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Wind and Airflow
Published in James Jones, Demetri Telionis, Aeroform, 2023
As we will explain later, a wing at an angle of incidence generates on its upper side pressures lower than the ambient and on its lower side pressures higher than the ambient. The ambient pressure is the pressure of the surrounding medium, such as a gas or liquid far from the object. Engineers and architects employ the terms pressure side and suction side to denote sides that experience higher and lower than the ambient pressure. A quick observation of the distribution of pressures over the wing of Figure 3.13 indicates that the net effect is a force pointing up. This force is called lift. Engineers can calculate such flow forces during the design process, or measure them on laboratory models. Architects could make approximate estimates or employ powerful computer tools to calculate these forces such as lift on a roof during a high wind event. They could also conduct model experiments (Figure 3.14) or collaborate with engineers to run large-scale experiments.
Temperature
Published in Anders Andersson, Measurement Technology for Process Automation, 2017
As mentioned, the base for the Celsius temperature scale is the freezing and boiling temperature of water. In the International Temperature Scale (ITS), freezing, melting and boiling points of other materials are listed. These points are used as references in temperature measurement laboratories. To create a foundation for traceable temperature calibrations, very pure substances that can be melted and measured are therefore needed. Ambient pressure will affect the boiling temperature, but not the freezing point. It seems quite strange, but this means that if pressure is low enough, a liquid can boil and freeze at the same temperature. This condition is called the triple point, where, for example, water is in solid (ice), liquid and gas (steam) phase at the same time. The materials listed in ITS tables cover an approximate range from −270 °C to 1500 °C. Reference temperatures according to ITS are listed in Appendix.
Temperature Distribution of Coal Mine Tunnel Fire During Dynamic Sealing Process: A Numerical Study
Published in Combustion Science and Technology, 2022
Ruizhi Guo, Li Ma, Jing Fan, Weifeng Wang, Gaoming Wei, Lifeng Ren
Based on the belt-transportation tunnel of a coal mine in Guizhou Province, a full-scale model is set to 60 m long, 4 m high, 4 m wide, and the slope was 0%. The two ends of the mine tunnel are set as open, and the sealing walls are set at 3 m away from the left and right ends, respectively. The fire source is located at the center of the longitudinal axis of the mine tunnel, and 0.5 m from the floor. The fire source fuel is set as polyurethane. The material of the mine tunnel ceiling, floor, sidewall and the sealing wall is set as “concrete.” The values used for concrete were such as density of 2280 kg/m3, specific heat of 1.04 kJ/(kg·K) and the thermal conductivity of 1.8 W/(m·K). The ambient temperature is 20°C, and the ambient pressure is standard atmospheric pressure of 101 kPa. The ambient oxygen mass fraction is 0.232378 kg/kg. The schematic drawing of the mine tunnel model is shown in Figure 1.
Spray characteristics of biodiesel-polyoxymethylene dimethyl ethers (PODE) blends in a constant volume chamber
Published in Combustion Science and Technology, 2022
Yu Liu, Junjian Tian, Fengyu Li, Kai Han, Lin Bao, Wenliang Zhou, Qizhao Lin
It can also be found from the figure that the injection pressure has little effect on the fuel spray cone angle, and the average cone angle increases slightly with the increase of injection pressure, which is consistent with the previous research (Hawi et al. 2019). However, the ambient pressure has a tremendous influence on spray cone angle. The difference of cone angle under different ambient pressures is even greater than that between different fuels, up to 54%. The higher the ambient pressure, the higher the corresponding ambient density. Therefore, the aerodynamic drag in penetration process is significantly greater, and the huge axial resistance slows down the axial development of the spray, which greatly enhances the radial dispersion. Therefore, the spray becomes thicker and shorter under high ambient pressure (as shown in Figure 4) and has a larger spray cone angle.
Extraction of polyphenols from Clinacanthus nutans Lindau (C. nutans) by vacuum solvent-free microwave extraction (V-SFME)
Published in Chemical Engineering Communications, 2021
Siti N. S Othman, Ana N. Mustapa, Ku Halim Ku Hamid
In principle, dried plant sample can burn during certain stage of heating when there is no more water to evaporate from the sample and producing residue that could contaminate the oil yield (Božović et al. 2017). Therefore, vacuum condition is introduced to SFME method to overcome this problem, enhance the amount of extraction yield and reduce the degradation of thermosensitive compounds. The application of vacuum condition allows boiling point of the water becoming lower than at ambient pressure (Destandau et al. 2013). Thus, the water can continuously boil and refluxed at lower temperature and reduced pressure. This would give advantages for the sample to mix thoroughly with solvent and extracting the compounds while preventing it from degrade (Wang et al. 2008; Xiao et al. 2009). Polyphenols are classified as thermosensitive compounds and can simply degraded at higher temperature (Destandau et al. 2013). Therefore, extraction of polyphenols using SFME and application of vacuum in the extraction is important to maintain the temperature at higher level without exposing the plant sample to thermal degradation.