V.H. Morcos

Optimum tilt angle and orientation for solar collectors in Assiut, Egypt

One of the important parameters that affects the performance of a flat plate solar collector is its angle of tilt with the horizontal. This is due to the fact that the variation of tilt angle changes the top loss coefficient and the amount of solar radiation reaching the absorber plate. Also, concentrating solar collectors must be oriented to track the sun so that beam radiation will be directed onto the absorbing surface. A mathematical model was developed for calculating the total radiation on a sloped surface. The model was then used to determine the optimum tilt angles for a flat plate collector and the optimum tilt and surface azimuth angles (orientation) for concentrating solar collectors in Assiut, Egypt on a daily basis, as well as for a specified period. These optimum angles were found by searching for the values for which the total radiation on the collector is a maximum for a particular day or a specified period. The results show that changing the tilt angle eight times in a year is necessary to maintain the total radiation on the collector in Assiut near its maximum value. This achieves a yearly gain in total radiation of 6.85% more than the case of a flat plate collector with a fixed slope of 27°, which is equal to the latitude angle of Assiut. Also, it is observed that changing the hourly surface azimuth angle twelve times and the tilt angle six times in a year for a concentrating solar collector maintains the total radiation near its maximum value (found by changing the surface azimuth and tilt angles daily to their optimum values). This achieves a yearly gain in total radiation of 29.18% more than the case of a concentrating solar collector facing south at fixed tilt equal to the latitude angle.

Investigation of a latent heat thermal energy storage system

Abstract An experimental investigation of a shell-and-tube heat exchanger concept for use in a latent thermal energy storage system for solar heating applications has been carried out. The thermal analysis provides the influence of the water inlet temperature and mass flow rate on the storage charging/discharging times and temperature gradients for heat flow into or out of two different storage substances: paraffin wax and asphalt. Results indicate the capability of the heat exchanger concept to operate within small temperature potentials (

Performance of shell-and-dimpled-tube heat exchangers for waste heat recovery

Abstract This paper presents an experimental study of waste heat recovery shell-and-tube heat exchangers. The exchanger heat duty, overall heat transfer coefficient, effectiveness and tubeside friction factor are investigated as functions of the tube surface geometry (plain or dimpled), the flow type (counter or parallel), the tube Reynolds number and the shellside heat capacity rate. Water and the exhaust gases of a Diesel engine are passed inside the tube and the shell, respectively. The heat transfer characteristics increase with an increase in tube Reynolds number and the shellside heat capacity rate, for all the flow types and the surface geometries examined. The counter-flow, shell-and-dimpled-tube heat exchanger, compared with that exchanger having a plain tube, increases the heat duty and the overall heat transfer coefficient by 80%, and the heat exchanger -effectiveness increases by 35%. For the parallel-flow, shell-and-dimpled-tube heat exchanger, the heat duty, the overall heat transfer coefficient and the effectiveness increase by 30, 55, and 25%, respectively. At the same time the dimpled tube increases the tubeside friction factor by 600% over that of the plain tube. The rate of waste heat recovered from the exhaust gases of the Diesel engine by the counter-flow, shell-and-dimpled-tube heat exchanger is equal to 10% of the maximum brake power of the engine running at 1500 rpm, and the tube Reynolds number equal to 8875.

Testing of an arrow-head vertical-axis wind turbine model

A vertical-axis wind turbine (VAWT) with an arrow-head rotor was tested in the laboratory at wind tunnel speeds of 16.3, 18.05 and 19.75 m/s. The power and torque coefficients were studied as functions of the blade section (rectangular and aerofoil blade sections), the blade angle θ (12, 55 and 90°), the attack angle ф (0, 30 and 90°), the blade-length ratio L/Lmax (0.50, 0.75 and 1.0) and finally the tip-speed ratio U/V. The analysis of the experimental results showed that the power and torque coefficients of the rectangular blade section were higher than those of the aerofoil blade section and they increased with a decrease in the blade angle and the blade-length ratio. They increased with an increase in the attack angle. The power coefficient increased to a maximum value and then decreased again with an increase in the tip-speed ratio, while the torque coefficient decreased directly with an increase in the tip-speed ratio. The arrow-head wind turbine performed best with the rectangular blade section with a blade angle of 12°, blade-length ratio of 0.75 and attack angle of 30°.

Performance analysis of industrial bag filters to control particulate emissions

Variations of collection efficiencies and pressure drops through bag filters have been investigated experimentally. It was found that the collection efficiencies decreased exponentially or linearly with increases of particle diameter or dust loading, respectively; they increased exponentially with the filter surface area, were found to be independent of dust-particle material and filtration velocity, and had the greatest values for P&S and Egyptex fabric materials. The pressure drop across the fabric and collected dust layer increased exponentially from 14 to 36 mm of water with an increase of dust loading on the filter from 0 to 1300 g/m2. The experimental results were fitted to an empirical equation.

Some experimental and theoretical studies of a single basin solar still

This paper consists of experimental and theoretical results carried out on a single basin solar still under various modes of operation. The solar still was located in Nag Hammadi (latitude = 26°14′N, longitude = 32°E and altitude = 90 m), Egypt. The variations of daily distillate with basin water mass and salinity have been measured for the simple still. The effects of: (i) film distillation with and without addition of a small quantity of black dye to the basin water and; (ii) flat plate collector coupled to the still with film distillation and black dye operating on the thermosyphon circulation mode, on the daily distillate of the solar still were also studied. The best performance was found in the case of the coupled still under thermosyphon circulation using film distillation with black dye. The measured monthly average variations of the total solar radiation on a horizontal surface in Nag Hammadi were compared with those variations calculated using ASHRAE and Hottel models. Numerical calculations have been carried out for a typical cold and hot day, 22 November 1992 and 11 June 1993, in Nag Hammadi to predict the hourly variations of distilled water for a simple single basin solar still.

Aerodynamic performance analysis of horizontal axis wind turbines

The present work studies the wind energy resources in Egypt and the aerodynamic performance of propeller type and multi-bladed horizontal axis wind turbines with three different airfoil blade sections (flat-plate, symmetric and circular-arc airfoils). Power, thrust and torque coefficients were investigated as functions of wind turbine design parameters (blade angle, rotor solidity, drag-to-lift coefficient ratio and blade section) and operating conditions (tip-speed ratios). Axial and tangential induction factors and drag coefficient were introduced in the calculations. Recommended design and operating values are given for each wind turbine. The analysis of the theoretical results shows that flat-plate and symmetric airfoil blade sections operate at a wider range of tip-speed ratios than that of circular-arc airfoil blade sections, so they are recommended for small and large sized wind turbines, respectively. Also, the analysis of the available local wind speed measurements indicates that the future potential of wind energy conversion systems in Egypt is promising. Several sites along the Mediterranean and Red Sea coasts have high annual average wind speed and power density of 6.4 m s−1 and 160 W m−2, respectively.

Performance Analysis of a Plastic Shell-and-Tube Heat Exchanger

This paper presents an experimental investigation of the performance of an all-plastic heat exchanger. Plastic conical turbulators were inserted in the exchanger tubes to enhance the overall heat transfer process 1.5 to 3.5 folds. The results of performance tests indicated a limiting value for the overall heat transfer coefficient corresponding to the thickness and the conductive thermal resistance of the plastic tubes. In addition, the results did not show significant increase in the total tube-side pressure drop due to the use of turbulators. The heat transfer enhancement was evaluated on a thermoeconomic basis using a dimensionless exergy destruction function. Physical and chemical characteristic tests conducted on the plastic material used, prevealed its excellent solubility resistance and relatively high softening temperature, which makes it attractive in some heat recovery applications.

Energy recovery from municipal solid waste incineration. A review

Abstract Heat recovery from the incineration of municipal solid waste (MSW) can make a useful contribution to the nations energy needs. This paper reviews the literature on the field of energy recovery from MSW incineration. This review includes (1) An historical background on the MSW methods of disposal and the recent trends. (2) The potential role of waste as a fuel from the knowledge of its analysis, heating value and quantity. (3) The alternative methods of waste disposal including the thermal (mass incineration, refuse-derived fuel and pyrolysis), the mechanical and the biochemical processes. (4) Some economic considerations regarding MSW disposal costs. (5) The combustion characteristics of MSW and waste combustion plants. (6) Heat recovery from waste burning including the main types of waste heat boilers; the heat recovery rates; heat exchange boundary conditions; fouling, erosion and corrosion of waste heat boilers; control of waste incineration particulate emissions and finally the control of nitrogen oxides emissions. The intensive data given here is essential to the proper design and operation of any MSW-to-energy plant. The design needs to be undertaken with careful consideration of the experience that already exists in order to achieve success.

Performance characteristics of a water-in-oil-fired steam generator for a 300-MW power plant

Results are presented of a theoretical study to assess the viability of using water-in-oil emulsions for power-station boilers to reduce pollutant emissions, deposit buildup on heat-transfer surfaces and excess-air requirements while improving boiler efficiency. The variables studied include the water concentration (0–10%) and percentage of maximum output (40–100%). SOx and NOx emissions are reduced by 20 and 5.5 kg/h, respectively. The dirt factor of the water-wall tubes drops by 27% without a significant change in the tube temperature. The excess-air coefficient is reduced by 13% and the boiler efficiency is increased by 0.75%. The maximum gas-temperature rise and decrease along the boiler pass are ∼ +50 and ∼ −5K, respectively, as the water concentration is increased from 0 to 10%.