Holographic Interferometric Study of Heat Transfer Associated With a Single Vapor Bubble Sliding Along a Downward-Facing Heater Surface

2003 ◽  
Author(s):  
Sathish Manickam ◽  
Vijay Dhir
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Volume Growth ◽  
High Speed Photography ◽  
Heater Surface ◽  
Growth Data ◽  
Volumetric Growth ◽  
Experimental Conditions ◽  
Fringe Patterns

Heat transfer associated with a single vapor bubble sliding along a downward-facing heater surface was studied experimentally to understand the mechanisms contributing to heat transfer enhancement. Heater surface was made of polished silicon wafer of length 185 mm and width 49.5 mm. Saturated and subcooled performance fluid PF 5060 at atmospheric pressure was used as the test liquid. The heater surface was at 75° inclination to the vertical for the experiments reported here. Single vapor bubbles were generated at an artificially formed cavity at the bottom end of the heater surface. Holographic interferometry was used to obtain the temperature profile around the bubble as it slides along the heater surface near the top end of the heater plate. From the fringe patterns, the temperature gradient around the bubble interface was measured and heat transfer into or out of the bubble was computed. In addition to these experiments, the volumetric growth of the vapor bubble as it slides along the heater surface was obtained using direct high-speed photography for the same experimental conditions. Heat transfer from the wall was estimated utilizing inputs from both interferometry studies as well as the volume growth data. Results are given for a range of liquid subcoolings and wall superheats, and are compared with previously published works.

Laser Interferometric Investigation of the Microlayer Evaporation Phenomenon

1975 ◽  
Vol 97 (1) ◽  
pp. 88-92 ◽  
Author(s):  
C. M. Voutsinos ◽  
R. L. Judd
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Laser Interferometry ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Heater Surface ◽  
Nucleate Boiling Heat Transfer ◽  
Interferometric Investigation ◽  
Microlayer Evaporation ◽  
Laser Interferometric

An experimental investigation is presented in which the growth and evaporation of the microlayer underlying a bubble forming on a glass heater surface has been studied using laser interferometry and high speed photography. The results presented for a single bubble indicate that the microlayer thickness is of the order of 5 μm. Subsequent analysis of these results confirms that the microlayer evaporation phenomenon is a significant heat transfer mechanism, representing approximately 25 percent of the total nucleate boiling heat transfer rate for the conditions investigated.

Effect of Pressure on Bubble Growth Within Liquid Droplets at the Superheat Limit

1982 ◽  
Vol 104 (4) ◽  
pp. 750-757 ◽  
Author(s):  
C. T. Avedisian
Keyword(s):  
Vapor Bubble ◽  
Bubble Growth ◽  
High Speed ◽  
Ambient Pressure ◽  
Organic Liquid ◽  
Liquid Droplets ◽  
Growth Data ◽  
Two Phase ◽  
Photographic Evidence ◽  
Good Agreement

A study of high-pressure bubble growth within liquid droplets heated to their limits of superheat is reported. Droplets of an organic liquid (n-octane) were heated in an immiscible nonvolatile field liquid (glycerine) until they began to boil. High-speed cine photography was used for recording the qualitative aspects of boiling intensity and for obtaining some basic bubble growth data which have not been previously reported. The intensity of droplet boiling was found to be strongly dependent on ambient pressure. At atmospheric pressure the droplets boiled in a comparatively violent manner. At higher pressures photographic evidence revealed a two-phase droplet configuration consisting of an expanding vapor bubble beneath which was suspended a pool of the vaporizing liquid. A qualitative theory for growth of the two-phase droplet was based on assuming that heat for vaporizing the volatile liquid was transferred across a thin thermal boundary layer surrounding the vapor bubble. Measured droplet radii were found to be in relatively good agreement with predicted radii.

Thermal Bubble Dynamics Under the Effect of Acoustic Vibration

2009 ◽  
Author(s):  
Xiaopeng Qu ◽  
Huihe Qiu
Keyword(s):  
Heat Transfer ◽  
Acoustic Field ◽  
Vapor Bubble ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Bubble Dynamics ◽  
Acoustic Vibration ◽  
Micro Electro Mechanical System ◽  
Mems Technology ◽  
Enhanced Boiling

The effect of acoustic field on the dynamics of micro thermal bubble is investigated in this paper. The micro thermal bubbles were generated by a micro heater which was fabricated by standard Micro-Electro-Mechanical-System (MEMS) technology and integrated into a mini chamber. The acoustic field formed in the mini chamber was generated by a piezoelectric plate which was adhered on the top side of the chamber’s wall. The dynamics and related heat transfer induced by the micro heater generated vapor bubble with and without the existing of acoustic field were characterized by a high speed photograph system and a micro temperature sensor. Through the experiments, it was found that in two different conditions, the temperature changing induced by the micro heater generated vapor bubble was significantly different. From the analysis of the high speed photograph results, the acoustic force induced micro thermal bubble movements, such as forcibly removing, collapsing and sweeping, were the main effects of acoustic enhanced boiling heat transfer. The experimental results and theoretical analysis were helpful for understanding of the mechanisms of acoustic enhanced boiling heat transfer and development of novel micro cooling devices.

Experiments and Modeling of a Liquid Droplet Transported by a Gas Stream Impinging on a Heated Surface: Evaporative Regime

2009 ◽  
Author(s):  
Ryan P. Anderson ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Single Phase ◽  
Heat Dissipation ◽  
Liquid Droplet ◽  
Heated Surface ◽  
Thin Liquid Film ◽  
Spray Cooling ◽  
High Speed Photography ◽  
Transfer Coefficients

Understanding the transport mechanisms involved in a single droplet impinging on a heated surface is imperative to the complete understanding of droplet and spray cooling. Evidence in the literature suggests that gas assisted sprays and mist flows are more efficient than sprays consisting only of liquid droplets. There has been few if any fundamental studies on gas-assisted droplets or spray cooling, in which a carrier gas or vapor stream propels the droplet to the target surface. The current work extends previous studies of a droplet impinging on a heated surface conducted by the same group from the single phase regime into the evaporative regime. For both regimes, understanding the transport physics due to the heat transfer from the heated surface to the droplet and then by convection and evaporation to the airflow is of fundamental importance. High-speed photography was used to capture the spreading process and yielded results that correlated well with previously published isothermal and single-phase results. The heat transfer was measured with a fitting approach by which the instantaneous temperature profile was matched to an analytic solution to determine the instantaneous value of the centerline heat transfer coefficient. A very large increase in the heat dissipation was observed when compared to previously published single-phase results. Heat transfer was optimized at Reynolds numbers that produced an optimally thin liquid film and high heat and mass transfer coefficients on the surface of the film.

Heat Transfer Controlled Collapse of a Cylindrical Vapor Bubble in a Vertical Isothermal Tube

1977 ◽  
Vol 99 (3) ◽  
pp. 392-397 ◽  
Author(s):  
D. R. Pitts ◽  
H. C. Hewitt ◽  
B. R. McCullough
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Experimental Results ◽  
Heat Transfer Analysis ◽  
Experimental Program ◽  
Bubble Collapse ◽  
Electric Heater ◽  
Vapor Bubbles ◽  
Experimental Apparatus

An experimental program was conducted to determine the collapse rate of slug-type vapor bubbles rising due to buoyancy through subcooled parent liquid in a vertical isothermal tube. The experimental apparatus included a vertical glass tube with an outer glass container providing a constant temperature water bath for the inner tube. The inner tube contained distilled, deaerated water, and water vapor bubbles were generated at the bottom of this tube with a pulsed electric heater. The parent liquid was uniformly subcooled with respect to the vapor bubble resulting in heat transfer controlled bubble collapse. Collapse rates and rise velocities were recorded by high-speed motion picture photography. Over a limited range of subcooling, the bubble collapse was well behaved, and a simple, quasi-steady boundary layer heat transfer analysis adapted from slug flow over a flat plate correlated the experimental results with a high degree of accuracy. Experimental results were obtained with tubes having inside diameters of 0.0127, 0.0218, and 0.0381 m and for a range of subcooling from 0.5 to 9.0 K.

Correlation Between Behaviors of the Vapor Bubbles and the Characteristics of the Heat Transfer Over the Heated Surface on MEB

2013 ◽  
Author(s):  
Takahito Saiki ◽  
Tomohiko Osawa ◽  
Ichiro Ueno ◽  
Chungpyo Hong
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Heated Surface ◽  
High Heat ◽  
Frame Rate ◽  
High Heat Flux ◽  
Heated Plate ◽  
Thin Wire ◽  
Vapor Bubbles

A series of experiments on subcooled pool boiling on a plate and on a thin wire are carried out. We focus on the condensation and collapse processes of vapor bubbles generated on the heated surface. We find the different patterns of the vapor bubble behaviors resulting in the emission of the microbubbles around the heated plate and the thin wire by employing high-speed observation with frame rate up to 150,000 frame per second (fps). From the experimental results, we provide a physical explanation on the correlation between the behavior of the vapor bubble at a high heat flux and the heat transfer characteristics. We propose this simple core-periphery model as a qualitative model for understanding the generation of the MEB.

scholarly journals Dynamics of dry spots in the liquid film moved by the gas flow in the mini-channel under intensive local heating

2018 ◽  
Vol 194 ◽  
pp. 01059
Author(s):  
Egor Tkachenko
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Gas Flow ◽  
Local Heating ◽  
Experimental Studies ◽  
Heater Surface ◽  
Two Phase ◽  
Heat Transfer Crisis ◽  
Typical Size ◽  
Dry Spot

Experimental studies of hydrodynamics and the heat transfer crisis were carried out for a two-phase stratified flow in a mini-channel with intensive heating from a heat source of 1x1 cm2. It has been established that as the heat flow increases, the total area of dry spots on the heater increases, but when a certain temperature of the heater surface reaches ≈100 °C, the area of dry spots begins to decrease. With the help of high-speed visualization (shooting speed 100000 frames per second), several stages of formation of a dry spot (a typical size of the order of 100 microns) were isolated. It was found that at a heat flux of 450 W/cm2 about 1 million dry spots per 1 second are formed and washed on the surface of the heater (1 cm2). The speed of the contact line when dry spot is forming reaches 10 m/s.

scholarly journals The Mechanical and Reaction Behavior of PTFE/Al/Fe2O3 under Impact and Quasi-Static Compression

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Jun-yi Huang ◽  
Xiang Fang ◽  
Yu-chun Li ◽  
Bin Feng ◽  
Huai-xi Wang ◽  
...  
Keyword(s):  
High Speed ◽  
Xrd Analysis ◽  
High Speed Photography ◽  
Experimental Conditions ◽  
Static Compression ◽  
Reaction Behavior ◽  
Drop Weight ◽  
Weight Test ◽  
Drop Weight Test ◽  
Quasi Static Compression

Quasi-static compression and drop-weight test were used to characterize the mechanical and reaction behavior of PTFE/Al/Fe2O3 composites. Two kinds of PTFE/Al/Fe2O3 composites were prepared with different mass of PTFE, and the reaction phenomenon and stress-strain curves were recorded; the residuals after reaction were analyzed by X-ray diffraction (XRD). The results showed that, under quasi-static compression condition, the strength of the materials is increased (from 37.1 Mpa to 77.2 Mpa) with the increase of PTFE, and the reaction phenomenon occurred only in materials with high PTFE content. XRD analysis showed that the reaction between Al and Fe2O3 was not triggered with identical experimental conditions. In drop-weight tests, PTFE/Al/Fe2O3 specimens with low PTFE content were found to be more insensitive by high-speed photography, and a High Temperature Metal Slag Spray (HTMSS) phenomenon was observed in both kinds of PTFE/Al/Fe2O3 composites, indicating the existence of thermite reaction, which was confirmed by XRD. In PTFE/Al/Fe2O3 system, the reaction between PTFE and Al precedes the reaction between Al and Fe2O3.

A Comprehensive Model for Nucleate Pool Boiling Heat Transfer Including Microlayer Evaporation

1976 ◽  
Vol 98 (4) ◽  
pp. 623-629 ◽  
Author(s):  
R. L. Judd ◽  
K. S. Hwang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Speed ◽  
Methylene Chloride ◽  
Significant Proportion ◽  
Laser Interferometry ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Evaporation Heat ◽  
Microlayer Evaporation

The results of an experimental investigation are presented in which dichloromethane (methylene chloride) boiling on a glass surface was studied using laser interferometry and high-speed photography. New data for active site density, frequency of bubble emission, and bubble departure radius were obtained in conjunction with measurements of the volume of microlayer evaporated from the film underlying the base of each bubble for various combinations of heat flux and subcooling. These results were used to support a model for predicting boiling heat flux incorporating microlayer evaporation, natural convection, and nucleate boiling mechanisms. Microlayer evaporation heat transfer is shown to represent a significant proportion of the total heat transfer for the range of heat flux and sub-cooling investigated.

Influence of System Pressure on Microlayer Evaporation Heat Transfer

1978 ◽  
Vol 100 (1) ◽  
pp. 49-55 ◽  
Author(s):  
H. S. Fath ◽  
R. L. Judd
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Speed ◽  
Methylene Chloride ◽  
Laser Interferometry ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
System Pressure ◽  
Evaporation Heat ◽  
Microlayer Evaporation

Evaporation of the microlayer underlying a bubble during nucleate boiling heat transfer is experimentally investigated by boiling dichloromethane (methylene chloride) on an oxide coated glass surface using laser interferometry and high speed photography. The influence of system pressure (51.5 kN/m2—101.3 kN/m2) and heat flux (17 k W/m2—65 kW/m2) upon the active site density, frequency of bubble emission, bubble departure radius and the volume of the microlayer evaporated have been studied. The results of the present investigation indicate that the microlayer evaporation phenomenon is a significant heat transfer mechanism, especially at low pressure, since up to 40 percent of the total heat transport is accounted for by microlayer evaporation. This contribution to the overall heat transfer decreases with increasing system pressure and decreasing heat flux. The results obtained were used to support the model propounded by Hwang and Judd for predicting boiling heat flux incorporating microlayer evaporation, natural convection and transient thermal conduction mechanisms.

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