Chapter 009, Heat Transfer

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The videos on Study. Students in online learning conditions performed better than those receiving face-to-face instruction. Explore over 4, video courses. Find a degree that fits your goals. Mechanisms of Heat Transfer: In this video lesson you'll learn about each one, and identify the differences between them. Try it risk-free for 30 days. An error occurred trying to load this video.

Try refreshing the page, or contact customer support. Register to view this lesson Are you a student or a teacher? I am a student I am a teacher. What teachers are saying about Study. Are you still watching? Your next lesson will play in 10 seconds. Add to Add to Add to. Want to watch this again later? Heat Transfer Through Convection: Heat Transfer Through Conduction: The Zeroth Law of Thermodynamics. What is Conduction in Science? The Structure of the Atmosphere. Air Conditions of Different Types of Breezes. Effects on Earth's Temperature. Developing a Scientific Hypothesis.

Middle School Life Science: Prentice Hall Conceptual Physics: Practice and Study Guide. Ohio Assessments for Educators - Chemistry There are three main ways that heat is transferred between substances or objects. Heat Is Mobile Have you ever touched a hot pan and burned yourself, how about warmed yourself in front of a nice campfire on a cold night?

Conduction If someone pours you a hot cup of coffee, you're likely going to pick it up from the handle instead of around the main part of the mug. Convection Remember how I said houses in the North commonly have their air vents on the floor while houses in the South have theirs on the ceiling? Radiation When you sit in front of a campfire, you are warmed by its heat.

Try it risk-free No obligation, cancel anytime. Want to learn more? Select a subject to preview related courses: Lesson Summary Heat is very friendly - it likes to move, transfer and travel. Learning Outcomes When this lesson is over, you should be able to: Define conduction Differentiate between conductors and insulators Describe convection and radiation Understand the significance of terrestrial radiation.

Heat Is Mobile

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Life Cycle of Glaciers. Professional Development Basic Genetics for Teachers: Professional Development Biology for Teachers: Professional Development Microbiology for Teachers: Professional Development Pathophysiology for Teachers: Professional Development General Chemistry for Teachers: Tutoring Solution Understanding Earthquakes: Tutoring Solution Understanding Volcanoes: Tutoring Solution Shaping the Earth's Surface: This version of the HTD is not a repeat of the Layton and Lienhard [ 1 ] history; rather, it is a perspective of the division over the past 75 years through a different pair of lenses, revisiting some highlights of the first 50 years with the addition of some details, but with a greater focus on the past 35 years or so.

Many individuals have helped make the HTD one of the strongest divisions in all of ASME; regrettably, many deserving contributors are not included here, not because their work isn't important, but simply because of space limitations. A history of the division cannot be written without an acknowledgement and appreciation of the significant contributions of John Lienhard IV Fig. Starting in , he worked as an engineer and educator and has been active in history since the s.

John is also a knowledgeable, delightful, and gifted speaker, and he has received several awards in recognition of his many contributions. Sweet and others in response to numerous steam boiler pressure vessel failures, and Robert Thurston Fig.

Thurston was an educator who first worked in the machine shop at his father's steam engine manufacturing company, the first of its kind in the United States. He later served as the first president of Stevens Institute of Technology and for 18 years as the first director of the Sibley College at Cornell University. At Cornell, he created a college of engineering with emphasis on scientific classroom work and more laboratory testing. So, from its very beginnings, ASME was involved with processes, i. In the late s and early s it was clear that Europe—England, France, and Germany—especially the Germans, had considerable interest and expertise in heat transfer.

Ludwig Prandtl in created the concept of the boundary layer. In , Wilhelm Nusselt proposed the dimensionless groups now known as the principal parameters in the similarity theory of heat transfer. Max Jakob, a German physicist born in , made major contributions toward understanding steam at high pressure, measuring thermal conductivity, and the mechanisms of boiling and condensation.

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Eckert, who was born in Prague, Austria-Hungary in , carried out research dealing with rocket and jet engine science at the Aeronautical Research Institute in Braunschweig. By the early s the U. Therefore, it is not surprising that the Chemical Engineering Department at the University of Delaware developed a strong program in process engineering and heat and mass transfer. In , Allan P.

From to , the ChE Department at Delaware carried out a comprehensive research program on shell-side fluid flow and heat transfer in shell-and-tube heat exchangers under Olaf Bergelin and Colburn. Kenneth Bell, who later spent most of his career at Oklahoma State University, played a key role in this project. However, in Germany major problems were coming to the fore. When Adolf Hitler became chancellor of Germany in January , his anti-Semitic Nazi regime immediately began the purge of Jewish professionals, resulting in the loss of some of its best scientific talent including fluid and heat transfer specialists.

Theodore von Karman Fig. But, von Karman was also a critical thinker and under his leadership, up to and during World War II, Koppes [ 3 ] wrote:. The GALCIT group made fundamental breakthroughs in the theoretical and applied aspects of both solid- and liquid-rocketry. These advances played an important role in converting rocketry from science fiction into respectable science and engineering. He also played a major role in the development of jet assisted takeoff JATO and in the founding of Aerojet Corporation. As discussed by Layton and Lienhard [ 1 ] there were—at the risk of oversimplification—two different approaches to heat transfer in the U.

Eckert [ 4 ] authored a history of heat transfer in conjunction with ASME's th anniversary and described the situation this way:. A vigorous activity developed in the United States … two names stand out among the early scholars in this development: In this book McAdams collected, screened, and correlated the available information on heat transfer processes, supplemented it by his own research, and presented through three editions an up-to-date, concise, and unified picture of the state-of-the-art. He created a standard text which served the heat transfer community as a reference book through many years.

He had the gift of attracting talented students and implanting in them interest and love for engineering research. Drew, who received acclaim for the first systematic use of heat, mass, and momentum transfer fundamentals in industrial applications McAdams's book [ 5 ] ultimately sold 50, copies over three editions, which even by today's standards is phenomenal for a technical book.

In contrast, on the West Coast good use was made of the German literature. Boelter began his long career in teaching with his appointment as instructor in electrical engineering at Berkeley in , but moved to mechanical engineering in Although there were discussions about which of the two approaches was best, they are actually quite complementary, and today we use both. Wilkes, and the laboratory itself, previously in the Physics Department, were moved to Mechanical Engineering in In , Warren Rohsenow Fig.

Ten years later Rohsenow took over direction of the laboratory and its name was changed to the Heat Transfer Laboratory, a better description of the work being done in the lab at that time. Laboratory activity increased when funding became more readily available after World War II. In , John A. Clark who later moved to the University of Michigan and Peter Griffith joined the faculty.

Boris Mikic, Arthur Bergles, and Leon Glicksman joined the faculty in the sixties, and, thus, the groundwork was laid for heat transfer at MIT to become one of the outstanding programs in the U. In , the laboratory was upgraded by John Lienhard V, now a senior member of the faculty, and renamed the Rohsenow Heat and Mass Transfer Laboratory [ 6 ].

Rohsenow's fundamental and applied research touched nearly all modes of heat transfer. His teaching emphasized fundamentals and practice-oriented problems. In the end, heat transfer excellence at MIT had transferred from chemical engineering to mechanical engineering: But heat transfer activity was not restricted to just the East and West Coasts, Kezios [ 7 ].

One of the objectives of these visits was to introduce Jakob to a variety of schools for the purpose of obtaining a faculty position.

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Ultimately, Jakob accepted a professorship at IIT which allowed him to serve as director of armour research as well. He quickly established himself as a leading heat transfer figure in the U. One of his first students was Stoethe P. Scotty Kezios, who carried out his doctoral work under Jakob. Kezios later became one of his faculty colleagues, and completed Jakob's volume 2 after his death.

Potter ASME's 52nd president in —34 , to learn more about the fundamentals of heat transfer. Hawkins later earned his Ph. Grosh's doctoral studies in radiation heat transfer. Viskanta quickly established himself as one of the premier researchers in radiative heat transfer, while Incropera and DeWitt went on to coauthor Fundamentals of Heat and Mass Transfer now in its 7th edition, written by Bergman et al. Collectively, this group built Purdue's heat transfer program into one of the best in the country. And for good measure, Boelter, Eckert, and Jakob all served as visiting professors at Purdue over a period of many years.

Mechanisms of Heat Transfer: Conduction, Convection & Radiation

While there, Robert Drake, Jr. Drake, coauthored Eckert's two later books [ 13 , 14 ]. After a nationwide search Eckert joined the Department of Mechanical Engineering at the University of Minnesota in Over his career Eckert published more than scientific papers and books, and the Eckert number in convective heat transfer was named after him. After Boelter left Berkeley, mechanical engineering continued its way to a premier heat transfer program with faculty members such as Robert Drake, Jr. Tien, the youngest engineering faculty member at Berkeley, later became department chair, dean, and chancellor of the university.

He advised many doctoral students and was extremely active in the HTD. Among his many technical interests, he became engaged in micro- and nanoscale heat transfer.

Tragically, his life was cut short due to illness. Here, in part, is what John had to say about Ralph Seban who had a distinguished career and was a recipient of the 50th Anniversary Award:. Ralph Seban, was the smartest and most feared faculty member at Berkeley when I was a student there. Seban was a rude, arrogant, and deeply caring person. In his almost desperate impatience he tore visiting seminar speakers apart. In the classroom, details were your problem. You could correct the plus and minus signs.

He simply sketched ideas from his encyclopedic memory. You had to go read the details in the journals. What Seban did was to mold students into worthy adversaries. He lured them into debates which, it seemed, they could not win. Then, one day, something remarkable happened. You found that, when you fully engaged your own mind, you could stay with him. And he would hold you there until you collapsed from exhaustion. Seban's students left Berkeley—left those marathons—with a deep-seated confidence.

If Berkeley had used teacher ratings, he would've flunked. Yet he was, without doubt, one of the most effective teachers I've known. In , Boelter became dean at UCLA, started the School of Engineering, and played a major role in laying a foundation for heat transfer excellence. Edwards radiation heat transfer , V.

Denny transport processes , Anthony Mills heat and mass transfer , Ivan Catton natural convection and nuclear energy , Vijay Dhir boiling heat transfer and two-phase flow , and Adrienne Lavine convective heat transfer, manufacturing processes. As Dean of Dartmouth College's Thayer School of Engineering, he led the faculty in developing a new curriculum based on engineering design and entrepreneurship. Tribus saw hands-on engineering design as being essential at all levels of the curriculum. Boelter believed in a general approach to engineering education and did not like the idea of separate departments, so the program became known as the School of Engineering and Applied Science SEAS.

Faculty members with expertise in one discipline were expected to teach courses outside their primary areas. However, after he retired, the school eventually abolished this approach and formed traditional engineering departments. Dean Boelter's qualities as a teacher and a man were perhaps best described in by a group of colleagues and former students in the preface to the Boelter Anniversary Volume on Heat Transfer, Thermodynamics and Education [ 16 ], which stated in part:.

It has been written elsewhere that L. Boelter is known for his integrity, imagination, and vision. We, his colleagues and students, have seen this side of the man. His way of teaching by precept and example has made us feel that these virtues are the requisites for a successful career, and we have grown so accustomed to them as Boelter's traits that we have taken them for granted. The other side of the man, seen only by his associates, has endeared him to us.

We refer to his compassion, his way of treading softly to avoid hurting even those who have fought against his ideas, and his willingness to sacrifice himself and his health for the sake of others. These common characteristics must be recorded here for the benefit of those who, less fortunate than we, could not be touched by them directly. We treasure these qualities, for they give life its meaning. In he was appointed the sixth dean of SEAS, and under his leadership both the size and stature of the school have grown significantly.

In the summer of , Louis London Fig. However, the paper was not published until [ 17 ].

The first serious attempt to obtain heat transfer and friction factor data for compact heat exchangers began at the U. This work continued at Stanford for the next 24 years, until The classic Compact Heat Exchangers by William Kays and London came out of that work, and is now in its 3rd edition [ 18 ]. In the preface of Shah et al. My principal recollection of that period was continually writing reports for ONR, reports that were widely distributed throughout the country, and I think this series of reports was what originally put us on the map.

English composition had always been one of my weak points, but here is where Lou was a teacher par excellence. I would lay out the report and write a draft, and then turn it over to Lou. A few days later he would call me in and we would sit down to go over it. Not a single sentence was left untouched. It was agony, but it was a great learning experience, and one for which I will always be indebted to Lou.

Kays and London became lifelong friends and Kays went on to a distinguished career at Stanford where he served as department head and dean. Ramesh Shah, another of London's students, and London offered a very popular short course on compact heat exchangers. Another student, Robert Moffat, became well known for his experimental heat transfer research and his short courses on experimental methods. In the s Edward Vincent gained international recognition for his heat transfer work in gas turbine rotor disks. Under Mechanical Engineering Department Chairman Gordon Van Wylen's leadership, the department established expertise in space technology as a key player in cryogenic research.

A solar energy laboratory was developed in under John Clark. The two departments thus provided breadth as well as depth in heat transfer at Michigan. However, the actual formation of the Heat Transfer Division as an independent division did not occur until three years later. The first chairman of the professional group in was J. Sengstaken, and the first chairman of the Heat Transfer Division, in , was E. However, for historical purposes is generally considered to be the official beginning of the division. The chairmen during the first 15 years included Thomas Drew, L.

If several of those names sound like chemical engineers you would be correct. The chairs for the Heat Transfer Division over the past 75 years, shown in Table 1 , include many familiar names. It should be recalled that serving as chair was not just a grueling 1-year assignment, but one had to serve for several years on the executive committee prior to the year as chair, followed by the obligatory year as past chair. But most people who served as chair, on reflection, will say it was more than worth the effort.

Through the years the HTD explored and implemented many ways to expand its programs and reach both academic and practicing members of the division. Although the exhibits broke even or made a small profit, they were never as successful as the division leadership or ASME had hoped; however, the book exhibits sponsored by the publishing companies were always well received. This feature was copied by a number of divisions. The division introduced poster sessions as a way to promote and facilitate discussions between authors and participants, especially those individuals who were interested in specific papers.

Panel discussion sessions were initiated in an attempt to bring in more industrial participants for whom publications were frequently not an option, for proprietary reasons. In , the division introduced Heat Transfer—Recent Contents , a monthly publication consisting of the title pages of relevant heat transfer journals. Although this initiative was financially successful, the advent of the Internet and other search options essentially obsoleted this approach.

Kreith then worked at JPL for four years where he had the opportunity to collaborate with Theodore von Karman. The Solar Heat Division was the first branch established and Kreith was appointed as its director. Kreith is a strong proponent of sustainable energy, especially solar and nuclear energy, and remains active in this field. Representatives from the National Laboratories have been active in and strong supporters of the Heat Transfer Division for many years.

Since then, the informal group has grown and luncheons are regularly scheduled at ASME meetings and other conferences Fig. The luncheon meetings are primarily social. This venue gives the women an opportunity to visit, share their experiences, discuss their concerns, and encourage each other. A topic of major interest and discussion through the years has been that of balancing the work environment while having children and raising a family. Leslie Phinney [ 22 ] of Sandia National Laboratories shared her thoughts regarding the luncheons:. The senior women are very welcoming and inclusive to more junior colleagues.

The lunches are wonderful opportunities to meet and maintain contact with colleagues from a variety of institutions and backgrounds. As my career progressed, my appreciation for these luncheons deepened upon learning from women colleagues in other research areas that such events are not a part of the conferences that they attend. This fun and enjoyable support group includes a university president, deans, and department chairs as well as faculty members engaged in teaching and research.

The HTD has had a long and impressive record of leadership within the division from its inception. However, the division has also provided a strong contingent of leadership for the entire society going back at least to the s. Each of these individuals made unique contributions to the society, Heat Transfer Division, and engineering profession. From a single professional group in , the division has grown significantly.

There are currently 13 technical committees and several administrative committees including the Executive Committee. As of September , the primary membership of the division was 3, including students , with a secondary membership of 3, including 42 students. A total of 14, ASME members have designated heat transfer as one of their top five technical divisions.

The division is taking on a more international character; for example, at the National Heat Transfer Conference in Puerto Rico the participants represented 37 different countries. The division sponsors a number of awards and participates in several society awards; however, space limitations permit only a brief background and a partial description of them. The awards are administered through the seven-person Honors and Awards Committee. Heat Transfer Memorial Award. Principle of hot-air balloon. Buoyancy of a compressible fluid can be treated in a straightforward manner because the volume is inversely proportional to the temperature.

On the other hand, the volume change of an incompressible fluid is difficult to quantify. Because of this, the buoyancy of an incompressible fluid is approximated using a force that is proportional to temperature difference. This approximation is called the Boussinesq approximation. The error caused by the Boussinesq approximation is large when the temperature difference is very large.

The flow of fluid is classified in two ways depending on what is driving the flow. The two methods are: With natural convection , heat flows without any assistance from external sources, e. Natural convection is driven by buoyancy which is caused by differences in the fluid temperature. On the other hand, with forced convection , heat flow is caused by an external source such as a fan or pump, which moves the fluid. In a of Figure 4. This is natural convection.

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On the other hand, as shown in b of Figure 4. This is an example of forced convection. Natural convection and forced convection. For forced convection, the buoyancy effect is small compared to the inertia force. This is a characteristic of flows driven by an external force such as a fan.

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