Geometry optimization, factors screening, and introduce a predicting mathematical model of inhalation exposure chamber’s performance.

Background Optimizing the geometry of an inhalation exposure chamber (IEC) results in a uniform and stable distribution of the test atmosphere and enables the modeling of its performance. This study was conducted for the first time to optimize and model the performance of an IEC.Methods The current study was performed on the initial design of the ASRA chamber and to optimize and model it. The matrix of experiments was determined by the design expert software (DE7). The mean of particle concentration (MPC) in the respiratory zone of animals as the response variable, and height of the cylindrical section of the chamber, carrier gas density, inlet concentration, and particle aerodynamic diameter ( da ) as independent variables were considered. Experiments were performed by numerical simulation using ANSYS Workbench package. Particle concentration sampling was measured in 40 points at the opening of each holder in CFD-Post software. To determine the optimal range of the chamber's height, the different of MPC among the holders’ opening was investigated by the ANOVA test. The final mathematical model was achieved by analyzing the response variables in DE7.Results Thirty designs in five geometries with different heights were introduced as the matrix of experiments by DE7. The optimal height was obtained 2-2.5 times the radial of the cylindrical section. Analysis of the results suggested a linear model (2FI) with coefficients of recognition higher than 99%. The final model was significant with the presence of the inlet concentration and da . Gas density and height had no significant effect and were removed ( P >0.05).Conclusion The optimization of the geometry of the ASRA chamber resulted in a uniform and stable distribution of the particles and provided an accurate mathematical model to predict the particle concentration in the target zone.

Determination of benzene, toluene, ethylbenzene and xylene in field and laboratory by means of cold fiber SPME equipped with thermoelectric cooler and GC/FID method

A simple and effective cooling device based on a thermoelectric cooler was applied to cool the SPME fiber. The device was used for quantitative extraction of aromatic hydrocarbons in the air. Several factors such as coating temperature, extraction temperature and relative humidity in the laboratory setting were optimized. Comparison of the results between the cold fiber SPME (CF-SPME) and NIOSH 1501 method on standard test atmosphere indicated a satisfactory agreement. The CF-SPME and SPME method were also compared. The results revealed that CF-SPME has the most appropriate outcome for the extraction of aromatic hydrocarbons from the ambient air. The cold fiber SPME technique showed good results for several validation parameters. Under the optimized conditions, the limits of detection (LOD) and the limits of quantification (LOQ) ranged from 0.00019 to 0.00033 and 0.0006 to 0.001 ng ml−1, respectively. The intra-day relative standard deviation (RSD) showed ranging from 4.8 to 10.5%.

Development and Application of Test Equipment for Torsion Strength of Non-Metal Materials

In order to determine the torsion strength of non-metal materials at ambient and high temperature, a kind of equipment with inductive heating, infrared thermometer and torque loading by mechanical electrical rider was development. This equipment has advantages such as quick heating, accurate temperature test and controlling, easy controlling and continues of torque loading and test atmosphere can be controlled. The torsion strength of fireclay bricks with sample size of 40 mm × 40 mm × 230 mm, were tested separately at room temperature, 800°C, 1000°C, 1100°C and 1200°C, using this equipment. Results indicated that for the same batch of samples, the torsion strength determined by this equipment has good consistency, and mean while, it was found that the torsion strength decreased with the increase of test temperature obviously. In additional, developed equipment could be used for the determination of torsion creep at high temperature, the highest temperature of fracture under certain torque during the heating process, torque cycle fatigue failure of materials and so on.

Effect of an interferent on the performance of two direct-reading organic vapor monitors

Direct-reading organic vapor monitors (DROVMs) are widely used by industrial hygienists and emergency responders as survey tools for the assessment of volatile organic compounds (VOCs) in occupational or emergency response settings. Although these monitors provide real-time information for expedient decision making, their utility in determining compliance with specific exposure limits is not well established. In addition, other VOCs that may be present in the same environment can act as interferents and adversely affect performance. This study assessed the effect of an interferent (hexane) on the performance of two representative commercially available monitors when measuring cyclohexane. The instrument readings were compared with concentrations measured with sorbent tubes, a standard compliance monitoring technique. Infrared-based concentration measurements were more precise at the two middle challenge concentrations (144 and 289 ppm), indicating a shift in instrument precision at the low and high end of the recommended operating range. Both photoionization detection and infrared-based concentration measurements were affected by the presence and amount of hexane in the test atmosphere. Emergency response personnel and industrial hygienists should be aware of the limitations of DROVMs in the assessment of hazardous situations involving VOCs.

The Effect of Water Vapour and Sulphur on Corrosion Mechanisms of Steels

It is well known that water vapour accelerates oxidation; however different gas conditions and material compositions affect the mechanism. The paper addresses this issue from two different application areas; biomass and kraft recovery boilers. In these applications water vapour and sulphur are simultaneously affecting the corrosion mechanism, though the mechanisms are different. Low-alloyed steels were exposed to an atmosphere containing different amounts of water vapour at temperatures of 420, 550 and 600°C. Under oxidising conditions increasing water content generally accelerates oxidation. However, presence of SO2 in moist atmosphere retards oxidation at high temperatures. The phenomenon is seen at low temperatures with higher chromium contents. Stainless steel 304L was tested in an atmosphere containing hydrogen sulphide and carbon monoxide with and without water vapour at a temperature of 440°C to simulate elevated kraft recovery boiler furnace conditions. The tests showed that water vapour in the test atmosphere produces a protective spinel oxide on the metal surface. In tests without water vapour, the initial scales at metal surface were different sulphur compounds and intensive sulphidation occurred. The effect of water vapour on the sulphidation mechanism is addressed in the paper through the described tests and thermodynamic modelling.