Name: pool-boiling heat-transfer enhancement on cylindrical surfaces with hybrid wettable patterns
Uploaded: 2017-04-10T14:00:00.000+00:00
Duration: 7 min 32 s
Description: Watch this Scientific Journal Video about Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns at JoVE.com

The authors gratefully acknowledge funding support from the Ministry of Science and Technology, MOST (project numbers: MOST 104-2218-E-002 -004, MOST 105-2218-E-002-019, MOST 105-2221-E-002 -107 -MY3, MOST 102-2221-E-002 -133 -MY3, and MOST 102-2221-E-002 -088 -MY3).

修飾された表面の調製<ol><li>手動＃2,000エメリーを用いて15分間、試験片（40 mmの長さ（L）と中空銅シリンダー、25 mmの外径（D 0）、および18 mmの内径（D i）を ）磨きます紙。 DI水に続いてアセトンでそれを濯ぐことにより研磨面を清掃してください。 </li><li> 120℃の一定温度で2時間オーブンで研磨試験片を置き。 </li><li>次の手順を使用して超親水たSiO 2ナノ粒子溶液を準備します。 <ol><li>テトラエトキシシランと、DI水の4モル比：1を混合して溶液Aを調製。 37％の2滴の溶液Aに濃HClを加え、2時間撹拌しました。 </li><li>エタノール及び脱イオン水の3モル比：1を混合して溶液Bを作ります。 </li><li>溶液Bの80 mLに溶液Aを1mLを混合し、2時間撹拌しました。 </li><li>調製ソルに対するSiO 2ナノ粒子（40-nmの直径）の32グラムを追加1時間ションと攪拌。 </li></ol></li><li> 5mm /分の速度でディップコーティング装置を用いて調製した溶液中に試験片を浸し。 1時間120℃のオーブンでコーティングされた試験片を保ちます。 </li><li>次の手順を使用して（ 図1に示すように）軸方向に沿って異なる方向を有する2、4、8 interlinedハイブリッドパターンを準備します。 <ol><li> 0°方位で2インター表面のための適切な配向（とインターラインの必要数に応じて絶縁テープを用いて被覆されていないれるべき領域をマスク中央インターラインを調整し、超親水性領域（被覆されるべき領域）上面側が、一方、90°の向きのために、1つのトップでのインター及び下部に別のものを調整し、180°の配向のために、底部に超親水性領域を調整し、中央にインターライン同様に、調整異なるOで4,8 interlined面の位置図1に示すようにrientation）。 </li><li> 5mm /分の遅い速度で高い浸漬速度と立ち上がりでディップコーティング装置、ディップを使用して調製した溶液中にマスクされた試験片を浸し。 1時間120℃のオーブンでコーティングされた試験片を保ちます。 </li><li>正しい向きで中間ラインの必要数を取得するためにマスクされた領域から絶縁テープを外します。 </li></ol></li></ol><img alt="図1" src="/files/ftp_upload/55387/55387fig1.jpg" /> 図1.各種Interlined表面の選択。 （a）は、異なる配向を有する種々 interlined面の概略。すべての条件で1：プレーン銅表面と超親水性表面の面積比は1です。 （b）は、方位選択基準。 （C）2インター0°の角度配向面の等角図。配向は、ベースラインとコーティングとの間の角度として選択されます上面側から第一の親水性パターンの中心線とは、時計方向に測定されます。 <a href="http://ecsource.jove.com/files/ftp_upload/55387/55387fig1large.jpg" target="_blank">この図の拡大版をご覧になるにはこちらをクリックしてください。</a> 2.実験方法<ol><li>絶縁テープを使用して、コーティングされた試験片の各円形の基部に一方のガラス管を固定します。 </li><li>インターラインの必要な位置に係るシリコンペーストを使用して（ 図2に示すように）水平方向に140〜X 140〜X 160 mmの室に、このアセンブリを固定します。 </li><li> 550-W、18 mmの直径、及び試験片の穴に円周領域にサーマルペーストの薄膜40 mmの長カートリッジヒーターを配置。 </li><li>直流（DC）電源ユニットにカートリッジヒーターを接続します。 </li><li> 図に示すように、5mmから7mmで交互の深さ8等間隔1 mmの穴に置きT型熱電対3データロガーに接続します。 </li><li>抵抗温度検出器（RTD）、還流冷却器、及び上部カバーに設けられたスペースに補助ヒータを挿入して固定します。沸騰室の上にそれらを修正。 </li><li>プール沸騰チャンバ内のDI水1400ミリリットルを埋めます。 </li><li> 5℃に維持された冷却室に還流冷却器を接続します。 </li><li>実験前に、激しく補助ヒーターを用いて30分間、プール沸騰チャンバ内のDI水を沸騰。 </li><li>補助ヒータを使用して、飽和沸騰条件でDI水を保ちます。続いて、電源をオンにし、0.1 Aの初期電流を与えます</li><li>定常状態に到達するために2分間待ってください。次いで、0.3 A.単位で電流を増加させます</li><li>データロガーを使用して、各電源入力での温度を記録します。 4 Aの最大電流に到達するまで実験を継続します。一方、バブルダイナミクスFを記録<html>又は試験片に焦点を当てているプール沸騰室の前方に配置されたCCDカメラを用いて、各電源入力。 </li></ol><img alt="図2" src="/files/ftp_upload/55387/55387fig2.jpg" /> プール沸騰商工会議所の図2の回路図。ガラス管は、シリコンペーストと中空銅シリンダの両側に接続されています。これは、シリコンペーストでプール沸騰チャンバに固定されています。 <a href="http://ecsource.jove.com/files/ftp_upload/55387/55387fig2large.jpg" target="_blank">この図の拡大版をご覧になるにはこちらをクリックしてください。</a> <img alt="図3" src="/files/ftp_upload/55387/55387fig3.jpg" /> 3.熱電対の配置図。 8つの熱電対は、直径20mmで試験片の代わりに、円周方向に直径1mmの穴の内部に配置されています。代替直径1mmの穴の深さは5mmでそれぞれ7ミリメートルに固定されています。/files/ftp_upload/55387/55387fig3large.jpg」ターゲット= 『_空白』&gt;この図の拡大版をご覧になるにはこちらをクリックしてください。 3.データ削減<ol><li>次式19を用いて、熱入力（Q）を計算します Q = I V（1） 注：IとVはそれぞれ、アンペアでの入力電流とボルトで電圧です。 </li><li>式19を使用して、2つの側面からの熱損失（Q 損失 ） を推定します。 <img alt="式（2）" src="/files/ftp_upload/55387/55387eq2.jpg" /> （2） 注：kは、銅の熱伝導率です。 T 7ミリメートルとT 5mmで 、それぞれ、7ミリメートルと5ミリメートルの深さでの温度の平均値です。 ΔX（2ミリメートル）の深さとの差です。そして <img alt="式2B" src="/files/ftp_upload/55387/55387eq2b.jpg" />試験Pの断面積であります<html> IECE。 </li><li>下記式19を用いて熱流束（Q「」を）決定します。 <img alt="式3" src="/files/ftp_upload/55387/55387eq3.jpg" /> （3） 注：A =πD O lは試験片の周方向の領域です。 </li><li>次の式19を使用して（壁面過熱を計算します。 <img alt="式4" src="/files/ftp_upload/55387/55387eq4.jpg" /> （4） 注：T mは、T 7ミリメートルとT 5ミリメートルの平均は、で試験片の試験片、R 0（12.5 mm）の試験片の外半径r M（10mM）を半径の長さであります図4に示すように穴を測定し、T SATは DI水の飽和温度です。 </li><li>以下の式19を使用して、HTC（α）を計算します。 PLOAD / 55387 / 55387eq5.jpg」/&gt;（5） </li></ol><img alt="図4" src="/files/ftp_upload/55387/55387fig4.jpg" /> 壁面温度解析の図4の回路図。壁温度を測定した平均温度と知られている円筒形の熱抵抗を用いて計算されます。 <a href="http://ecsource.jove.com/files/ftp_upload/55387/55387fig4large.jpg" target="_blank">この図の拡大版をご覧になるにはこちらをクリックしてください。</a>

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The authors declare that they have no competing financial interests.

The main goal of this investigation was to develop a pool-boiling heat sink for high heat dissipation applications, such as nuclear reactors, boilers, and heat pipes, by introducing the hybrid wettable surface, as described in the protocol section. These surfaces can produce better pool-boiling performances than homogeneous wettable surfaces (hydrophilic and hydrophobic). The improvement in the boiling heat-transfer performance is due to an increase in active nucleation sites and the easy detachment of the formed bubbles...

10-10 5 W / cm 2の範囲で冷却提供高い熱フラックス維持システムは、エレクトロニクス、防衛、航空電子工学、および核のデバイス開発の新興分野で必要とされます。空気と従来の冷却は、自由及び強制対流の両方の条件のために低い熱伝達係数（HTC）をこれらの用途には不十分です。千W / cm 2と1 -例えば、プール沸騰のような相変化ベースの冷却技術は、沸騰する流れ、10のオーダーの高い熱流束を除去するのに十分です。二相熱伝達プロセスが等温であるため、冷却装置の温度は、その表面にわたってほぼ一定です。 、表面に沿った温度の無視できる変化に、デバイスの熱衝撃をなくすことができます。しかし、伝熱沸騰における主要な制限パラメータは、温度の異常上昇を引き起こす臨界熱流束（CHF）であり、2 </sup&gt;。 過去数十年で、広範な研究は、表面改質、ナノ流体、及び表面コーティング3、4、5、6、7、8、9、10、11を用いてCHFを改善するために行われています。様々な方法の中で、表面コーティングは、表面の面積の大幅な増加にCHFを改善するための最良の方法であることが見出されています。表面コーティングは、一般的にフィンアクション、気孔率の影響、及び表面湿潤性12によって熱伝達を増加させます。表面濡れ性は、熱伝達を沸騰で重要な役割を果たしています。これまでの研究では、低熱流束条件で、疎水性表面が原因の早期核に、より良いHTCを示していることを示しています。しかし、時より高い熱流束は、形成される気泡の剥離は、表面に向かって水の低親和性に遅いです。これは、下のCHF 3でバブル合体し、結果につながります。一方、親水性の表面が形成されるため、気泡の高速剥離の、より高いCHFを生成し、それは、気泡核生成13における遅延に起因する低熱流束に低いHTCを与えます。 ハイブリッド構造は、疎水性および親水性14、15、16の複合効果による全熱流束のための伝熱を沸騰著しい向上を示します。スーら。マスクされた銅表面上に超親水Siナノ粒子をコーティングすることにより不均質湿潤性表面を生成しました。彼らは、コーティング時間を変えることによって、異なる濡れ性比を達成しました。沸騰の開始は時間に比べ異種表面に早く発生しました実質的に壁を低減omogeneous表面は、17を過熱しました。ジョーら。親水性、疎水性、および異種湿潤表面に核沸騰熱伝達の研究を行いました。異種湿潤表面は、親水性表面上の疎水性パターン化されたドットから構成されていました。彼らは、親水性表面と比較して高いのHTCと異質表面に同じCHFを得ました。伝熱沸騰の改善が直接表面上及び沸騰条件18時のドットの数に依存します。 本研究では、軸ハイブリッド湿潤性パターンは、浸漬コーティング技術を用いて、円筒状の銅表面上に作製しました。プール沸騰熱伝達の研究は、インターラインの数のハイブリッド湿潤性パターンの向きの効果を決定するために行きました。沸騰熱流束、HTC、およびバブルダイナミクスは、すべてのコーティングされた基板と、私たちのために分析しました。銅基板に比べて再。

<table><tbody><tr><td>Deionized water</td><td></td><td></td><td></td></tr><tr><td>Silica nanopowder,40 nm</td><td>UniRegion Bio-Tech</td><td>60676860</td><td></td></tr><tr><td>Ethanol</td><td>ECHO Chemical co. Ltd</td><td>64175</td><td></td></tr><tr><td>Hydrochloric acid</td><td>SHOWA Chemical co. Ltd.</td><td>7647010</td><td></td></tr><tr><td>Tetraethoxysilane</td><td>SHOWA Chemical co. Ltd.</td><td>78104</td><td></td></tr><tr><td>Acetone</td><td>UNI-ONWARD CORP.</td><td>67641</td><td></td></tr><tr><td>Cartridge Heater</td><td>Chung Shun Heater &amp;amp; Instrument Co, Ltd.</td><td></td><td></td></tr><tr><td>Pyrex glass&amp;nbsp;</td><td>Automotive Glass service , Taiwan</td><td></td><td></td></tr><tr><td>Ordinary toughened glass</td><td>Automotive Glass service , Taiwan</td><td></td><td></td></tr><tr><td>Thermal paste</td><td>Electrolube</td><td>EG-30&amp;nbsp;</td><td></td></tr><tr><td>Insulation Tape</td><td>Chuan Chi Trading Co. Ltd</td><td>Kapton Tape</td><td></td></tr><tr><td>Sandpaper</td><td>Chuan Chi Trading Co. Ltd</td><td>#2000</td><td></td></tr><tr><td>Heating furnace</td><td>Chung Chuan</td><td>Hong Sen HS-101</td><td></td></tr><tr><td>Electronic scales</td><td>A&amp;amp;D co. Ltd</td><td>GX400</td><td></td></tr><tr><td>Ultrasonic cleaner</td><td>Bransonic</td><td>Bransonic 3510</td><td></td></tr><tr><td>Magnet stirrer</td><td>Yellow line</td><td>MST D S1</td><td></td></tr><tr><td>Data logger&amp;nbsp;</td><td>Yokogawa</td><td>MX-100</td><td></td></tr><tr><td>CCD camera</td><td>JVC</td><td>LY35862-001A</td><td></td></tr><tr><td>Silicon paste</td><td>Permatex</td><td>599BR</td><td></td></tr><tr><td>Power supply</td><td>Gwinstek</td><td>GPR-20H50D</td><td></td></tr><tr><td>Teflon tape&amp;nbsp;</td><td>Chuan Chi Trading Co. Ltd</td><td>CS170000</td><td></td></tr><tr><td>Contact Angle Goniometer</td><td>Sindatek</td><td>Model 100SB</td><td></td></tr><tr><td>Auxiliary Heater</td><td>Chuan Chi Trading Co. Ltd</td><td></td><td></td></tr><tr><td>T- type thermocouples</td><td>Chuan Chi Trading Co. Ltd</td><td></td><td></td></tr><tr><td>Reflux Condenser&amp;nbsp;</td><td>Chuan Chi Trading Co. Ltd</td><td></td><td></td></tr><tr><td>Fiber glass</td><td>Professional Plastics, Taiwan</td><td></td><td></td></tr></tbody></table>

pool-boiling heat-transfer enhancement on cylindrical surfaces with hybrid wettable patterns

In this study, pool-boiling heat-transfer experiments were performed to investigate the effect of the number of interlines and the orientation of the hybrid wettable pattern. Hybrid wettable patterns were produced by coating superhydrophilic SiO2 on a masked, hydrophobic, cylindrical copper surface. Using de-ionized (DI) water as the working fluid, pool-boiling heat-transfer studies were conducted on the different surface-treated copper cylinders of a 25-mm diameter and a 40-mm length. The experimental results showed that the number of interlines and the orientation of the hybrid wettable pattern influenced the wall superheat and the HTC. By increasing the number of interlines, the HTC was enhanced when compared to the plain surface. Images obtained from the charge-coupled device (CCD) camera indicated that more bubbles formed on the interlines as compared to other parts. The hybrid wettable pattern with the lowermost section being hydrophobic gave the best heat-transfer coefficient (HTC). The experimental results indicated that the bubble dynamics of the surface is an important factor that determines the nucleate boiling.

プール沸騰熱伝達実験は、概略、図5に示す実験装置を用いたハイブリッド湿潤性円筒面で行いました。インターラインの数及びプール沸騰の性能上のハイブリッド湿潤性パターンの配向の影響を調査しながら、プール沸騰実験手順は、プロトコルセクションのステップ2で説明したが正常に行われました。壁過熱に対する熱流束および熱流束対HTC：異なる...

Watch this Scientific Journal Video about Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns at JoVE.com

Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns

プール沸騰熱伝達実験は、熱伝達係数（HTC）のハイブリッド湿潤性パターンの影響を観察するために実施しました。調査のパラメータは、インターラインの数および修飾湿潤性表面のパターンの向きです。

ハイブリッド湿潤性パターンを持つ円筒面上のプール沸騰熱伝達の強化

In this study, pool-boiling heat-transfer experiments were performed to investigate the effect of the number of interlines and the orientation of the ...

pool-boiling-heat-transfer-enhancement-on-cylindrical-surfaces-with

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

9.0K ビュー.  National Taiwan University. プール沸騰熱伝達実験は、熱伝達係数（HTC）のハイブリッド湿潤性パターンの影響を観察するために実施しました。調査のパラメータは、インターラインの数および修飾湿潤性表面のパターンの向きです。 

ビデオ: Pool-Boiling Heat-Transfer Enhancement on Cylindrical Surfaces with Hybrid Wettable Patterns

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

表面移動に高速液体ジェット宿便の可視化

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

工学

Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer coefficient as a function of the liquid flow rate in a transparent pipe. With certain amendments, the approach is extended to gas-liquid flows, with a particular emphasis on the effect of a single elongated (Taylor) air bubble on heat transfer enhancement. A non-invasive thermography technique is applied to measure the instantaneous temperature of a thin metal foil heated electrically. The foil is glued to cover a narrow slot cut in the pipe. The thermal inertia of the foil is small enough to detect the variation in the instantaneous foil temperature. The test section can be moved along the pipe and is long enough to cover a considerable part of the growing thermal boundary layer.
At the beginning of each experimental run, a steady state with a constant water flow rate and heat flux to the foil is attained and serves as the reference. The Taylor bubble is then injected into the pipe. The heat transfer coefficient variations due to the passage of a Taylor bubble propagating in a vertical pipe is measured as function of the distance of the measuring point from the bottom of the moving Taylor bubble. Thus, the results represent the local heat transfer coefficients. Multiple independent runs preformed under identical conditions allow accumulating sufficient data to calculate reliable ensemble-averaged results on the transient convective heat transfer. In order to perform this in a frame of reference moving with the bubble, the location of the bubble along the pipe has to be known at all times. Detailed description of measurements of the length and of the translational velocity of the Taylor bubbles by optical probes is presented.

This manuscript describes methods aimed at measuring the local instantaneous convective heat transfer coefficients in a single or two-phase pipe flow. A simple optical method to determine the length and the propagation velocity of an elongated (Taylor) air bubble moving at a constant velocity is also presented.

管内の単相およびフロー ローカル瞬時対流熱伝達の測定

This manuscript provides step by step description of the manufacturing process of a test section designed to measure the local instantaneous heat transfer ...

Uncoupling Coriolis Force and Rotating Buoyancy Effects on Full-Field Heat Transfer Properties of a Rotating Channel

An experimental method for exploring the heat transfer characteristics of an axially rotating channel is proposed. The governing flow parameters that characterize the transport phenomena in a rotating channel are identified via the parametric analysis of the momentum and energy equations referring to a rotating frame of reference. Based on these dimensionless flow equations, an experimental strategy that links the design of the test module, the experimental program and the data analysis is formulated with the attempt to reveal the isolated Coriolis-force and buoyancy effects on heat transfer performances. The effects of Coriolis force and rotating buoyancy are illustrated using the selective results measured from rotating channels with various geometries. While the Coriolis-force and rotating-buoyancy impacts share several common features among the various rotating channels, the unique heat transfer signatures are found in association with the flow direction, the channel shape and the arrangement of heat transfer enhancement devices. Regardless of the flow configurations of the rotating channels, the presented experimental method enables the development of physically consistent heat transfer correlations that permit the evaluation of isolated and interdependent Coriolis-force and rotating-buoyancy effects on the heat transfer properties of rotating channels.

Here, we present an experimental method for decoupling the interdependent Coriolis-force and rotating-buoyancy effects on full-field heat transfer distributions of a rotating channel.

連結を解くコリオリの力と全視野熱回転浮力の影響回転チャネルのプロパティを転送します。

An experimental method for exploring the heat transfer characteristics of an axially rotating channel is proposed. The governing flow parameters that ...

Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren system is constructed from a Hoffman modulation contrast microscope, which provides easy access to the rear focal plane of the objective lens, by removing the slit plate and replacing the modulator with a knife-edge. The working principle of microscale schlieren technique relies on detecting light deflection caused by variation of refractive index1-3. The deflected light either escapes or is obstructed by the knife-edge to produce a bright or a dark band, respectively. If the refractive index of the mixture varies linearly with its composition, the local change in light intensity in the image plane is proportional to the concentration gradient normal to the optical axis. The micro-schlieren image gives a two-dimensional projection of the disturbed light produced by three-dimensional inhomogeneity.
To accomplish quantitative analysis, we describe a calibration procedure that mixes two fluids in a T-microchannel. We carry out a numerical simulation to obtain the concentration gradient in the T-microchannel that correlates closely with the corresponding micro-schlieren image. By comparison, a relationship between the grayscale readouts of the micro-schlieren image and the concentration gradients presented in a microfluidic device is established. Using this relationship, we are able to analyze the mixing inhomogeneity from associate micro-schlieren image and demonstrate the capability of microscale schlieren technique with measurements in a microfluidic oscillator4. For optically transparent fluids, microscale schlieren technique is an attractive diagnostic tool to provide instantaneous full-field information that retains the three-dimensional features of the mixing process.

Herein, we describe a procedure that employs microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. Through calibration, distribution of concentration gradient can be derived from the micro-schlieren image.

マイクロスケールシュリーレン法によるマイクロ流体デバイス内の混合不均一性の分析

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren ...

生物工学

Scalable Stamp Printing and Fabrication of Hemiwicking Surfaces

Hemiwicking is a process where a fluid wets a patterned surface beyond its normal wetting length due to a combination of capillary action and imbibition. This wetting phenomenon is important in many technical fields ranging from physiology to aerospace engineering. Currently, several different techniques exist for fabricating hemiwicking structures. These conventional methods, however, are often time consuming and are difficult to scale-up for large areas or are difficult to customize for specific, nonhomogeneous patterning geometries. The presented protocol provides researchers with a simple, scalable, and cost-effective method for fabricating micro-patterned hemiwicking surfaces. The method fabricates wicking structures through the use of stamp printing, polydimethylsiloxane (PDMS) molding, and thin-film surface coatings. The protocol is demonstrated for hemiwicking with ethanol on PDMS micropillar arrays coated with a 70 nm thick aluminum thin-film.

A simple protocol is provided for the fabrication of hemiwicking structures of varying sizes, shapes, and materials. The protocol uses a combination of physical stamping, PDMS molding, and thin-film surface modifications via common materials deposition techniques.

Hemiwicking 表面の作製とスケーラブルなスタンプ印刷

Hemiwicking is a process where a fluid wets a patterned surface beyond its normal wetting length due to a combination of capillary action and imbibition. ...

Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars

We present microfabrication protocols for rendering intrinsically wetting materials repellent to liquids (omniphobic) by creating gas-entrapping microtextures (GEMs) on them comprising cavities and pillars with reentrant and doubly reentrant features. Specifically, we use SiO2/Si as the model system and share protocols for two-dimensional (2D) designing, photolithography, isotropic/anisotropic etching techniques, thermal oxide growth, piranha cleaning, and storage towards achieving those microtextures. Even though the conventional wisdom indicates that roughening intrinsically wetting surfaces (&#952;o &#60; 90&#176;) renders them even more wetting (&#952;r &#60; &#952;o &#60; 90&#176;), GEMs demonstrate liquid repellence despite the intrinsic wettability of the substrate. For instance, despite the intrinsic wettability of silica &#952;o &#8776; 40&#176; for the water/air system, and &#952;o &#8776; 20&#176; for the hexadecane/air system, GEMs comprising cavities entrap air robustly on immersion in those liquids, and the apparent contact angles for the droplets are &#952;r &#62; 90&#176;. The reentrant and doubly reentrant features in the GEMs stabilize the intruding liquid meniscus thereby trapping the liquid-solid-vapor system in metastable air-filled states (Cassie states) and delaying wetting transitions to the thermodynamically-stable fully-filled state (Wenzel state) by, for instance, hours to months. Similarly, SiO2/Si surfaces with arrays of reentrant and doubly reentrant micropillars demonstrate extremely high contact angles (&#952;r &#8776; 150&#176;&#8211;160&#176;) and low contact angle hysteresis for the probe liquids, thus characterized as superomniphobic. However, on immersion in the same liquids, those surfaces dramatically lose their superomniphobicity and get fully-filled within &#60;1 s. To address this challenge, we present protocols for hybrid designs that comprise arrays of doubly reentrant pillars surrounded by walls with doubly reentrant profiles. Indeed, hybrid microtextures entrap air on immersion in the probe liquids. To summarize, the protocols described here should enable the investigation of GEMs in the context of achieving omniphobicity without chemical coatings, such as perfluorocarbons, which might unlock the scope of inexpensive common materials for applications as omniphobic materials. Silica microtextures could also serve as templates for soft materials.

Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars

This work presents microfabrication protocols for achieving cavities and pillars with reentrant and doubly reentrant profiles on SiO2/Si wafers using photolithography and dry etching. Resulting microtextured surfaces demonstrate remarkable liquid repellence, characterized by robust long-term entrapment of air under wetting liquids, despite the intrinsic wettability of silica.

再入可能および二重再入可能なキャビティまたは柱を含むガスを覆うマイクロテクスチャを彫ることによってSiO2/Si表面をレンダリングする

We present microfabrication protocols for rendering intrinsically wetting materials repellent to liquids (omniphobic) by creating gas-entrapping ...

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO2/Si/SiO2 Wafers for Green Desalination

Desalination through direct contact membrane distillation (DCMD) exploits water-repellent membranes to robustly separate counterflowing streams of hot and salty seawater from cold and pure water, thus allowing only pure water vapor to pass through. To achieve this feat, commercial DCMD membranes are derived from or coated with water-repellent perfluorocarbons such as polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF). However, the use of perfluorocarbons is limiting due to their high cost, non-biodegradability, and vulnerability to harsh operational conditions. Unveiled here is a new class of membranes referred to as gas-entrapping membranes (GEMs) that can robustly entrap air upon immersion in water. GEMs achieve this function by their microstructure rather than their chemical make-up. This work demonstrates a proof-of-concept for GEMs using intrinsically wetting SiO2/Si/SiO2 wafers as the model system; the contact angle of water on SiO2 is &#952;o &#8776; 40&#176;. Silica-GEMs had 300 &#956;m-long cylindrical pores whose diameters at the (2 &#956;m-long) inlet and outlet regions were significantly smaller; this geometrically discontinuous structure, with 90&#176; turns at the inlets and outlets, is known as the &#34;reentrant microtexture&#34;. The microfabrication protocol for silica-GEMs entails designing, photolithography, chrome sputtering, and isotropic and anisotropic etching. Despite the water loving nature of silica, water does not intrude silica-GEMs on submersion. In fact, they robustly entrap air underwater and keep it intact even after six weeks (&#62;106 seconds). On the other hand, silica membranes with simple cylindrical pores spontaneously imbibe water (&#60; 1 s). These findings highlight the potential of the GEMs architecture for separation processes. While the choice of SiO2/Si/SiO2 wafers for GEMs is limited to demonstrating the proof-of-concept, it is expected that the protocols and concepts presented here will advance the rational design of scalable GEMs using inexpensive common materials for desalination and beyond.

Proof-of-Concept for Gas-Entrapping Membranes Derived from Water-Loving SiO2/Si/SiO2 Wafers for Green Desalination

Presented here is a stepwise protocol for realizing gas-entrapping membranes (GEMs) from SiO2/Si wafers using integrated circuit microfabrication technology. When silica-GEMs are immersed in water, the intrusion of water is prevented, despite the water-loving composition of silica.

水を愛するSiO2 /Si/SiO2ウェハーから得られるガス包み込み膜の概念実証

Desalination through direct contact membrane distillation (DCMD) exploits water-repellent membranes to robustly separate counterflowing streams of hot and ...

Preparation of Free-Surface Hyperbolic Water Vortices

Free surface vortices are present in industry in flow regulation, energy dissipation, and energy generation. Although investigated extensively, detailed experimental data regarding free surface vortices are lacking, particularly regarding the turbulence at the interface. The present paper reports on a special type of free surface vortex first proposed by Walter Schauberger in the 1960s that has an oxygen volumetric mass transfer coefficient exceeding the value of similar systems. This special type of vortex forms in a hyperbolic funnel. Different stable regimes can be stabilized with different hydraulic characteristics. Other advantages of this technology are its energy efficiency, simple design, and scalability. The flow in this hyperbolic funnel is characterized by strong turbulence and an increased surface area of the air-water interface. The local pressure strongly varies along the surface, resulting in a pronounced wavey air-water boundary layer. Due to the helical flow, these perturbations move inward, pulling the boundary layer with them. The resultant pressure gradient draws a certain air volume into the water vortex. The construction of the basic hyperbolic funnel setup and operational examples, including high-speed visualization for three different stable regimes, are presented in this work.

This paper describes how three different water vortex regimes in a hyperbolic Schauberger funnel can be created, their most important characteristics, and how associated parameters such as the oxygen transfer rates can be calculated.

自由表面双曲水渦の作製

Free surface vortices are present in industry in flow regulation, energy dissipation, and energy generation. Although investigated extensively, detailed ...

Testing the Heat Transfer Efficiency of a Finned-tube Heat Exchanger

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Heat exchangers transfer heat from one fluid to another fluid. Multiple classes of heat exchangers exist to fill different needs. Some of the most common types are shell and tube exchangers and plate exchangers1. Shell and tube heat exchangers use a system of tubes through which fluid flows1. One set of tubes contains the liquid to be cooled or heated, while the second set contains the liquid that will either absorb heat or transmit it1. Plate heat exchangers use a similar concept, in which plates are closely joined together with a small gap between each for liquid to flow1. The fluid flowing between the plates alternates between hot and cold so that heat will move into or out of the necessary streams1. These exchangers have large surface areas, so they are usually more efficient1.
The goal for this experiment is to test the heat transfer efficiency of a finned-tube heat exchanger (Figure 1) and compare it to the theoretical efficiency of a heat exchanger without fins. The experimental data will be measured for three different flow rates of monoethylene glycol (MEG). Two different water flow rates for each MEG flow rate will be used. Using the Wilson plot method the heat transfer coefficients will be determined from the experimental data. Additionally, the Reynold&#39;s number and the amount of heat transferred will be compared for flow with and without the fins to evaluate heat transfer efficiency.
<img alt="Figure 1" src="/files/ftp_upload/10437/10437fig1.jpg" /> 
Figure 1: Finned-tube Heat Exchanger. 1) MEG outlet temperature 2) water inlet temperature 3) MEG inlet temperature 4) water outlet temperature 5) water meter 6) MEG accumulation sight glass/cylinder.

Heat Transfer Efficiency Test of a Finned-tube Heat Exchanger

フィンドチューブ熱交換器の熱伝達効率のテスト

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA
Heat exchangers transfer ...

Education

JoVE Science Education

化学工学

Quenching and Boiling

Source: Alexander S Rattner, Sanjay Adhikari, and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
Controlled heating followed by rapid cooling is an important element of many materials processing applications. This heat-treating procedure can increase material hardness, which is important for cutting tools or surfaces in high wear environments. The rapid cooling stage is called quenching, and is often performed by immersing materials in a fluid bath (often water or oil). Quenching heat transfer can occur due to forced convection - when the action of rapidly moving material through coolant drives the heat transfer process, and due to free convection - when the reduced density of hot fluid near the material surface causes buoyancy-driven circulation and heat transfer. At high material temperatures, the coolant can boil, leading to increased heat transfer effectiveness. However, when extremely hot materials are quenched, they can be blanketed in relatively low thermal conductivity coolant vapor, leading to poor heat transfer.
In this experiment, quenching heat transfer will be measured for a heated copper cylinder, which is representative of small heat-treated parts. The transient sample temperature profile will be measured during quenching and compared with theoretical results for free convection heat transfer. Boiling phenomena will also be investigated qualitatively.

Quenching, Boiling, Convection and Nusselt Number

焼入れと沸騰

Source: Alexander S Rattner, Sanjay Adhikari, and Mahdi Nabil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, ...

ハイブリッド湿潤性パターンを持つ円筒面上のプール沸騰熱伝達の強化

要約

さらに動画を探す

この動画の章

表面移動に高速液体ジェット宿便の可視化

管内の単相およびフローローカル瞬時対流熱伝達の測定

連結を解くコリオリの力と全視野熱回転浮力の影響回転チャネルのプロパティを転送します。

マイクロスケールシュリーレン法によるマイクロ流体デバイス内の混合不均一性の分析

Hemiwicking 表面の作製とスケーラブルなスタンプ印刷

再入可能および二重再入可能なキャビティまたは柱を含むガスを覆うマイクロテクスチャを彫ることによってSiO₂/Si表面をレンダリングする

水を愛するSiO2 /Si/SiO₂ウェハーから得られるガス包み込み膜の概念実証

自由表面双曲水渦の作製

フィンドチューブ熱交換器の熱伝達効率のテスト

焼入れと沸騰

ハイブリッド湿潤性パターンを持つ円筒面上のプール沸騰熱伝達の強化

要約

さらに動画を探す

この動画の章

表面移動に高速液体ジェット宿便の可視化

管内の単相およびフロー ローカル瞬時対流熱伝達の測定

連結を解くコリオリの力と全視野熱回転浮力の影響回転チャネルのプロパティを転送します。

マイクロスケールシュリーレン法によるマイクロ流体デバイス内の混合不均一性の分析

Hemiwicking 表面の作製とスケーラブルなスタンプ印刷

再入可能および二重再入可能なキャビティまたは柱を含むガスを覆うマイクロテクスチャを彫ることによってSiO2/Si表面をレンダリングする

水を愛するSiO2 /Si/SiO2ウェハーから得られるガス包み込み膜の概念実証

自由表面双曲水渦の作製

フィンドチューブ熱交換器の熱伝達効率のテスト

焼入れと沸騰

管内の単相およびフローローカル瞬時対流熱伝達の測定

再入可能および二重再入可能なキャビティまたは柱を含むガスを覆うマイクロテクスチャを彫ることによってSiO₂/Si表面をレンダリングする

水を愛するSiO2 /Si/SiO₂ウェハーから得られるガス包み込み膜の概念実証