Temperature gas-phase

RotationaUy resolved spectra of molecules present in the flame allow for temperature determination of the gas phase [3]. The emission intensity, of a rotational-vibrational band of an excited molecule correlates to the temperature of the molecule, T, via the following equation [34] 

The temperature of the molecule can be determined from the slope of the trace according to 

Wang et al. [34] have determined the rotational-vibrational temperature for gaseous species in a spectral flare composition given below 

20wt% polytetrafluoroethylene 40wt% ammonium perchlorate 10wt% manganese dioxide 5 wt% binder 

As the gas-phase molecules are in thermal equilibrium, determination of one species allows assessment of the overall gas-phase temperature of the combustion flame. 

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Determination of the Gas-Phase Temperature. The development given above is in terms of interface conditions, bulk Hquid temperature, and bulk gas enthalpy. Often the temperature of the vapor phase is important to the designer, either as one of the variables specified or as an important indicator of fogging conditions in the column. Such a condition would occur if the gas temperature equaled the saturation temperature, that is, the interface temperature. When fogging does occur, the column can no longer be expected to operate according to the relations presented herein but is basically out of control. 

Gas-phase temperatures have been obtained by an extension of the graphical method illustrated (22). When equation 30 is divided by equation 34, the result is... 

The basic scheme for the numerical solution is the same as that used for the 1 -D model, except that in this case the solid temperature field used to solve the DAE system for each monolith channel must be calculated from the three-dimensional solid-phase energy balance equation. The three-dimensional energy balance equation can be solved by a nonlinear finite element solver (such as ABAQUS) for the solid-phase temperature field while a nonlinear finite difference solver for the DAE system calculates the gas-phase temperature and... 

It is assumed that there are no heat losses from the column and that there is zero heat exchange between the gas and liquid phases. Consequently the gas phase temperature will remain constant throughout the column. A liquid phase heat balance, for element of volume dV is given by... 

An expression for the net rate of phase change can also be derived by assuming that the phase-change process is controlled solely by the rate at which heat can be transferred between the bulk liquid and the liquid surface. In this penetration theory approach, the liquid surface temperature is assumed to equal the gas-phase temperature. The heat transfer within a liquid element is assumed to occur by pure conduction, and therefore... 

Summary of literature data on methane decomposition catalysts and preferred temperature range. Catalysts 1 = nickel, 2 = iron, 3 = carbon, and 4 = other transition metals (Co, Pd, Pt, Cr, Ru, Mo, W). The dotted line arbitrarily separates heterogeneous (catalytic) and homogeneous (noncatalytic, gas phase) temperature regimes of the methane decomposition reaction. 

Use of sensors to measure gas phase NO2 concentration, electrical conductivity of the reaction mass, and gas phase temperatures at several critical points in semi-continuous nitration reactors permits safe operation of nitration processes [10], The use of non-aqueous titration analysis in the control of nitration processes in explosives manufacture is discussed [11],... 

The burning rate of a double-base propellant can be calculated by means of Eq. (3.59), assuming the radiation from the gas phase to the burning surface to be negligible. Since the burning rate of a double-base propellant is dominated by the heat flux transferred back from the fizz zone to the burning surface, the reaction rate parameters in Eq. (3.59) are the physicochemical parameters of choice for describing the fizz zone. The gas-phase temperature, Tg, is the temperature at the end of the fizz zone, i. e., the dark-zone temperature, as obtained by means of Eq. (3.60). 

Tq, of gas-generating pyrolants such as fuel-rich AP-HTPB and fuel-rich nitropoly-mer pyrolants are lower than those of rocket propellants such as AP-HTPB and nitropolymer propellants. The gas-phase temperature is low and hence the heat flux feedback through the wires is low for the gas-generating pyrolants as compared with propellants. However, r /ro appears to be approximately the same for both pyrolants and propellants. The obtained burning-rate augmentations are of the order of 2-5. 

If the channel wall temperature is specified then the thermal consequences of the surface chemistry do not directly affect the surface temperature itself. Nevertheless the surface chemistry may affect the gas-phase temperature. Beginning with the conservation of energy for the system... 

Profiles of measured temperatures (°C) and silane density (in units of 1016 molecules / cm3) versus height above the surface (measured at this axial position) are found in the file silaneprofiles550C.csv. Plot measured and calculated gas-phase temperatures (at this axial position). Plot measured and calculated silane density profiles (with and without thermal diffusion). 

Heat transfer is an extremely important factor in CVD reactor operation, particularly for LPCVD reactors. These reactors are operated in a regime in which the deposition is primarily controlled by surface reaction processes. Because of the exponential dependence of reaction rates on temperature, even a few degrees of variation in surface temperature can produce unacceptable variations in deposition rates. On the other hand, with atmospheric CVD processes, which are often limited by mass transfer, small susceptor temperature variations have little effect on the growth rate because of the slow variation of the diffusion with temperature. Heat transfer is also a factor in controlling the gas-phase temperature to avoid homogeneous nucleation through premature reactions. At the high temperatures (700-1400 K) of most... 

Using thermal CVD methods with B2H6-NH3-H2 [98, 99] or BC13-NH3-H2 [100] gas mixtures, different BN-layers can be deposited e.g., h-BN, t-BN, or a-BN. BN with higher boron contents can be deposited at enhanced deposition temperatures. To deposit crystalline h-BN from the gas phase, temperatures above 1100 °C and a N/B ratio of 10 1 are necessary. 

Fig. 2. The predictions of the pneumatic drying model for (a) gas phase velocity, (b) dispersed phase velocity, (c) gas phase temperature, (d) dispersed phase temperature, (e) gas humidity, (f) particle s moisture content and (g) particle s diameter along stream lines and the dryer length.

As previously pointed out, the 33S NMR signal is often difficult to detect. Acquiring 33S spectra with an acceptable S/N may require from a few minutes to several days, depending on the symmetry of the sulphur electronic environment and molecular size. Therefore, a suitable choice of acquisition parameters and other experimental conditions (e.g. solvent and concentration in liquid phase, density in gas phase, temperature and so on) is particularly important. In addition, signal-processing methodologies can be critical for extracting all the information contained in a FID, especially when the S/N is not satisfactory. 

Heating was provided by two heating tapes one for the preheater and the other for the reactor to compensate for thermal losses from the windows. The gas phase temperature was controlled by manual adjustment of the input voltage to the heating tapes. Thermal Insulation was provided by l"-thick layer of Fiberfrax (The Carborundum Co.). 

CaldweU, G. Magnera, T. F Kebarle, P. Sj 2 reactions in the gas phase. Temperature dependence of the rate constants and energies of the transition states. Comparison with solution, J. Am. Chem. Soc. 1984,106, 959-966. 

The maximum local gas phase temperature must be equal to or greater than... 

A method for obtaining integral equation solutions to Equations 2, 3, and 4 for the quasi-steady gas-phase temperature and weight fraction... 

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