Wall heat transfer in the inverted annular film boiling regime

2020 ◽  
Vol 363 ◽  
pp. 110660 ◽  
Author(s):  
Qingqing Liu ◽  
Xiaodong Sun
Keyword(s):  
Heat Transfer ◽  
Film Boiling ◽  
Wall Heat Transfer ◽  
Boiling Regime ◽  
Inverted Annular Film Boiling ◽  
Annular Film

scholarly journals HEAT TRANSFER MODELLING OF TWO-PHASE FLOW IN ISOLATED CHANNEL

2018 ◽  
Vol 14 ◽  
pp. 49
Author(s):  
Daniel Vlček ◽  
Vojtěch Caha ◽  
Martin Ševeček
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
Boiling Crisis ◽  
Simple Geometry ◽  
Inverted Annular Film Boiling ◽  
Transfer Modelling ◽  
Annular Film

This paper deals with Post-CHF (critical heat flux) heat transfer with the focus on different regimes of film boiling. The new thermal-hydraulic code TUBE 2.0 is presented. This code uses the equation of energy conservation and predefined correlations to establish wall temperature, the departure of nucleate boiling ratio as well as other parameters of cooling in a simple geometry - an isolated channel. With experimental data of inverted annular film boiling from Stewart, the best-performing correlation for calculation of post-CHF heat transfer in the channel was determined. Finally, the new presented code TUBE 2.0 and subchannel code SUBCAL owned by Chemcomex a.s. are compared using results of various experiments conducted by Becker. Data from Stewart could not be used because of inability to predict the onset of boiling crisis with several correlations.

Rewetting of Vertical Hot Surface in a Centrally Heated Annulus and a 6×6 Rod Bundle Geometry During Reflood Phase

2006 ◽  
Author(s):  
Seok Cho ◽  
Sang-Ki Moon ◽  
Ki-Yong Choi ◽  
Se-Young Chun ◽  
Moon-Ki Chung ◽  
...  
Keyword(s):  
Flow Regime ◽  
Flow Channel ◽  
The Other ◽  
Film Boiling ◽  
Rod Bundle ◽  
Inverted Annular Film Boiling ◽  
Group A ◽  
Annular Film ◽  
Hot Surface ◽  
Liquid Wall

A series of bottom reflood tests were carried out to investigate thermal-hydraulic characteristics during the reflood phase. This paper includes descriptions of three related groups of reflood tests categorized by the geometry of a flow channel and an electric power shape of heater rods. A centrally-heated annular geometry with an outer-visualizing tube was adopted for the first two groups of tests (group-A and -B), and a 6×6 rod bundle geometry for the other group of tests (group-C). The ranges of experimental parameters are 2∼8 cm/s of flooding velocity, 20∼80 °C of inlet subcooling temperature, and 500∼700 °C of initial wall temperature. In the single rod annular flow channel reflood test, quench front behavior can be easily observed through the visualizing window and a dominant flow regime near downstream of quench front is inverted annular film boiling regardless of the flooding velocity. For the case of the 6×6 rod bundle experiments, on the other hand, the dominant flow regime is dispersed flow film boiling (DFFB), and therefore the thermal hydraulic behavior becomes more complicated and chaotic due to the interaction between liquid phase such as droplet and liquid film and vapor phase generated from liquid-wall heat transfer.

Experimental Investigation of Inverted Annular Film Boiling in a Rod Bundle during Reflood Transient

2015 ◽  
Vol 190 (3) ◽  
pp. 301-312 ◽  
Author(s):  
L. Mohanta ◽  
M. P. Riley ◽  
F. B. Cheung ◽  
S. M. Bajorek ◽  
J. M. Kelly ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Film Boiling ◽  
Rod Bundle ◽  
Inverted Annular Film Boiling ◽  
Annular Film

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2001 ◽  
Vol 1 (1) ◽  
pp. 32
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

Experimental Investigation of Influence of Dissolved Salts and Surfactant on Heat Transfer in Atomized Spray Quenching of Metal

2010 ◽  
Author(s):  
Umair Alam ◽  
Khalid Abd alrahman ◽  
Eckehard Specht
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Temperature Measurement ◽  
Pure Water ◽  
The Other ◽  
Film Boiling ◽  
Wetting Front ◽  
Maximum Heat ◽  
Boiling Regime ◽  
Front Position

Spray quenching is widely used in industrial applications. In atomized spray quenching (ASQ), water and air are supplied to the nozzle at a certain flow rate and pressure to produce a full cone spray consisting of discrete droplets. Impingement density of spray i.e. coolant mass flow per unit area per second is considered to be the most influential parameter for heat transfer. Impingement density varies with radius and so as the heat flux. Water quality is altered by adding five different salts i.e. NaCl, Na2SO4, NaHCO3, Na2CO3, and MgSO4 in de-ionized water with various concentrations. On the other hand, a surfactant Ethoxylated ester, which is commonly added in cooling water in cast houses of metals, is added to pure water in different concentrations i.e 50, 100, 200 and 500ppm. A circular disc made of Nickel of thickness 2mm is heated to 600°C and sprayed on one side by atomized spray and the temperature distribution with respect to time is measured using Infrared camera on the other side of the disc. By this IR thermography, transient temperature measurement can be done within the window of 320×80 pixels with a minimum pixel real distance of 1mm on the sheet surface. Frequency of measurement is 150Hz. Since the temperature measurement and cooling sides are opposite at 2mm thickness apart, inverse heat conduction problem is solved by applying finite element method for calculating temperature and heat flux on the quenched side of metal sheet with respect to space and time. It has been observed that increasing the concentration of salts increase the leidenfrost point and shortens the film boiling regime. While addition of surfactants decrease the leidenfrost point and prolong the film boiling regime. Maximum heat flux position is considered as the wetting front position. There is an abrupt variation of heat flux at wetting front position due to the change of boiling phenomenon. Wetting front velocity has been compared for salt solutions, surfactant and de-ionized or pure water.

scholarly journals ELETRIC FIELD ENHANCEMENT AND DETERIORATION OF BOILING HEAT TRANSFER AND CRITICAL HEAT FLUX IN DIELECTRIC FLUIDS

2002 ◽  
Vol 1 (1) ◽  
Author(s):  
P. M. Carrica ◽  
V. Masson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Electric Fields ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Film Boiling ◽  
Two Phase ◽  
Boiling Regime ◽  
Dielectric Fluids

We present the results of an experimental study of the effects of externally imposed electric fields on boiling heat transfer and critical heat flux (CHF) in dielectric fluids. The study comprises the analysis of geometries that, under the effects of electric fields, cause the bubbles either to be pushed toward the heater or away from it. A local phase detection probe was used to measure the void fraction and the interfacial impact rate near the heater. It was found that the critical heat flux can be either augmented or reduced with the application of an electric field, depending on the direction of . In addition, the heat transfer can be slightly enhanced or degraded depending on the heat flux. The study of the two-phase flow in nucleate boiling, only for the case of favorable dielectrophoretic forces, reveals that the application of an electric field reduces the bubble detection time and increases the detachment frequency. It also shows that the two-phase flow characteristics of the second film boiling regime resemble more a nucleate boiling regime than a film boiling regime.

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