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.

Pool Boiling Characteristics of Heat Transfer Surface With Micro Structures Created by Using MEMS Technology

2010 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Takato Sato
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Small Diameter ◽  
Nucleate Boiling ◽  
Micro Electro Mechanical System ◽  
Heat Transfer Surface ◽  
Wall Superheat ◽  
Straight Line ◽  
Mems Technology ◽  
Cylindrical Cavities

Pool nucleate boiling heat transfer experiments were performed for water by using well-controlled and -defined heat transfer surfaces. The silicon wafers of 0.200 mm thickness were used as the heat transfer surfaces. Artificial-cylindrical cavities, micro-straight-line grooves or micro-crossing-straight-line grooves (square pillars) were created on the silicon plate by utilizing the Micro-Electro Mechanical System (MEMS) technology. In the case of the straight-line grooves and the crossing-straight-line grooves, the grooves were wetted after the heat transfer surface experienced subcooling. Once the grooves were wetted, only small diameter cavities which were formed during the MEMS processing at the bottom of the grooves functioned at the inception of boiling. Thus, a large overshooting of the wall superheat at the inception of boiling was observed. In this point, the micro grooves and micro pillars are not advantageous to cooling a body that periodically generates heat such as MPUs and electro devices. In the fully developed nucleate boiling region, the general trend was similar to that of the usual heat transfer surface. In the case of the artificial-cylindrical cavities, nuclei were well preserved in cavities even after the heat transfer surface experienced subcooling. Thus, no overshooting of the wall superheat at the inception of boiling was observed. As the number of the artificial-cylindrical cavities was increased, the wall superheat shifted to a low wall superheat side. The boiling heat transfer coefficient of the heat transfer surface that had the artificial-cylindrical cavities of the 1 mm pitch was better than that of a usual copper heat transfer surface. The artificial-cylindrical cavities are advantageous to get reliable and better cooling efficiency.

Acoustic Driven Micro Thermal Bubble Dynamics in a Microchannel

2009 ◽  
Author(s):  
Xiaopeng Qu ◽  
Huihe Qiu
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Video Recording ◽  
Digital Camera ◽  
Microfluidic Devices ◽  
Acoustic Vibration ◽  
Micro Electro Mechanical System ◽  
Bubble Nucleation ◽  
Potential Applications ◽  
Micro Mixer

Understanding the effects of acoustic vibration on micro thermal bubble dynamics in a microchannel is the key to develop acoustic-thermal-bubble based microfluidic devices. For that purpose, in the current research, a series of experiments were carried out to study the acoustic-thermal-bubble dynamics in a microchannel. The thermal bubble was generated by a micro heater which was fabricated by MEMS (Micro-Electro-Mechanical-System) technique. Using a high-speed digital camera, the thermal bubble dynamics was studied in two different conditions: normal condition and acoustic condition. Through theoretical analysis, the whole bubble dynamic process in two conditions can be roughly divided into four steps, which are bubble nucleation, satellite bubbles movement, bubble evolution, and bubble shrinkage and remove. The effects of acoustic vibration on all these four steps were found to be significant. The mechanisms behind these effects are discussed by analyzing the high speed video recording results. The current experimental investigation has some potential applications in microfluidic devices, and a prototype of micro mixer based on acoustic-thermal-bubble was successfully tested.

Study on Pool-Nucleate Boiling Heat Transfer Characteristics by Using Artificial Cavities

2006 ◽  
Author(s):  
Ryo Hateruma ◽  
Takato Sato ◽  
Yasuo Koizumi ◽  
Hiroyasu Ohtake
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Natural Circulation ◽  
Nucleate Boiling ◽  
Heat Transfer Surface ◽  
Finished Surface ◽  
Nucleate Boiling Heat Transfer ◽  
Mems Technology ◽  
Artificial Cavity

Pool boiling heat transfer experiments were performed by using the well-controlled/defined heat transfer surface for water. Uni-size and -shape artificial cavities were created on the mirror-finished silicon plate by utilizing the MEMS technology. Experimental results agreed well with what were predicted by the traditional boiling theory. The mirror-finished surface showed only the tendency of natural circulation heat transfer. The artificial-cavity heat transfer surface followed the pool-nucleate boiling trend. The onset of the pool-nucleate boiling was well predicted by the traditional pool-nucleate boiling theory. These results indicated that the artificial cavities behave just like natural cavities. The results indicated the artificial cavities are quite useful and promising to examine the true features of complicated boiling that have been overshadowed by complicatedness. From recorded high speed video pictures, the coalescence of bubbles that were growing on the cavities were classified into four categories; the normal lift (no coalescence), the vertical coalescence, the declining coalescence and the horizontal coalescence. As the cavity interval was increased, the horizontal coalescence decreases to zero, the vertical coalescence also decreases, and on the contrary to these, vertical coalescence and normal lift increase. The cavity interval 3 mm (S/Lc ≈ 1.2) seemed to be the border whether the horizontal coalescence occurs or not.

Wettability Effect on Flow Boiling in an MEMS-Based Single Glass Microchannel

2008 ◽  
Author(s):  
Chiwoong Choi ◽  
Cheol Huh ◽  
Dongeok Kim ◽  
Moohwan Kim
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
Hydrophobic Surface ◽  
Micro Electro Mechanical System ◽  
Hydrophilic Surface ◽  
Self Assembled Monolayer ◽  
Long Distance ◽  
Rectangular Microchannel

Many studies have investigated boiling heat transfer in microchannels; however, such phenomena are not yet fully understood, and conflicting results have been reported. There are many important parameters that govern behavior in microsystems, including channel shape, roughness, and choice of material. One potentially important parameter is hydrophobicity of the microchannel surface, as interfacial forces play an increasing role at microscales. We developed a new method of fabricating a single glass rectangular microchannel and microheater using the MEMS (Micro-Electro-Mechanical System) fabrication technique. The glass was used as a hydrophilic surface, and a self-assembled monolayer was coated with OTS (Octadecyl-Trichloro-Silane) to obtain a hydrophobic surface. We conducted an experiment of boiling heat transfer in a microchannel using two surfaces of contrasting hydrophobicity. The resulting flow was observed using a long-distance microscope and a high-speed camera. This approach enables a qualitative analysis of the hydrophobicity effect on the flow regime.

Enhanced boiling heat transfer in mesochannels

2009 ◽  
Vol 52 (25-26) ◽  
pp. 5802-5813 ◽  
Author(s):  
John D. Schwarzkopf ◽  
Steven G. Penoncello ◽  
Prashanta Dutta
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Enhanced Boiling

Microscale Vapor Bubble Interactions During Subcooled Nucleate Boiling on a Heated Wire

2007 ◽  
Author(s):  
Lu Zhang ◽  
David M. Christopher
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Bubble Behavior ◽  
Transfer Rates ◽  
Bubble Interactions ◽  
Heated Wire ◽  
Nucleate Boiling Heat Transfer ◽  
Transfer Mechanisms

Bubbles have been observed moving along heated wires during subcooled nucleate boiling as they are driven by Marangoni convection around the bubbles. This paper presents more detailed observations of the vapor bubble interactions and moving bubble behavior during subcooled nucleate boiling on a heated microwire. The experimental results show that moving bubbles coalesce or rebound from other bubbles and that bubbles hop on the wire. These observations show how bubble interactions significantly affect nucleate boiling heat transfer rates and how Marangoni flow plays an important role in microscale nucleate boiling heat transfer mechanisms.

scholarly journals Effect of Uniformly and Nonuniformly Coated Al2O3 Nanoparticles over Glass Tube Heater on Pool Boiling

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Nitin Doifode ◽  
Sameer Gajghate ◽  
Abdul Najim ◽  
Anil Acharya ◽  
Ashok Pise
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
High Speed ◽  
Pool Boiling ◽  
Glass Tube ◽  
Al2o3 Nanoparticles ◽  
High Speed Camera ◽  
Coated Nanoparticles ◽  
Nucleation Sites ◽  
Coated Surface

Effect of uniformly and nonuniformly coated Al2O3 nanoparticles over plain glass tube heater on pool boiling heat transfer was studied experimentally. A borosilicate glass tube coated with Al2O3 nanoparticle was used as test heater. The boiling behaviour was studied by using high speed camera. Result obtained for pool boiling shows enhancement in heat transfer for nanoparticle coated surface heater and compared with plain glass tube heater. Also heat transfer coefficient for nonuniformly coated nanoparticles was studied and compared with uniformly coated and plain glass tube. Coating effect of nanoparticles over glass tube increases its surface roughness and thereby creates more nucleation sites.

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