Solidification Enhancement in a Multi-Tube Latent Heat Storage System for Efficient and Economical Production: Effect of Number, Position and Temperature of the Tubes.

Thermal energy storage is an important component in energy units to decrease the gap between energy supply and demand. Free convection and the locations of the tubes carrying the heat-transfer fluid (HTF) have a significant influence on both the energy discharging potential and the buoyancy effect during the solidification mode. In the present study, the impact of the tube position was examined during the discharging process. Liquid-fraction evolution and energy removal rate with thermo-fluid contour profiles were used to examine the performance of the unit. Heat exchanger tubes are proposed with different numbers and positions in the unit for various cases including uniform and non-uniform tubes distribution. The results show that moving the HTF tubes to medium positions along the vertical direction is relatively better for enhancing the solidification of PCM with multiple HTF tubes. Repositioning of the HTF tubes on the left side of the unit can slightly improve the heat removal rate by about 0.2 in the case of p5-u-1 and decreases by 1.6% in the case of p5-u-2. It was found also that increasing the distance between the tubes in the vertical direction has a detrimental effect on the PCM solidification mode. Replacing the HTF tubes on the left side of the unit negatively reduces the heat removal rate by about 1.2 and 4.4%, respectively. Further, decreasing the HTF temperature from 15 °C to 10 and 5 °C can increase the heat removal rate by around 7 and 16%, respectively. This paper indicates that the specific concern to the HTF tube arrangement should be made to improve the discharging process attending free convection impact in phase change heat storage.

Assessment of human health risks and pollution index for heavy metals in farmlands irrigated by effluents of stabilization ponds.

Areas contaminated with heavy metals can pose major risks to human health and ecological environments. The aims of this study are to assess human health risk and pollution index for heavy metals in agricultural soils irrigated by effluents of stabilization ponds in Birjand, Iran. The results revealed that the levels of Cr, Mn, Zn, Fe, Cu, Cd, and Pb were in range of 70.3-149.65, 355-570, 31.15-98.45, 23,925-29,140, 22.75-25.95, 0.17-6.51, and 8.5-23.5 mg/kg in topsoils, respectively. Total hazard index values from heavy metals through three exposure routes for adults and children were 9.13E-01 and 1.10, respectively, indicating that there was non-carcinogenic risk for children. The total risk of carcinogenic metals (Cr, Cd, and Pb) through the three exposure routes for adults and children was 1.06E-04 and 9.76E-04, respectively, which indicates that the metals in the soil will not induce carcinogenic risks to these age groups. Pollution levels of heavy metals in soil samples including enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geo-accumulation index (Igeo) showed heavy metal contamination of agricultural soils. The results of the present study provide basic information about heavy metal contamination control and human health risk assessment management in the study area.

Assessment of carbon monoxide concentration in indoor/outdoor air of Sarayan city, Khorasan Province of Iran.

Nowadays, air pollution by humans is considered a serious problem. One of the main sources of air pollution is carbon monoxide which is called the silent killer. With the increasing rate of population growth in Iran and subsequent acceleration of vehicle and fossil fuel usage, the mortality rate of carbon monoxide has increased. The aim of this study is assessment of the concentration of carbon monoxide in indoor and outdoor air of Sarayan city, Khorasan Province of Iran. In this descriptive-analytic study, the air condition of a residential area and outdoor environment of Sarayan city has been monitored for determining the carbon monoxide concentration during a 3-month period from January to March 2017. Overall, 25 stations with uniform distribution were located in the city. Fifty samples were taken monthly and by considering 3-month period, a total of 150 samples were gathered. The samples were taken in kitchens between 11 a.m. and 3 p.m., and by considering the respiratory height of the human body, the carbon monoxide meters (TES model, Taiwan) were placed at a height of 75-150 cm. The descriptive statistics were presented after entering data into SPSS-16, and, by applying Mann-Whitney and Kruskal-Wallis tests in the case of α = 0.05, the data were analyzed. The average concentrations of carbon monoxide in indoor and outdoor environments were 0.84 ± 3.21 ppm and 0.27 ± 0.92 ppm, respectively. The maximum carbon monoxide concentration in February in an outdoor environment was 6 ppm (station no. 4) and the least one was 0 ppm. In March, for an indoor area, the maximum carbon monoxide concentration was 41 pm for station no. 11. The indoor-to-outdoor (I-to-O) ratio in March was higher than other months, and in January, was less than others. The study reveals that the indoor and outdoor carbon monoxide indices of Sarayan city are at acceptable levels.

Exposure assessment to dust and free silica for workers of Sangan iron ore mine in Khaf, Iran.

We aimed to conduct an exposure assessment to dust and free silica for workers of Sangan iron ore mine in Khaf, Iran. The maximum concentrations of total dust and free silica were measured in crusher machine station at 801 ± 155 and 26 ± 7 mg/m(3), respectively. Meanwhile, the minimum concentrations were measured in official and safeguarding station at 8.3 ± 2 and 0.012 ± 0.002 mg/m(3), respectively. Also, the maximum concentrations of respirable dust and free silica were measured in Tappeh Ghermez drilling no. 1 at 66 ± 13 and 1.5 ± 0.4 mg/m(3), respectively, while the minimum concentrations were measured in pneumatic hammer at 5.26 ± 3 and 0.01 ± 0.005 mg/m(3), respectively. Considerate to Iranian standard for respirable dust concentrations (0.11 mg/m(3)) and international standards (ACGIH = 0.1 and NIOSH = 0.05 mg/m(3)), it was found that dust and free silica amounts were much higher than national and international standard levels in this mine.