Liquids friction

This represents the fraction of the total available head between points A and B, which represents the sensible heating zone. This neglects liquid friction in the sensible zone and assumes the liquid level in the distillation column is maintained even with the top of the tubesheet. Equation 10-170 then gives the fractional tube length devoted to sensible heating. Refer to Figure 10-110 and note that ... 

Control valves, 90-96 Dowtherm liquid, friction loss chart, 94 Dowtherm vapor, 113 Equivalent feel concept, 86 Equivalent feet, non-viscous liquids, 89 Fittings, 71... 

A pipe transporting liquid is shown in Figure 4-6. A pressure gradient across the pipe is the driving force for the movement of liquid. Frictional forces between the liquid and the wall of the pipe convert kinetic energy into thermal energy. This results in a decrease in the liquid velocity and a decrease in the liquid pressure. 

The only liquid frictional pressure gradient is given by... 

Dl. Davis, W. J., Effect of the Froude Number in Estimating Vertical Two-Phase Gas-Liquid Friction Losses. Presented at A.I.Ch.E. Nat. Meeting, Los Angeles, February, 1962. 

The liquid friction factor and liquid Reynolds number (and vapor friction factor/g and gas Reynolds number with the gas viscosity) are obtained from... 

As expected, it has been measured that the large soUd-liquid friction achieved in the impregnated Wenzel state, results in a no-slip BC at the surface as illustrated by the values of fceff — 0 reported in Fig. 3 ( ). In the Fakir (Cassie) state, however, the trapped air is responsible for a finite slip length, the evolution of which is shown in Fig. 3 (o) as a function of the roughness lateral scale L. The measured values... 

The results obtained from pPIV analysis are presented in Figure 4.7, in this case the translation of microdroplets through linear microchaimels (transport velocity 7.6 mm s ). For small segments, the contribution of the liquid/liquid friction to the phase internal flow is determinant and liquid/wall friction is minimal due to its low interface area. As Figure 4.7, shows, the flow field is symmetrical with respect to the channel direction. Impulse transfer occurs at the four regions with maximum flow at the interface [22]. 

In contrast, no recirculation motion is observed near the free surface of the liquid. It is clear that the eddies at the bottom of the tank are induced by the liquid friction on the bottom wall. 

Colburn, A.P. 1933. A method of correlating forced convection heat transfer data and a comparison with liquid friction. Trans AIChE 29 174—210. 

The hysteresis phenomenon was also observed by Luzhnov [133] when studying the static friction of soot powder (see Fig. III.4). In these experiments the upper branch of the hysteresis loop characterizes the change in the coefficient of static friction with increasing relative humidity and the lower with falling humidity, In the present case the failure of the curves to coincide is apparently associated with the replacement of dry by semi-liquid or liquid friction, which is always accompanied by a reduction in the friction coefficient. 

There is a significant limitation on punp operation called Net Positive Suction Head (NPSH). Its origin is as follows. Although the effect of a pump is to raise the pressure of a liquid, frictional losses at the... 

X. N. Meng, et al., Mechanism of Eiqilaining Liquid Friction and Flux Consumption during Non-sinusoidal Oscillation in Slab Continuous Casting Mould , Canadan Metallurgical... 

A liquid possesses a definite volume at a given temperature and pressure, but no definite shape it takes up the shape of the containing vessel. This process may be accomplished very rapidly, as in the case of water under normal conditions, or it may take a considerably longer time, as with thick treacle. When a liquid undergoes a continuous deformation under the action of gravity or of an externally applied force, the process is called flow. As a flow process takes time to complete, the liquid must be offering some resistance to flow, which may be called, quite generally, a liquid friction. 

When the applied shear stress system is removed from an elastically deformed solid, the solid regains its original shape completely and the work of deformation is also recovered. No such recovery occurs in a liquid the work done in producing a given rate of shear is completely dissipated against the liquid friction forces. The resistance to flow offered by a liquid when it is subjected to a shear stress is called a viscous force and the liquid is said to possess viscosity. 

Meanwhile it also happens that sols, which have isotropic spherical particles, exhibit streaming double refraction the cause then lies in the pressure which the particle experiences perpendicular to the direction of flow as a result of the liquid friction. 

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