Cloud characteristics

The cloud detonation analysis started with the cloud characteristics at 60 msec and with second event initiation by a centrally-located... 

Sensitivity studies are needed to understand the relative importance of different feedbacks. First experience of Enviro-HIRLAM indicates some sensitivity to effective droplet size modification in radiation and cloud characteristics (Korsholm et al. in this volume). 

The space probe neared its target in July 1995 and released a probe carrying instruments capable of measuring the temperature, pressure, and chemical composition of the atmosphere, as well as cloud characteristics, sunlight, and internal planetary energy. The probe survived for 59 minutes, during which it penetrated about 125 miles (200 km) into the Jovian atmosphere. At that point surrounding pressures caused the probe to melt and/or vaporize, and it lost contact with Earth stations. 

This equation describes the solid-angle dependent emission of mass from sources with rotationally symmetric lobe-shaped vapour cloud characteristics. With n = 1, Knudsen-cell evaporator, it is identical with other published [253,254] calculations. With n = 0, point source or spherical source, there are slight differences with other published values which generally consider evaporation in the total space to = 4n, whereas here, evaporation is only considered in the half-space above the vapour source. 

Liquid water is one of the most important cloud characteristics for atmospheric chemistry. The liquid water content of an air parcel starts from almost zero during cloud formation, reaches a maximum for a mature cloud, and returns to zero during cloud evaporation. 

Transition Different criteria are used to check whether transition to passive behavior occurs. When transition takes place, a transition model is used to match the final dense-gas cloud characteristics to those of the initial passive cloud (Jagger, 1981). 

The inference of cloud characteristics is based on much less sophisticated approaches than those for determining thermal stmcture and gas abundances. Clouds tend to be quite inhomogeneous compared with gaseous mixtures and require more parameters for adequate definition. Also, the appropriate equation of transfer [Eq. (2.1.40)] is considerably more complex than Eq. (8.2.1), and not nearly as amenable to inversion techniques. Even so, direct techniques are sometimes capable of leading to rather definitive conclusions about cloud and aerosol systems. We illustrate with an example concerning the abundance of the photochemical aerosol in Titan s stratosphere. 

A37. Lelieveld, J. Cmtzen, P.J. Rodhe, H., 1989 Zonal Average Cloud Characteristics for Global Atmospheric Chemistry Modelling , Report CM-76, UDC 551.510.4, Glomac 89/1. International Meteorological Institute in Stockholm, University of Stockholm, 54 pp. 

Soluble Layers on Mineral Dust Particles and the Impact on Clouds Characteristics , Final Report to GIF, April 2002. 

The characteristics of diesel fuel taken into account in this area are the cloud point, the pour point, and the cold filter plugging point (CFPP). 

At lower temperatures, the crystals increase in size, and form networks that trap the liquid and hinder its ability to flow. The pour point is attained which can, depending on the diesel fuel, vary between -15 and -30°C. This characteristic (NF T 60-105) is determined, like the cloud point, with a very rudimentary device (maintaining a test tube in the horizontal position without apparent movement of the diesel fuel inside). 

The properties of straight run diesel fuels depend on both nature of the crude oil and selected distillation range. Thus the paraffinic crudes give cuts of satisfactory cetane number but poorer cold characteristics the opposite will be observed with naphthenic or aromatic crudes. The increasing demand for diesel fuel could lead the refiner to increase the distillation end point, but that will result in a deterioration of the cloud point. It is generally accepted that a weight gain in yield of 0.5% could increase the cloud point by 1°C. The compromise between quantity and quality is particularly difficult to reconcile. 

Performance can be illustrated for example by the time necessary for deaeration or de-emulsification of oils, anti-rust properties, copper strip corrosion test, the flash point in closed or open cup, the cloud and pour points, the foaming characteristics, etc. 

In 1930, London [1,2] showed the existence of an additional type of electromagnetic force between atoms having the required characteristics. This is known as the dispersion or London-van der Waals force. It is always attractive and arises from the fluctuating electron clouds in all atoms that appear as oscillating dipoles created by the positive nucleus and negative electrons. The derivation is described in detail in several books [1,3] and we will outline it briefly here. 

In the dense interstellar medium characteristic of sites of star fonuation, for example, scattering of visible/UV light by sub-micron-sized dust grains makes molecular clouds optically opaque and lowers their internal temperature to only a few tens of Kelvin. The thenual radiation from such objects therefore peaks in the FIR and only becomes optically thin at even longer wavelengths. Rotational motions of small molecules and rovibrational transitions of larger species and clusters thus provide, in many cases, the only or the most powerfiil probes of the dense, cold gas and dust of the interstellar medium. 

Evaluating the Characteristics of Vapor Cloud Explosions, Elash Eires, and BLEVEs Technical Management of Chemical Process Safety (Corporate)... 

Propylene is a colorless gas under normal conditions, has anesthetic properties at high concentrations, and can cause asphyxiation. It does not irritate the eyes and its odor is characteristic of olefins. Propjiene is a flammable gas under normal atmospheric conditions. Vapor-cloud formation from Hquid or vapor leaks is the main ha2ard that can lead to explosion. The autoignition temperature is 731 K in air and 696 K in oxygen (80). Evaporation of Hquid propylene can cause skin bums. Propylene also reacts vigorously with oxidising materials. Under unusual conditions, eg, 96.8 MPa (995 atm) and 600 K, it explodes. It reacts violentiy with NO2, N2O4, and N2O (81). Explosions have been reported when Hquid propylene contacts water at 315—348 K (82). Table 8 shows the ratio TJTp where is the initial water temperature, and T is the superheat limit temperature of the hydrocarbon. 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

The effectiveness of a fluidized bed as a ehemical reactor depends to a large extent on the amount of convective and diffusive transfer between bubble gas and emulsion phase, since reaction usually occurs only when gas and solids are in contact. Often gas in the bubble cloud complex passes through the reactor in plug flow with little back mixing, while the solids are assumed to be well mixed. Actual reactor models depend greatly on kinetics and fluidization characteristics and become too complex to treat here. 

Figure 9.2-2 shows a data input screen in which general characteristics are input by radio buttons and numerical data is typed. The program calculates distances to specified in.sic concentrations and other requested consequence levels automatically. Results are available in a variety of formats including cloud footprints, sideview, cross section, pool evaporation rate, concentration vs distance and heat flux contours. Figure 9.2-3 shows the calculated results as a toxic plume. superimposed on the map with and without oligomerization. 

This text is intended to provide an overview of methods for estimating the characteristics of vapor cloud explosions, flash flies, and boiling-liquid-expanding-vapor explosions (BLEVEs) for practicing engineers. The volume summarizes and evaluates all the current information, identifies areas where information is lacking, and describes current and planned research in the field. 

Accident scenarios leading to vapor cloud explosions, flash fires, and BLEVEs were described in the previous chapter. Blast effects are a characteristic feature of both vapor cloud explosions and BLEVEs. Fireballs and flash fires cause damage primarily from heat effects caused by thermal radiation. This chapter describes the basic concepts underlying these phenomena. 

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