Heating viscous

Xu et al. [124] numerically computed the adiabatic temperature rise in a micro channel due to viscous heating and expressed their results by a correlation based on dimensionless groups. They introduced a dimensionless temperature rise AT = AT/Tjgf with a reference temperature of 1 K. The correlation they found is given by 

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Material solidifies Monitor and control temperature in feed system or is too viscous, Heat trace and/or insulate lines and plugs lines. Potential for proper line break procedures exposure while Use personal protective equipment (PPE) correcting, proper lockout-tagout and confined space problem. entry procedures CCPS G-23 CCPS G-29 Fisher 1990... 

The Br is a measure of the extent to which viscous heating is important relative to an impressed temperature difference. This can be of some concern in the scale-up design, v usually increasing, with other properties remaining constant. A comparison of the Br for a pilot scale (0.05-m screw) and an industrial (0.15-m screw) unit yields values of ca. 0.65, and 5.73, respectively, for the Br with A = 0.5 w/m K and rj = 500 Pa.s at 60 rpm. The numbers suggest that viscous dissipation will be important and will be much more pronounced in the case of an industrial unit. 

The dependence of the measured rise in fluid mixed-cup temperature on Reynolds number is illustrated in Fig. 3.12. The difference between outlet and inlet temperatures increases monotonically with increasing Re at laminar and turbulent flows. Under conditions of the given experiments, the temperature rise due to energy dissipation is very significant AT = 15—35 K at L/ i = 900—1,470 and Re = 2,500. The data on rising temperature in long micro-tubes can be presented in the form of the dependence of dimensionless viscous heating parameter Re/[Ec(L/(i)] on Reynolds number (Fig. 3.13). 

Fig. 3.13 Variation of the viscous heating parameter Re/[Ec(L/

Celata et al. (2005) evaluated the effect of viscous heating on friction factor for flow of an incompressible fluid in a micro-channel. By integrating the energy equation over the micro-channel length, a criterion that determines conditions when viscous dissipation effect is signiflcant was obtained ... 

Celata GP, Moiini GL, Marconi V, McPhail SS, Zummo G (2005) Using viscous heating to determine the friction factor in micro-channels an experimental validation, in Proceedings of ECI international Conference on Heat Transfer and Fluid Flow in MicroChannel, Caste/Vecchio Pascoli, Italy, 25-30 September 2005... 

A detailed study of the influence of viscous heating on the temperature field in micro-channels of different geometries (rectangular, trapezoidal, double-trapezoidal) has been performed by Morini (2005). The momentum and energy conservation equations for flow of an incompressible Newtonian fluid were used to estimate... 

Since the kinetic energy is related to Ma, the adiabatic wall temperature might be reduced by a function of Ma for the cases where the viscous heat dissipation is negligibly small. Then, the values of Tw/Tstg for all channels are plotted as a function of Ma in Fig. 4.20. 

Morini GL (2005) Viscous heating in liquid flows in micro-channels. Int J Heat Mass Transfer 48 3637-3647... 

Equations (18) and (19) are valid too, in hydrod5mamic regions for calculating surface temperature, if we assume that viscous heating concentrates on the middle layer of lubricating films and temperature varies linearly across the film [20]. TheFourier law of heat conduction gives rise to the following expressions ... 

The compound has a uniform temperature. Viscous heating is neglected... 

Although viscous heating has been neglected in the modeling of the clearance flow it can be easily understood that a varying compound temperature (and therefore varying viscosity) will cause... 

Special equipment required Column chemistry limited Carry-over Viscous heating Detection at low wavelength (blending noise) Increased care due to high pressure Rapid SIM method development Isomer separation SIM with highest complexity Separations with challenging matrices, e.g. LFCs... 

The energy equation for an ideal gas neglecting viscous heating is (Bird et al, 1960)... 

Viscous heating of explosive rapidly extruded between the impacting surfaces or grains. 

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