هذا العمل كان تدعمه "مؤسسة العلوم إسرائيل"، منحة # 281/14.

<ol>
	<li>Hetsroni, G., Rozenblit, R., Yarin, L. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+hot-foil+infrared+technique+for+studying+the+temperature+field+of+a+wall.">A hot-foil infrared technique for studying the temperature field of a wall.</a> Meas. Sci. Tech. 7, 1418 (1996).</li><li>Babin, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Experimental investigation of the local heat transfer in gas-liquid slug flow. , (2015).</li><li>Babin, V., Shemer, L., Barnea, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+instantaneous+heat+transfer+around+a+raising+single+Taylor+bubble.">Local instantaneous heat transfer around a raising single Taylor bubble.</a> Int. J. Heat Mass Transfer. 89 (9), 884-893 (2015).</li><li>Fershtman, A., Shemer, L., Barnea, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Instantaneous+heat+transfer+rate+around+consecutive+Taylor+bubbles.">Instantaneous heat transfer rate around consecutive Taylor bubbles.</a> Int. J. Heat Mass Transfer. 95, 865-873 (2016).</li><li>Fershtman, A., Shemer, L., Barnea, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transient+convective+heat+transfer+in+a+pipe+due+to+impulsively+initiated+downward+flow+and/or+heat+flux.">Transient convective heat transfer in a pipe due to impulsively initiated downward flow and/or heat flux.</a> Int. J. Heat Mass Transf. 111, 1181-1191 (2017).</li><li>Hetsroni, G., Hu, B. G., Yi, B. G., Mosyak, A., Yarin, L. P., Ziskind, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+Transfer+in+Intermittent+Air-Water+Flow-Part+I:+Horizontal+Tube.">Heat Transfer in Intermittent Air-Water Flow-Part I: Horizontal Tube.</a> Int. J. Multiphase Flow. 24, 165 (1998).</li><li>Hetsroni, G., Hu, B. G., Yi, B. G., Mosyak, A., Yarin, L. P., Ziskind, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+Transfer+in+Intermittent+Air-Water+Flow-Part+II:+Upward+Inclined+Tube.">Heat Transfer in Intermittent Air-Water Flow-Part II: Upward Inclined Tube.</a> Int. J. Multiphase Flow. 24, 188 (1998).</li><li>Hetsroni, G., Mewes, D., Enke, C., Gurevich, M., Mosyak, A., Rozenblit, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+transfer+to+two-phase+flow+in+inclined+tubes.">Heat transfer to two-phase flow in inclined tubes.</a> Int. J. Multiphase Flow. 29, 173-194 (2003).</li><li>Ghajar, A. J., Tang, C. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heat+Transfer+Measurements,+Flow+pattern+maps+and+flow+visualization+for+non-boiling+two-phase+flow+in+horizontal+and+slightly+inclined+pipe.">Heat Transfer Measurements, Flow pattern maps and flow visualization for non-boiling two-phase flow in horizontal and slightly inclined pipe.</a> Heat Transfer Eng. 28, 525 (2007).</li><li>Franca, F. A., Banneart, A. C., Camargo, R. M. T., Goncalves, M. A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanistic+modelling+of+the+convective+heat+transfer+coefficient+in+gas-liquid+intermittent+flows.">Mechanistic modelling of the convective heat transfer coefficient in gas-liquid intermittent flows.</a> Heat Transfer Eng. 29, 984-998 (2008).</li><li>Kim, D., Ghajar, A. J., Dougherty, R. L., Ryali, V. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+20+two+phase+heat+transfer+correlations+with+seven+Sets+of+experimental+data,+including+flow+pattern+and+tube+inclination+effects.">Comparison of 20 two phase heat transfer correlations with seven Sets of experimental data, including flow pattern and tube inclination effects.</a> Heat Transfer Eng. 20, 15 (1999).</li><li>Nicklin, D. J., Wilkes, J. O., Davidson, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-phase+flow+in+vertical+tubes.">Two-phase flow in vertical tubes.</a> Trans. Inst. Chem. Eng. 40, 61 (1962).</li><li>Donnelly, B., O'Reilly Meehan, R., Nolan, K., Murray, D. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+dynamics+of+sliding+air+bubbles+and+the+effects+on+surface+heat+transfer.">The dynamics of sliding air bubbles and the effects on surface heat transfer.</a> Int. J. Heat Mass Transfer. 91, 532-542 (2015).</li><li>Liu, T., Pan, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infrared+thermography+measurement+of+two-phase+boiling+flow+heat+transfer+in+a+microchannel.">Infrared thermography measurement of two-phase boiling flow heat transfer in a microchannel.</a> Applied thermal engineering. 94, 568-578 (2016).</li><li>Dumitrescu, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stromung+an+einer+Luftblase+im+senkrechten+Rohr.">Stromung an einer Luftblase im senkrechten Rohr.</a> Z. Ang. Math. Mech. 23, 139 (1943).</li><li>Davies, R. M., Taylor, G. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mechanics+of+large+bubbles+rising+through+extended+liquids+and+trough+liquid+in+tubes.">The mechanics of large bubbles rising through extended liquids and trough liquid in tubes.</a> Proc. R. Soc. London, Ser. A. 200, 375 (1949).</li></ol>

التحقيق التجريبي لنقل الحرارة المحلية في تدفق الأنابيب عابر مهمة معقدة تتطلب أدوات قياس الراقية والأساليب، فضلا عن إنشاء مرفق تجريبي المواصفات، على وجه الخصوص، قسم اختبار مصممة خصيصا. يعرض هذا البروتوكول تقنية الحراري والتي قادرة على قياس التغيرات الزمنية سريعة في درجة حرارة الجدار وفي...

تم إجراء العديد من الدراسات التجريبية لنقل الحرارة الحمل الحراري، باستخدام تقنيات مختلفة لقياس الجدار و/أو درجة حرارة السوائل في مجموعة متنوعة من تكوينات التدفق، خلال العقود الماضية. واحدة من العوامل التي تحد من دقة قياسات درجات الحرارة في العمليات متقلب هو الاستجابة البطيئة من أجهزة الاستشعار. لتسجيل درجة الحرارة المحلية الجدار لحظية، لديه معدات قياس الاستجابة بسرعة كافية، بينما السطح الذي يتم تسجيل درجة الحرارة يجب أن تكون في حالة توازن حراري مع تدفق تعتمد على الوقت. وهكذا، قد القصور الحراري من السطح إلى أن تكون صغيرة بما فيه الكفاية. المقاييس الزمنية ذات الصلة التي تحددها هيدرودينامية الظواهر التي تسبب التغيير في نقل الحرارة الحمل الحراري. وبالتالي الاستجابة الوقت السريع أمر حاسم لتسجيل درجة الحرارة تعتمد على الوقت في تدفق عابرة.
للوفاء بهذه المتطلبات، يتم استخدام كاميرا الأشعة تحت الحمراء لتسجيل مقطع اختبار الذاتي مصنعة خاصة التي تسمح درجة حرارة بسرعة استجابة لأي تغيير في التدفق. قطع جزء من الجدار الأنابيب واستبداله بإحباط الفولاذ المقاوم للصدأ رقيقة. نهج مماثل كان يستخدمها هيتسروني et al. 1، ومع ذلك، تم إحباط أنها تستخدم سميكة جداً لقياس التغيرات في درجات الحرارة لحظية بدقة وعرض درجات الحرارة بلغ متوسط الوقت فقط. تقليل سمك إحباط تحسن الاستجابة وقت كبير. 2 تم تطبيق هذا الأسلوب في مختبر لقياس معاملات نقل الحرارة الحمل الحراري في تدفق مرحلتين3،4 والظواهر العابرة في مرحلة واحدة أنابيب تدفق5.
تخطيط تخطيطي مرفق تدفق مرحلتين يرد في الشكل 1، معلومات إضافية عن الجهاز مدخل الهواء فريد من نوعه ويمكن الاطلاع على في بابين et al. 3
التحقيق في نقل الحرارة الحمل الحراري في مرحلتين تدفق معقد للغاية بسبب سلوك تدفق عابرة والأثر لكسر الفراغ في المقطع العرضي الأنابيب. لذلك، العديد من الدراسات قد قدمت فقط معامل نقل حرارة الحمل الحراري متوسط لنظام تدفق معين كدالة لتدفق محددة الشروط6،،من78،9،10 , 11-غير أن الورقات التي دونيلي et al. 12 وليو et al. 13 تمثل أمثلة لدراسات نقل الحرارة الحمل الحراري المحلية ذات مرحلتين.
وتتناول هذه الدراسة قياسات نقل الحرارة حول فقاعة (تايلور) واحد ممدود حقن الراكدة أو تدفق السائل في أنبوب. فقاعة تايلور تنتشر في15،،من14ثابت سرعة متعدية الجنسيات16. يتم تحديد سرعة نشر فقاعة استخدام الأسلوب المسابر الضوئية تتألف من مصدر ضوء الليزر والضوئي3،4.
المزيج من كاميرا الأشعة تحت الحمراء ومجسات بصرية يسمح قياسات لنقل الحرارة الحمل الحراري لحظية المحلية كدالة للمسافة من تايلور فقاعة أعلى أو أسفل.
يمكن استخدام درجة حرارة الجدار لحظية لحساب معامل نقل الحرارة الحمل الحراري، و حاء، وعدد نوسيلت:
<img alt="Equation 1" src="/files/ftp_upload/57437/57437eq1.jpg">، (1)
حيث q هو تدفق الحرارة إلى إحباط، تيدبليو و تي∞ الجدار وحرارة المياه مدخل على التوالي، ك الموصلية السائل وهو مد أنابيب قطرها. تم قياس درجة حرارة الجزء الأكبر الذي يستخدم عادة لتحديد معاملات نقل الحرارة لا بغية تجنب إدخال أي تدخل للتدفق.

<table><tbody><tr><td>Infra red camera</td><td>Optris</td><td>PI-1450</td><td></td></tr><tr><td>Thermocouples A/D card&amp;nbsp;</td><td>National Instruments</td><td>NI cDAQ-9714.</td><td></td></tr><tr><td>Labview program</td><td>National Instruments</td><td></td><td></td></tr><tr><td>Epoxy DP-460</td><td>3M Scotch-weld</td><td></td><td></td></tr></tbody></table>

measurements of local instantaneous convective heat transfer in a pipe - single and two-phase flow

ويقدم هذا المخطوط وصف خطوة بخطوة لعملية التصنيع من مقطع اختبار مصمم لقياس معامل نقل الحرارة الآنية المحلية كدالة لمعدل تدفق السائل في أنبوب شفاف. مع بعض التعديلات، يتم توسيع النهج إلى تدفق الغاز السائل، مع تركيز بشكل خاص على تأثير فقاعة هواء (تايلور) ممدود واحد على تعزيز نقل الحرارة. يتم تطبيق تقنية الحراري وغير الغازية قياس درجة حرارة لحظية رقائق معدنية رقيقة يسخن كهربائياً. التصاق إحباط لتغطية فتحه ضيقة قطع في الأنابيب. القصور الحراري لإحباط صغيرة بما يكفي للكشف عن الاختلاف في درجة الحرارة إحباط لحظية. مقطع الاختبار يمكن نقلها على طول الأنابيب وطويل بما يكفي لتغطية جزء كبير من الطبقة الحدودية الحراري المتزايد.
في بداية كل تشغيل تجريبي، هو تحقيق حالة مستقرة مع تدفق مياه مستمر تدفق معدل والحرارة لإحباط ويخدم كالمرجع. ثم يتم حقن فقاعة تايلور في الأنابيب. يتم قياس الاختلافات معامل نقل الحرارة بسبب مرور فقاعة تايلور نشر في أنبوب عمودي كدالة لمسافة نقطة القياس من أسفل الفقاعة تايلور تتحرك. وهكذا، تمثل النتائج معاملات نقل الحرارة المحلية. يدير مستقلة متعددة بريفورميد تحت ظروف مماثلة السماح بتراكم ما يكفي من البيانات لحساب نتائج موثوق بها الفرقة في المتوسط على نقل الحرارة الحمل الحراري عابرة. للقيام بهذا في إطار مرجعي تتحرك مع الفقاعة، قد موقع فقاعة على طول الأنابيب يكون معروفا في جميع الأوقات. ويرد وصف مفصل لقياسات طول وسرعة الفقاعات تايلور من المسابر الضوئية متعدية الجنسيات.

مثال من أجهزة الاستشعار البصرية الإخراج السجلات ويرد في الشكل 4 لفقاعة تايلور واحد ارتفاع في أنبوب عمودي مليئة بالمياه الراكدة. يمثل الانخفاض الكبير الأولى افتتاح الدارة بسبب نصيحة فقاعة تايلور، بينما وقت لاحق قطرات أقصر كثيرا في أعقاب الارتفاع إلى القي...

Watch this Scientific Journal Video about Measurements of Local Instantaneous Convective Heat Transfer in a Pipe - Single and Two-phase Flow at JoVE.com

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

هذه المخطوطة يصف الأساليب التي تهدف إلى قياس معاملات نقل الحرارة الحمل الحراري لحظية المحلية في تدفق أنابيب واحدة أو مرحلتين. ويرد أيضا أسلوب بصري بسيط لتحديد الطول وسرعة نشر ممدود فقاعة هواء (تايلور) تتحرك سرعة ثابتة.

قياسات لنقل الحرارة الحمل الحراري لحظية المحلية في أنبوب--تدفق واحد ومرحلتين

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

measurements-local-instantaneous-convective-heat-transfer-pipe-single

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

7.1K Views.  Tel-Aviv University. هذه المخطوطة يصف الأساليب التي تهدف إلى قياس معاملات نقل الحرارة الحمل الحراري لحظية المحلية في تدفق أنابيب واحدة أو مرحلتين. ويرد أيضا أسلوب بصري بسيط لتحديد الطول وسرعة نشر ممدود فقاعة هواء (تايلور) تتحرك سرعة ثابتة.

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

Echo Particle Image Velocimetry

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 Consequently, a prerequisite for understanding, predicting, and controlling fluid flows is the capability to measure the velocity field with adequate spatial and temporal resolution.2 For velocity measurements in optically opaque fluids or through optically opaque geometries, echo particle image velocimetry (EPIV) is an attractive diagnostic technique to generate "instantaneous" two-dimensional fields of velocity.3,4,5,6 In this paper, the operating protocol for an EPIV system built by integrating a commercial medical ultrasound machine7 with a PC running commercial particle image velocimetry (PIV) software8 is described, and validation measurements in Hagen-Poiseuille (i.e., laminar pipe) flow are reported.
For the EPIV measurements, a phased array probe connected to the medical ultrasound machine is used to generate a two-dimensional ultrasound image by pulsing the piezoelectric probe elements at different times. Each probe element transmits an ultrasound pulse into the fluid, and tracer particles in the fluid (either naturally occurring or seeded) reflect ultrasound echoes back to the probe where they are recorded. The amplitude of the reflected ultrasound waves and their time delay relative to transmission are used to create what is known as B-mode (brightness mode) two-dimensional ultrasound images. Specifically, the time delay is used to determine the position of the scatterer in the fluid and the amplitude is used to assign intensity to the scatterer. The time required to obtain a single B-mode image, t, is determined by the time it take to pulse all the elements of the phased array probe. For acquiring multiple B-mode images, the frame rate of the system in frames per second (fps) = 1/&delta;t. (See 9 for a review of ultrasound imaging.)
For a typical EPIV experiment, the frame rate is between 20-60 fps, depending on flow conditions, and 100-1000 B-mode images of the spatial distribution of the tracer particles in the flow are acquired. Once acquired, the B-mode ultrasound images are transmitted via an ethernet connection to the PC running the PIV commercial software. Using the PIV software, tracer particle displacement fields, D(x,y)[pixels], (where x and y denote horizontal and vertical spatial position in the ultrasound image, respectively) are acquired by applying cross correlation algorithms to successive ultrasound B-mode images.10 The velocity fields, u(x,y)[m/s], are determined from the displacements fields, knowing the time step between image pairs, &Delta;T[s], and the image magnification, M[meter/pixel], i.e., u(x,y) = MD(x,y)/&Delta;T. The time step between images &Delta;T = 1/fps + D(x,y)/B, where B[pixels/s] is the time it takes for the ultrasound probe to sweep across the image width. In the present study, M = 77[&mu;m/pixel], fps = 49.5[1/s], and B = 25,047[pixels/s]. Once acquired, the velocity fields can be analyzed to compute flow quantities of interest.

An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.

صدى الجسيمات Velocimetry صورة

The transport of mass, momentum, and energy in fluid flows is ultimately determined by spatiotemporal distributions of the fluid velocity field.1 ...

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.

We describe the use of micro-thermocouples to estimate local temperature gradients in steady laminar boundary layer diffusion flames. By extension of the Reynolds Analogy, local temperature gradients can be further used to estimate the local mass burning rates and heat fluxes in such flames with high accuracy.

منهجية تجريبية لتقدير محلي الحرارة تدفقاتها وحرق الأسعار ثابتة رقائقي الحدود النيران انتشار طبقة

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex ...

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.

Pool-boiling heat-transfer experiments were carried out to observe the effects of hybrid wettable patterns on the heat-transfer coefficient (HTC). The parameters of investigation are the number of interlines and the pattern orientation of the modified wettable surface.

تعزيز بركة الغليان نقل الحرارة على أسطواني السطوح مع أنماط قابل للبلل الهجين

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

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.

قوة كوريوليس يفصل وآثار الطفو الدورية على الحرارة كامل-ميدان نقل خصائص قناة الدورية

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

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

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

Chemical Engineering

Piping Networks and Pressure Losses

Source: Alexander S Rattner, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
This experiment introduces the measurement and modeling of pressure losses in piping networks and internal flow systems. In such systems, frictional flow resistance from channel walls, fittings, and obstructions causes mechanical energy in the form of fluid pressure to be converted to heat. Engineering analyses are needed to size flow hardware to ensure acceptable frictional pressure losses and select pumps that meet pressure drop requirements.
In this experiment, a piping network is constructed with common flow features: straight lengths of tubing, helical tube coils, and elbow fittings (sharp 90&#176; bends). Pressure loss measurements are collected across each set of components using manometers - simple devices that measure fluid pressure by the liquid level in an open vertical column. Resulting pressure loss curves are compared with predictions from internal flow models.

Pressure Losses in Piping Networks and Internal Flow Systems

Source: Alexander S Rattner, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
This experiment ...

Mechanical Engineering

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

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

Heat Exchanger Analysis

Source: Alexander S Rattner and Christopher J Greer; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA
Heat exchangers transfer thermal energy between two fluid streams, and are ubiquitous in energy systems. Common applications include car radiators (heat transfer from hot engine coolant to surrounding air), refrigerator evaporators (air inside refrigerator compartment to evaporating refrigerant), and cooling towers in power plants (condensing steam to evaporating water and ambient air). The objective of this experiment is to introduce experimental measurement (rating) and modeling procedures for heat exchangers.
In this experiment, a water-to-water tube-in-tube heat exchanger will be constructed, and evaluated. Temperature and flow rate measurements will be employed to determine the heat transfer rate (Q) and overall conductance (UA). The measured heat exchanger UA will be compared with predicted values for the geometry and operating conditions.

Rating and Modeling Procedures for Heat Exchangers

Source: Alexander S Rattner and Christopher J Greer; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, ...

Measuring Turbulent Flows

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
Turbulent flows exhibit very high frequency fluctuations that require instruments with high time-resolution for their appropriate characterization. Hot-wire anemometers have a short enough time-response to fulfill this requirement. The purpose of this experiment is to demonstrate the use of hot-wire anemometry to characterize a turbulent jet.
In this experiment, a previously calibrated hot-wire probe will be used to obtain velocity measurements at different positions within the jet. Finally, we will demonstrate a basic statistical analysis of the data to characterize the turbulent field.

Measuring Turbulent Flows Using Hot-Wire Anemometers

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
Turbulent flows ...

Mass Conservation and Flow Rate Measurements

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
The purpose of this experiment is to demonstrate the calibration of a flow passage as a flowmeter using a control volume (CV) formulation [1, 2]. The CV analysis focuses on the macroscopic effect of flow on engineering systems, rather than the detailed description that could be achieved with a detailed differential analysis. These two techniques should be considered complementary approaches, as the CV analysis will give the engineer an initial basis on which route to pursue when designing a flow system. Broadly speaking, a CV analysis will give the engineer an idea of the dominant mass exchange in a system, and should ideally be the initial step to take before pursuing any detailed design or analysis via differential formulation.
The main principle behind the CV formulation for mass conservation is to replace the details of a flow system by a simplified volume enclosed in what is known as the control surface (CS). This concept is imaginary and can be defined freely to cleverly simplify the analysis. For instance, the CS should &#39;cut&#39; inlet and outlet ports in a direction perpendicular to the dominant velocity. Then, the analysis would consist of finding the balance between the net mass flux through the CS and the rate of change of mass inside the CV. This technique will be demonstrated with the calibration of a smooth contraction as a flowmeter.

Control Volume Analysis for Mass Conservation and Calibration of a Flow Passage

Source: Ricardo Mejia-Alvarez and Hussam Hikmat Jabbar, Department of Mechanical Engineering, Michigan State University, East Lansing, MI
The purpose of ...