Ch.E 327 SPRING 2013

HEAT AND MASS TRANSFER OPERATIONS

FALL 2005

Instructor&Assistant / Office / Phone / e-mail
H. Önder Özbelge / EZ-40 / 2628 /
Mustafa Yasin Aslan / CZ-12 / 4353 /

Wednesday 13:40 14:40 at Z120, Friday 11:40 12:40 at Z120

Textbook

Frank, P. Incropera & David P. Dewitt, “Fundamentals of Heat and Mass Transfer”, 7th ed., John Wiley&Sons, 2013

References

I. Tosun, “Modelling in Transport Phenomena”, Elsevier, 2002

R. B. Bird, W. E. Stewart and E. N. Lightfoot, “Transport Phenomena”, 2nd ed., John Wiley&Sons, 2002

C. J. Geankoplis,“Transport Processes and Unit Operations”, 4th ed., Prentice Hall, 2003

S. Middleman,“An Introduction to Mass and Heat Transfer”, John Wiley&Sons, 1998

Exam Dates

Midterm 1: Apr. 3, 2013

Midterm 2: May 15, 2013

Final : to be announced

Grading

Midterm 1 25 % Homework 15 %

Midterm 2 25 % Final 35 %

Course Objectives

At the end of this course you will be able to

  1. Understand the basic principles of heat transfer by conduction, convection and radiation
  2. Understand the basic principles of mass transfer by diffusion and convection
  3. Understand analogies between heat and mass transfer
  4. Design heat exchangers
  5. Work in teams

Policies & Procedures

  • A web page has been constructed for the course. All the course materials (syllabus, homework assignments, etc.) will be made available at my home page.

You need to visit the site on a regular basis to get recent homework assignments and other relevant announcements.

  • All MT’s will bepartly closed book and partly open-book and open-notes (no photocopies, only your own handwritten notes and class handouts). It is your responsibility to understand the exam questions. If you have difficulty with English, you may bring a dictionary with you.
  • Starting from the first week of the semester ATTEND all the lectures, be sure that you understood the subject of the lecture, otherwise do not hesitate to ASK QUESTIONS during the lecture, be sure to REVIEW the material of the previous lecture before you come to the class, otherwise you will have difficulty to understand the lecture.
  • If you miss an exam with a certified medical excuse, you may take a makeup exam at a designated time near the end of the semester. It will be CHALLENGING!
  • You must work in groups of three on the required homework. The groups will be formed such that each group will contain at least one student with a cumulative grade point average (CGPA) of 2.00 or higher. However, each group may contain no more than two students with a CGPA of 3.00 or higher. One group member will be designated the leader for each assignment. The leader will be responsible for coordinating the work and making sure everyone in the group understands all the problem solutions before they are handed in. After being a group leader, an individual may not be leader again until everyone else in the group has held the position.
  • Required homework will be due at the beginning of the period on the due date - one solution set per group. Use A-4 size paper and one side of each page. Follow the format provided below:

- Problem statement

- Given

- Find

- Schematic

- System

- Physical properties and equilibrium data

- Assumptions

- Analysis

You will draw a lot of graphs in this course. Each and every graph that you draw

should have a title to identify it. Each coordinate axis should be labeled accordingly

(e.g., y, mole fraction in the gas phase, dimensionless, or L, liquid phase flow rate,

kg/hr, etc.)

If a student’s name appears on a solution set, it certifies that he/she has participated in solving the problems and understood all the solutions. If this turns out not to be the case, both the student in question and the group leader will be considered to have cheated and will be dealt with accordingly.

To get an AA in this course, you must attempt and do satisfactory work on all homework problems in addition to getting the necessary weighted average grade on tests.

Late homework will be accepted up to one week after the due date and will receive a maximum grade of 60 %. However, if a group abuses this privilege by routinely handing in homework late, the privilege will be withdrawn.

  • There will be a gray area between each two letter grades in the final distribution, so that two students getting the same weighted average could get different letter grades. If you are in one of these gray areas, whether you get the higher or lower grade depends on three factors:

a)Class attendance and participation in class. Attendance less than 70% of the classeswill result with an NA in this course,

b)Your performance on homework problems,

c)Whether your midterm exams and homework performance has been improving (your grade goes up) or declining (it goes down).

SAMPLE HOMEWORK

TITLE PAGE

Ch.E. 327

HEAT AND MASS TRANSFER OPERATIONS

HOMEWORK: 1

(Date due: Oct.1, 2005)

Submitted by : Group C

Group Leader:………….

Group Members:…………

Submitted to : Prof……….

Problem No: 1

Drought conditions in the Antalya region have prompted officials to question whether the operation of swimming pools at the five-star hotels should be permitted. As an engineer, you have been asked to estimate the daily water loss due to pool evaporation.

As representative conditions, you may assume water and ambient air temperatures of 25oC, an ambient relative humidity of 60 %, pool surface dimensions of 6 m x 12 m, and a wind speed of 2 m/s in the direction of the long side of the pool. You may assume the freestream turbulence of the air to be negligible and the surface of the water to be smooth and level with the pool deck. What is the water loss for the pool in kilograms per day? DAB = 2.6x10- 5 m2/s.

SOLUTION

Given:Tair = Twater = 25oC

Relative humidity = 60 %

Wind speed = 2 m/s

DAB = 2.6x10- 5 m2/s

Find:The daily water loss,

Schematic:

System: Water in the pool

Assumptions:

  1. Steady-state
  2. Negligible air turbulence
  3. Water surface is smooth and it leaves with the pool deck at all times

Physical Properties:

For air at 25oC: ρ = 1.1845 kg/m3; ν = 15.54x10- 6 m2/s

The vapor pressure of water at 25oC is 23.8 mmHg.

Analysis:

  • Calculation of Sc and Re

Since ReL > 1x105, both laminar and turbulent conditions exist on the plate. The corresponding correlation is

  • Calculation of <Sh>
  • Calculation of <kc
  • Calculation of saturation concentration

Assuming ideal gas behavior, the saturation concentration of water can be calculated from

where “A” stands for H2O.

  • Calculation of water loss

where MA is the molecular weight of water.

Therefore, the amount of water evaporated from the pool in one hour is

The daily water loss is

Note: If required, you have to use a graph paper to plot your results!

TIPS FOR TEST TAKERS

I. PREPARATION

  • Study in small groups.

Make sure your study group contains only students who are serious about studying, at least some of whom are of your ability or better.

Go over as many different problems as you can but do not solve the same problem twice. Do not quit on a problem until you are convinced you could do it yourself.

Brainstorm possible things you could be asked and answers you might give.

  • Make up a crib sheet as though you were going to cheat on a closed-book exam. If the test is closed-book, know what is on the sheet. If its open-book, bring the sheet with you.
  • Try to avoid all-nighters the night before the test.
  • Think about a backup system for your alarm clock on the morning of the test, e.g., a second alarm clock or a wake-up call from a friend.
  • Be sure you have good batteries in your calculator and a backup pencil.

II. TAKING THE TEST

  • Read the whole test first. Then start with the problem that looks easiest to you and progress to more difficult ones.
  • STAY IN MOTION! Work on a problem until you are not sure what to do next. Think about it for a minute or two and if nothing comes then drop it and go on to another problem. You will often find that when you get away from a sticky problem and then later get back to it, the solution procedure magically appears.
  • Budget your time. Do not spend 30 minutes sweating out an additional five points on a problem and run out of time leaving a 40-point problem untouched.
  • Show your work. You may be able to do the whole problem in your head and just write down the answer, but don’t. If you are wrong, you will get zero credit, and even if you are right the instructor may suspect you of having copied the answer.
  • Try to keep it legible. If an instructor cannot read you wrote, he/she will probably not assume what you did is correct.
  • Do not panic. If you feel yourself sweating, hyperventilating, etc., put down your pencil, close your eyes, take a few deep breaths, and consciously relax any muscles that you are clenching (jaw and stomach muscles are good candidates for this). When you are calmer, go back to the test.
  • Check your answers if you have time at the end. Have you answered each part of every question or did you overlook something? Do your solutions look reasonable? Can you reproduce your numbers? (Save that one for last).

Note:You may also refer to “Making the A: How to Study for Tests” Diane Loulou,