Mass transfer in gas-liquid flow in small-diameter tubes

Data on the rate of liquid-phase controlled mass transfer in a small-diameter tube (ID 4 mm) are presented. The motivation is to model the performance of compact contact devices consisting of short, narrow passages. The mean volumetric mass transfer coefficient, K(L)a, is measured for a wide range of superficial gas and liquid velocities (U-GS = 0.1-30 m s(-1) and U-LS = 0.01-1 m s(-1)). Results are related to flow regime transitions and are correlated in terms of Jepsen's (1970, A.I.Ch.E. J. 16, 705-711) fractional energy dissipation parameter. (C) 1997 Elsevier Science Ltd. All rights reserved

Experimental investigation of the liquid volumetric mass transfer coefficient for upward gas-liquid two-phase flow in rectangular microchannels

The gas-liquid two-phase mass transfer process in microchannels is complicated due to the special dynamical characteristics. In this work, a novel method was explored to measure the liquid side volumetric mass transfer coefficient kLa. Pressure transducers were utilized to measure the pressure variation of upward gas-liquid two-phase flow in three vertical rectangular microchannels and the liquid side volumetric mass transfer coefficient kLa was calculated through the Pressure-Volume-Temperature correlation of the gas phase. Carbon dioxide-water, carbon dioxide-ethanol and carbon dioxide-n-propanol were used as working fluids, respectively. The dimensions of the microchannels were 40 µm×240 µm (depth×width), 100 µm×800 µm and 100 µm×2000 µm, respectively. Results showed that the channel diameter and the capillary number influence kLa remarkably and that the maximum value of kLa occurs in the annular flow regime. A new correlation of kLa was proposed based on the Sherwood number, Schmidt number and the capillary number. The predicted values of kLa agreed well with the experimental data

Bite force evaluation in subjects with cleft lip and palate

The purpose of this study was to evaluate the masticatory function of subjects with cleft lip and palate by analyzing the bite force developed by these individuals. Bite force was evaluated in a group of 27 individuals with repaired unilateral cleft lip and palate (14 males and 13 females - aged 18-26 years) and compared to the data achieved from a group of 20 noncleft subjects (10 males and 10 females - aged 18-26 years). Measurement was achieved on three positions within the dental arch (incisors, right molars and left molars), three times at each position considering the highest value for each one. Statistical analysis was performed by ANOVA and Mann-Whitney test ( α = 5%). There was a significant deficit in bite force in male individuals with cleft lip and palate compared to the male control group (p=0.02, p=0.004, p=0.003 for incisors, right and left molars, respectively). For the female group, the difference was not statistically significant (p=0.79, p=0.06, p=0.47). In the group of individuals with clefts, 92.6% were under orthodontic treatment, which could be a reason for the present findings, since it can decrease the bite force more remarkably in males than in females. In conclusion, the bite force is significantly reduced in men when comparing the cleft group to the noncleft group. In females, this reduction was not significant in the same way. However, the main reason for this reduction and for the different behavior between genders should be further investigated