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Similar Temperature Profiles

A series of new ethers has been obtained by alkylation of dianhydrohexitols (i. e. iso-sorbide, isomannide, isoidide) under the action of microwave irradiation and PTC conditions. Yields exceeded 90%, a dramatically improvement compared with those from conventional heating, despite similar temperature profiles. The best yields, for example from isosorbide, were obtained in the presence of a small amount of xylene and TBAB as catalyst at 140 °C (Eq. 9 and Tab. 5.6) [20],... [Pg.154]

Loupy et al. [84] have synthesized new diethers by alkylation of dianhydrohexitol under the action of irradiation with PTC conditions. The yields were very good (>90%) within a few minutes. Even when similar temperature profiles were used the yields were much lower under the action of conventional heating (Scheme 8.60). [Pg.281]

It seems reasonable to assume that similar temperature profiles will also exist when viscous dissipation is important. Attention will first be given to the adiabatic wall case. If the wall is adiabatic and viscous dissipation is neglected, then the solution to the energy equation will be T = Ti everywhere in die flow. However, when viscous dissipation effects are important, the work done by the viscous forces leads to a rise in fluid temperature in the fluid. This temperature will be related to the kinetic energy of the fluid in the freestream flow, i.e., will be related to u /2cp. For this reason, the similarity profiles in the adiabatic wall case when viscous dissipation is important are assumed to have the form ... [Pg.142]

The fact that an ordinary differential equation has been obtained indicates that the assumption of similar temperature profiles is valid. [Pg.501]

Figure 9-12. The self-similar temperature profile given by Eq. (9-240) for forced convection heat transfer from a heated (or cooled) solid sphere in a uniform velocity field at small Re and large Pe. The function g( i]) represents the dependence of the thermal boundary-layer thickness on // and is given by (9-237). Figure 9-12. The self-similar temperature profile given by Eq. (9-240) for forced convection heat transfer from a heated (or cooled) solid sphere in a uniform velocity field at small Re and large Pe. The function g( i]) represents the dependence of the thermal boundary-layer thickness on // and is given by (9-237).
Figure 11-4. The self-similar temperature profile for the thermal boundary layer in the limit Re //> 1, Pr 3> 1. Figure 11-4. The self-similar temperature profile for the thermal boundary layer in the limit Re //> 1, Pr 3> 1.
Loupy [72] described the synthesis of polyethers derived from isoidide and isosorbide by phase-transfer catalysis under the action of conventional heating and microwave irradiation (Scheme 5.29). Although similar temperature profiles were observed in these reactions (Fig. 5.21), noticeably different results were obtained under the action of microwave irradiation ... [Pg.252]

Similar temperature profile to the free enzyme has been obtained for our immobilized form (Figure 15). An optimum temperature has been obtained at 55°C. This similarity indicates that the microenvironment of the immobilized enzyme is identical to that of the free one, so absence of internal pore diffusion, illustrates the main drawback of the immobilization process, and the success of surface immobilization to overcome this problem. The confirmation of this conclusion has come from determination of the activation energy for both the free and immobilized form [29], which was found very close in value, 6.05 Kcal/mole for the free and 6.12 Kcal/mole for the immobilized forms respectively. [Pg.274]

Similar temperature profile to the free enzyme has been obtained for our immobilized form (Fig. 21.15). An optimum temperature has been obtained at 55 °C. This... [Pg.294]

In the past, the use of scale models was not used because of the difficulties of establishing a relationship of heat flow between the two models, and the inability to achieve similarities in the temperature profiles. Some authors examined not only the potential of using small but simple analysis techniques to rate, calculated and established the structural requirements models. Using a normalized fire curve and the laws change over time scales to generate a similar temperatures profile in the model and in the test prototype were verified by experimental tests [ 16]. [Pg.441]

In contrast to the terrestrial atmospheres, differences between cloudy and less cloudy areas or between low and high latitudes are much less pronounced on the giant planets. An example of how clouds affect the spectrum of Jupiter is shown in Fig. 6.3.5. The two observed spectra are almost identical in the 300 to 700 cm interval and have comparable emission angles, indicating that the vertical temperature structures of the upper tropospheres of the south polar and north temperate regions are almost identical. Downward extrapolations of these temperature structures should lead to very similar temperature profiles for these two regions at the... [Pg.322]

Two types of thermal similarities can be used equal average end temperatures and similar temperature profiles. The concept of equal average end temperatures can be applied if the extruder operates adiabatically or if Br 1. In this case scaling-up has to proceed according to equal motor power per unit throughput ... [Pg.225]


See other pages where Similar Temperature Profiles is mentioned: [Pg.62]    [Pg.325]    [Pg.32]    [Pg.500]    [Pg.352]    [Pg.161]    [Pg.2122]    [Pg.2108]    [Pg.261]    [Pg.1094]    [Pg.979]    [Pg.442]    [Pg.219]    [Pg.228]   


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