Thermal radiation Intensity

The thermal radiation intensity of a flash fire can be calculated after parameters such as cloud shape and gas or vapor concentration distribution have been determined through dispersion calculations. Subsequently, the thermal radiation intensity is calculated through the following steps ... 

Thermal radiation becomes important at higher temperatures, especially above 2000°F, when thermal destruction of the monolith substrate probably takes place. Thermal radiation intensities are proportional to the emissivity of the surface multiplied by the absolute temperature raised to the fourth power. The thermal emissivity of the monolith may be close to 1.0 due to the blackened surfaces from deposition of platinum. Each point of the channel is completely visible from any other point of the channel. The... 

The thermal radiation intensity and tlie time duration of fires often are used to estimate injury and damage due to a fire. Various tables litive been compiled to set up criteria for fire damage to people and properly. Table 7.3.1 shows a relationsliip between heat radiation intensity and bum injury. ... 

The hazards of a fire above a pool of flammable liquid can be described in terms of thermal radiation intensity and dnration of exposnre. The EPA standard specifies a radiant-heat endpoint of 5 kilowatts per sqnare meter (or 0.12 calorie per second per square centimeter) and a duration of 40 seconds. The thermal dose thus corresponds to 20 joules/cm or 4.8 calories/cm and could cause second-degree bums on unexposed skin, but is unlikely to ignite clothing [26, 27]. 

The EPA equation for the second-degree bum hazard distance at which the combination of thermal-radiation intensity and duration of exposure would correspond to 5000 watts/m and 40 seconds, respectively, is (approximately)... 

Saturation vapor pressure of the flashing liquified gas at the temperature of interest, in psia. Thermal-radiation intensity, in BTU/second/feeF. 

Several other important recommendations API 521 makes include restricted access area to personnel, use of radiation shielding, and location of ladders and platforms fhese recommendations are summarized with an illustration in Figure 30.11. The API 521 states that "personnel are commonly protected from high thermal radiation intensity by restricting access to any area where the thermal radiation can exceed 2000 Btu/ hr-fti." Some plants locate fences and warning signs around areas where flare radiation levels can exceed 2000 Btu/hr-fti. 

Personnel are commonly protected from high thermal radiation intensity by restricting access to any area where the thermal radiation can exceed 2000 Btu/hr—ft "... 

Thermal emission from a single-wall carbon nanotube (CNT) has been analyzed in the dipole approximation using the fluctuation-dissipative theorem. A strong resonance enhancement of the thermal radiation intensity of metallic CNTs in the far zone is predicted at frequencies of the electromagnetic surface wave resonances. 

The heated sample emits thermal radiation, which is used for temperature determination. The spectrum collected was measured in the wavelength range 515-820 nm corresponding to the range of maximal quantum efficiency of our CCD detector. To determine the temperature we fitted the Planck formula with a wavelength independent emissivity to the measured spectrum. The Planck formula [10] contains the temperature and the wavelength dependence of the thermal radiation intensity /bb( j of the black body (BB) ... 

Modeling health effects from various hazard levels is a difficult task. Risk assessments are typically based on the risk of death or serious injury. Obviously there are no experimental data available on the dose-response relationship of material concentration and exposure duration, thermal radiation intensity or blast overpressures on humans. What little there is has been inferred from actual accidents. Models that predict the impact of exposure to hazardous materials are heavily influenced by animal experiments. Typically, they have large safety factors built in. It is believed that models based primarily on exposure of experimental animals are conservative when applied to humans, especially when, on a body weight difference, the animals are much smaller than humans. In fact, many will argue that they are too conservative. These estimates are difficult to make, and unfortunately little can be done to improve the degree of uncertainty. 

Schubach (1995) provides a review of thermal radiation targets for risk analysis. He concludes that (1) the method of assuming a fixed intensity of 12.6 kW/m to represent fatahty is inappropriate due to an inconsistency with probit functions and (2) a thermal radiation intensity of 4.7 kW/m is a more generally accepted value to represent injury. This value is considered high enough to trigger the possibility of injiuy for people who are unable to be evacuated or seek shelter. That level of heat radiation would cause injury after 30 s of exposure. 

Solution From Figure 4.11, the flux levels corresponding to 50% fatalities for 10 and 100 s are 90 and 14 kW/m, respectively. Using the Eisenberg probit method, Eq. (4.7) is rearranged to solve for the thermal radiation intensity I ... 

According to the Rayleigh-Jeans law, at microwave frequencies the thermal radiation intensity is proportional to the absolute temperature and so... 

Blackbody Radiation Engineering calculations of thermal radiation from surfaces are best keyed to the radiation characteristics of the blackbody, or ideal radiator. The characteristic properties of a blackbody are that it absorbs all the radiation incident on its surface and that the quality and intensity of the radiation it emits are completely determined by its temperature. The total radiative fliix throughout a hemisphere from a black surface of area A and absolute temperature T is given by the Stefan-Boltzmann law ... 

A flash fire is the nonexplosive combustion of a vapor cloud resulting from a release of flammable material into the open air, which, after mixing with air, ignites. In Section 4.1, experiments on vapor cloud explosions were reviewed. They showed that combustion in a vapor cloud develops an explosive intensity and attendant blast effects only in areas where intensely turbulent combustion develops and only if certain conditions are met. Where these conditions are not present, no blast should occur. The cloud then bums as a flash fire, and its major hazard is from the effect of heat from thermal radiation. 

Thermal effects depend on radiation intensity and duration of radiation exposure. American Petroleum Institute s Recommended Practice 521 (1982) reviews the effects of thermal radiation on people. In Table 6.5, data on time to reach pain threshold are given. As a point of comparison, the solar radiation intensity on a clear, hot summer day is about 1 kW/m (317 Btu/hr/ft ). Criteria for thermal damage are shown in Table 6.6 (CCPS, 1989) and Figure 6.10 (Hymes 1983). 

Eisenberg et al. (1975) developed estimates of fatalities due to thermal radiation damage using data and correlations from nuclear weapons testing. The probability of fatality was found to be generally proportional to the product where t is the radiation duration and 7 is the radiation intensity. Table 6.7 shows the data used to develop estimates of fatalities from thermal radiation data. 

Pape, R. P., et al. (Working Group, Thermal Radiation), 1988. Calculation of the intensity of thermal radiation from large fires. Loss Prev. Bull. 82 1-11. 

We still need to consider the coherence properties of astronomical sources. The vast majority of sources in the optical spectral regime are thermal radiators. Here, the emission processes are uncorrelated at the atomic level, and the source can be assumed incoherent, i. e., J12 = A /tt T(ri) (r2 — ri), where ()(r) denotes the Dirac distribution. In short, the general source can be decomposed into a set of incoherent point sources, each of which produces a fringe pattern in the Young s interferometer, weighted by its intensity, and shifted to a position according to its position in the sky. Since the sources are incoherent. 

Calculation of the Intensity of Thermal Radiation From Large Fires." 1990. First Report of the Major Hazards Assessment Panel, Thermal Radiation Working Group. 

The height of a flare is fixed on the basis of the heat generated and the resulting potential damage to equipment and humans. The usual design criterion is that the heat intensity at the base of the stack is not to exceed 1500 Btu/hr/ft2. The effects of thermal radiation are shown in the following table ... 

Flare height and thermal radiation The height of an elevated flare is based on the minimum distance from the flare flame to an object whose exposure to thermal radiation must be limited. Industrial flares are normally designed so that personnel in the vicinity are not exposed to a heat intensity greater than 1500 to 2000 Btu/(h ft2) when flaring at the maximum design rates. 

IChemE. 1989. Calculation of the Intensity of Thermal Radiation from Large Fires. 

Effect of turbulence on flame radiation) (Authors measured the radiation intensity from propane flames and found a decrease in radiation with turbulence. Radiation is not thermal, but appears to be a luminescent phenomenon) 11) T.E. Holland et al, JApplPhys 28, 1217(1957)... 

The most widely used detection mode relies on the thermal effect of IR radiation. Because of absorption by the sample and the range of wavelengths involved, the radiation intensity that reaches the detector is weak. 

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