Temperature profile, typical

During the catalyst operation the yield of PA decreased by 2 - 6 wt.%. Gradual deactivation of the catalyst results from the severe thermal conditions which prevail in the reactor. The oxidation of the hydrocarbons does not proceed uniformly along the bed. The temperature profile typical of such oxidation exhibits a maximum - a so-called hot spot, which appears in... 

The longitudinal and transverse relaxation times for both samples 2 and 5 show in Figures 1 and 2 inverse temperature profiles typical of adsorbed systems for all the coverages except the 100% RH for sample 5. This implies a shallow Ti minimum, a drastic spreading out of the Ti curve, and may include a shoulder effect or maximum as T2 increases with temperature (20,21). Logarithmic Gaussian temperature-independent (B = constant) distributions have been used to model these systems and is discussed below. Because of the similarity of these profiles, the motional characteristics of the adsorbed water is probably similar for the different conditions listed in Figures 1 and 2. The data in Table II support this view since (except for sample 5 at 100% RH)... 

The adhesion promotion advantages associated with vacuum plasma processes include its low temperature profile, typically 40-120 °C, which avoids material damage under a low density discharge. Plasma discharges under low pressure also increase the mean free path length of plasma species, creating higher kinetic... 

Nonisothermal Gas Absorption. The computation of nonisothermal gas absorption processes is difficult because of all the interactions involved as described for packed columns. A computer is normally required for the enormous number of plate calculations necessary to estabUsh the correct concentration and temperature profiles through the tower. Suitable algorithms have been developed (46,105) and nonisothermal gas absorption in plate columns has been studied experimentally and the measured profiles compared to the calculated results (47,106). Figure 27 shows a typical Hquid temperature profile observed in an adiabatic bubble plate absorber (107). The close agreement between the calculated and observed profiles was obtained without adjusting parameters. The plate efficiencies required for the calculations were measured independendy on a single exact copy of the bubble cap plates installed in the five-tray absorber. 

Processing. SAN copolymers may be processed using the conventional fabrication methods of extmsion, blow mol ding, injection molding, thermoforming, and casting. Small amounts of additives, such as antioxidants, lubricants, and colorants, may also be used. Typical temperature profiles for injection mol ding and extmsion of predried SAN resins are as follows (101). 

Reducing agents are employed to return the Fe to Fe . By starting at a lower temperature, the heat of reaction can be balanced by the sensible heat of the water in the emulsion. Temperature profiles from 20 to 70°C are typical for such systems. Care must be taken when working with redox systems to... 

Polyaryl ether ketones may be processed on conventional injection moulding and extrusion equipment, providing sufficiently high temperatures can be achieved. Melt temperatures required are typically 370°C for unreinforced PEEK, 390°C for reinforced PEEK and both unreinforced and reinforced PEK and unreinforced PEEKK, and 410°C for reinforced PEEKK. For the latter material a temperature profile from feed zone to nozzle would be... 

Fig. 4.61 illustrates typical temperature profiles during the rotational moulding of polyethylene. A ith typical values of oven temperatures and data for an aluminium mould... 

Figure 10-78. Typical condenser temperature profiles for 43% propane-57% n-butane mixture at 176 psi abs.—up-flow. (Used by permission Clements, L. D., and Colver, C. P. AlChE Heat Transfer Symposium, V. 131, No. 69, 1973. American Institute of Chemical Engineers. All rights reserved.)...

The heat transfer problem which must be solved in order to calculate the temperature profiles has been posed by Lee and Macosko(lO) as a coupled unsteady state heat conduction problem in the adjoining domains of the reaction mixture and of the nonadiabatic, nonisothermal mold wall. Figure 5 shows the geometry of interest. The following assumptions were made 1) no flow in the reaction mixture (typical molds fill in <2 sec.) ... 

Figure 1. Typical reactor temperature profile for continuous addition polymerization a plug-flow tubular reactor. Kinetic parameters for the initiator 1 = 10 ppm Ea = 32.921 kcal/mol In = 26.492 In sec f = 0.5. Reactor parameter [(4hT r)/ (DpCp)] = 5148.2. [(Cp) = heat capacity of the reaction mixture (p) = density of the reaction mixture (h) = overall heat-transfer coefficient (Tf) = reactor jacket temperature (r) = reactor residence time (D) = reactor diameter].

Figure 2.6 shows a typical temperature profile.t l The temperature boundary layer is similar to the velocity layer. The flowing gases heat rapidly as they come in contact with the hot surface of the tube, resulting in a steep temperature gradient. The average temperature increases toward downstream. 

For the analysis of the chemical structure of flames, laser methods will typically provide temperature measurement and concentration profiles of some readily detectable radicals. The following two examples compare selected LIF and CRDS results. Figure 2.1 presents the temperature profile in a fuel-rich (C/O = 0.6) propene-oxygen-argon flame at 50 mbar [42]. For the LIF measurements, 1% NO was added. OH-LIF thermometry would also be possible, but regarding the rather low OH concentrations in fuel-rich flames, especially at low temperatures, this approach does not capture the temperature rise in the flame front [43]. The sensitivity of the CRDS technique, however, is superior, and the OH mole fraction is sufficient to follow the entire temperature profile. Both measurements are in excellent agreement. For all flames studied here, the temperature profile has been measured by LIF and/or CRDS. 

In most shell and tube exchangers the flow will be a mixture of co-current, counter-current and cross flow. Figures 12.186 and c show typical temperature profiles for an exchanger with one shell pass and two tube passes (a 1 2 exchanger). Figure 12.18c shows a temperature cross, where the outlet temperature of the cold stream is above that of the hot stream. 

Figure 24. Typical temperature profiles of a LHS system for charging (c) and discharging (d) operations...

Figure 15.2 Curie-point pyrolysis Temperature profile and Curie points of typical ferromagnetic alloys used.

Fig. 16. Schematic of a typical temperature profile in a crystallization experiment and the resulting evolution of the fraction of crystalline polymer and dynamic moduli with time. The preheating temperature Tp is above the melting temperature Tm...

The results of the calculation of Cel for the different coatings using the typical oven temperature profiles raises several questions ... 

Comparisons for the full solid cylinders, with and without heat sinks, were made in Nijemeisland et al. (2004) for conditions near the inlet of the reactor tube. These showed that temperature profiles changed drastically when heat sinks were included. In Figs. 33 and 34, we show a similar comparison for conditions typical of the middle of the reactor tube. We compare the planes at the midpoint of the third stage, for the cases where the outer 5% of the particle was active and where the entire particle was inactive. These are shown in Fig. 33. 

Let us examine methanol. Its flashpoint temperature is 12 to 16 °C (285-289 K) or, say, 15 °C. If this is in an open cup, then the concentration near the surface is Xl = 6.7 %. Performed under normal room temperatures of, say, 25 °C, the temperature profile would be as in Figure 6.2. This must be the case because heat must be added from the air to cause this evaporated fuel vapor at the surface. This decrease in temperature of an evaporating surface below its environment is sometimes referred to as evaporative cooling. If the convective heat transfer coefficient, typical of natural convection, is,... 

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