves downward along the plate, and if the flow of water is very small, then it is heated up and evaporated. The vapor is transferred to an adjacent compartment where it is condensed and collected. The main features of this concept are: 1. Elimination of condensation on the glazing thereby increasing solar radiation reaching the absorber plate. 2. Increasing the temperature difference between the evaporator and the condenser, which leads to an increase in the productivity of the basin-type stills. It is believed that such an increase affects positively the new concept. In the present work the still was designed, bui...

Numerical model for the behaviour of a salt-gradient solar-pond greenhouse-heating system

This paper reports a parametric study of a salt-gradient solar-pond greenhouse-heating system under Jordanian climatic conditions, using a one-dimensional numerical model which has been solved using a definite difference technique. The model makes use of several empirical correlations for calculating solar fluxes, and heat losses from the solar pond. The parameters considered include the surface area of the pond, the non-convective zone (NCZ) and the lower convective-zone (LCZ) thicknesses, the inclination wall angles of the pond, the greenhouse area, the greenhouse cover transmittance, and the thermal load extracted. It has been found that, under Jordanian climatic conditions, the solar pond can provide 30% of the heating load for the greenhouse.

Oscillating pendant drop: A method for the measurement of dynamic surface and interface tension

A method is described for measuring dynamic surface and interface tension. The technique is essentially a variation of the pendant drop method in which the drop is allowed to oscillate after sudden formation at the tip of a syringe. Immediately after the oscillation stops but before the drop detaches, there is an instant of rest. At this moment, the profile of the drop is obtained using high‐speed photography. The boundary tension is then calculated from the profile using established methods. The technique is demonstrated on systems consisting of aqueous solutions of sodium stearate or oleate on one hand and mineral oil or air on the other hand. Surface or interface tensions may be obtained within 0.25 to 5 s after surface formation.

Fuel oil heating by a trickle solar collector

Abstract A new type of flat plate solar collector was utilized for heating fuel oil. In a previous work, two identical flat plate collectors of the conventional fin tube configuration were investigated. One collector was filled with fuel oil, and the other was filled with water. It was found that the efficiency of the fuel oil collector was 25% less than that of the water collector. In this work, two collectors were tested. One was the same conventional water collector, and the other was a trickle collector whose working fluid was fuel oil. It was found that the efficiency of the fuel oil collector was 15–19% less than that of the water collector. Comparing the results of this work with those of the previous one, it was found that the efficiency of the fuel oil-trickle collector is 4–9% larger than that of a conventional one filled with fuel oil. It is concluded that a considerable portion of the efficiency lost formerly due to changing the working fluid from water to fuel oil in the conventional collector was almost regained by changing the collector type to be a trickle one.

THE INVERTED TRICKLE FLAT PLATE SOLAR COLLECTOR

A new method, called the inverted water trickle method is developed for use in flat-plate collectors. This method basically depends on passing the heal transfer liquid on the back of the absorber plate. The liquid is kept attached to the plate by means of wire screen welded to it. Surface tension forces between the absorber-wire screen combined surface and the liquid prevents the latter from falling off the surface. A back plate, however, is provided below the trickling water, but without touching it. The purpose of this plate is to protect the insulation from wetting by drops that might fall from the trickle. In this method, the problem of conducting the heat through the width of the absorber plate is solved by eliminating it. Consequently the fin efficiency of this new configuration equals to 1.0. This approach resulted in a simple, cheap and far more efficient design. A collector based on the above idea is designed, built and tested. The performance of the new design is superior to the conventional one...

Utilization of solar energy for heating fuel oil

A new application for solar energy is investigated. It may be applied mainly in industries which use fuel oil as a major source of energy. Because this fuel is highly viscous at ambient temperature, it is usually heated to about 50°C and stored at that temperature. This temperature level is typically achieved in solar applications by the use of flat-plate collectors. A conventional flat-plate collector is filled with fuel oil, and its performance is studied both theoretically and experimentally. The collector is also compared in performance with another identical collector which is filled with water. It was found that, for the same inlet temperature and incident radiation, the exit temperature from the fuel oil collector is higher than that for water. The instantaneous efficiency for the fuel oil collector, however, was found to be less than that for water by about 25%.