Phthalates in Chinese vehicular environments: Source emissions, concentrations, and human exposure.

Phthalates are typical air pollutants in vehicular environment since numerous synthetic materials that might contain phthalates are widely used to fabricate vehicle interiors (e.g., seat cushions, floor mats and dashboards). Hitherto, the importance of phthalate pollution in vehicular environment is not well-recognized because people spend only a small portion (around 8%) of their time in vehicles. In this study, the mass fractions of six phthalates in nine materials commonly used in Chinese vehicles (floor mats and seat cushions) were measured. Two phthalates, di-n-butyl phthalate (DnBP) and di-2-ethylhexyl phthalate (DEHP), were identified in most materials (the other phthalates were not detected). The emission characteristics of DnBP and DEHP from these materials were further investigated. The measured emission parameters were used as input for a mass-transfer model to estimate DnBP and DEHP concentrations in cabin air. Finally, the ratios between human exposures (via inhalation and dermal absorption from the gas phase) in vehicular environment and the total exposures in typical indoor environments (e.g., residences and offices) were estimated to be up to 110% and 20% for DnBP and DEHP, respectively. Based on these results, the vehicular environment might be a considerable site for human exposure to airborne phthalates.

Effect of valve opening on starting performance of pump as turbine.

The study on transient characteristics of pump as turbines during atypical startup has not been deeply explored yet. In order to reveal the transient characteristics of a small centrifugal pump reversing as turbine during startup process in this paper, the transient hydraulic performance experiments are conducted for three steady rotational speed cases. Under the condition of each case, three, five and, three valve opening scenarios are completed to measure the performance. The dimensionless analysis are also employed so as to better reveal transient behavior of the pump as turbine during atypical startup. The results show that the rise rate of each performance parameter is different, wherein the shaft power and rotational speed have the fastest rising rate, followed by the flow rate, and the head rise is the slowest. It is clearly seen that the shock phenomenon in static pressure easily occurs at the outlet of pump as turbine. With the increase of valve opening, the dimensionless flow rate, head and, power coefficient all show the evolution trend of gradually increasing.

Experimental Investigation on High Capacity Stove-Powered Thermoelectric Generator Incorporated with a Novel Heat Collector.

It is vital to supply necessary electric power during natural disasters and in deprived regions. A novel heat collector is proposed to improve the capacity of the stove-powered thermoelectric generator (SPTEG). Enclosed combustion walls are constructed with four W-shape copper plates, and act as a whole to be an exceptional heat collector, which was not previously reported in TEG studies. Forty TE modules are installed and two DC-DC converters are employed to stabilize the electric power. Owing to the novel heat collector, the generated electric power reaches 0.024 W/K per unit temperature difference for an individual TE module, which is 200% higher than the previous record (0.008 W/K) when forty TE modules are incorporated. The proposed SPTEG is able to generate a net electric power of 119 W, which is considerably larger than the previous record (75.2 W). The corresponding TE efficiency reaches 3.12%, which is measured at a temperature difference of 140 °C. The startup performance, power load feature, and cooling water flow rate of the SPTEG are studied in detail. Furthermore, one-dimensional theoretical analyses are conducted to explore the SPTEG performance. The theoretical electric power agrees well with the experimental data when DC-DC converters are not involved. Applying DC-DC converters to stabilize the electric power will alter the impendence of the SPTEG, resulting in much lower electric power output than that without DC-DC converters.

Nano-silica extracted from rice husk and its application in acetic acid steam reforming.

Nano-silica extracted from rice husk and its application in acetic acid steam reforming was studied in the paper. A simple and efficient heat treatment method was used to extract high specific surface area silica from rice husk. It was found that the acid leaching process was beneficial for the removal of metal impurities and the decomposition of organic substances. The carbon residue decreased and sample purity increased with increasing temperature. At 600 °C, silica with the yield of 21.7% and the purity of 99.45% was obtained. The specific surface area was as high as 335 m2 g-1, and the corresponding average pore diameter was 4.95 nm. Nano-silica extracted from rice husk was applied as a support in the preparation of an acetic acid steam reforming catalyst (Ni/RH-SiO2). Ni/RH-SiO2 showed a better performance than Ni/SiO2, which may be due to the higher interaction between Ni and SiO2 in Ni/RH-SiO2. When the reforming temperature was 700 °C, carbon conversion of 95.3% and H2 yield of 2.38 mol mol-1 were obtained. Carbon deposition was found after a 6 h test, mainly in the form of filamentous carbon. The carbon deposition amount of spent-Ni/RH-SiO2 was lower than that of spent-Ni/SiO2.

Numerical modeling of ultrasonic cavitation by dividing coated microbubbles into groups.

Homogeneous cavitation models usually use an average radius to predict the dynamics of all bubbles. However, bubbles with different sizes may have quite different dynamic characteristics. In this study, the bubbles are divided into several groups by size, and the volume-weighted average radius is used to separately calculate the dynamics of each group using a modified bubble dynamics equation. In the validation part, the oscillations of bubbles with two sizes are simulated by dividing them into 2 groups. Comparing with the predictions by the Volume of Fluid (VOF) method, the bubble dynamics of each size are precisely predicted by the proposed model. Then coated microbubbles with numerous sizes are divided into several groups in equal quantity, and the influence of the group number is analyzed. For bubble oscillations at f = 0.1 MHz and 1 MHz without ruptures, the oscillation amplitude is obviously under-estimated by the 1-group model, while they are close to each other after the group number increases to 9. For bubble ruptures triggered by Gaussian pulses, the predictions are close to each other when more than 5 groups are used.

Testing and Optimizing a Stove-Powered Thermoelectric Generator with Fan Cooling.

In order to provide heat and electricity under emergency conditions in off-grid areas, a stove-powered thermoelectric generator (STEG) was designed and optimized. No battery was incorporated, ensuring it would work anytime, anywhere, as long as combustible materials were provided. The startup performance, power load feature and thermoelectric (TE) efficiency were investigated in detail. Furthermore, the heat-conducting plate thickness, cooling fan selection, heat sink dimension and TE module configuration were optimized. The heat flow method was employed to determine the TE efficiency, which was compared to the predicted data. Results showed that the STEG can supply clean-and-warm air (625 W) and electricity (8.25 W at 5 V) continuously at a temperature difference of 148 °C, and the corresponding TE efficiency was measured to be 2.31%. Optimization showed that the choice of heat-conducting plate thickness, heat sink dimensions and cooling fan were inter-dependent, and the TE module configuration affected both the startup process and the power output.

Modulation on coherent vortex structures by dispersed solid particles in a three-dimensional mixing layer.

Large-scale vortex structures and their effects on the dispersion of particles in turbulent free shear flows are very important in many industrial applications, such as combustion, pollution control, and materials processing. In order to understand large-scale vortex structures and particle dispersion in depth, as well as their interaction effects, a two-way-coupled three-dimensional mixing layer laden with particles at a Stokes number of 5 initially located in the upper half region is studied numerically. A pseudospectral method was used to directly simulate the flow fluid, and the Lagrangian approach was used to trace particles. The concept of computational particles is introduced to vary the mass loading of particles. The momentum coupling effect introduced by a particle approximates to a point force. The simulation results show that coherent structures are still dominant in the mixing layer, but the flow dynamics and particle dispersion are modulated. The length of large-scale vortex structures is shortened and the pairing is delayed. Higher mass loading results in lower energy of the fluid in the phase of Kelvin-Helmholtz rolling up, while in the pairing process of large-scale vortex structures, the energy of the fluid increases as the mass loading increases. Higher mass loading also leads to larger mixed fluid thickness and Reynolds stresses of the flow. In addition, the particle dispersion along the transverse direction differs from that along the spanwise direction, which indicates that the effects of the addition of a particle on the spanwise large-scale vortex structures are different from those on the streamwise large-scale vortex structures.