scholarly journals Behavior of the effective heat transfer coefficient and global thermal resistance in freezing of fruit juice model solutions in cylindrical packages

2020 ◽  
Vol 40 (4) ◽  
pp. 993-999
Author(s):  
Cristina Guimarães PEREIRA ◽  
Jaime Vilela de RESENDE
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Fruit Juice ◽  
Effective Heat ◽  
Model Solutions ◽  
Effective Heat Transfer Coefficient

Analysis of Laminar Heat Transfer on Super-Hydrophobic Surface With Slip Velocity

2009 ◽  
Author(s):  
Wei Sun ◽  
Yuhong Zhou ◽  
Xinxin Fan ◽  
Tianqing Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Slip Velocity ◽  
Structural Parameters ◽  
Hydrophobic Surface ◽  
Trapped Air ◽  
Effective Heat ◽  
Effective Heat Transfer Coefficient

It is still in suspense for the effects of slip velocity and structural parameters on the heat transfer on a super-hydrophobic surface. It is thus necessary to study it in both theory and experiments. In this paper, the convective heat transfer with constant heat flux condition inside a circular microchannel was investigated. The velocity and temperature profiles when slip velocity exists were derived firstly, and then the heat transfer coefficient and Nusselt number were obtained. Furthermore, an effective conduction model for the super-hydrophobic surface with different structural parameters was proposed and the thermal resistance of the surface with trapped air was calculated. Finally, the effective heat transfer coefficient of super-hydrophobic surface was found with the integration of heat transfer coefficient and surface thermal resistance. The calculation results show that 1) the slip of fluid on a super-hydrophobic surface makes the temperature profile inside the channel more uniform, and the heat transfer coefficient or Nusselt number increased, 1.8 times higher maximally under constant heat flux condition; 2) the thermal resistance of super-hydrophobic surface increases with trapped air volume; 3) the effective heat transfer coefficient on super-hydrophobic surface declines seriously with trapped air volume, especially with the trapped air area; 4) there exists a critical thickness for the trapped air on a super-hydrophobic surface with given surface structural parameters, under which the effective heat transfer coefficient is not less than that on normal surfaces without slip. Therefore, it is necessary to consider the structural parameters of super-hydrophobic surfaces, such as rib height and distance between ribs, so that the heat transfer on the super-hydrophobic surface will not be impacted by the trapped air.

Characterization and Modeling of the Heat Transfer Performance of Nanostructured Cu Micropost Wicks

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Youngsuk Nam ◽  
Stephen Sharratt ◽  
Gilhwan Cha ◽  
Y. Sungtaek Ju
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Management ◽  
Critical Heat Flux ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Effective Heat ◽  
Effective Heat Transfer Coefficient

Micro heat pipes incorporating advanced wicks are promising for the thermal management of power electronics. We report the heat transfer performance of superhydrophilic Cu micropost wicks fabricated on thin silicon substrates using electrochemical deposition and controlled chemical oxidation. For a fixed post diameter, the interpost spacing and hence solid fraction is found to be a main design factor affecting the effective heat transfer coefficient and critical heat flux. The effective heat transfer coefficient >10 W/cm2 K and the critical heat flux >500 W/cm2 over 2 mm × 2 mm heating areas are demonstrated. Copper oxide nanostructures formed on the micropost surfaces significantly enhance the critical heat flux without compromising the effective heat transfer coefficient. An approximate numerical model is developed to help interpret the experimental data. A surface energy minimization algorithm is used to predict the static equilibrium shape of a liquid meniscus, which is then imported into a finite element model to predict the effective heat transfer coefficient. The advanced wick structures and experimental and modeling approaches developed in this work will help develop thin and lightweight thermal management solutions for high-power-density semiconductor devices.

Sign in / Sign up

Export Citation Format

Share Document