多孔物料干燥时的耦合传热传质效应

Based on Luikov’s set of differential equations, the coupled heat and mass transfer duringthe drying of a capillary porous sheet is investigated. The influences of heat transfer on themass flux distribution are illustrated by numerical examples. And the drying characteristicsof the different heating methods are presented.

具有传质传热及扩散效应的双气泡的相互作用

利用修正的Keller-Miksis方程与Noble-Abel-Stiffend-Gas状态方程相结合的模型,研究了超声作用下具有传质传热及扩散效应的双气泡间的相互作用,并与Mettin等[Mettin R,Akhatov I,Parlitz U,Ohl C D,Lauterborn W 1997 Phys.Rev.E 562924]给出的没有传质传热及扩散效应的双气泡间的相互作用进行了比较.结果表明,具有传质传热及扩散效应的双气泡间的次Bjerknes力和气泡归一化最大半径都大于没有传质传热及扩散效应的双气泡的相应量.随着其中一个气泡的初始半径的增大和驱动声压的增大,两种情况给出的次Bjerknes力的差别逐渐增大,而随着驱动频率的增大,两种情况给出的次Bjerknes力的差别逐渐减小.由此可见,传质传热和扩散效应对空化气泡间相互作用的次Bjerknes力具有重要影响.

An Experimental Study of Liquid-Liquid Microflow Pattern Maps Accompanied with Mass Transfer

This paper presents the experimental results of liquid-liquid microflows in a coaxial microfluidic device with mass transfer.Three working systems were n-butanol + phosphoric acid(PA) + water,methyl isobutyl ketone(MIBK) + PA + water,30% kerosene in tri-n-butylphosphate(TBP) + PA + water.The direction and intensity of mass transfer were adjusted by adding PA in one of two phases mutual saturated in advance.When PA transferred from the organic phase to the aqueous phase,tiny aqueous droplets may generate inside the organic phase by mass transfer inducement to form a new W/O/W flow pattern directly on some special cases.Once the PA concentration was very high,violent Marangoni effect could be observed to throw part of organic phase out of droplets as tail.The interphase transfer of PA could expand the jetting flow region,in particular for systems with low or medium inter-facial tension and when the mass transfer direction was from the aqueous phase to the organic phase.

Measurement and Correlation of Pressure Drop for Gas-Liquid Two-phase Flow in Rectangular Microchannels

The pressure drop of gas-liquid two-phase flow in microchannel is of fundamental importance in heat and mass transfer processes. In this work,the pressure drop of gas-liquid two-phase flow in horizontal rectangular cross-section microchannels was measured by a pressure differential transducer system. Water,ethanol and n-propanol were used as liquid phase to study the effects of capillary number on pressure drop;air was used as the gas phase. Four microchannels with various dimensions of 100 μm× 200 μm,100 μm× 400 μm,100 μm× 800 μm and 100 μm× 2000 μm(depth × width) were used for determining the influence of configuration on the pressure drop. Experimental results showed that in micro-scale,the capillary number also affected the pressure drop remarkably,and in spite of only one-fold difference in aspect ratio,the variation of pressure drop reached up to near three times under the same experimental conditions. Taking the effects of aspect ratio and surface tension into account,a modi-fied correlation for Chisholm parameter C in the Chisholm model was proposed for predicting the frictional multi-plier,and the predicted values by the proposed correlation showed a satisfactory agreement with experimental data.

Convective heat and mass transfer analysis on peristaltic flow of Williamson fluid with Hall effects and Joule heating

This paper deals with the peristaltic flow of an incompressible and electrically conducting Williamson fluid in a symmetric planar channel with heat and mass transfer. Hall effects, viscous dissipation and Joule heating are also taken into consideration. Mathematical model is presented by using the long wavelength and low Reynolds number approximations. The differential equations governing the flow are highly nonlinear and thus perturbation solution for small Weissenberg number （0 〈 We 〈 1） is presented. Effects of the heat and mass transfer Biot numbers and Hall parameter on the longitudinal velocity, temperature, concentration and pumping characteristics are studied in detail. Main observations are presented in the concluding section, The streamlines pattern and trapping are also given due attention.

MHD peristaltic flow in an inclined channel with heat and mass transfer

This paper addresses the peristaltic flow of magnetohydrodynamic viscous fluid in an inclined compliant wall channel. Different wave amplitudes and phases ensure asymme- try in the channel flow configuration. Simultaneous effects of heat and mass transfer are also considered. Viscous dissipation effect is present. The flow and heat transfer are investigated under long wavelength and low Reynolds number assumption. The expres- sions for stream function, axial velocity, temperature and concentration are obtained. The solution expressions for physical quantities are sketched and discussed. It is found that Brinkman and Hartman numbers have reverse effect on the temperature.