Transient Film Boiling of Water on a Horizontal Wire

1968 ◽  
Vol 90 (4) ◽  
pp. 476-481 ◽  
Author(s):  
D. R. Pitts ◽  
H. H. Yen ◽  
T. W. Jackson
Keyword(s):  
Heat Transfer ◽  
Growth Rate ◽  
High Speed ◽  
Analytical Investigation ◽  
Film Boiling ◽  
Growth Time ◽  
Transfer Rates ◽  
Vapor Growth ◽  
Large Step ◽  
Vapor Formation

This paper reports an experimental and analytical investigation of transient film boiling of water from a horizontal submerged platinum wire following a large step change in wire temperature. Experimental vapor growth rate data were obtained from high-speed motion pictures with pool temperatures very close to saturation and wire temperatures ranging from 1245 to 1739 deg F. An analytical solution for vapor growth rate which assumes the primary mode of heat transfer within the vapor to be conduction is presented. Heat transfer rates based on the characteristic vapor growth time were calculated from measured vapor formation data.

Paper 8: Heat Transfer from a Wire in the Critical Region

1967 ◽  
Vol 182 (9) ◽  
pp. 52-57 ◽  
Author(s):  
U. Grigull ◽  
E. Abadzic
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Natural Convection ◽  
Critical Point ◽  
Critical Region ◽  
High Speed ◽  
Nucleate Boiling ◽  
Flow Patterns ◽  
Film Boiling ◽  
High Speed Camera

This work deals with experimental results on boiling from a horizontal platinum wire, 0·1 mm in diameter, submerged in saturated liquids as carbon dioxide (CO2) and Freon 13 (CF3Cl) in the critical region. Three discrete regimes without steady transition could be observed: natural convection, nucleate boiling, and film boiling. Near the critical point particular flow patterns appeared in the rising vapour in film boiling: regular bubbles, vapour columns, and vapour hazes with garland-like boundaries. These flow patterns could be simulated in model experiments with liquids and were also photographed with a high-speed camera.

Heat Transfer and Pumping on a Rotating Disk With Freely Induced and Forced Cooling

1970 ◽  
Vol 92 (3) ◽  
pp. 342-348 ◽  
Author(s):  
Darryl E. Metzger
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Rotating Disk ◽  
Turbine Rotor ◽  
Experimental Facility ◽  
Heat Transfer Characteristics ◽  
Flow Rates ◽  
Transfer Rates ◽  
Small Flow ◽  
Forced Cooling

An experimental study of the heat transfer characteristics of flows between a high speed rotating disk and a parallel stationary shroud is presented. Flow and disk heat transfer rates have been determined for various combinations and rates of freely induced and forced flows supplied at both the hub and rim of the disk. The study models a practically important class of turbine rotor cooling problems where small flow rates similar in magnitude to the disk pumping flows are of interest. The experimental facility and procedures are described in detail. They have been designed to facilitate rapid and economical acquisition of rotor cooling characteristics in situations where the particular rotor-shroud geometry makes existing correlations inadequate.

Destabilization of Film Boiling Due to Arrival of a Pressure Shock—Part I: Experimental

1981 ◽  
Vol 103 (3) ◽  
pp. 459-464 ◽  
Author(s):  
A. Inoue ◽  
S. G. Bankoff
Keyword(s):  
Heat Transfer ◽  
Horizontal Tube ◽  
Nucleate Boiling ◽  
Transient Heat Transfer ◽  
Film Boiling ◽  
Vapor Film ◽  
Pressure Shock ◽  
Transfer Rates ◽  
Vapor Explosions ◽  
Film Collapse

Transient heat transfer from an electrically-heated 3 mm o.d. horizontal tube, initially in subcooled film boiling, was measured immediately after passage of a shock wave of 1–5 × 105 N/m2 over-pressure. The fluids tested were Freon-113 and 95 percent ethanol-5 percent water at initially 0.5–2 × 105 N/m2 at 22–24° C. Transient heat transfer rates, averaged over 0.5–1 ms after vapor film collapse, ranged up to 20 times the steady-state value. The maximum transient flux occurred at supercritical contact temperatures, with frequently a minimum in the range of contact temperatures between the homogeneous nucleation and the critical temperature. Photography at 5000 frames/s showed apparently complete vapor film collapse within one or two frames, followed by re-establishment of film boiling in ∼1 ms, and eventually nucleate boiling in ∼100 ms. The surface temperature which gave the highest peak transient flux shifted appreciably with increasing shock pressure, which indicates some compressibility even after “contact” was made. Implications for vapor explosions are discussed.

Steady and Transient Analyses of Natural Convection in a Horizontal Porous Annulus With the Galerkin Method

1987 ◽  
Vol 109 (4) ◽  
pp. 919-927 ◽  
Author(s):  
Y. F. Rao ◽  
K. Fukuda ◽  
S. Hasegawa
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Galerkin Method ◽  
Initial Conditions ◽  
Analytical Investigation ◽  
Flow Structures ◽  
Transfer Rates ◽  
Inner Surface ◽  
The Galerkin Method ◽  
Branching Solutions

Steady and transient analytical investigation with the Galerkin method has been performed on natural convection in a horizontal porous annulus heated from the inner surface. Three families of convergent solutions, appearing one after another with increasing RaDa numbers, were obtained corresponding to different initial conditions. Despite the fact that the flow structures of two branching solutions are quite different, there exists a critcal RaDa number at which their overall heat transfer rates have the same value. The bifurcation point was determined numerically, which coincided very well with that from experimental observation. The solutions in which higher wavenumber modes are dominant agree better with experimental data of overall heat transfer.

Production of Carbon Dioxide Snow by Flash-Atomization for Material Cleaning Process

2012 ◽  
Vol 569 ◽  
pp. 282-285 ◽  
Author(s):  
Yi Jun Shen ◽  
Tien Chu Lin ◽  
Muh Ron Wang
Keyword(s):  
Carbon Dioxide ◽  
Growth Rate ◽  
High Speed ◽  
Spray Angle ◽  
Growth Time ◽  
Cleaning Process ◽  
Liquid Carbon ◽  
Liquid Carbon Dioxide ◽  
Liquid Co2 ◽  
Mass Flowrate

This paper investigates the production of CO2 snow by flash-atomization of liquid carbon dioxide for material cleaning process. The evolution of flash-atomization processes was recorded by means of high-speed shadowgraph. Results shows that the degree of superheat condition of liquid CO2 greatly influence the atomization modes, bobbles growth rate and concentration, and thus result in difference spray angle, spray pattern, and the structure of liquid jet which is suitable for different material cleaning applications. It is found that the spray angle first slowly increases with increase in the degree of superheat (ΔT) under external flash atomization processes. It is increased drastically as the spray transform from external-flashing to internal-flashing mode. Finally the spray angle is decreased again because of the decrease of mass flowrate due to the internal flashing processes . Moreover, the spray angle is increased as the length-to-diameter ratio (L/D) is increased. This is due to the higher bobble growth rate in terms of different pressure distribution and bobble growth time. It is also found that the external-flashing disappears at higher L/D because of the heat transfer to the liquid carbon dioxide. It is concluded that the superheated condition is useful in the control of the spray angle for material cleaning processes.

Vaporization of Drops of a Denser, Volatile Liquid Dropped Onto a Surface of Another Liquid

1985 ◽  
Vol 107 (2) ◽  
pp. 384-391 ◽  
Author(s):  
T. Nosoko ◽  
Y. H. Mori
Keyword(s):  
Heat Transfer ◽  
Ethylene Glycol ◽  
Direct Contact ◽  
High Speed ◽  
Surface Film ◽  
Film Boiling ◽  
Heat Transfer Characteristics ◽  
Operational Conditions ◽  
Volatile Liquid ◽  
The Common

Experiments were performed with single R 113 (C2Cl3F3) drops dropped onto the surface of immiscible ethylene glycol or water, or miscible n-tridecane in contact with the common vapors of the two liquids. Five different vaporization modes were distinguished in the immiscible systems: film boiling on the surface, film boiling in the bulk (only in R 113/ethylene glycol system), and three other modes in which the two liquids make direct contact. The latter three were replaced, in the miscible system, by an immediate dissolving of drops into the medium. The details of dynamic process in each mode have been revealed with the aid of high-speed cinephotography. Operational conditions required for the occurrence of respective modes and heat transfer characteristics in those modes have also been discussed.

Whole Field Measurements to Understand the Role of Varying Depths of Nucleation Site on Vapor Bubble Dynamics and Heat Transfer Rates

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Surya Narayan L ◽  
Pasi Vijaykumar ◽  
Atul Srivastava
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Bubble Formation ◽  
Nucleation Site ◽  
Heat Transfer Process ◽  
Cavity Depth ◽  
Bulk Fluid ◽  
Transfer Rates ◽  
Transfer Processes

Abstract This work studies the possible effects of varying depths of cavity on bubbling features and the associated heat transfer rates in nucleate pool boiling regime. A single vapor bubble has been generated on a substrate with a cylindrical cavity at its center that acts as the nucleation site. Experiments have been conducted for three cavity depths (250, 500, and 1000 μm), while keeping its throat diameter constant at 200 μm. With the bulk fluid maintained under saturated conditions, for each cavity depth, surface superheat level has been varied in the range of ΔTsuperheat = 8, 10 and 12 °C. A gradient-based visualization technique, coupled with a high speed camera, has been employed to simultaneously map the changes in thermal gradients during the formation of the vapor bubble as well as bubble dynamic parameters. The image sequence obtained has been qualitatively and quantitatively analyzed to elucidate the dependence of bubbling features and various heat transfer processes on cavity depth. With an increase in the depth of cavity, the net effect of reduction in the available thermal energy due to the increased convection effects and significant depletion of superheated layer are identified as the dominant heat transfer processes that influence the bubbling features. Furthermore, based on the statistics of bubble departure characteristics, the cavity with higher depth (1000 μm) showed a much stable bubble formation with minimal variation in the bubble departure frequency as compared to the bubbling features from a cavity with smaller depth (250 μm). Evaporative heat transfer process has been identified as the primary cause for increased inconsistency of bubbling features at high superheat conditions for experiments performed for low cavity depths.

scholarly journals CHF Phenomena by Photographic Study of Boiling Behavior due to Transient Heat Inputs

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Jongdoc Park ◽  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Speed ◽  
Video Camera ◽  
Nucleate Boiling ◽  
Horizontal Cylinder ◽  
Heat Transfer Process ◽  
Film Boiling ◽  
Bubble Behavior ◽  
Camera System

The transient boiling heat transfer characteristics in a pool of water and highly wetting liquids such as ethanol and FC-72 due to an exponentially increasing heat input of various rates were investigated using the 1.0 mm diameter experimental heater shaped in a horizontal cylinder for wide ranges of pressure and subcooling. The trend of critical heat flux (CHF) values in relation to the periods was divided into three groups. The CHF belonging to the 1st group with a longer period occurs with a fully developed nucleate boiling (FDNB) heat transfer process. For the 2nd group with shorter periods, the direct transition to film boiling from non boiling occurs as an explosive boiling. The direct boiling transition at the CHF from non-boiling regime to film boiling occurred without a heat flux increase. It was confirmed that the initial boiling behavior is significantly affected by the property and the wettability of the liquid. The photographic observations on the vapor bubble behavior during transitions to film boiling were performed using a high-speed video camera system.

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