Channel length

Tmoves to the left, reducing the effective channel length, but the drain current remains nearly constant. See text (26). 

Confined boiling of water and surfactant solutions under condition of natural convection causes a heat transfer enhancement. Additive of surfactant leads to enhancement of heat transfer compared to water boiling in the same gap size however, this effect decreased with decreasing gap size. For the same gap size, CHF decreases with an increase in the channel length. CHF in surfactant solutions is significantly lower than in water. 

Latent heat High, depth Subcooling parameter Thermal conductivity Surface roughness Channel length Mass flow rate Power, number of sample Number of channels Pressure, precession limit Heat rate Heat flux... 

Radius, ration of channel length to block width... 

AP is the pressure drop on a channel length L, d is the characteristic size. 

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 ... 

Estimation of adiabatic increase in the liquid temperature in circular micro-tubes with diameter ranging from 15 to 150 pm, under the experimental conditions reported by Judy et al. (2002), are presented in Table 3.7. The calculations were carried out for water, isopropanol and methanol flows, respectively, at initial temperature Tin = 298 K and v = 8.7 x 10" m /s, 2.5 x 10 m /s, 1.63 x 10 m /s, and Cp = 4,178 J/kgK, 2,606J/kgK, 2,531 J/kgK, respectively. The lower and higher values of AT/Tm correspond to limiting values of micro-channel length and Reynolds numbers. Table 3.7 shows adiabatic heating of liquid in micro-tubes can reach ten degrees the increase in mean fluid temperature (Tin -F Tout)/2 is about 9 °C, 121 °C, 38 °C for the water d = 20 pm), isopropanol d = 20 pm) and methanol d = 30 pm) flows, respectively. 

The relation of hydraulic diameter to channel length and the Reynolds number are important factors that determine the effect of the viscous energy dissipation on flow parameters. 

Under certain conditions the energy dissipation may lead to an oscillatory regime of laminar flow in micro-channels. The relation of hydraulic diameter to channel length and the Reynolds number are important factors that determine the effect of viscous energy dissipation on flow parameters. The oscillatory flow regime occurs in micro-channels at Reynolds numbers less than Recr- In this case the existence of velocity fluctuations does not indicate change from laminar to turbulent flow. 

Parameters 7c,onb, s.onb, and 74,onb change in the range of 0 < 7 < 1. They account for a specific temperature field in heated micro-channels and are criteria for the relative micro-channel length. Note, if 7 < 1 the value of parameter 7 is significantly less than unity. The paper by Celata et al. (1997) reports the results of experimental research of the onset of subcooled water boiling in the circular... 

Fig. 6.23 The top and cross-section views of the test section with a trapezoid micro-channel (length shown not in scale). Reprinted from Lee et al. (2004) with permission...

Ml is the liquid velocity and is the front velocity relative to the liquid, is the liquid length domain and L is the total channel length. Reprinted from Peles et al. (2001) with permission... 

The classification of possible regimes of flow are proposed. It is based on a non-dimensional parameter accounting for the ratio of the micro-channel length to the capillary height. It is shown that in the generic case the governing system of equations, which describes capillary flow, has three stationary solutions two stable and one (intermediate) unstable. 

Initial width of fluid channel Final width of fluid channel Height of fluid channel Metal plate thickness Metal thickness at the edges Channel length Volumetric polymer flowrate Polymer inlet temperature Temperature of Dowtherm Polymer density Polymer heat capacity Polymer thermal conductivity Metal thermal conductivity... 

Fig. 4 Variations of methanol consumption flux along the channel length with increasing the reformer temperature = 1 bar, W/F = 6.72 kg-s/mol)...

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