When a hot utility needs to be at a high temperature and/or provide high heat fluxes, radiant heat transfer is used from combustion of fuel in a furnace. Furnace designs vary according to the function of the furnace, heating duty, type of fuel, and method of introducing combustion air. Sometimes the function is to purely provide heat sometimes the furnace is also a reactor and provides heat of reaction. However, process furnaces have a number of features in common. In the chamber where combustion takes place, the heat is transferred mainly by radiation to tubes around the walls of the chamber, through which passes the fluid to be heated. After the flue gas leaves the combustion chamber, most furnace designs extract further heat from the flue gas in a convection section before the flue gas is vented to the atmosphere.  [c.188]

High temperature. The use of high temperatures in combination with high pressures greatly increases stored energy in a plant. The heat required to obtain a high temperature is often provided by furnaces. These have a number of hazards, including possible rupture of the tubes carrying the process fluid and explosions in the radiant zone. There are also materials of construction problems associated with high-temperature operation. The main problem is creep, which is the gradual extension of a material which is under a steady tensile stress over a prolonged period of time.  [c.267]

Object dimension is defined as the viewing angle in radiant minutes under which the eye observes tbe object. With increasing dimension, the visibility increases.  [c.670]

This is known as the Planck radiation law. Figure A2.2.3 shows this spectral density fiinction. The surface temperature of a hot body such as a star can be estimated by approximating it by a black body and measuring the frequency at which the maximum emission of radiant energy occurs. It can be shown that the maximum of the Planck spectral density occurs at 2.82. So a measurement of yields an estimate of the  [c.411]

The faet that the lowest two orbitals of the reaetants, whieh are those oeeupied by the four 71 eleetrons of the reaetant, do not eorrelate to the lowest two orbitals of the produets, whieh are the orbitals oeeupied by the two a and two n eleetrons of the produets, will be shown later in Chapter 12 to be the origin of the aetivation barrier for the thermal disrotatory rearrangement (in whieh the four aetive eleetrons oeeupy these lowest two orbitals) of 1,3-butadiene to produee eyelobutene.  [c.190]

If the reaetants eould be prepared, for example by photolysis, in an exeited state having orbital oeeupaney 7112713 713, then reaetion along the path eonsidered would not have any symmetry-imposed barrier beeause this singly exeited eonfiguration eorrelates to a singly-exeited eonfiguration of the produets. The faet that the reaetant and produet  [c.190]

In constructing the CCD, one must traee the energies of all four of the above CSFs (aetually there are more beeause the singlet and triplet exeited CSFs must be treated independently) along the proposed reaetion path. In doing so, one must realize that the le lo CSF has low energy on the reaetant side of the CCD beeause it eorresponds to orbital oeeupaney, but on the produet side, it eorresponds to orbital oeeupaney and is thus of very high energy. Likewise, the le 2e CSF has low energy on the produet side where it is but high energy on the reaetant side where it eorresponds to. The low-lying singly exeited CSFs are q 2q o at both reaetant and produet  [c.293]

These alloys are of vital importance in the construction of modern aircraft and rockets. Aluminum, evaporated in a vacuum, forms a highly reflective coating for both visible light and radiant heat. These coatings soon form a thin layer of the protective oxide and do not deteriorate as do silver coatings. They are used to coat telescope mirrors and to make decorative paper, packages, toys.  [c.32]

Luminous intensity candela cd Luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 X 10 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.  [c.77]

Irradiance (radiant flux re- EM) W m E = d dA  [c.87]

Radiant energy density p, w J m- p = Q V  [c.87]

Radiant exitance, emitted M W m  [c.87]

Spectral radiant energy density  [c.87]

Radiant energy a w Rhombic rh  [c.106]

Radiant energy density p, w Rhombohedral rh-hed  [c.106]

Radiant exitance M Root-mean-square rms  [c.106]

Radiant flux received E Rotational constants  [c.106]

Radiant intensity I In frequency A. B, C  [c.106]

Radiant intensity at time t I(t) In wavenumber A B C  [c.106]

Radiant power Rotation-reflection Sn  [c.106]

Radiant power incident on Po Rydberg, unit of energy Ry  [c.106]

Spectral radiant energy Q, dQ/dk Summation sign S  [c.107]

Spectral radiant energy den- Surface charge density (J  [c.107]

Spectral radiant energy flux d(j)/dk Surface pressure 7T  [c.107]

Mass Absorption Coefficients. Radiation traversing a layer of substance is diminished in intensity by a constant fraction per centimeter thickness x of material. The emergent radiant power P, in terms of incident radiant power Pq, is given by  [c.704]

Laws of Photometry. The time rate at which energy is transported in a beam of radiant energy is denoted by the symbol To for the incident beam, and by P for the quantity remaining unabsorbed after passage through a sample or container. The ratio of radiant power transmitted by the sample to the radiant power incident on the sample is the transmittance T  [c.728]

When a beam of monochromatic light, previously rendered plane parallel, enters an absorbing medium at right angles to the plane-parallel surfaces of the medium, the rate of decrease in radiant power with the length of light path (cuvette interior) b, or with the concentration of absorbing material C (in grams per liter) will follow the exponential progression, often referred to as Beer s law.  [c.728]

Analyte T reatment Precipitant Precipitate  [c.250]

M. D. Graham, J. G. Kevrekidis, K. Asakura, J. Lauterbach, K. Krischer, H. H. Rotemund, and G. Ertl, Science, 264, 80 (1994). See also K. Asakura, J. Lauterbach, H. H. Rotermund, and G. Ertl, J. Chem. Phys., 102, 8175 (1995).  [c.754]

The transition from k to on the low-pressure side ean be eonstnieted using iiiidtidimensional unimoleeular rate theory [1, 44], if one knows the barrier height for the reaetion and the vibrational frequeneies of the reaetant and transition state. The transition from to k y ean be deseribed in temis of Kramers theory [45]  [c.847]

For solids and non-volatile liquids accurate heat capacity measurements are generally made in an adiabatic calorimeter. A typical low temperature aneroid-type adiabatic calorimeter used to make measurements between 4 K and about 300 K is shown in figure B 1.27.1. The primary fimction of the complex assembly is to maintain the calorimeter proper at any desired temperature between 4 K and 300 K. The only energy gain should be from the addition of electrical energy during a measurement. The upper part of the calorimeter contains vessels for holding liquid nitrogen and helium that provide low temperature heat sinks. Construction materials are generally those having high thennal conductivity (e.g. copper) plated with reflectant material (e.g. cliromium) to reduce radiant energy transfer. The calorimeter proper and its surrounding adiabatic shield are suspended by silk lines and can be raised to bring them into good thennal contact with the lower tank, thereby cooling the calorimeter. Wlien the calorimeter proper has reached its desired temperature, thennal contact is broken by lowermg the calorimeter and the adiabatic shield. Adiabatic conditions are maintained by keeping the temperature of the adiabatic shield at the temperature of the calorimeter and heat conduction is  [c.1905]

Coneerted ehemieal reaetions involving simultaneous bond breaking and forming, beeause to do so would require the foree-field parameters to evolve from those of the reaetant bonding to those for the produet bonding as the reaetion proeeeds  [c.520]

See pages that mention the term Rytander : [c.189]    [c.148]    [c.808]    [c.808]    [c.888]    [c.918]    [c.2294]    [c.603]    [c.264]    [c.442]    [c.99]    [c.186]    [c.78]    [c.87]    [c.87]    [c.87]    [c.87]    [c.106]    [c.210]   
Organic syntheses based on name reactions and unnamed reactions (1994) -- [ c.97 ]