A Performance Analysis on Pressure Loss and Airflow Diffusion in a Chamber with Perforated V-Profile Diffuser Designed for Air Handling Units (AHUs)

Outlet cross-sectional area of fans used in air handling units is smaller than cross-sectional area of chambers which are located next to the fan. In order to ensure efficiently operating of the air handling units, it is required that the air flows through a perforated diffuser to create a uniform air diffusion from fan outlet to following chamber with a minimum pressure loss and uniform velocity distribution. In this concept, numerical simulations and experiments were performed for the chamber with perforated V-profile diffuser, which is often used in air handling units because of its simple geometry and easy manufacturing. Pressure losses were firstly obtained experimentally for different air velocities in the chamber. Then a performance analysis on the air flow diffusion and pressure losses inside chamber with perforated V-profile diffuser for different geometric parameters such as entry length, apex angle, geometry and pattern of hole, plate thickness, porosity and surface roughness has been carried out numerically. It is seen that the experimental results validated with the numerical turbulence model results

Analysis of gamma emitting radionuclides (terrestrial and anthropogenic) in soil samples from Kilis province in south Anatolia, Turkey

In recent years, there has been great concern about analysis of radionuclide content in environmental samples (soil, water, etc.) in many countries. The aim of the present study is to analyze the activity concentrations of terrestrial (226Ra, 232Th and 40K) and anthropogenic (137Cs) radionuclides in surface soil samples collected from different locations in and around Kilis province using the high-resolution gamma spectrometer with HPGe detector and evaluate external ionizing radiation exposure in outdoor air. The mean values of the activity concentrations of 226Ra, 232Th, 40K and 137Cs in the soil samples were analyzed as 16.1, 15.0, 206.0 and 9.5 Bq kg-1, respectively. Evaluated values of absorbed gamma dose rate in outdoor air and the corresponding external annual effective dose varied from 5 to 75 nGy h-1 with a mean value of 25 nGy h-1 and 6-92 µSv with a mean value of 31 µSv, respectively. These mean values were found to be within acceptable limits. © 2013 Elsevier Ltd. All rights reserved.

Effect of Needle Insertion Depth and Apical Diameter on Irrigant Extrusion in Simulated Immature Permanent Teeth

The aim of this study was to compare the amount of irrigant extrusion in simulated immature permanent teeth when the apical diameter and needle insertion depth were varied. Thirty single-rooted maxillary incisors with straight root canals were selected. The root length was standardized to a length of 9 mm. The teeth were divided into two experimental groups according to the degree of apical enlargement (n = 15). The apices were enlarged to a diameter of 1.10 mm or 1.70 mm by using a #3 or #6 peeso reamer, respectively, to simulate immature teeth. The irrigation solution was applied 2 or 4 mm short of the working length (WL) in each experimental group. The glass vial model was used for the collection of extruded irrigant beyond the root apex. A two-way repeated measures analysis of variance test showed that there was no significant difference between different needle insertion depths (2 and 4 mm short of the WL) in the group with an apical diameter of 1.70 mm (p > 0.05). In the group with an apical diameter of 1.10 mm, a 32% increase in irrigant extrusion was observed when the needle was positioned at 2 mm (p < 0.05). Regarding the effect of apical diameter, the group with a diameter of 1.70 mm showed more apical extrusion of the irrigant (34% increase for the needle positioned at 2 mm and 68% increase for the needle positioned at 4 mm). It was observed that the needle insertion depth and apical diameter have a significant effect on irrigant extrusion in immature permanent teeth.Wo