Gulf Organisation for Research & Development

Direct and indirect evaporative cooling system is experimentally investigated using a plate heat exchanger for hot climate conditions. The effects of chilled water and ambient temperatures, water flow rates, humidity, and the operating cooling mode on the supply air temperature was investigated for three configurations. The system dry bulb and wet effectiveness was estimated for all conditions under consideration. It was found that the dry bulb effectiveness approached 17%, while it was in the range of 72-98% for the wet bulb effectiveness. In addition, the secondary air saturation effectiveness was calculated with varying water flow rates. It was found that the increase of water quantity in the heat exchanger would increase the refrigeration capacity and lead to a higher secondary air temperature difference. This resulted in higher saturation effectiveness for the system. These results were compared with available numerical data for calibration and validation purposes.

Calcium sulfoaluminate cements are widely used as special cements and, because of their low specific carbon dioxide emissions relative to those of Portland cement, they have potential for use in general construction. However, their widespread application has been limited by the relatively high cost of aluminous raw materials. As part of a broad programme on the optimisation of these cements, the clinker mineralogy was reformulated to enhance the activity and strength contribution of the silicate phases. Preservation of the α′ dicalcium silicate phase to ambient is described in this paper. Commercially available raw materials and reagent-grade chemicals were used and clinker syntheses were conducted. Preservation of the α-belite phase to ambient temperature was achieved by a combination of chemical doping with control of the furnace atmosphere and fast cooling of the clinker. A clinker with α′-belite, ye'elimite and ferrite can be optimised to create a new generation of low-cost sulfoaluminate cements with improved performance and large potential energy savings relative to Portland cement.

An experimental investigation of the performance of a fresh air handling unit integrating indirect evaporative and vapor compression cooling is conducted. Temperature and relative humidity measurements at main points within the cooling unit were logged using a wireless data acquisition system. Experimental data downloaded from the acquisition system is used for linear regression analysis, and to calculate the wet-bulb thermal effectiveness, cooling capacity and coefficient of performance of the unit. The air conditioning unit is a patented system designed and assembled at the Gulf Organisation for Research and Development (GORD) in Qatar. The peak wet-bulb thermal effectiveness of the system was found to be 1.3, and the COP was 3.4. The results showed that the unit could save as nearly 60% of the sensible cooling load required by a conventional vapor compression cooling unit. In addition, the unit could reduce power consumption by 36% when utilizing the indirect evaporative cooling cycle. Depending on ambient conditions, the investigated unit generated enough condensate to meet the water requirements of the indirect evaporative cooling cycle, which made the air conditioning system sustainable.

Salsola schweinfurthii is a perennial branched halophytic shrub that inhabits arid environments in and around the Arabian Peninsula. Its tolerance to extreme drought renders it suitable for urban arid landscaping. Germinability of intact and de-winged seeds (winged perianth removed) was determined under two photoperiods (0 and 12 hours light per day), three thermoperiods (daily low/high of 15/25, 20/30 and 25/35°C) and five salinity levels (0, 100, 200, 400 and 600 mM NaCl). Germination was maximised (93%) by de-winging and incubation in 12 hours light at 25/35°C. Intact and de-winged seeds both exhibited positive photoblastism. Germination of intact seeds was entirely prevented by the lowest level of salinity, and only slightly less prevented in de-winged seeds. Ability to germinate returned after saline solution was replaced with distilled water. The ability for S. schweinfurthii seeds to remain viable through a temporary period of salinity indicates an adaptation to unpredictable soil surface conditions in arid environments. Artificial propagation rates might be increased by removing perianths and sowing before or after mid-winter.

Bienertia cycloptera(Chenopodiaceae) produces two types of leaf foliage colour (reddish and yellowish). In order to determine the role of leaf colour variation in regulating the germination characteristics and salinity tolerance during germination, a study was conducted on seeds collected from plants of both colours. Seeds with and without pulp were germinated under two illumination conditions (12‐h light photoperiod and continuous dark), three alternating temperature regimes (15/25°C, 20/30°C and 25/35°C), and several salinity levels at 20/30°C. Germination percentage was significantly higher for seeds without pulp as compared to the seeds with pulp. The response ofB. cyclopteraseeds to salinity depended on the leaf colour. Thus, the seeds collected from reddish coloured plants were able to tolerate higher salinity compared to those of yellowish coloured plant. The germination recovery results indicate that the seeds from both coloured plants could remain viable in saline condition and they will be able to germinate once the salinity level are decreased by rain. The production of different foliage colours byB. cyclopteraseems to be an adaptative strategy which increases the possibility for establishment in unpredictable environments by producing seeds with different germination requirements and salinity tolerance.