M.G. Morsy

Performance of a small-scale solar-powered adsorption cooling system

ABSTRACT In this study, an experimental investigation on the performance of a small-scale residential-size solar-driven adsorption (silica gel-water) cooling system that was constructed at Assiut University campus, Egypt is carried out. As Assiut area is considered as hot, arid climate, field tests for performance assessment of the system operation during the summer season are performed under different environmental operating conditions. The system consists of an evacuated tube with a reflective concentration parabolic surface solar-collector field with a total area of 36 m2, a silica gel-water adsorption chiller of 8 kW nominal cooling capacity, and hot and cold water thermal storage tanks of 1.8 and 1.2 m3 in volume, respectively. The results of summer season field test show that under daily solar insolation varying from 21 to 27 MJ/m2, the solar collectors employed in the system had high and almost constant thermal efficiency. The daily solar-collector efficiency during the period of system operation ranged from about 50% to 78%. The adsorption chiller performance shows that the chiller average daily coefficient of performance (COP) was 0.41 with the average cooling capacity of 4.4 kW when the cooling-water and chilled-water temperatures were about 31°C and 19°C, respectively. As the chiller cooling water is cooled by the cooling tower in the hot arid area, the cooling water is at a higher temperature than the design point of the chiller. Therefore, an experiment was carried out using the city water for cooling. The results show that an enhancement in the chiller COP by 40% and the chilling power by 17% has been achieved when the city water was 27.7°C.

Skin Friction and Form Pressure Loss in Tube Bank Condensers

In this paper, the effect of condensation on both skin friction and form pressure loss in staggered tube bank have been studied. Skin friction distributions on cylinders in different positions within the bank have been measured by a newly developed technique. Form pressure losses were calculated from the measured static pressure distributions “round bank cylinders. Condensation was simulated by homogeneous suction of air through cylinder wall, and the effect of suction rate on both skin friction and form losses was studied. The results show that condensation favourably modifies both skin friction and form losses in the bank.

Towards less expensive fresh water from the sea

Abstract Despite the fact that the worlds need for fresh water is becoming more urgent, the ability to desalinate economically on a large scale still remains a goal rather than a reality. The tremendous increase of fuel price since 1973 and also the problems of pollution had shifted the economical balance towards the systems of less energy consumption at more capital investment and leave little hope for conventional distillation systems to compete towards less priced water production. In this paper a distillation system is proposed which could lead to a breakthrough towards significant reduction in the cost of fresh water production from the sea.