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ChE306: Heat and Mass Transfer

ChE306: Heat and Mass Transfer

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ChE306: Heat and Mass Transfer

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  1. ChE306: Heat and Mass Transfer • Course Overview • Syllabus • Teaching Philosophy • Study Method • Introduction of Heat Transfer Lecture 1

  2. Curriculum Flow Sheet

  3. ChE306 Course Description Theory of heat and mass transport. Unified treatment via equations of change. Analogies between heat and mass transfer. Shell balance solution to 1-D problems in heat and mass transfer. Analysis of chemical engineering unit operations involving heat transfer. Design principles for mass transfer equipment.

  4. ChE306 --- Syllabus Prerequisites: ChE 305 and Math 392 Lecture: Tu & Th 10:20-11:35 am, Jett Hall 283 Recitation: W: 5:30 pm, Jett Hall 283 Instructor: Dr. Shuguang Deng, Jett Hall 253 505-646-4346, sdeng@nmsu.edu Office hours: TuTh: 1:30 pm – 2:30 pm Teaching Assistant: Nasser Khazeni, JH151 TBD (Cell) khazeni@nmsu.edu Office hours: M: 1:00 - 3:00 pm

  5. Heat and Mass Transfer Textbook: Bergman, Lavine, Incropera, and DeWitt, "Fundamentals of Heat and Mass Transfer" 7th Edition, John Wiley & Sons, 2011 (ISBN: 978-0-470-50197-9) Available in NMSU Bookstore & Amazon.com

  6. ChE306 --- Syllabus Course Objectives: The goal of this course is for students to learn to apply the fundamentals of transport phenomena to solve problems relevant to chemical engineering practice: energy and mass transfer. In each case, we will work through examples that help to explore both the intuitive concepts and the formal mathematical framework necessary to make predictions. Transport phenomena, along with thermodynamics and reactor design, define the fundamental skill set necessary for solving the challenging problems that arise in the chemical engineering profession. At the completion of this course, the students will be able to:

  7. ChE306 --- Syllabus • Set up microscopic and macroscopic energy and mass balances (conservation principles); • Know the flux laws for heat and mass transport; • Apply the conservation principles and flux laws to model transport processes central to chemical engineering; • Use the physical and mathematical similarities between the processes of heat and mass transfer to solve new problems “by analogy”; • Perform basic unit operation design calculations for heat and mass transfer equipment.

  8. ChE306 --- Syllabus Contribution to Meeting the Professional Component: Heat and mass transfer as well as momentum transfer are the essential parts of the foundation of chemical engineering education and practice. This course will teach students the fundamentals of heat and mass transfer, and the skills of solving complex problems by applying the principles and methodologies similar to heat and mass transfer analysis learned in this course. This course will also develop students’ critical thinking ability and computational skills needed in the engineering professions.

  9. ChE306 --- Syllabus Four levels of learning objectives • Fundamental knowledge (concepts) Lecture, reading, quiz, HW, exam • Simple applications Example, HW, exam • Computational skills Example, HW, exam • Complex applications

  10. ChE306 --- Syllabus Relationship of the Course to Program Objectives The program objectives of the Department of Chemical Engineering which relate directly to curriculum development, delivery and improvement may be described (in short) as: 1. Developing ChE skills. 2. Will be able to obtain meaningful employment or be able to continue on in a graduate program. 3. Will be prepared for a long term successful career including lifelong learning. To assist in supporting these aforementioned objectives, ChE 306 will help you develop the following skills: 1. An ability to apply knowledge of mathematics, chemistry, physics, computing, safety and engineering. 2. An aility to design, conduct, analyze, interpret, and report on experimental relevant to chemical engineering practice 3. An ability to use the techniques, kills and modern engineering tools necessary for practicing chemical engineering.

  11. ChE306 --- Syllabus Attendance: Required for all lectures Recitation: Discussion sections will be conducted by the teaching assistant, who will return graded homework papers, discuss example problems, and answer questions. Attendance at one's assigned discussion section is expected for maintaining communication.

  12. ChE306 --- Syllabus Homework Policy: All students are required to finish homework assignments and submit them on time. Late homework will not be accepted for credit, except in the case of excused absence. Exams & Quizzes: 3 Midterm exams Final exam 10 in-class and take home quizzes

  13. ChE306 --- Syllabus Ethics and Misconduct: Students are expected to follow the highest of ethical, social and moral standards as specified in the Student Code of Conduct in the NMSU Student Handbook. Cheating will be disciplined as described in the “Academic Misconduct” section of Student Handbook. Student suspected of cheating will receive zero credit for the assignment and be recorded in the student’s file. It is encouraged to collaborate on homework assignments, but each student must submit his or her own solutions. Submission of identical homework solutions will be treated as Academic Misconduct.

  14. ChE306 --- Syllabus Homework Problem Solution Format:It is highly recommended that all problem solutions be presented in the following format: Known: State concisely what is known about the problem. Find: State concisely what must be found. Schematic: Draw a schematic of the physical system being considered. Properties: List the solid and/or fluid thermophysical properties used in your solution. Assumptions: It is important that you put all the assumptions in one place so that they can be reviewed. Analysis: Provide in sentence format, comments that make clear the logic and organization of your analysis.

  15. ChE306 --- Syllabus Grading for this course is as follows: • Mid-Term Exams (3) 45% • Final Exam 30% • Homework (10) 15% • Quizzes (10) 10% Your final grade will be awarded according to the following distribution: 90-100 = A 80-89 = B 70-79 = C 60-69 =D 0-59 =  F

  16. ChE306 --- Syllabus Re-grades: Re-grades can be done at the request of student within one week of the return date of the graded assignments. A memo explaining why a re-grade is necessary must be attached to the front page of the assignment. The score on the assignment may increase or decrease after re-grade.

  17. ChE306 ---Tentative Schedule 29 Sessions Midterm Exams (75 minutes) 9/27 11/1 11/13 Final Exam (120 minutes) 12/13, 10:30 am-12:30pm, JH 283 Review sessions before exams Homework & reading assignments

  18. Teaching Philosophy • Instructor is a facilitator & coordinator • Students take charge of the learning process • Active/interactive learning • Fundamentals & problem solving skills • Math & computer skills

  19. Suggested Study Method • Manage your time and stick to the schedule • Read the textbook before class • Take notes if necessary during class • Review the topics before doing HW • Finish HW independently • Good sleep before major exams

  20. Course Webpage • http://chemeng.nmsu.edu/ChE306/index.htm • Login name and password protection (?) • Update of class schedule and HW assignments • Solutions to HW, quiz and exam • Class notes • HW, quiz and exam scores

  21. Drug release from gel bead

  22. Heat Transfer: Physical Origins andRate Equations Chapter One Sections 1.1 and 1.2

  23. What is heat transfer? Heat Transfer and Thermal Energy Heat transfer is thermal energy in transit due to a temperature difference. • What is thermal energy? Thermal energy is associated with the translation, rotation, vibration and electronic states of the atoms and molecules that comprise matter. It represents the cumulative effect of microscopic activities and is directly linked to the temperature of matter.

  24. Heat Transfer and Thermal Energy (cont.) DO NOT confuse or interchange the meanings of Thermal Energy, Temperature and Heat Transfer

  25. Modes of Heat Transfer Modes of Heat Transfer Conduction: Heat transfer in a solid or a stationary fluid (gas or liquid) due to the random motion of its constituent atoms, molecules and /or electrons. Convection: Heat transfer due to the combined influence of bulk and random motion for fluid flow over a surface. Radiation: Energy that is emitted by matter due to changes in the electron configurations of its atoms or molecules and is transported as electromagnetic waves (or photons). • Conduction and convection require the presence of temperature variations in a material • medium. • Although radiation originates from matter, its transport does not require a material • medium and occurs most efficiently in a vacuum.

  26. Analogy for Heat Transfer Modes • Radiation • Conduction • Convection A Heat Transfer Textbook, 3rd Edition, by John H. Lienhard IV & V

  27. Conduction: General (vector) form of Fourier’s Law: Heat flux Thermal conductivity Temperature gradient Application to one-dimensional, steady conduction across a plane wall of constant thermal conductivity: Heat Transfer Rates: Conduction Heat Transfer Rates (1.2) Heat rate (W):

  28. Heat Transfer Rates: Convection Heat Transfer Rates Convection Relation of convection to flow over a surface and development of velocity and thermal boundary layers: Newton’s law of cooling: (1.3a)

  29. Energy outflow due to emission: (1.5) Heat Transfer Rates: Radiation Heat Transfer Rates Radiation Heat transfer at a gas/surface interface involves radiation emissionfrom the surface and may also involve the absorption of radiation incident from the surroundings (irradiation, ), as well as convection Energy absorption due to irradiation: (1.6)

  30. Irradiation: Special case of surface exposed to large surroundings of uniform temperature, (1.7) Heat Transfer Rates Radiation (cont.) Heat Transfer Rates

  31. Heat Transfer Rates: Radiation (cont.) Heat Transfer Rates Alternatively, (1.8) (1.9) For combined convection and radiation, (1.10)

  32. Summary of Heat Transfer Processes

  33. Example 1.1 (page 5) The wall of an industrial furnace is constructed from 0.15-m-thick fireclay brick having a thermal conductivity of 1.7 W/mK. Measurements made during steady-state operation reveal temperature of 1400 and 1150 K at the inner and outer surface, respectively. What is the rate of heat loss through the wall that is 0.5m by 1.2m on a side?

  34. Example 1.1 (page 5) Solution Known:Steady-state conditions with prescribed wall thickness, area, thermal conductivity, and temperatures Find:Wall heat loss Schematic:

  35. Example 1.1 (page 5) Schematic:

  36. Example 1.1 (page 5) Assumptions: • Steady-state conditions • 1-D conduction through the wall • Constant thermal conductivity Analysis:Apply the Fourier’s Law to calculate the heat flux. qx” = k T/L = 1.7 (W/mK) x 250K/0.15m = 2833 W/m2 Heat loss qx = qx”* A = 2833 *(0.5m * 1.2m) = 1700 W Comments:Note the direction of heat flow and the distinction between heat flux and heat rate.

  37. Problem 1.87 (a) Problem 1.87(a): Process identification for single-and double-pane windows

  38. Convection from room air to inner surface of first pane Net radiation exchange between room walls and inner surface of first pane Conduction through first pane Convection across airspace between panes Net radiation exchange between outer surface of first pane and inner surface of second pane (across airspace) Conduction through a second pane Convection from outer surface of single (or second) pane to ambient air Net radiation exchange between outer surface of single (or second) pane and surroundings such as the ground Incident solar radiation during day; fraction transmitted to room is smaller for double pane Process Identification Problem 1.87(a): Process identification for single-and double-pane windows Schematic:

  39. (a) If heat transfer is by natural convection, Problem: Electronic Cooling Problem 1.40: Power dissipation from chips operating at a surface temperature of 85C and in an enclosure whose walls and air are at 25C for (a) free convection and (b) forced convection. Schematic: Assumptions: (1) Steady-stateconditions, (2) Radiation exchange between a small surface and a large enclosure, (3) Negligible heat transfer from sides of chip or from back of chip by conduction through the substrate. Analysis: (b) If heat transfer is by forced convection,