M.A. Hamdan

Convective heat transfer and pressure drop characteristics of various array configurations to simulate the cooling of electronic modules

Abstract This paper reports an experimental investigation to explore the effects of the size of modules, the presence of a cylindrical module and the missing module on the heat transfer coefficient and pressure drop characteristics of array configurations composed of individual rectangular modules for three different Reynolds numbers namely; 1690, 2250 and 2625. Generally, it was found that using different sizes or shapes of modules in an array configuration tends to increase the Nusselt number by as much as 40% for the rectangular module and 28% for the cylindrical module. The presence of a missing module in the array resulted in a 37% enhancement in the Nusselt number downstream the missing module. Pressure drop results indicate that large size modules tend to enhance the pressure drop at their row locations by as much as 15%, while the cylindrical module tends to attenuate the pressure drop especially at low Reynolds number.

Thermal energy storage using a phase change material

Abstract A two-dimensional melting process of a solid phase change material is investigated theoretically. The material contained in a rectangular enclosure heated from one side, while all the other sides are assumed to be adiabatic ones. In this study convection mode was considered to be the dominant mode of heat transfer within the melted region, except within the region very close to the solid surface at the bottom where conduction mode was only taken into considerations. It was found that the obtained results are in good agreement with previous ones. Finally the present analysis was used to predict the melted fraction of the phase change material and hence the amount of stored energy.

COMPARISON OF DIFFERENT TWO-EQUATION TURBULENCE MODELS FOR PREDICTION OF FILM COOLING FROM TWO ROWS OF HOLES

The present investigation involves the prediction of film cooling from two rows of holes using different turbulence models. Predictions of film cooling effectiveness and the velocity field from two rows of holes inclined in the streamwise direction are presented using the k-ω model and a modified version of it, as well as the standard k-e model together with its nonisotropic version. Comparison between the predicted results using these models and previous experimental results indicates that the ability of a turbulence model to prediet the experimental results depends heavily on the blowing rate as well as on the distance downstream from the injection holes.

Wind speed and wind energy potential of Jordan

Abstract Routine wind data from 11 stations in Jordan have been analysed. Monthly average, and seasonal wind speed and average power density distributions were determined for each station. The monthly average wind speed for the two most potential sites Ras Muneef (RA) and Mafraq (MF) ranged from 3.0 to 7.4 m/sec and the average power density for these two sites ranged from 110 to 370 W/m2 at RA and from 105 to 470 W/m2 at MF. An application of wind power as supplementary power supply is suggested and cost analysis is given.

Assessment and applications of wind energy in Jordan

Abstract A technical and economic assessment has been made of the generation of electricity using windmills located at three most promising potential wind sites in Jordan: Ras Muneef (RA), Mafraq (MF), and Aqaba (AQ). The assessment was made for two different systems, one using a relatively large single windmill and the other using 25 small windmills arranged in a wind farm. The power output of each system at each site was determined, and the electricity-generating costs in each case were also determined and compared with the generating costs of generating electricity using steam or gas turbines, furnished by the Jordanian Electricity Authority (JEA). Finally, the possibility of water pumping from 30-m and 100-m deep wells using a windmill is investigated and the quantities of water pumping from these depths at each of the three sites are given.

Improvement of locally produced gasoline and studying its effects on both the performance of the engine and the environment

Abstract This study aims at investigating the effect of methyl-tertiary butyl ether (MTBE) addition to gasoline on its octane number and, hence, the performance of an engine. Also, its effect on the emitted gases was investigated. Locally produced gasoline was blended with five different percentages of MTBE, namely 0%, 5%, 10%, 15% and 20%. Then, these fuels were burned in an engine, which is coupled to a gas analyzer. It was found that the octane number of the gasoline increases continuously and linearly with MTBE percentage in the gasoline. The best performance of the engine occurs at around 10% MTBE addition, and this percentage also gives the best reduction in exhaust gases emissions.

Direct combustion of olive cake using fluidized bed combustor

A fluidized bed combustor of 0.146 m diameter and 1 m length was fabricated from stainless steel to burn olive cake. Initially, and in order to obtain fluidization, the system was operated under cold conditions using a sand with particle size in the range of 500 to 710 microns. The continuous combustion experiments were carried out under controlled conditions, such that the effects of bed temperature, olive cake feed rate, fluidization velocity, and particle size on combustion efficiency and flue gas composition were investigated. It was found that the combustion efficiency decreases with the bed temperature, fluidization velocity, and the feed rate, while it increases with the particle size used. Further, the gas products analysis carried out using a gas chromatography analyzer have shown a nonmeasured amountof SO2, and small amounts of CO. Finally, the temperature distribution along the bed indicated that the temperature throughout the bed is fairly uniform, demonstrating a good mixing of reactants, whi...

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...

Investigation of an inexpensive solar collector storage system

An integrated rock bed and solar collector system was investigated both experimentally and theoretically. The system consists of an insulated galvanized iron box containing rocks. It may act as both a solar collector and as a storage system. The measured parameters were the inlet and outlet air temperatures, the bed temperature, the ambient temperature and the solar insolation. Further, the measurements were performed at different values of tilt angle and mass flow rate of air. It was found that the bed had a maximum storage efficiency of 46% when it was tilted at an angle of 47°. Finally, the agreement between the experimental results and theoretical predictions was rather a good one.

Solar radiation data for amman

Measured solar radiation data for Amman were analysed. It was found that the annual average of daily total radiation was 20·4 MJ/m2 while that of the diffuse radiation was 4·5 MJ/m2. The monthly average of total clearness index was found to vary between 0·564 in January and 0·757 in July, and that of the diffuse radiation between 0·32 in January and 0·163 in July. Further, the histogram of frequencies of total clearness index indicated that the likelihood of having cloudy days, clear days, and partly-cloudy days was 9·5, 12·4 and 78·1% respectively. Finally, generalized charts were generated for Amman to estimate the ratio of hourly to daily radiation.