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Basic Chemical Hazards to Human Health and Safety — I
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
Vapor density is another characteristic we need to know about flammable or ignitable materials. The vapor density can be reported as a true density, weight of vapor per volume of air, or as a specific gravity related to the density of air. Temperature is critical with vapor density, because the volume of vapor may change drastically with a small increase or decrease in temperature; thus the density is vastly changed, too. Charles’ law can be used to determine volume and, hence, vapor density changes with temperature. The law of Charles states: If pressure remains constant, the volume of a given mass of gas is directly proportional to the absolute temperature. V/T=K;∴V1/T1=V2/T2where: k = a constantV = volumeT = absolute temperature.
Environmental Fate and Transport of Solvent-Stabilizer Compounds
Published in Thomas K.G. Mohr, William H. DiGuiseppi, Janet K. Anderson, James W. Hatton, Jeremy Bishop, Barrie Selcoe, William B. Kappleman, Environmental Investigation and Remediation, 2020
Thomas K.G. Mohr, James Hatton
The rate of evaporation of a chemical from dry soil is a function of soil, chemical, and air temperatures, wind speed, air turbulence and surface roughness, air humidity, solar radiation, and the relevant properties of the chemical, including total mass released, molecular weight, vapor pressure, vapor density, and diffusivity in air (Mackay et al., 1993; Thibodeaux, 1996). In particular, vapor pressure describes the concentration of a chemical as its partial pressure in the gas phase in air above a liquid sample, usually measured at 20°C or 25°C and reported in pressure units (e.g., mm Hg). Vapor density is the mass per unit volume of a chemical in the vapor phase at a fixed temperature, usually expressed as a ratio to air density. Vapors heavier than air are reported as a multiple of air density and measured at 25°C (e.g., perchloroethylene, vapor density = 5.7). Diffusion is the average rate of migration of a chemical in air in response to temperature, pressure, and concentration gradients exclusive of any chemical movement in response to advection. The air diffusion constant is sometimes called air diffusivity, often denoted as Da (expressed in units of cm2/s). Temperature affects the air diffusion constant, which affects the volatilization rate.
Terms and Definitions
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
Vapor density is similar to specific gravity, only it applies to vapors and gases, not solids or liquids. Vapor density is a ratio of a solid or liquid to air. Air is used as the standard and is given a value of 1. Something with a vapor density greater than 1 will sink in air. Less than 1 will float. For example, acetone has a vapor density of 2.0, so acetone vapor will sink because it is two times heavier than air. Ammonia has a vapor density of 0.6, so ammonia vapors will rise. Some resources use other terms for vapor density, such as specific gravity (gas). The NIOSH Pocket Guide to Chemical Hazards uses RGasD, relative gas density.
High-Energy Tritium Ion and α-Particle Release from the Near-Surface Layer of Lithium During Neutron Irradiation in the Nuclear Reactor Core
Published in Fusion Science and Technology, 2023
Erlan Batyrbekov, Mendykhan Khasenov, Mazhyn Skakov, Yuriy Gordienko, Kuanysh Samarkhanov, Andrey Kotlyar, Alexandr Miller, Vadim Bochkov
The research and development results provided brand new information on the processes in a nuclear-excited plasma of gas mixtures. Thus, in studying the luminescence of noble gases and their various mixtures, we noted the appearance of alkali metal lines and a sharp increase in the intensity of these lines at temperatures above 570 K. In atomic spectra, lines of transitions from 2p-levels of the heaviest gas atoms predominate up to temperatures of 600 K. Lines of alkali metal (Li, Na, K) atoms appear in the emission spectra of binary and ternary gas mixtures when the temperature rises. Besides, as in the case of unary and binary noble gases, the appearance of alkali metal lines is caused by evaporation during the release of α-particles and tritium nuclei from the lithium layer. The intensity of the bands of heteronuclear ion molecules decreases noticeably as the temperature rises up to 650 to 700 K, when intense radiation is observed on the lines of alkali metals. However, the appearance of strong lines of alkali metals does not affect the intensity of the atomic lines of noble gases. A vapor density is formed that is considerably higher than the saturated vapor density of lithium in ordinary thermal heating. It has been noted also that the population of the levels of lithium atoms has practically no effect on the population of the 2p-levels of atoms of noble gases.
Characterization of flat miniature loop heat pipe using water and methanol at different inclinations
Published in Experimental Heat Transfer, 2021
Sireesha Veeramachaneni, Srinivas Kishore Pisipaty, Dharma Rao Vedula, A. Brusly Solomon
Figure 19 shows the variation of capillary limit, entrainment limit, boiling limit, sonic limit of a miniature loop heat pipe at 33% filling ratio at different vapor temperatures. Capillary limit, entrainment limit and sonic limit increase with increase in vapor temperature whereas boiling limit decreases with increase in vapor temperature as it is transverse heat transport limit. The capillary heat transport limit is mainly influenced by surface tension, capillary radius in the evaporator, inclination of LHP and frictional forces due to liquid and vapor flow. The increase in capillary limit is higher than the entrainment and sonic limits up to 65°C. The increase in entrainment limit is due to increase in vapor density and that for sonic limit is due to vapor density as well as vapor temperature. The decreasing trend in boiling limit is due to increase in nucleate boiling phenomenon at higher operating temperatures.
Experimental benchmarking of diffusion and reduced models for convective drying of single rice grains
Published in Drying Technology, 2020
Kieu Hiep Le, Thi Thu Hang Tran, Abdolreza Kharaghani, Evangelos Tsotsas
The mass balance equation of the particle is written as where (kg dry solid) is the mass of dry particle, is the moisture content of the sample. (m2) is the particle surface area, assuming the particle is spherical. and (kg vapor/m3) are the vapor density at the sample surface and the vapor density of the hot air flow, respectively. Regarding Chen et al.,[19] the surface vapor density can be calculated from the saturated vapor density as where (J/mol) is the activation energy and R denotes the universal gas constant (J/mol K). The multiplier describes the additional resistance of the water from the partly saturated sample surface as compared to a free water surface. The surface vapor density decreases with the reduction of the moisture content and it approaches zero if the moisture content reaches the equilibrium moisture content. The saturated vapor pressure is correlated from the particle temperature[19] where the polynomial factors, i.e. , , , , , and is given in Kelvin degree.