scholarly journals Modeling Study on Heat Transfer in Marangoni Dropwise Condensation for Ethanol-Water Mixture Vapors

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6726
Author(s):  
Jinshi Wang ◽  
Ziqiang Ma ◽  
Yong Li ◽  
Weiqi Liu ◽  
Gen Li
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Temperature Difference ◽  
Diffusion Layer ◽  
Water Mixture ◽  
Dropwise Condensation ◽  
Heat Transfer Characteristics ◽  
Vapor Diffusion ◽  
Transfer Characteristics ◽  
Condensate Layer

In this paper, a model was developed to predict the heat transfer characteristics of Marangoni dropwise condensation. In accordance with the feature of Marangoni condensation, condensation was treated as dropwise condensation of mixture vapors. The condensation space was divided into two parts: the vapor diffusion layer and the condensate layer. For the condensate layer, the classical heat transfer calculation method of dropwise condensation was imitated to obtain the heat transfer characteristics. For the vapor diffusion layer, the heat transfer characteristics were achieved by solving the conservation equations. These heat transfer characteristics were coupled through the conjunct boundary, which was the vapor-liquid interface. The model was applied to the condensation of water-ethanol mixture vapors. A comparison with the existing experimental data showed that the developed model could basically reflect the influences of vapor-to-surface temperature difference, vapor concentration, vapor pressure, and vapor velocity on heat transfer characteristic of Marangoni condensation. Results showed that some differences existed between the calculation results and experimental results, but the prediction deviation of the model could be acceptable in the range of vapor-to-surface temperature difference where the condensation heat transfer coefficients reached peak values.

Evaporation of Single Drops of n-Pentane/n-Hexane Mixtures in Water

1992 ◽  
Vol 114 (4) ◽  
pp. 965-971 ◽  
Author(s):  
H. Shimaoka ◽  
Y. H. Mori
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Vapor Bubble ◽  
Experimental Results ◽  
Rise Velocity ◽  
Heat Transfer Characteristics ◽  
Two Phase ◽  
Transfer Characteristics ◽  
Preceding Work ◽  
Liquid Vapor

The evaporation of isolated drops (2.1−3.0 mm diameter) of nonazeotropic n-pentane/n-hexane mixtures in the medium of water was observed under pressures of 0.11−0.46 MPa and temperature differences up to 27 K. The mole fractions of n-pentane, x, in the mixtures were set at 0.9, 0.5, 0.1, and 0, to be completed by the condition x = 1 set in a preceding work (Shimaoka and Mori, 1990). Experimental results are presented in terms of the instantaneous rise velocity of, and an expression of instantaneous heat transfer to, each drop evaporating and thereby transforming into a liquid/vapor two-phase bubble and finally into a vapor bubble. The dependencies of the heat transfer characteristics on the pressure, the temperature difference, and x are discussed.

scholarly journals Study on Flow and Heat Transfer Characteristics of Supercritical Kerosene in a Round Tube

2020 ◽  
Vol 316 ◽  
pp. 03003
Author(s):  
Feng Gao ◽  
Qian Zhang ◽  
Hongyu Xiao ◽  
Fengli Chen ◽  
Xuefeng Xia
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Inlet Temperature ◽  
Wall Surface ◽  
Heat Transfer Characteristics ◽  
Navier Stokes Equation ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Wall Surface Temperature ◽  
Central Flow

The finite volume discrete solution of the Navier-Stokes equation and the RNG model of the turbulence model are used to numerically simulate the flow and heat transfer characteristics of supercritical kerosene in a circular tube. The results show that as the inlet mass flow increases, the wall surface temperature and the central flow oil temperature gradually decrease, and the pressure loss becomes larger. As the inlet temperature increases, the wall surface temperature and the central flow oil temperature both increase. When the heat flux density is constant, as the pressure increases, the deterioration of heat transfer will be weakened, and increasing the pressure can improve the effect of convection heat transfer.

Dropwise Condensation Heat Transfer on Superhydrophobic Surface in the Presence of Non-Condensable Gas

2010 ◽  
Author(s):  
Xuehu Ma ◽  
Sifang Wang ◽  
Zhong Lan ◽  
Aili Wang ◽  
Benli Peng
Keyword(s):  
Heat Transfer ◽  
Superhydrophobic Surface ◽  
Vertical Plate ◽  
Experimental Results ◽  
Dropwise Condensation ◽  
Heat Transfer Characteristics ◽  
Steam Condensation ◽  
High Concentration ◽  
Transfer Characteristics ◽  
Wetting Behaviors

Roughness-induced superhydrophobic surface was applied to promote dropwise condensation (DWC) on a vertical plate in the presence of non-condensable gas (NCG). The DWC heat transfer characteristics were investigated and the wetting behaviors of the condensate droplets were observed visually. The experimental results have shown that the roughness-induced superhydrophobic surface would enhance the heat transfer characteristics of steam condensation in the presence of NCG with high concentration. The underlined mechanism is analyzed in terms of the droplet wetting modes.

A Semi-Empirical Model for Condensation Heat Transfer Coefficient of Mixed Ethanol-Water Vapors

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Yang Li ◽  
JunJie Yan ◽  
JinShi Wang ◽  
GuoXiang Wang
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Empirical Model ◽  
Condensation Heat Transfer ◽  
Dropwise Condensation ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Transfer Characteristics ◽  
Semi Empirical

A semi-empirical model describing the heat transfer characteristics of the pseudo-dropwise condensation of binary vapor on a cooled vertical tube has been formulated. By ignoring the thin film always present on the condensation surface and the intensification of mass transfer caused by the Marangoni effect, the heat transfer characteristics of pseudo-dropwise condensation are tentatively formulated. The model involved an analysis of the diffusion process in the vapor boundary layer along with the heat transfer process through the condensate drops. This model was applied to the condensation of the saturated binary vapor of ethanol and water, and was examined using experimental data at vapor pressure values of 101.33 kPa (provided by Utaka and Wang, 2004, “Characteristic Curves and the Promotion Effect of Ethanol Addition on Steam Condensation Heat Transfer,” Int. J. Heat Mass Transfer, 47, pp. 4507–4516), 84.52 kPa and 47.36 kPa. Calculations using the model show a similar trend to the experimental measurements. With the change of the vapor-to-surface temperature difference, the heat transfer coefficients revealed nonlinear characteristics, with the peak values under all ethanol mass fractions of binary vapor. The heat transfer coefficients increased with decreasing ethanol mass fraction.

Inaccuracy of Heat Transfer Characteristics of a Metal Duct Neglecting Heat Radiation Effect in Ambient Air

2012 ◽  
Vol 516-517 ◽  
pp. 322-327 ◽  
Author(s):  
King Leung Wong ◽  
Wen Lih Chen ◽  
Yung Chin Chiu
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Radiation Effect ◽  
Ambient Air ◽  
Heat Radiation ◽  
Heat Transfer Characteristics ◽  
Circular Duct ◽  
Transfer Characteristics ◽  
Internal Fluid ◽  
Fluid Convection

A heat radiation equation contains 4th exponential order of temperature which makes mathematics analysis complicated and time-consumption. Most heat transfer experts and scholars believe, based on their own experiences, that the heat radiation effect can be ignored in situations of small temperature difference between duct surfaces and surroundings. This paper studies in detail for complete heat transfer characteristics of a circular duct with heat radiation effect taken into account. It is found that, in some practical conditions, the heat radiation effect can not be ignored especially in cases of lower ambient convection heat coefficients and larger surface emissivities, as well as the smaller the duct size and/or the greater the duct conductivity and/or internal fluid convection coefficients, even though the temperature-difference between inner and outer fluid-temperatures of duct is low to 1 °C. It is found that the conventional LMTD method (ignoring heat radiation) cannot be applied to calculate the total heat transfer rate of a single-duct heat exchanger located in ambient air, such as condenser and evaporator.

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