Liquid-Film Heat Transfer Coefficients

1937 ◽  
Vol 29 (8) ◽  
pp. 905-910 ◽  
Author(s):  
Donald S. Ullock ◽  
W. L. Badger
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Film Heat Transfer

The Effect of Liquid Film Evaporation on Flow Boiling Heat Transfer in a Micro Tube

2010 ◽  
Author(s):  
Youngbae Han ◽  
Naoki Shikazono ◽  
Nobuhide Kasagi
Keyword(s):  
Heat Transfer ◽  
Film Thickness ◽  
Liquid Film ◽  
Flow Boiling ◽  
Liquid Film Thickness ◽  
Periodic Pattern ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Micro Channels ◽  
Measured Liquid

Flow boiling in micro channels is attracting large attention since it leads to large heat transfer area per unit volume. Generated vapor bubbles in micro channels are elongated due to the restriction of channel wall, and thus slug flow becomes one of the main flow regimes. In slug flow, sequential bubbles are confined by the liquid slugs, and thin liquid film is formed between tube wall and bubble. Liquid film evaporation is one of the main heat transfer mechanisms in micro channels and liquid film thickness is a very important parameter to determine heat transfer coefficient. In the present study, liquid film thickness is measured under flow boiling condition and compared with the correlation proposed under adiabatic condition. The relationship between liquid film thickness and heat transfer coefficient is also investigated. Pyrex glass tube with inner diameter of D = 0.5 mm is used as a test tube. Working fluids are water and ethanol. Laser focus displacement meter is used to measure the liquid film thickness. Initial liquid film thickness under flow boiling condition can be predicted well by the correlation proposed under adiabatic condition. However, measured liquid film thickness becomes thinner than the predicted values in the cases of back flow and short slugs. These are considered to be due to the change of velocity profile in the liquid slug. Under flow boiling condition, liquid film profile fluctuates due to high vapor velocity and shows periodic pattern against time. Frequency of periodic pattern increases with heat flux. At low quality, heat transfer coefficients calculated from measured liquid film thickness show good accordance with heat transfer coefficients obtained directly from wall temperature measurements.

1987 Max Jakob Memorial Award Lecture: Dynamics and Stability of Thin Heated Liquid Films

1990 ◽  
Vol 112 (3) ◽  
pp. 538-546 ◽  
Author(s):  
S. G. Bankoff
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Liquid Films ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Molecular Forces ◽  
Memorial Award ◽  
Film Heat Transfer

This review covers the dynamics and tendency toward rupture of thin evaporating liquid films on a heated surface. Very large heat transfer coefficients can be obtained. The applications include various boiling heat transfer and film cooling devices. A relatively new area for study is heat transfer through ultrathin films, which are less than 100 nm in thickness, and hence subject to van der Waals and other long-range molecular forces. Some recent work employing lubrication theory to obtain an evolution equation for the growth of a surface wave is described. Earlier phenomenological work is briefly discussed, as well as the connection between forced-convection subcooled nucleate boiling and thin-film heat transfer.

Modeling of Wellbore Overall Heat Transfer in Circulation

2012 ◽  
Vol 260-261 ◽  
pp. 537-542
Author(s):  
Hui Fang Song ◽  
Rui He Wang ◽  
Hong Jian Ni
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Steady State ◽  
Radial Direction ◽  
Transfer Coefficients ◽  
Element Analysis ◽  
Heat Transfer Coefficients ◽  
Temperature Calculation ◽  
Wellbore Pressure ◽  
Film Heat Transfer

Heat is transferred between the fluid and the surroundings in the wellbore. Quantitative knowledge of wellbore heat transfer is important in drilling and production operations. A new model of wellbore heat transfer using finite element analysis is developed in this study. This solution assumes the heat transfer in the wellbore is steady state and only happens in radial direction. The model considers heat gained due to wellbore pressure loss in circulation, which is more accurate in temperature calculation. The overall heat resistance in the wellbore is analyzed, taking into account the film heat transfer coefficients difference between the tube and the annulus. Previous literature has been reviewed to determine the correlation which can be used in the model.

Cost-Optimal Operation of Heat Exchanger Network Considering Pressure Drop Constraints

2013 ◽  
Vol 634-638 ◽  
pp. 3898-3902
Author(s):  
Liang Zhao ◽  
Zhao Yi Huo ◽  
Lin Mu ◽  
Hong Chao Yin
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Optimal Operation ◽  
Extended Model ◽  
Transfer Coefficients ◽  
Heat Exchanger Network ◽  
Power Cost ◽  
Heat Transfer Coefficients ◽  
Film Heat Transfer

Considerable research effort has been reported in cost-optimal operation of heat exchanger network. However, most of them neglect the pressure drop influence and assume constant film heat transfer coefficients. Pressure drop of streams are important influencing factors for the performance of heat exchanger network operation. In this paper, a general cost-optimal operation model considering pressure drop constraints and removing the assumption of constant film heat transfer coefficients is proposed. It is necessary to determine the pumping power cost required as part of operating cost function. The extended model is applied to one example taken from previous research, and the results prove that the proposed method can obtain more real optimization results for HEN operational optimization problems.

Heat Transfer and Pressure Drop Characteristics of Condensation for R410A in a 3.78mm Circular Tube Under Normal and Micro Gravity

2016 ◽  
Author(s):  
Jingzhi Zhang ◽  
Wei Li ◽  
Tom I.-P. Shih ◽  
Yonghai Zhang ◽  
Yanping Shi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Transfer Coefficients ◽  
Bottom Part ◽  
Vapor Interface ◽  
Heat Transfer Coefficients ◽  
Micro Gravity ◽  
Liquid Vapor

Heat transfer and pressure drop characteristics of condensation for R410A inside horizontal tubes (dh = 3.78 mm) under normal and micro gravity are investigated numerically. The Volume of Fluid method is used to acquire liquid-vapor interface, while the low-Reynolds form of the Shear Stress Transport k∼ω (SST k∼ω) model is adopted to taking turbulent effect into account. The results indicate that the heat transfer coefficients decrease with increasing gravity accelerations, while the frictional pressure gradients increase with increases in gravity accelerations. The liquid film accumulates at the bottom of the tube, leading to a very thin liquid film attached to the upper part of inner tube wall. This accumulation effect decreases with decreases in gravitational accelerations. A more symmetrical liquid-vapor interface is obtained at lower gravity. The average liquid film thickness is nearly the same for different gravity accelerations at the same vapor quality (δave≈56 μm at x = 0.9 and δave≈230 μm at x = 0.5). The local heat transfer coefficients increase with increasing gravity at the top of the tube and decrease with increases in gravity at the bottom, while the bottom part of the tube has a limited contribution to the global heat transfer coefficient for stratified flow regime. The numerical data obtained under normal gravity agree well with well-known empirical correlations.

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