A Numerical Simulation of Pool Boiling Using CAS Model

2003 ◽  
Author(s):  
Jing Yang ◽  
Liejin Guo ◽  
Ximin Zhang
Keyword(s):  
Heat Transfer ◽  
Cellular Automata ◽  
Pool Boiling ◽  
Empirical Correlations ◽  
Dynamic Interactions ◽  
Macroscopic System ◽  
Simpler Algorithm ◽  
Boiling Process ◽  
Basic Features ◽  
The Heat Transfer Coefficient

This paper presents a new numerical model, called the CAS model, for boiling heat transfer. The CAS model is based on the cellular automata technique that is integrated into the popular—SIMPLER algorithm for CFD problems. In the model, the cellular automata technique deals with the microscopic non-linear dynamic interactions of bubbles while the traditional CFD algorithm is used to determine macroscopic system parameters such as pressure and temperature. The popular SIMPLER algorithm is employed for the CFD treatment. The model is then employed to simulate a pool boiling process. The computational results show that the CAS model can reproduce most of the basic features of boiling and capture the fundamental characteristics of boiling phenomena. The heat transfer coefficient predicted by the CAS model is in excellent agreement with the experimental data and existing empirical correlations.

scholarly journals AN EXPERIMENTAL STUDY OF THE EFFECT OF SURFACTANT AND TI02 NANOPARTICLES ADDITIVES IN R141B ON THE NUCLEATE POOL BOILING PROCESS

2017 ◽  
Vol 39 (5) ◽  
pp. 37-40
Author(s):  
O. Khliyeva ◽  
T. Gordeychuk ◽  
A. Nikulin ◽  
N. Lukianov ◽  
V. Zhelezny
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Tio2 Nanoparticles ◽  
Pool Boiling ◽  
Nucleate Pool Boiling ◽  
Boiling Process ◽  
The Heat Transfer Coefficient

The results of experimental study of effect of TiO2 nanoparticles (0.1 % mass.) and surfactant Span80 (0.1 % mass.) additives in refrigerant R141b on the heat transfer coefficient of nucleate pool boiling process at three values of pressure 0.2, 0.3 and 0.4 MPa and range of heat flux from 5 to 70 kWm-2 are presented in paper.  

Convective Heat Transfer at Minimum Fluidization Velocity for Gas-Solid Fluidized Beds

1999 ◽  
Author(s):  
Kal R. Sharma
Keyword(s):  
Heat Transfer ◽  
Fluidized Beds ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Minimum Fluidization Velocity ◽  
Heat Transfer Coefficients ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Semi Empirical ◽  
The Heat Transfer Coefficient

Abstract Experimentally measured values for the minimum fluidization velocities and time averaged local surface heat transfer coefficients are provided for 16 different cases of fluidizing conditions for gas-solid dense fluidized beds. Semi-empirical Correlations for the minimum fluidization velocity and the heat transfer coefficient at minimum fluidization velocities are provided. The implications of the Peclet number dependence in terms of diffusion and convection is discussed.

A Method for Measuring Contact Angle and the Influence of Surface-Fluid Parameters on the Boiling Heat Transfer Performance

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Alex P. da Cunha ◽  
Taye S. Mogaji ◽  
Reinaldo R. de Souza ◽  
Elaine M. Cardoso
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Contact Angle ◽  
Heat Transfer Performance ◽  
Sessile Drop ◽  
Pool Boiling ◽  
Transfer Performance ◽  
Transfer Coefficients ◽  
Experimental Apparatus ◽  
Boiling Process

Abstract An experimental apparatus and a computational routine were developed and implemented in order to obtain the sessile drop images and the contact angle measurement for different fluids and surface conditions. Moreover, experimental results of heat transfer coefficients (HTCs) during pool boiling of de-ionized water (DI water), Al2O3-DI water- and Fe2O3-DI water-based nanofluids are presented in this paper. Based on these results, the effect of surface roughness and nanofluid concentration on the surface wettability, contact angle, and the heat transfer coefficient was analyzed. The experiments were performed on copper heating surfaces with different roughness values (corresponding to a smooth surface or a rough surface). The coated surfaces were produced by the nanofluid pool boiling process at two different volumetric concentrations. All surfaces were subjected to metallographic, wettability and roughness tests. For smooth surfaces, in comparison to DI water, heat transfer enhancement up to 60% is observed for both nanofluids at low concentrations. As the concentration of the nanofluid increases, the surface roughness increases and the contact angle decreases, characterizing a hydrophilic behavior. The analyses indicate that the boiling process of nanofluid leads to the deposition of a coating layer on the surface, which influences the heat transfer performance in two-phase systems.

On the Influence of the Thickness and Thermal Properties of Heating Walls on the Heat Transfer Coefficients in Nucleate Pool Boiling

1975 ◽  
Vol 97 (2) ◽  
pp. 173-178 ◽  
Author(s):  
U. Magrini ◽  
E. Nannei
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Atmospheric Pressure ◽  
Metal Layer ◽  
Pool Boiling ◽  
Transfer Coefficients ◽  
Heating Wall ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient ◽  
Zinc Nickel

An experimental investigation was conducted under conditions of saturated pool boiling of water at atmospheric pressure on thin, horizontal, cylindrical walls of different metals and thicknesses, electrically heated. The heating walls, ranging in thickness from 5 to 250 μm, were obtained by plating copper, silver, zinc, nickel, and tin on nonmetallic rods. Experiments showed that the heat transfer coefficient can be affected, in particular conditions, by the heating wall thickness. In particular, it resulted that the smaller the thermal conductivity of the metal layer, the higher the influence of the thickness. A semiempirical correlation of the form ΔT = (q/A)nf(κd, √κρc) suitable to correlate the experimental data within ±15 percent in the whole range of variables here investigated is proposed.

scholarly journals Heat transfer investigations in a liquid that is mixed by means of a multi-ribbon mixer

2021 ◽  
Vol 23 (2) ◽  
pp. 66-72
Author(s):  
Tomasz Borowski ◽  
Dawid Sołoducha ◽  
Daniel Musik ◽  
Krzysztof Wójcik ◽  
Mariusz Chyla ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Process ◽  
Heat Transfer Process ◽  
Operational Parameters ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Flowing Liquid ◽  
The Heat Transfer Coefficient

Abstract The objective of this paper is to present the investigations of the heat transfer process carried out by means of the multi-ribbon mixer. It is shown that the heat transfer process for the synergic effect of the mixing process and the flowing liquid through the mixer has significantly higher values of the heat transfer coefficients than the mixer with motionless impellers. The empirical correlations between the heat transfer coefficient and the operational parameters obtained in this work can provide guidance for the design and operation of an apparatus equipped with the multi-ribbon impeller. These empirical correlations can be used to predict the heat transfer coefficient for the multi-ribbon mixer.

Efficacy of Microscopic Interconnected Channels and Surfactants on Enhancing Pool Boiling Heat Transfer

2007 ◽  
Author(s):  
Rene Reyes Mazzoco
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Liquid Mixtures ◽  
Vapor Flow ◽  
Pool Boiling Heat Transfer ◽  
The Heat Transfer Coefficient

Nucleate pool boiling heat transfer increases with certain liquid mixtures and some coatings over the heater’s surface. The effects of these modifications are best measured by the relative values of the convective heat transfer coefficient that quantify the ability for transferring heat. The mechanisms that increase pool boiling heat transfer are reflected in the formation of smaller bubbles that escape away from the heater’s surface at a higher velocity, than those formed under not enhanced conditions. The bubble diameter depends on a chemical effect from the liquid composition acting at the bubble’s interface, and on the physical effect of the porous coverings to break the bubbles and to allow the resulting vapor flow. The reduction in bubble diameter in liquid mixtures comes from the action of intermolecular forces at the liquid-vapor interface similar to those associated to surfactants. Several studies have concentrated on increasing the heat transfer coefficient in pool using surfactants in concentrations close to the critical micelle concentration (cmc) of the surfactant in the liquid. The surfactants achieve the highest reduction of bubble diameter by accommodating the lowest surface of their molecules at the interface. However, the mixture of 16% ethanol in water also showed an increase in the convective heat transfer coefficient by producing the lowest size of bubbles from any other ethanol-water mixture. Surface tension and sessile drop contact angle for this mixture have a behavior similar to the cmc; therefore, the mixture effect on boiling is explained through the presence of ethanol-hydrated-states accommodated at the interface. Other liquid mixtures, containing propylene glycol, ethylene glycol, ethanol and water, with cmc behavior had been found through surface tension and sessile contact angle measurements, and showed that they increased the heat transfer coefficient. The mechanical effect that increases the heat transfer coefficient with porous coverings has been explained as the breaking of emerging bubbles at the heater’s surface and the proper handling of the resulting vapor flow away from the covering. Experiments with a mesh located at a distance half the bubble diameter, at a specific power supplied, released the bubbles from the heater before finishing its formation increasing their departure frequency. An array of layers of the same mesh produced and additional increment in the heat transfer coefficient if the array is accommodated to favor the gas flow out of the heater’s region.

Boiling Characteristics of Refrigerant Mixture Flow in Micro Scale Heat Exchangers Enhanced With Micro-Coils

2007 ◽  
Author(s):  
Yasir M. Shariff
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Performance ◽  
Convective Boiling ◽  
Mixture Flow ◽  
Refrigerant Mixture ◽  
Boiling Process ◽  
Wire Coil ◽  
Saturated Boiling ◽  
The Heat Transfer Coefficient

Flow in three horizontal channels for subcooled and saturated boiling characteristics are reported in this study. An experimental setup composed of heating elements provided heat flux variations on the channels. The heat transfer coefficient was found to be dependent on both the heat flux as well as mass flux levels. Results show that micro-coil inserts enhanced the heat transfer performance over that in smooth channels by 25% as compared to correlations for wire-coil inserts and 30% as compared to correlation for convective boiling process.

Experiment of Enhanced Pool Boiling Heat Transfer on Coupling Effects of Nano-Structure and Synergistic Micro-Channel

2019 ◽  
Author(s):  
Linsong Gao ◽  
Jizu Lv ◽  
Minli Bai ◽  
Chengzhi Hu ◽  
Liqun Du ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Capillary Flow ◽  
Pool Boiling ◽  
Micro Channel ◽  
Nano Structure ◽  
Pool Boiling Heat Transfer ◽  
Wall Superheat ◽  
Nucleation Sites ◽  
The Heat Transfer Coefficient

Abstract The manipulation of micro- or nano-structure is a promising method to improve pool boiling heat transfer performance. However, most studies just focus on the micro- or nano-structure without considering the combination micro- and nano-structure. In this paper, we fabricated synergistic microchannel, nano-structure, and micro-nano structure surface on the nickel by different technologies. Pool boiling of DI water under saturated condition was experimentally investigated. Result shows at the wall superheat of 18 K, the heat transfer coefficient of micro-nano structure, nano-structure and synergistic micro-channel surface are 16400, 13050, and 13400 W/m2 K higher 89%, 50%, and 54% than that of smooth surface, respectively. The improved heat transfer is attributed to active nucleation sites and capillary flow.

Sign in / Sign up

Export Citation Format

Share Document