Application of smart models for prediction of the frost layer thickness on vertical cryogenic surfaces under natural convection

2017 ◽  
Vol 115 ◽  
pp. 1128-1136 ◽  
Author(s):  
Alireza Zendehboudi ◽  
Baolong Wang ◽  
Xianting Li
Keyword(s):  
Natural Convection ◽  
Layer Thickness ◽  
Frost Layer Thickness ◽  
Frost Layer

Experiment Study on Unsteady Frosting of Cryogenic Vertical Plate Surface under Natural Convection Conditions

2012 ◽  
Vol 516-517 ◽  
pp. 24-29 ◽  
Author(s):  
Shu Ping Chen ◽  
Fu Shou Xie ◽  
Shu Ting Yao ◽  
Hong Yin Han ◽  
Zhi Xin Chang
Keyword(s):  
Natural Convection ◽  
Vertical Plate ◽  
Test Bench ◽  
Tangential Direction ◽  
Flow State ◽  
Plate Surface ◽  
Moist Air ◽  
Working Medium ◽  
Frost Layer Thickness ◽  
Frost Layer

A frosting test bench was designed, and unsteady frosting on vertical plate surface was dynamically described with liquid nitrogen as working medium under natural convection conditions. The variation of frost thickness was analyzed, and the flow state of moist air and temperature distribution near the vertical plate were described. The experimental results show the unsteady frosting of vertical plate surface under natural convection and cryogenic condition actually includes several steps: formation of frost crystals, growth of frost crystals and growth of frost layer. The initial frosting rate is large, but the rate decreases as time goes on until the frost layer thickness is unchanged. Moist air conducts a top-down flow near the vertical plate, and the rest of moist air flows into the main flow. The temperature of moist air decreased systematically along the tangential direction of vertical plate from top to bottom and along the normal direction of vertical plate from far to vertical plate surface.

scholarly journals Frost layer thickness measurement and calculation: A short review

2017 ◽  
Vol 142 ◽  
pp. 3812-3819 ◽  
Author(s):  
Song Mengjie ◽  
Dang Chaobin ◽  
Liu Shengchun ◽  
Sun Zhili ◽  
Mao Ning
Keyword(s):  
Layer Thickness ◽  
Short Review ◽  
Thickness Measurement ◽  
Frost Layer Thickness ◽  
Frost Layer

Enhancement of natural-convection boiling heat transfer by using frost layer

2019 ◽  
Vol 2019.29 (0) ◽  
pp. J404
Author(s):  
Takayuki MOROKUMA ◽  
Hidetoshi OHKUBO ◽  
Yoshio UTAKA ◽  
Toshiki HIROTANI ◽  
Taiyo SUGINO
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Boiling Heat Transfer ◽  
Frost Layer

Analysis of entropy generation and natural convection in an inclined partially porous layered cavity filled with a nanofluid

2017 ◽  
Vol 95 (3) ◽  
pp. 238-252 ◽  
Author(s):  
T. Armaghani ◽  
Muneer A. Ismael ◽  
Ali J. Chamkha
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Layer Thickness ◽  
Porous Layer ◽  
Entropy Generation ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Numerical Study ◽  
Nanoparticle Volume Fraction ◽  
Thermodynamic Irreversibility

The present numerical study investigates the analysis of thermodynamic irreversibility generation and the natural convection in inclined partially porous layered cavity filled with a Cu–water nanofluid. The finite difference method with up-wind scheme is used to solve the governing equations. The study is achieved by examining the effects of nanoparticle volume fraction, inclination angle, and the porous layer thickness. Besides, the computations are achieved within the laminar range of the Rayleigh number. The results show that at Ra = 104, a reduction of total entropy generation is recorded with increasing nanoparticle volume fraction when the porous layer thickness is greater than 0.2. Moreover, when Ra is less than 105, the nanoparticle volume fraction increases the heat transfer irreversibility, and improves the overall thermal performance. It is found also that for a low Rayleigh number, the largest porous layer thickness and the highest cavity orientation improve the thermal performance. On the contrary, at high Rayleigh numbers, these parameter ranges give the worst thermal performance.

Estimation of a Nusselt Correlations for Numerical Prediction of Frost Thickness Growth over a Cold Cylinder

2014 ◽  
Vol 875-877 ◽  
pp. 771-775
Author(s):  
Raquel da Cunha Ribeiro da Silva ◽  
Carlos T. Salinas ◽  
Kamal A.R. Ismail
Keyword(s):  
Numerical Solution ◽  
Experimental Studies ◽  
Optimization Method ◽  
Cylinder Surface ◽  
Frost Formation ◽  
Modeling Process ◽  
Numerical Predictions ◽  
New Correlation ◽  
Frost Layer Thickness ◽  
Frost Layer

This paper evaluates numerically some of the parameters involved in modeling the process of frost formation over a cold cylinder surface subject to the flow of humid air. Was utilized for numerical predictions the empirical Nusselt correlation from the literature, obtained in experimental studies on frost formation phenomena of frost grow over a cold cylinder surface. To predict frosting process a numerical solution was utilized, and a new correlation for Nusselt number based on the experimental correlation of Kim was estimated. For the new Nusselt correlation an optimization method that adjusts the numerical solution of modeling the frost formation process with experimental results of the frost layer thickness was used. The calculation procedure allows the estimation of the parameter K of equation. The modeling process was validated by comparison with available experimental data.

Effect of Cooling Surface Temperature on Frosting Phenomena Under Natural Convection

2007 ◽  
Author(s):  
Hidetoshi Ohkubo ◽  
Masahiro Matsumura ◽  
Masayuki Ueno ◽  
Koji Yamashita
Keyword(s):  
Mass Transfer ◽  
Water Vapor ◽  
Natural Convection ◽  
Surface Temperature ◽  
Air Conditioning ◽  
Absolute Humidity ◽  
Solidification Temperature ◽  
Transfer Characteristics ◽  
Cooling Surface ◽  
Frost Layer

Frosting is a phenomenon that takes place on a surface that has been cooled to a temperature below solidification temperature of water vapor in air. Frosting occurs by either sublimation or by solidification of condensate on the surface, and frost layer is a porous layer of ice and air. Advances in air-conditioning and refrigeration technology have brought about frosting issues in several fields as well as a broadening of the temperature range in which frosting occurs. In the present work, we investigated mass transfer characteristics in frosting phenomenon under natural convection condition in order to establish mass transfer in the process of frosting; the parameter of study was the cooling surface temperature, which was changed between −10 to −114°C. The effects of the cooling surface temperature and absolute humidity on the mass transfer characteristics in the frosting process were clarified.

Onset of natural convection in layered aquifers

2015 ◽  
Vol 767 ◽  
pp. 763-781 ◽  
Author(s):  
Don Daniel ◽  
Amir Riaz ◽  
Hamdi A. Tchelepi
Keyword(s):  
Boundary Layer ◽  
Natural Convection ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Onset Of Convection ◽  
Transient Nature ◽  
Gradient Of Permeability ◽  
Permeability Variation ◽  
Vorticity Production ◽  
The Stability

AbstractThe stability of gravitationally unstable, transient boundary layers in heterogeneous saline aquifers is examined with respect to the onset of natural convection. Permeability is assumed to vary periodically across the thickness of the aquifer. We study the interaction between permeability variation and concentration perturbations within the boundary layer. We observe that the instability decreases with an increase in the permeability variance if the boundary layer thickness is large compared with the permeability wavelength. On the other hand, when the boundary layer thickness is smaller than the permeability wavelength, the behaviour of instability as a function of variance depends on the phase of permeability variation. Such behaviours are shown to result from the interaction of two modes of vorticity production related to the coupling of concentration and velocity perturbations with the magnitude and gradient of permeability variation, respectively. We show that these two modes of vorticity production, when coupled with the transient nature of the boundary layer, determine the evolutionary paths followed by the most amplified perturbations that trigger the onset of convection. When the permeability variance is large, we find that small changes in the permeability field can lead to large changes in the onset times for convection.

Mixing in internally heated natural convection flow and scaling for a quasi-steady boundary layer

2014 ◽  
Vol 763 ◽  
pp. 352-368 ◽  
Author(s):  
Tae Hattori ◽  
John C. Patterson ◽  
Chengwang Lei
Keyword(s):  
Boundary Layer ◽  
Natural Convection ◽  
Theoretical Analysis ◽  
Layer Thickness ◽  
Mixed Layer ◽  
Water Body ◽  
Temperature Stratification ◽  
Convection Flow ◽  
Natural Convection Flow ◽  
Penetration Length

AbstractThis study considers the natural convection flow in a water body subjected to heating by solar radiation. The investigation into this type of natural convection flow has been motivated by the fact that it is known to play a crucial role in the daytime heat and mass transfer in shallow regions of natural water reservoirs and lakes, with a resultant impact on biological activity. An analytical solution for temperature in such an internally heated system shows that the temperature stratification consists of an upper stable stratification and a lower unstable stratification. One of the important consequences of such a nonlinear temperature stratification is the limitation of the mixing driven by rising thermal plumes with the penetration length scale of the plumes determining the lower mixed layer thickness. A theoretical analysis conducted in the present study suggests that in relatively deep waters, the lower mixed layer thickness is equal to the attenuation length of the radiation, which has important implications for water quality, including the transport of pollutants and nutrients in the water body. Scalings are also obtained for the quasi-steady boundary layer. The theoretical analysis is validated against numerical simulations.

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