Radiant heat effects

Use of SRC-II distillates in stationary gas combustion turbines is also of significant interest. The low levels of trace metals and inorganics suggest minimal difficulty in regard to turbine blade erosion or corrosion. The higher radiant heat effect on the combustor walls caused by the lower hydrogen content... 

Question by C. B. Hood, Cryovac, Inc. Do radiant heat effects from the surroundings change the apparent sticking coefficient due to warming of the film surface ... 

Table 14.2 Radiant Heat Effects Item Intensity (Btu/h fP)...

Table 7.3 Radiant Heat Effects Item Solar radiation on a hot summer day Intensity BTU hr ft 320...

Strain-gauge load cells are sensitive to temperature gradients induced by, for example, radiant heat from the sun or resulting from high temperature wash down. Load cells should be shielded from such effects or given time to stabilize before use. 

Fixed orSlowlj M-OvingFeds. For fuel-bed burning on a grate, a distillation effect occurs. The result is that hquid components which are formed volatilize before combustion temperatures are reached cracking may also occur. The ignition of coal in a bed is almost entirely by radiation from hot refractory arches and from the flame burning of volatiles. In fixed beds, the radiant heat above the bed can only penetrate a short distance into the bed. 

Elevated Flares See Flares for a general definition. The elevated flare, by the use of steam injection and effective tip design, operates as a smokeless combustion device. Flaring generally is of low luminosity up to about 20 % of maximum flaring load. Steam injection tends to introduce a source of noise to the operation, and a compromise between smoke elimination and noise is usually necessary. When adequately elevated (by means of a stack) this type of flare displays the best dispersion characteristics for malodorous and toxic combustion products. Visual and noise pollution often creates nuisance problems. Capital and operating costs tend to be high, and an appreciable plant area can be rendered unavailable for plant operations and equipment because of excessive radiant heat. 

In contrast, most equipment can safely tolerate higher degrees of heat density than those defined for personnel. However, if anything vulnerable to overheating problems is involved, such as low melting point construction materials (e.g., aluminum or plastic), heat-sensitive streams, flammable vapor spaces, or electrical equipment, then the effect of radiant heat on them may need to be evaluated. When this evaluation is required, the necessary heat balance is performed to determine the resulting surface temperature, for comparison with acceptable temperatures for the equipment. 

A is less than the skin area A y because some of the skin of fingers, arms, legs, and feet radiates to other skin and is not as effective for radiant heat loss. Equation (5.15) can be rearranged to... 

In all warm-air design applications, consideration must be given to the effects of stratification in tall buildings. Stratification increases the roof and high-wall fabric losses and the air change rate by the stack effect, and hence the ventilation loss. These effects may increase the heat loss by 25% over that of a radiant heating system. 

Effective radiant heat flow The heat exchange by radiation between the walls of the enclosure and the human body, E,if, in W m-T... 

Of historical interest is Tyndall s observation, made so long ago as 1865, that gases with an odour possess the power of absorbing radiant heat to a marked degree. Grijns - in 1919 was not able to detect any relation between the intensity of the odour and its power of absorbing radiant heat, and he therefore concluded that the stimulation of the olfactory apparatus is not effected by the liberation of energy absorbed from radiant heat. 

Surfaces will absorb radiant heat and this factor is expressed also as the ratio to the absorptivity of a perfectly black body. Within the range of temperatures in refrigeration systems, i.e. - 70°C to + 50°C (203-323 K), the effect of radiation is small compared with the conductive and convective heat transfer, and the overall heat transfer factors in use include the radiation component. Within this temperature range, the emissivity and absorptivity factors are about equal. 

Different plastics absorb radiant heat more efficiently at various wavelengths, which in turn are effected by the temperature of the emitting heater. Thus it requires that the proper wavelength be used for what the... 

A lower max response at resonance was noted for poly butadiene-acrylic acid-containing pro-pints compared with polyurethane-containing opaque proplnts. Comparison of the measured response functions with predictions of theoretical models, which were modified to consider radiant-heat flux effects for translucent proplnts rather than pressure perturbations, suggest general agreement between theory and expt. The technique is suggested for study of the effects of proplnt-formulation variations on solid-proplnt combustion dynamics... 

Whilst the calculation of the radiant heat flux from a gas to an adjoining surface embraces inherent spectral and directional effects, a simplified approach has been developed by Hottel and Manglesdorf 54, which involves the determination of radiation emission from a hemispherical mass of gas of radius L, at temperature 7, ... 

If the release forms a vapor cloud that premixes with air before ignition occurs, and turbulence is developed (for example, by the flame front propagating through a process structure), the flame speed can accelerate sufficiently to cause a blast. This event is referred to as a vapor cloud explosion. In addition to blast effects, radiant heat and flame contact effects may also occur. Flashback to the source may cause a pool and/or jet fire. 

BLEVEs/Pressure-volume Ruptures/Physical Explosions. Rapid loss of containment of materials confined under pressure at temperatures above their normal boiling point may result in a BLEVE, with blast, radiant heat (if flammable material is involved), as well as fragment effects. These effects can be experienced for considerable distances, depending upon the types and volumes of material stored. 

It is evident that different roasting practices will produce a variety of chemical effects in the bean. Recycling of hot effluent gases, perforation of the rotating drum, and use of radiant heat will each give different chemical character to the final roasted coffee bean. 

Effect of pressure Figure 2.40 shows the heat transfer coefficients for film boiling of potassium on a horizontal type 316 stainless steel surface (Padilla, 1966). Curve A shows the experimental results curve B is curve A minus the radiant heat contribution (approximate because of appreciable uncertainties in the emissivities of the stainless steel and potassium surfaces). Curve C represents Eq. (2-150) with the proportionality constant arbitrarily increased to 0.68 and the use of the equilibrium value of kG as given by Lee et al. (1969). 

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