166 Abstracts for The 3rd World Conference

Wall-to-Bed Heat Transfer in Three-Phase Fluidized Boiling Gu Junjie Li Xiulun Wen Jianping Huang Hongding Chemical Engineering Department Tianjin University Tianjin, China

In order to solve the fouling problems in boiling pro- cesses, a new boiling device was designed by adding solid particles to the boiling tube. In this paper, theoretical analysis and experimental study of boiling heat transfer in the three-phase fluidized bed were carried out. On the basis of the analysis of the heat transfer characteristics of three-phase fluidized beds, a mathematical model of the heat transfer coefficient of three-phase fluidized boiling was developed. The experiments show that, due to the presence of the particulate solids, the boiling heat transfer is enhanced. The boiling heat transfer coefficient of the three-phase fluidized boiling is about 2 times that of the vapor-liquid two-phase one, and the flow stability of the boiling process in the three-phase fluidized boiling is better than that in the vapor-liquid two-phase boiling. The fluidized particles can rub the heat transfer wall to pre- vent and to clean the fouling.

Heat Transfer to Boiling Liquid Mixtures in a Vertical Tube Thermosiphon Reboiler Hamid Ali S. S. Alam Department of Chemical Engineering Aligarh Muslim University Aligarh, India

Boiling heat-transfer data were obtained for water, ace- tone, ethanol, ethylene glycol, and their binary mixtures under natural convective flow through a vertical tube, as encountered in thermosiphon reboiler. The heat-transfer section consisted of an electrically heated stainless-steel tube of 25.56 mm inner diameter and 1900 mm length. The heat flux values ranged from about 2300-40000 W / m 2. The liquid submergences expressed in percentages were maintained around 100, 75, 50, and 30. All the data were generated at one atmosphere with increasing heat flux.

The heat-transfer coefficients for binary mixtures were found to be lower than the weighted average of the pure component values, and this reduction may be attributed to the effect of mass diffusion on heat transfer. An empirical correlation in terms of dimensionless numbers has been proposed to predict the heat-transfer coefficient in the boiling region for all the test liquids.

Prediction of Incipient Point of Boiling of Binary Mixtures in a Reboiler Tube Hamid Ali S. S. Alam Department of Chemical Engineering Aligarh Muslim University Aligarh, India

Experiments were performed to develop a fundamental understanding of the boiling incipience conditions in a

vertical tube thermosiphon reboiler. Three binary systems, acetone-water, ethanol-water, and water-ethylene glycol,

were used for a variety of concentrations. The test section was an electrically heated stainless-steel tube of 25.56 mm inner diameter and 1900 mm length. The uniform heat flux values used were in the range of 2310-33654 W/m 2, while inlet liquid subcooling was varied from 0.2-12.9°C. The liquid submergence was maintained around 100, 75, and 50%. All the data were generated at 1.0 atm pressure. The effect of heat flux and submergence on the variation of wall temperatures are graphically presented and dis- cussed. The maximum superheats attained around boiling incipience were taken from the wall temperature distribu- tions and correlated with heat flux and physical properties of binary mixtures using the expression of Yin and Abdelmessih.

Disintegration of Liquid and Slurry Jets Traversing Subsonic Airstreams T. Inamura N. Nagai T. Watanabe Department of Aeronautics and Space Engineering Tohoku University Aramaki Aza Aoba Aoba-ku Sendai, Japan N. Yatsuyanagi National Aerospace Laboratory Kakuta, Japan

Wave characteristics and spray characteristics of liquid jets and metalized slurry jets injected transversely into the subsonic airstreams were investigated experimentally. Wave behavior is classified into two regions. One is the region close to the liquid nozzle, where the liquid injec- tion velocity is dominant over the wave velocity. Another is the region far from the liquid nozzle, where the air velocity is dominant over the wave velocity. The boundary between these two regimes almost corresponds to the jet breakup point.

Further downstream, the profiles of mean droplet size in the plane including jet axis are almost uniform, and mean droplet size decreases downstream. The droplet velocities of the spray in the core region are smaller than those of the spray in the peripheral mixing region and increase downstream. The spray droplets are accelerated up to about 80% of air velocity at the exit of test section.

The droplet size of the spray in the core region is larger than that in the peripheral mixing region at the location close to the jet breakup point. The Sauter's mean droplet size of the water is almost equal to that of the slurry. However, the droplet size distributions of both jets are quite different. The slurry spray includes finer droplets than water spray.

Heat-Transfer Analysis of Single Spherical Capsule and Packed Bed for Heat Storage by Latent Heat T. Akiyama H. Nogami R. Takahashi J. Yagi Institute for Advanced Materials Processing Tohoku University Aoba-ku, Katahira, Sendai, Japan

A method of storage by latent heat for unrecovered heat of high temperature over 500 K was investigated by using