The Intertube Falling Film: Part 1—Flow Characteristics, Mode Transitions, and Hysteresis

1996 ◽  
Vol 118 (3) ◽  
pp. 616-625 ◽  
Author(s):  
X. Hu ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Horizontal Tube ◽  
Falling Film ◽  
Flow And Heat Transfer ◽  
Transition Criteria ◽  
Continuous Sheet ◽  
Mode Transitions ◽  
Regime Map ◽  
Flow Regime Map

When a liquid film falls from one horizontal tube to another below it, the flow may take the form of discrete droplets, jets, or a continuous sheet; the mode plays an important role in the wetting and heat transfer characteristics of the film. Experiments are reported that explore viscous, surface tension, inertial, and gravitational effects on the falling-film mode transitions. New flow classifications, a novel flow regime map, and unambiguous transition criteria for each of the mode transitions are provided. This research is part of an overall study of horizontal-tube, falling-film flow and heat transfer, and the results may have important implications on the design and operation of falling-film heat exchangers.

Investigation on Intertube Falling-Film Heat Transfer and Mode Transitions of Aqueous-Alumina Nanofluids

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Binglu Ruan ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Horizontal Tube ◽  
Sodium Dodecylbenzene Sulfonate ◽  
Falling Film ◽  
Dodecylbenzene Sulfonate ◽  
Reynolds Number Increase ◽  
New Type ◽  
Aqueous Aluminum ◽  
Mode Transitions ◽  
Film Heat Transfer

Horizontal-tube falling-film heat transfer characteristics of aqueous aluminum oxide nanofluids at concentrations of 0 vol %, 0.05 vol %(0.20 wt %), 0.5 vol %(1.96 wt %), 1 vol %(3.86 wt %) (with and without sodium dodecylbenzene sulfonate), and 2 vol %(7.51 wt %) are investigated and compared with predictions developed for conventional fluids. The thermophysical properties of the nanofluids, including thermal conductivity, kinematic viscosity, and surface tension, are reported, as is the mode transition behavior of the nanofluids. The experimental results for heat transfer are in good agreement with predictions for falling-film flow and no unusual Nu enhancement was observed in the present studies. Additionally, a 20% mode transitional Reynolds number increase was recorded for transitions between sheets and jets and jet-droplet mode to droplet mode. Although the findings with water-alumina nanofluids are not encouraging with respect to heat transfer, the results extend nanofluid data to a new type of flow and may help improve our understanding of nanofluid behavior. Moreover, this work provides a basis for further work on falling-film nanofluids.

The Intertube Falling Film: Part 2—Mode Effects on Sensible Heat Transfer to a Falling Liquid Film

1996 ◽  
Vol 118 (3) ◽  
pp. 626-633 ◽  
Author(s):  
X. Hu ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Falling Film ◽  
Mode Effects ◽  
Nusselt Numbers ◽  
Transfer Behavior ◽  
Continuous Sheet

When a liquid film falls from one horizontal tube to another below it, the flow may take the form of discrete droplets, jets, or a continuous sheet; the mode plays an important role in the heat transfer. Experiments are reported that explore the local heat transfer behavior for each of these flow patterns, and the results are related to the important features of the flow. Spatially averaged Nusselt numbers are presented and discussed, and new mode-specific design correlations are provided. This research is part of an overall study of horizontal-tube, falling-film flow and heat transfer.

Numerical analysis on flow and heat transfer of a tube bundle in a horizontal-tube falling film evaporator

2014 ◽  
Vol 55 (12) ◽  
pp. 3336-3342 ◽  
Author(s):  
Luopeng Yang ◽  
Chengyong Gu ◽  
Zhexuan Xu ◽  
Xiaohong Zhang ◽  
Shengqiang Shen
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Tube Bundle ◽  
Horizontal Tube ◽  
Falling Film ◽  
Film Evaporator ◽  
Flow And Heat Transfer

Analysis of Runback Water Flow on Anti-Icing Surface Using Volume-of-Fluid Method

2017 ◽  
Author(s):  
Mei Zheng ◽  
Wei Dong ◽  
Zhiqiang Guo ◽  
Guilin Lei
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Thin Liquid Film ◽  
Flow Characteristics ◽  
Volume Of Fluid ◽  
Complex Model ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Liquid Film Flow ◽  
The Mathematical Model

The runback water flow and heat transfer on the surface of aircraft components has an important influence on the design of anti-icing system. The aim of this paper is to investigate the water flow characteristics on anti-icing surface using numerical method. The runback water flow on the anti-icing surface, which is caused by the impinging supercooled droplets from the clouds, is driven by the aerodynamic shear forces and the pressure gradient around the components. This is a complex model of flow and heat transfer that considers flow field, super-cooled droplets impingement and runback water flow simultaneously. In this case of gas-liquid two phase flow, the Volume-of-Fluid (VOF) method is very suitable for the solution of thin liquid film flow so that it is applied to simulate the runback water flow on anti-icing surfaces in this paper. Meanwhile, the heat and mass transfer of the runback water flow are considered in the calculation using the User-Defined Functions (UDFs) in ANASYS FLUENT. The verification is conducted by the comparison with the results of the experimental measurement and the mathematical model calculation. The effect of the airflow velocity and contact angle on the water flow are also considered in the numerical simulation.

scholarly journals Heat transfer and flow region characteristics study in a non-annular channel between rotor and stator

2012 ◽  
Vol 16 (2) ◽  
pp. 593-603 ◽  
Author(s):  
M. Nili-Ahmadabadi ◽  
H. Karrabi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Characteristics ◽  
Annular Channel ◽  
Flow Region ◽  
Air Gap ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Slip Ring

This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000<Rez<30000. Heat transfer and pressure drop coefficients are deduced from the obtained data based on a theoretical investigation and are expressed as a formula containing effective Reynolds number. To confirm the results, a comparison is presented with Gazley?s (1985) data report. The presented method and established correlations can be applied to other electric machines having similar heat flow characteristics.

Numerical Simulation of the Liquid Flowing and Heat-Transfer outside the Tube of the Horizontal-Tube Falling Film Evaporator

2012 ◽  
Vol 614-615 ◽  
pp. 296-300 ◽  
Author(s):  
Wei Kang Hu ◽  
Li Yang ◽  
Lei Hong Guo
Keyword(s):  
Heat Transfer ◽  
Horizontal Tube ◽  
Water Desalination ◽  
Falling Film ◽  
Transfer Enhancement ◽  
Film Evaporation ◽  
Film Evaporator ◽  
Spray Density ◽  
Performance Of Heat Transfer ◽  
Falling Film Evaporation

This paper mainly studies the falling film evaporator in the field of water desalination. Using the method of fluent simulates the process of the liquid flowing and heat-transfer on the horizontal-tube falling film evaporation. The author analyses the distribution of the liquid film, and obtain the rule that spray density, evaporation temperature, temperature difference and pipe diameter affect the performance of heat-transfer in a certain range. So the paper plays a guiding role in heat transfer enhancement in the falling film evaporator.

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