Ali K. Abdel-Rahman

COMPUTATIONAL HEAT AND MASS TRANSPORT IN CONCRETE WALLS EXPOSED TO FIRE

A numerical method has been developed for the prediction of coupled heat and mass transfer and related processes in porous media exposed to elevated temperatures. The computer model predictions have been validated against experimental results of carbonate aggregate concrete slabs subjected to the ASTM E119 standard fire exposure. Output from the model depicts the coupled relationships between the temperature, moisture content, and pore pressure histories and distributions. This article investigates the numerical effect of grid spacing on the pore pressure fluctuations and the influence of the pore pressure on the spalling potential of concrete exposed to elevated temperatures.

Performance enhancement of vapor compression cycle using nano materials

The performance of a vapor compression cycle with nanomaterials additives to the working fluid is investigated theoretically and experimentally. Polyolester (POE) oil with AL2O3 nanomaterials additives is used to enhance the performance in the vapor compression cycle with R-143a refrigerant. The stability of nanofluid was first tested by using sedimentation test. The performance of cycle with the nanomaterials was then studied using energy consumption and freezing capacity tests. Theoretical analysis shows that the heat transfer coefficient in the evaporator with nanorefrigerant increases by 50%. Moreover, exergy loss decreases by 28 % when nanorefrigerant is used .The experimental results indicate that R-134a and Polyolester (POE) oil with AL2O3 nanoparticles enhance the vapor compression cycle performance by 10.5 % with 13.5 % lees energy consumption. These results were obtained with 0.1% mass fraction of nano-lubricant oil.

Experimental Study of Alumina Nanofluids Effects on Thermal Performance Efficiency of Flat Plate Solar Collectors

Flat-plate solar collectors (FPSC) heaters are widely utilized for heating water in residential buildings and other commercial and industrial applications. The main disadvantage of solar water heater is their low efficiency. Improving the thermal characteristics of the working fluid in solar water heater can dramatically increase its thermal efficiency. The aim of the present experimental investigation is to study the effect of using Alumina nanofluids as a working fluid for the solar water heater on its efficiency. Triton X-100 (Iso-Octyl Phenoxy Polyethxy Ethanol) was used as a surfactant and its stability and aggregation of the suspension was investigated. Outdoor experiments have been carried out in New Borg El-Arab city, Alexandria, Egypt according to ASHRAE Standard 86-93. Two similar water heaters systems using pure water and the nanofluids were tested at the same time, locations and similar conditions. The results showed that using nanofluid of 0.15% Alumina particles improves the FPSC thermal efficiency by 18%. More than concentration of surfactant were tested and the results showed that more stable nanofluid could be prepared to employ suitable surfactant concentration and by sophisticating preparation protoco