00454 Experimental studies on a novel roof pond configuration for the cooling of buildings

13 Space 04100449 Reconformation of polyvinylamine adsorbed on glass fibers Widmaier, J. et al. Journal of Colloid and Interface Science, 2003, 264, (l), 277-283. Surface area exclusion chromatography was used to investigate the reconformation of fully hydrolysed polyvinylamine. The polymer is adsorbed on stacked glass fibre filters constituting the stationary phase while the polymer solution is injected at the inlet of the chromatography column. From numerical simulation and experimental chromatograms of non-reconforming polyelectrolytes, the amount of polymer adsorbed per filter represented as a function of the filter position along the column (the histogram) was determined to be continuously decreasing and not to depend on the rate of elution. For polyvinylamine, the histograms are peaked and the height of the peak was determined to depend greatly on the rate of polymer supply to the column that was controlled by monitoring the polymer concentration and/or the rate of elution (mass-transfer-controlled adsorption). Modifications in the adsorption on the successive filters were converted into changes in the interfacial area of adsorbed molecules taking into account model histograms as well as experimental adsorption histograms of non-re-conforming systems. Macromolecule concentration in the mobile phase and contact time between solute and adsorbed molecules were determined to be the two parameters controlling the extent of polymer desorption. The unusual shape of the histogram thus was attributed to reconformation of the adsorbed polymer, which was stimulated by interfacial exchange between segments belonging to trains of adsorbed macromolecules and chain segments of solute ones. 04/00450 Rigid amorphous fractions and glass transitions in poly(oxy-2,6-dimethyl-1.4-phenylene) Pak, J. et al. Macro-molecules, 2003, 36: (2), 495499. Semicrystal poly(oxy-2,6-dimethyl-1,4-phenylene), PPO, is the first example of a polymer that has the glass transition of the rigid amorphous fraction (RAF) above the melting temperature of the crystals. Such phase structure does not allow fast melting below the glass transition and hinders recrystallization The PPO is analysed by temperature-modulated differential scanning calorimetry. In the std. DSC of PPO with about 30% crystallinity, a melting peak appears at 515 K, but no glass transition can be seen. The reversing heat capacity of the semicrystal PPO shows not melting, but a glass transition at about 502 K. Annealing below the beginning of melting causes not only the development of a glass transition as known from amorphous PPO but also a reduction in crystallinity. The RAF was calculated from the deficiency between the measured, reversing heat capacity and the expected thermodynamic heat capacity calculated from the data bank. 04/00451 Thermal shock-resistant ceramic filters containing graphitized carbon for molten metal filtration Bali, H. Eur. Pat. Appl. EP 1,288,178 (Cl. C04B38/00), 5 Mar 2003, Appl. 2001/121,044. High thermal shock resistance ceramic filters for molten metal filtration comprise a bonded network of graphitized carbon. The ceramic filters are fabricated by impregnating a thermoplastic foam (such as polyurethane) with slurry containing a graphitized carbon bonded precursor (such as coal-tar pitch), ceramic powders and optionally other additives such as binders, dispersants, thickeners, plasticizers or anti-oxidization agents. The impregnated foam is then dried and optionally coated one or two more times with the slurry before final drying and firing at 500-1000” to convert the carbon precursor to a bonded network of graphitized carbon. 04/00452 Thermodynamic stability of waste glasses compared to leaching behaviour Perret, D. et al. Applied Geochemistry, 2003, 18, (8), 1165-l 184. The thermodynamic stability of products obtained from the hightemperature treatment of municipal solid wastes and their associated residues (bottom ash, fly ash, filter cake, optional additives) can be estimated by calculation of their free energy of hydration AGh.,dr by a polyhedral approach. This approach has been applied on a series of 23 samples originating from high-temperature treatment processes operated under a range of conditions, and three thoroughly characterized standards. For vitreous or vitrocrystalline samples, it is demonstrated that Si and Ca contents clearly control their thermodynamic stability, and that the type of incineration process plays only a minor role. Silicon directly influences the durability of the samples, while Ca governs the pH during corrosion, which in turn affects the thermodynamic stability. It is also shown that there is a tight inverse relationship between the calculated thermodynamic stability of the samples and their rates of dissolution under aggressive conditions of corrosion. Attempts to compare the results to the large literature database of results obtained from nuclear high-level waste glasses, their proxies and other analogs (ancient and commercial glasses) are limited by sample preparation constraints. It is however concluded that the calculated thermodynamic stability of these ‘waste glasses’ offers a valid estimate for their relative quality and, in turn, for their durability.

13 SPACE HEATING COOLING

heating

and cooling

AND

04100453 A ventilated courtyard as a passive cooling strategy in the warm humid tropics Rajapaksha, I. Renewable Energy, 2003, 28, (ll), 1755-1778. The paper investigates the potential of a courtyard for passive cooling in a single storey high mass building in a warm humid climate. The inclusion of an internal courtyard in building design is attributed to the optimization of natural ventilation in order to minimize indoor overheating conditions. However, the efficiency of this strategy greatly depends on the design details of the building composition in providing appropriate airflow pattern to the courtyard. From the results of thermal measurements, a significant correlation between wall surface temperatures and indoor air temperatures is evident. A reduction of indoor air temperature below the levels of ambient is seen as a function of heat exchange between the indoor air and high thermal mass of the building fabric. However, this behaviour is affected by indoor airflow patterns, which are controlled through the composition between envelope openings and the courtyard of the building. From a computational analysis, several airflow patterns are identified. A relatively better indoor thermal modification is seen when the courtyard acts as an air funnel discharging indoor air into the sky, than the courtyard acts as a suction zone inducing air from its sky opening. The earlier pattern is promoted when the courtyard is ventilated through openings found in the building envelope. The computational simulation utilizing the standard k-turbulent model with isothermal condition agrees closely with the measurements taken from the field investigation.

04/00454 Experimental studies on a novel roof pond configuration for the cooling of buildings Tang, R. et al. Renewable Energy, 2003, 28, (lo), 1513-1522. In this study, a new evaporation based passive cooling technology was tested. The technology is based on the exposure of ‘floating’ wetted cloth to the ambient air. It was compared to various other passive cooling techniques, with very favourable results. Two identical shallow ponds were constructed. One of them was covered with white cotton towels stretched on a densely perforated PVC panel supported by pieces of waterproof polystyrene keeping it just floating on the water surface. Five comparable experiments of different cooling techniques have been carried out. The results indicate that the new cooling technique performed slightly better than the pond with movable insulation, which is widely considered as one of the best roof cooling techniques based on evaporation. It seems that the higher efficiency of the tested technique is due to the thermal stratification created in the water inside the pond, which more effectively resists the transfer of heat gains from the sun and ambient air into the deep water of the pond. In turn, the water temperature near the floor of the pond is lower, thus heat flow from the building to the pond is increased. During the experiment, all the ponds which were compared were ranked according to performance (from best to worse): shaded pond with towels floated on it, pond with towels floated on it and pond with movable insulation, shaded open pond, open pond, covered pond.

04/00455 Feasibility study of using agriculture waste as desiccant for air conditioning system Khedari, J. et al. Renewable Energy, 2003, 28, (lo), 1617-1628. This research was aimed at investigating the feasibility of using dried agricultural waste as desiccant for an open cycle air conditioning system. The natural fibres are, therefore, intended to replace chemical desiccant such as silica gel, molecular sieves etc. The investigation was limited to coconut coir (Cocos nucifera) and durian peels (Durio zibethhus). Experimental results confirmed that dry coconut coir and durian peel can absorb 30 g and 17 g H20 per 100 g dry product, respectively, from air at the average condition of 32°C and 75% relative humidity. The optimum airflow rate is about 84 and 98 m3,‘h-100 g dry product, respectively. Therefore, the dry coconut coir is more suitable than the dry durian peel. Comparison between the dry coconut coir and silica gel showed that the average adsorption rate of coconut coir is less than that of silica gel by about 5 g/h-100 g dry product at an airflow rate of 84 m3/h and 60 min operating time. However, it is still an interesting option to replace silica gel in open cycle air conditioning system, as the decrease of average adsorption rate is rather small. The other extremely interesting advantage of coconut coir is that during moisture absorption the heat generated during the process is less important. That means the air leaves the coconut coir bed at a lower temperature compared to that with a silica gel. Therefore, the saving of cooling energy is much more important. Fuel

and

Energy

Abstracts

January

2004

53