polycyclic aromatic hydrocarbons (pahs) are a group of organic compounds made up of two or more fused benzene rings in linear, angular or cluster arrangements. the pahs are formed by incomplete combustion or high temperature pyrolytic process involving organic matter. thirty sampling sites were selected to characterize the pahs concentrations in ambient air in tehran. sixteen pahs were measured...

this paper addresses an experimental investigation in the hydrodynamic behavior of a modified slotted sieve tray. slotted sieve tray (push valve sieve tray) is a sieve tray that the push valves have been utilized on the tray deck to eliminate liquid gradients and non-uniformity of liquid distribution on the tray. the air-water system was used in an industrial scale experimental rig with an inte...

this research includes both experimental and cfd investigation in the hydrodynamic behavior of a new type of column tray introduced as “concap” tray. the proposed column tray is used in contactor columns especially in stripping columns. the hydrodynamics of this concap tray is investigated in a 1.2m in diameter column. using air-water system, the experiments were performed for different liquid ...

Ceiling-Fan-Integrated-Air Conditioning (CFIAC) is a heating ventilation and air conditioning (HVAC) design approach that jets supply into the vicinity of ceiling fans to be mixed distributed within room. This eliminates terminal ductwork diffusers provides very efficient cooling for occupants. Two previously published papers have described velocity, temperature, thermal comfort fields in space...

There is a demand for reduced power consumption in the vapor compression refrigeration cycle. Coefficient of performance of window-air conditioners considerably decreases and power consumption increases under very hot conditions. These problems have encouragecl studies aimed at improving the performance of window-air-conditioners by enhancing the heat transfer rate in the condenser. In this ar...

The purpose of the air distribution system in a fluidised bed combustor is to provide a reasonably uniform spread of combustion air over the entire horizontal cross-sectional area of the bed. One of the simplest, and hence cheapest, forms of air distributor is the sparge pipe design, in which an array of horizontal pipes is fitted at the base of the bed. Combustion air is then supplied to one e...

the estimation of pollution fields, especially in densely populated areas, is an important application in the field of environmental science due to the significant effects of air pollution on public health. in this paper, we investigate the spatial distribution of three air pollutants in tehran’s atmosphere: carbon monoxide (co), nitrogen dioxide (no2), and atmospheric particulate matters less ...

Despite the progress made in controlling local air pollution, urban areas show increasing signs of environmental stress and air quality is one of the major concerns. The findings of several studies provide evidence that the shape of a city and the land use distribution determine the location of emission sources and the pattern of urban traffic, affecting urban air quality. This work focuses on ...

The results from a steady, viscous flow simulation of the main flowpath of a modern jet engine transonic highpressure turbine, transition duct, and first vane of the low-pressure turbine, coupled with the secondary-air system under the high-pressure turbine, is presented. The secondary-air system configuration includes the lower cavity near the centerline, the mid-cavity with the tangential onb...

The troubled introduction of an American air computerized reservation system at French Railways reflects the difficulty of transforming European public rail transport into a market-oriented industry. Computerized reservation systems played an important role in supporting increased competition, providing a global strategic advantage and modifying market structures in the US air industry. However...