Pool Boiling Mechanism of HFE-7100

Volume 4 ◽  
2004 ◽  
Author(s):  
Saeed Moghaddam ◽  
Kenneth T. Kiger
Keyword(s):  
Experimental Data ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Transient Heat Conduction ◽  
Constant Heat Flux ◽  
Current Data ◽  
Heated Wall ◽  
Superheated Liquid ◽  
Fundamental Parameters ◽  
Boiling Mechanism

To study the pool boiling mechanism of HFE-7100, a micro array of forty-four Resistance Temperature Detectors (RTD’s) covering a 1mm in diameter circular area was microfabricated around a single cylindrical cavity on a thin silicon membrane. Constant heat flux was applied to the surface using a thin film heater microfabricated on the backside of the membrane. Images of the bubbles and the temperature of the heated wall underneath and around the bubble were recorded during the pool boiling process. Using the images of the bubbles, their volume, velocity, and frequency of departure was calculated. The acquired experimental data provided the fundamental parameters required for evaluating several boiling models whose development was based on the bubble diameter, frequency of departure, and velocity. For the conditions of this experiment, it seems that the current data can be best explained by transient heat conduction to the liquid adjacent to the heated wall and subsequent pumping of the superheated liquid by the bubbles. However, more experimental data in different conditions are required before solid conclusions can be reached. Details of the experimental results, models, and comparison between the two are presented in this paper.

STUDY ON SUPERHEATED LIQUID LAYER IN POOL BOILING

2018 ◽  
Author(s):  
Mao Takeyama ◽  
Tomoaki Kunugi ◽  
Takehiko Yokomine ◽  
Zensaku Kawara
Keyword(s):  
Liquid Layer ◽  
Pool Boiling ◽  
Superheated Liquid

CH4 Direct Reduction of In-Flight Fe3O4 Concentrate Particles

2018 ◽  
Vol 14 (1) ◽  
Author(s):  
Bahador Abolpour ◽  
M. Mehdi Afsahi ◽  
Ataallah Soltani Goharrizi
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Fine Particles ◽  
Direct Reduction ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Dynamic Motion ◽  
Magnetite Ore ◽  
Model Predictions ◽  
Kinetics Of

Abstract In this study, reduction of in-flight fine particles of magnetite ore concentrate by methane at a constant heat flux has been investigated both experimentally and numerically. A 3D turbulent mathematical model was developed to simulate the dynamic motion of these particles in a methane content reactor and experiments were conducted to evaluate the model. The kinetics of the reaction were obtained using an optimizing method as: [-Ln(1-X)]1/2.91 = 1.02 × 10−2dP−2.07CCH40.16exp(−1.78 × 105/RT)t. The model predictions were compared with the experimental data and the data had an excellent agreement.

Forced Convective Boiling of Refrigerant HCFC123 in a Mini-Tube

2010 ◽  
Author(s):  
Koichi Araga ◽  
Keisuke Okamoto ◽  
Keiji Murata
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flux ◽  
Pool Boiling ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Convective Boiling ◽  
Frictional Pressure Drop ◽  
Heat Transfer Coefficients

This paper presents an experimental investigation of the forced convective boiling of refrigerant HCFC123 in a mini-tube. The inner diameters of the test tubes, D, were 0.51 mm and 0.30 mm. First, two-phase frictional pressure drops were measured under adiabatic conditions and compared with the correlations for conventional tubes. The frictional pressure drop data were lower than the correlation for conventional tubes. However, the data were qualitatively in accord with those for conventional tubes and were correlated in the form φL2−1/Xtt. Next, heat transfer coefficients were measured under the conditions of constant heat flux and compared with those for conventional tubes and for pool boiling. The heat transfer characteristics for mini-tubes were different from those for conventional tubes and quite complicated. The heat transfer coefficients for D = 0.51 mm increased with heat flux but were almost independent of mass flux. Although the heat transfer coefficients were higher than those for a conventional tube with D = 10.3 mm and for pool boiling in the low quality region, they decreased gradually with increasing quality. The heat transfer coefficients for D = 0.30 mm were higher than those for D = 0.51 mm and were almost independent of both mass flux and heat flux.

Numerical Simulation and Experimental Validation of the Dynamics of a Single Bubble During Pool Boiling Under Constant and Time-Varying Reduced Gravity Conditions

2003 ◽  
Author(s):  
H. S. Abarajith ◽  
D. M. Qiu ◽  
V. K. Dhir
Keyword(s):  
Numerical Simulation ◽  
Heated Surface ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Growth Period ◽  
Single Bubble ◽  
Time Varying ◽  
Reduced Gravity ◽  
System Pressure ◽  
Vapor Liquid

The numerical simulation and experimental validations of the growth and departure of a single bubble on a horizontal heated surface during pool boiling under reduced gravity conditions have been performed here. A finite difference scheme is used to solve the equations governing mass, momentum and energy in the vapor liquid phases. The vapor-liquid interface is captured by level set method, which is modified to include the influence of phase change at the liquid-vapor interface. The effects of reduced gravity conditions, wall superheat and liquid subcooling and system pressure on the bubble diameter and growth period have been studied. The simulations are also carried out under both constant and time-varying gravity conditions to benchmark the solution with the actual experimental conditions that existed during the parabolic flights of KC-135 aircraft. In the experiments, a single vapor bubble was produced on an artificial cavity, 10 μm in diameter microfabricated on the polished silicon wafer, the wafer was heated electrically from the back with miniature strain gage type heating elements in order to control the nucleation superheat. The bubble growth period and the bubble diameter predicted from the numerical simulations have been found to compare well with the data from experiments.

scholarly journals Lattice Boltzmann Simulation of Nucleate Pool Boiling in Saturated Liquid

2011 ◽  
Vol 9 (5) ◽  
pp. 1347-1361 ◽  
Author(s):  
Yoshito Tanaka ◽  
Masato Yoshino ◽  
Tetsuo Hirata
Keyword(s):  
Lattice Boltzmann ◽  
Solid Wall ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Immiscible Fluids ◽  
Nucleate Pool Boiling ◽  
Two Phase ◽  
Boiling Process

AbstractA thermal lattice Boltzmann method (LBM) for two-phase fluid flows in nucleate pool boiling process is proposed. In the present method, a new function for heat transfer is introduced to the isothermal LBM for two-phase immiscible fluids with large density differences. The calculated temperature is substituted into the pressure tensor, which is used for the calculation of an order parameter representing two phases so that bubbles can be formed by nucleate boiling. By using this method, two-dimensional simulations of nucleate pool boiling by a heat source on a solid wall are carried out with the boundary condition for a constant heat flux. The flow characteristics and temperature distribution in the nucleate pool boiling process are obtained. It is seen that a bubble nucleation is formed at first and then the bubble grows and leaves the wall, finally going up with deformation by the buoyant effect. In addition, the effects of the gravity and the surface wettability on the bubble diameter at departure are numerically investigated. The calculated results are in qualitative agreement with other theoretical predictions with available experimental data.

A FRACTAL ANALYSIS OF SUBCOOLED NUCLEATE POOL BOILING

Fractals ◽  
2008 ◽  
Vol 16 (01) ◽  
pp. 1-9 ◽  
Author(s):  
BOQI XIAO ◽  
ZONGCHI WANG ◽  
BOMING YU
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Fractal Model ◽  
Nucleate Pool Boiling ◽  
Empirical Constant ◽  
Pool Boiling Heat Transfer ◽  
Model Predictions ◽  
Conventional Models

A fractal model for the subcooled nucleate pool boiling heat transfer is proposed in this paper. The analytical expressions for the subcooled nucleate pool boiling heat transfer are derived based on the fractal distribution of nucleation sites on boiling surfaces. The proposed fractal model for the subcooled nucleate pool boiling heat transfer is found to be a function of wall superheat, liquid subcooling, fractal dimension, the minimum and maximum active cavity size, the contact angle and physical properties of fluid. No additional/new empirical constant is introduced, and the proposed model contains less empirical constants than the conventional models. The model predictions are compared with the existing experimental data, and fair agreement between the model predictions and experimental data is found for different liquid subcoolings.

Channel Flow Along a Wavy Heated Wall

2011 ◽  
Author(s):  
S. Barboy ◽  
A. Rashkovan ◽  
G. Ziskind
Keyword(s):  
Vertical Channel ◽  
Turbulence Models ◽  
Momentum Equation ◽  
Constant Heat Flux ◽  
Heated Wall ◽  
Coupling Scheme ◽  
Wall Region ◽  
Pressure Gradients ◽  
Wavy Wall ◽  
Flow And Heat Transfer

The present study deals with the effects of wall geometry on the fluid flow and heat transfer in a vertical channel with a wavy wall. The waviness is characterized by wave amplitude and period. The wavy wall is heated with a constant heat flux. A detailed parametric investigation of the effect of waviness is performed for different flow conditions. An enhanced version of the turbulence models is required in order to resolve the near-wall region. In particular, a single wall law for the entire wall region can be achieved by blending linear (viscous) and logarithmic (turbulent) laws-of-the-wall. This approach allows the fully turbulent law to be easily modified and extended to take into account other effects such as pressure gradients or variable properties. Second order discretization scheme for momentum equation and turbulence scalar equations was used. SIMPLE pressure-velocity coupling scheme was employed. The results show how the flow and geometry parameters, namely, the Reynolds number and the amplitude and period of waviness, affect such features as the existence of flow separation, its location and size of the recirculation zones. These features determine the temperature distribution on the wavy wall. An attempt is done to assess the effect of flow and geometry parameters quantitatively.

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