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Ambient Relative Humidity (ambient + relative_humidity)

Distribution by Scientific Domains
Engineering75%

Selected Abstracts

Infiltration into effluent irrigation-induced repellent soils and the dependence of repellency on ambient relative humidity

HYDROLOGICAL PROCESSES, Issue 17 2007
R. Wallach
Abstract As a result of water scarcity and as a means of wastewater disposal, reuse of treated sewage effluent in irrigated agriculture is practiced worldwide. Among the detrimental aspects of wastewater re-use in agriculture is the possibility that soils will be rendered water repellent. The current study focuses on time dependent variation of infiltration rate in effluent-induced repellent soils, and time dependent variation in water repellency at different levels of ambient relative humidity (RH). The shape of the cumulative infiltration curve of water was found to depend on the repellency degree (concave for wettable and slightly repellent soils, convex for severely repellent soil). Compared with infiltration rates in the wettable and slightly repellent soils, infiltration rates in the severely repellent soil were very low at the beginning and then increased. When the liquid-vapor surface tension was reduced by means of ethanol addition to the infiltrating solution, the cumulative infiltration curve of the severely repellent soil also became concave. Repellency degree (as measured by WDPT) was found to be essentially constant over a large range of ambient RH values (<10 , ,81%), and to increase sharply at values above 90%. The relative increase in water drop penetration time (WDPT) at high RH was greatest for the least repellent soil (10-fold increase in WDPT), and least for the most repellent soil (2-fold increase in WDPT). At RH > 90%, the time to reach equilibrium with respect to WDPT and soil moisture content was similar. In contrast, at values of ambient RH ranging from < 10 to 81%, WDPT was invariant over the course of reaching equilibrium with respect to moisture content. However, after reaching moisture content equilibrium, WDPT declined with increasing time. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Performance enhancement of gas turbines by inlet air-cooling in hot and humid climates

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2006
Majed M. Alhazmy
Abstract In this paper, a model to study the effect of inlet air-cooling on gas turbines power and efficiency is developed for two different cooling techniques, direct mechanical refrigeration and an evaporative water spray cooler. Energy analysis is used to present the performance improvement in terms of power gain ratio and thermal efficiency change factors. Relationships are derived for an open gas turbine cycle with irreversible compression and expansion processes coupled to air-cooling systems. The obtained results show that the power and efficiency improvements are functions of the ambient conditions and the gas turbine pressure ratio. The performance improvement is calculated for, ambient temperatures from 30 to 50°C, the whole range of humidity ratio (10,100%) and pressure ratio from 8 to 12. For direct mechanical refrigeration air-cooling, the power improvement is associated with appreciable drop in the thermal efficiency. The maximum power gain can be obtained if the air temperature is reduced to its lowest limit that is the refrigerant evaporation temperature plus the evaporator design temperature difference. Water spray cooling process is sensitive to the ambient relative humidity and is suitable for dry air conditions. The power gain and efficiency enhancement are limited by the wet bulb temperature. The performance of spray evaporative cooler is presented in a dimensionless working graph. The daily performance of the cooling methods is examined for an ABB-11D5 gas turbine operating under the hot humid conditions of Jeddah, Saudi Arabia. The results indicate that the direct mechanical refrigeration increased the daily power output by 6.77% versus 2.57% for the spray air-cooling. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Right-first-time production in batch dyeing of wool,,

COLORATION TECHNOLOGY, Issue 6 2001
U M Adamiak
Powder dyes exhibit even more pronounced sorption behaviour than fibres. The moisture content and weight of the dyes and yarns change according to the ambient relative humidity. In this study, the variations determined in dyehouse stores caused weight changes and subsequent dyeings showed differences of ,,E* and ,,L* beyond permissible levels. The detrimental influence on the ability to reach right-first-time level of acceptance substantially diminishes the profit margin. The consequence for computer colour-matching should be the integration of the moisture content of dyes and goods in the recipe calculation. From a technological viewpoint, however, it seems preferable to avoid any fluctuation in relative humidity where dyes and goods are stored. The costs incurred for investment in humidity control will pay in the long run and the factor of moisture content may be entirely negligible. [source]