Field synergy analysis of different flow patterns in falling-film dehumidification system with horizontal pipes

Effects of the flow pattern of intertubular liquid film on mass and heat transfer synergies in a falling-film dehumidification system with horizontal pipes are studied.A flow model of the dehumidifying solution between horizontal pipes is established using Fluent software,the rule of transitions of the flow pattern between pipes is studied,critical Reynolds numbers of flow pattern transitions are obtained,and the accuracy of the model is verified by experiments.The mass transfer synergy angle and heat transfer synergy angle are respectively used as evaluation criteria for the mass transfer synergy and heat transfer synergy,and distribution laws of the synergy angles for droplet,droplet columnar and curtain flow patterns are obtained.Simulation results show that the mass transfer synergy angles corresponding to droplet,droplet columnar and curtain flow patterns all rise to a plateau with time.The mean mass-transfer synergy angle is 98°for the droplet flow pattern,higher than 96.5°for the droplet columnar flow pattern and 95°for the curtain flow pattern.The results show that the mass transfer synergy of the droplet flow pattern is better than that of the droplet columnar flow pattern and that of the curtain flow pattern.

Spray Characteristics Study of Combined Trapezoid Spray Tray

The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally investigated by using a high-speed camera, and a theoretical model of the average droplet size was established according to the unstable wave theory. The results demonstrated that gas velocity passing through the hole is the key factor affecting the spray angle, which increases gradually with an increase in the gas velocity. When the gas velocity exceeds 7.5 m/s, the spray angle becomes stable at around 55°. The average flow velocity of the liquid sheet at the spray-hole increases significantly with an increase in the gas velocity, and decreases slightly with an increase in the liquid flow rate; moreover, it increases from the bottom of spray hole upward to the top. The density of liquid drops distribution in the spray area can be described by the RosinRammler function. In addition, the liquid drops are mainly concentrated in the area of spray angle ranging from 20° to 40°, and they gradually become uniform with the increase in the gas velocity and the liquid flow rate. The average liquid drop size deceases with an increase in the gas velocity, and increases slightly with an increasing liquid flow rate. In the normal working range, the average liquid drop size is about 1.0 mm to 2.5 mm in diameter.

Effect of flow control mold on flow field during high-speed continuous casting

An experimental mold was built to study the flow in a flow control mold under high speed continuous casting. The effect of the magnetic field on the flow was investigated using mercury. The results show that the magnetic field can not only dampen the flow of liquid metal but also change its direction, and then redistribute the flow in the mold. When maintaining a constant distance between magnets, the fluctuation of the free surface is dampened because of the increasing magnetic flux density. The flow at the free surface is improved, and the penetration depth of the downward stream is reduced. The decrease in the dis- tance between magnets promotes the brake effect and the flow is dampened in the upper eddy.

The Spatial and Temporal Evolution Behavior of Fluid Flow in Round Strands Continuous Casting Under Intermittently Reversing Direction Electromagnetic Stirring

Liquid metal flow behavior in round strands continuous casting under intermittently reversing direction electromagnetic stirring was measured by ultrasonic Doppler velocity-meter in a physical simulation system in order to investigate the effects of time interval(t_i)of periodically reversed magnetic field on the spatial and temporal flow.The results show that under electromagnetic stirring with direction reserved magnetic field,there's a periodically change of the metal flow velocity and rotation direction with the periodically direction changing of the magnetic field.From both the experimental and mathematical model calculation results,it is found that when t_i is nearly equal to the time required for the metal flow speeding to the maximum velocity from still and decreases to zero again,there is a critical value of the rate of dynamic pressure,which means the wash effect of the liquid metal flow.On this point,rate of dynamic pressure was proposed to be a criterion for optimization the processing of electromagnetic stirring.

Single-and two-phase flow model in low-permeability reservoir

In petroleum development,low-permeability reservoir means having permeability of porous media lower than 50 micro-Darcy.The mathematical model of liquid flow in low-permeability reservoirs has been difficult to describe for a long time,and an ideal model has not been available until now because of the threshold pressure gradient.With the boundary adhesion layer model of a micro-channel as basis,a new liquid flow model was derived for low-permeability reservoirs in this study.The no-movement liquid layer close to the solid surface was defined as the boundary adhesion layer regarded as the negative slip length.Using the exponential function of the boundary stick layer to the pressure drop gradient,the formulae of the liquid velocity and flow rate of a round channel were derived.The liquid flows model in low permeability reservoirs was then obtained.Finally,the flow model was tested by examples,and applications to a low-permeability reservoir were demonstrated.The analysis results show that the new non-linear model of liquid flows exhibits clear physical definition,and can be easily used to describe liquid flows in low-permeability media.