Chapter 009, Heat Transfer

This force is called buoyancy. A hot-air balloon, as shown in Figure 4. 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. On the other hand, as shown in b of Figure 4. This is an example of forced convection. Natural convection and forced convection. 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.

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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.

Mechanisms of Heat Transfer: Conduction, Convection & Radiation

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. The original concept was to have a Heat Transfer Division Memorial Award to recognize excellence in literature and creative activities. The original concept included two parts: It was decided that the memorial award could be given in two categories: Later a third General category was added.

The award was initially a division award which also called for the establishment of a custodian fund to support the award. The first award was given in to N. It was elevated to a society level award in , and an annuity to provide support for the awards was eventually established through division funding.

Max Jakob Memorial Award. Internationally, the Jakob Award is the most prestigious of all the heat transfer awards and is a society award. The award is bestowed in recognition of eminent achievement of distinguished service in the area of heat transfer. It is made annually without regard to society affiliation or nationality. The award was established by the HTD in in honor of Max Jakob, who passed away in , commemorating his outstanding contributions as a researcher, educator, and author.

Of the award recipients, the majority have gone to U. Best Conference Paper Award. This society award was established in and is bestowed triennially to recognize outstanding technical contributions in the field of thermophysical properties. Funding for the award was provided by Purdue University to honor the contributions of Yeram Touloukian. The first recipient was Akira Nagashima in This society award is given to a young engineer who is under 36 years of age, received a Ph.

It was established by the HTD in , and the award was funded through the efforts of Art Bergles and Warren Rohsenow, both well-known for their heat transfer research and mentoring of young researchers. The first recipient was Srinath V. It is perhaps surprising that this award has been bestowed only a few times, given the number of individuals who have provided outstanding service to the division.

With the many division and committee activities, it is impossible to present even a cursory overview of the past 75 years. However, a few selected highlights including recent trends are summarized here. In the early s when mainframe computers became available, there was an explosion in the amount of work done in numerical solutions. The computer allowed previously intractable problems to be revisited. Investigators of that era will remember the required stack of IBM cards and the challenge to get as many runs during a day as possible. Some of the earliest and best work was done by Stuart Churchill and his students at the University of Michigan.

He later moved to the University of Pennsylvania. Much of that work was focused on natural convection. In the early work, investigators wrote their own finite difference programs; later, more generic codes were written.

Basic Course of Thermo-Fluid Analysis | Software Cradle

Issues of stability and especially convergence were addressed on an ad hoc basis. Of course, many others were involved. Over the history of the HTD, radiation heat transfer research moved from methods to aid in the design of industrial furnaces to space applications and solar energy.

The search goes on for the most efficient numerical techniques to handle multimode heat transfer where radiation is a significant contributor. All of these continue to drive active research, but recently, much research has centered on microscale and nanoscale effects. The Heat Transfer Equipment Committee is one of the few committees where there has been strong industrial participation. This committee focuses on applications where heat transfer equipment is an essential component and provides a strong link between heat transfer art and science.

Relevant topics include enhanced heat transfer, fouling, compact heat exchangers, heat transfer equipment in the power and process industries, and flow maldistribution. HTRI were mainstays of the committee for many years. Its Generation and Use [ 23 ]. HTRI was organized in as a for-profit, industrially owned consortium by users, designers, and manufacturers of heat transfer equipment to promote systematic, application-oriented research in the field of heat transfer.

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The company was originally located at C. Jerry Taborek was the first technical director and the driving force in the company for over 20 years. Joseph Palen and Stanley Kistler were for many years key techical resources in the firm. One of the major paradigm shifts within the HTD during the last decade relates to microscale and nanoscale heat transport. It became apparent that there was much more to learn. Guo's keynote lecture asserted that advanced experimental techniques were needed to accurately understand microscale transport.

It was enthusiastically agreed that an international conference on this subject should be pursued. It became a meeting ground for researchers worldwide. Later, under the ASME umbrella, nanochannels were added to the conference theme. It went to Canada in and , and then to Puerto Rico in As a direct outcome of the conference, more than technical papers have been presented, many of them published later in technical journals.

The subject of enhanced heat transfer has reached a significant level of stature within the division and the heat transfer community. Bergles was the pioneer in this area and when Webb moved from the Trane Company, where he had gained a wealth of practical experience in applied heat transfer, to Penn State he pursued this topic with vigor. Many sessions on this subject were conducted through the years, and they always generated considerable interest. Webb initiated and became the first editor of the Journal of Enhanced Heat Transfer , and also wrote the well-regarded Principles of Enhanced Heat Transfer [ 24 ].

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A festschrift for Bergles was held at Georgia Tech in [ 25 ]. Allan Kraus, who did a lot of work in extended surfaces, an important enhancement technique, coauthored the well-known Kern and Kraus [ 26 ]. Due to the importance of future energy solutions and other emerging needs, thermal engineering research has been growing, as evidenced by the increase in participants and presentations at recent heat transfer conferences.

For example, the biannual international conference series on microscale and nanoscale heat and mass transfer MNHMT has been held three times with an attendance exceeding each time. Many advocates and researchers have become involved with micro- and nanotechnology, but none has made a greater impact than Arun Majumdar. Tien gave a talk on the challenges and opportunities in microscale heat transfer. An important sub-area that had received less attention than its counterparts, until recently, is nanoscale thermal radiation and radiative properties of nanostructures.

Due to its importance in harvesting solar energy, this sub-area has grown rapidly in the past decade. This is a multidisciplinary field, coupled strongly with recent advances in photonics and metamaterials. Science is an evolutionary design in which what we know—what is true and what works—becomes simpler, more accessible, and easier to teach. The merger of mechanics with caloric theory into thermodynamics in the s was not the end of this morphing by simplification and replacement.

The caloric line continues to this day as thermometry, calorimetry and heat transfer. Although the first two were incorporated unchanged into thermodynamics, heat transfer developed into a self-standing discipline, with a major impact on applied mathematics, fluid mechanics and aerodynamics. Still, its proper place is in thermodynamics along with all the other caloric teachings. Bejan predicted the merger of heat transfer with thermodynamics in the preface of his book [ 27 ], and his prediction came at least partially true in the two decades that followed.

The science of heat transfer expanded in new directions, most vigorously in constructal theory and design. The constructal law was first stated in by Bejan [ 28 ], where he formulated the volume-point heat flow problem, which unveils an evolving tree-shaped architecture Fig. The constructal law is a law of physics that unifies science physics, biology, engineering, and social sciences , and places the concepts of life, design and evolution in physics:.

The constructal law field is expanding rapidly. By , the society had developed a tradition of conducting two technical meetings each year: One of the 25 technical papers was presented by L. By the mid-fifties, the technical divisions were being encouraged to hold summer meetings. AIChE was approached immediately, as were several other groups, for joint participation in the conference. Participants slept in the student dorms and ate in the cafeteria.

The chemical engineers brought diversity and a strong applications perspective to the conference, especially through the process industries; non-Newtonian flow and heat transfer; fouling of heat transfer surfaces; and mass transfer. In , the HTD celebrated its 50th anniversary with a variety of activities.

Lienhard [ 33 ]. Elizabeth Jakob wrote a biography of her famous father, Max Jakob. Frank Kreith wrote about L. July 26, was a typical hot, humid summer day in Houston; however, in the early evening of the 26th, in the air-conditioned comfort of the Hyatt Regency Hotel, a very special event took place: The master of ceremonies was L. James Chenoweth, the division chair, who always took care of details, designed a 50th anniversary logo for the occasion. Chenoweth recognized the division's past chairs with 24 of the 50 present Fig.

Of the 50, several served more than one term. Drew served three terms: Norris, Mueller, and Nottage all played keys roles in the formation of the division. A total of 18 past chairs were deceased by Fletcher presented the 50th Anniversary Awards to 23 of the 31 recipients who were present Fig. Of the 31 living recipients only three were unable to attend.

The citation read as follows:. On the occasion of the 50th Anniversary of the Heat Transfer Division the Executive Committee of the Division recognizes the many members who by their contributions and service have established the excellent stature that the Division has attained.

In particular the Committee, by the 50th Anniversary Award, cites for their special and distinguished contributions 31 individuals:. For refrigerants at supercritical conditions, the factors that seem to have the most effect are the dynamic viscosity and density of a fluid. Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal. Some tools below are only available to our subscribers or users with an online account. Customize your page view by dragging and repositioning the boxes below.

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Citing articles are presented as examples only. All you need to read in the other general jounals BMJ ;