UNIVERSITY OF WATERLOO DEPARTMENT OF CHEMICAL ENGINEERING ChE 100
CHEMICAL ENGINEERING CONCEPTS 1
FALL 2009
Instructors Lecturer:
Dr. Eric Croiset Room DWE 2513F e-mail:
[email protected]
Ext. 36472
Tutorials:
Dr. Eric Croiset Room DWE 2513F e-mail:
[email protected]
Ext. 36472
Eng. Comm. Lab.:
Dr. Michael Fowler Room DWE 3513A e-mail:
[email protected]
Ext. 33415
Teaching Assistants:
Noorlisa Harun Room DWE 2536B email:
[email protected]
Ext. 36097
Sheng Lu Room DWE 1505 email:
[email protected]
Ext. 36864
Karachakorn Panha Room DWE 3523 email:
[email protected]
Ext. 36164
Monrudee Phongaksorn Room DWE 1535 email:
[email protected]
Ext. 36981
Faraz Syed Room DWE 3523 email:
[email protected]
Ext. 36164
WEEF TAs:
Kim Broten,
[email protected] Ryan Egli,
[email protected] Linda Zacaj,
[email protected]
Texts Elementary Principles of Chemical Processes, R.M. Felder and R.W. Rousseau, 3rd Edition, J. Wiley & Sons, 2005. Introduction to Professional Engineering in Canada. Andrews et al., Prentice Hall, 2006. Course support on the internet All online materials for CHE 100 can be at UW-ACE: https://uwangel.uwaterloo.ca/uwangel Lecture Outline The course covers material from Chapters 1-5 Felder and Rousseau. About 4 weeks of lectures will be spent on Introduction and Engineering Problem Analysis, 7 weeks on Material Balances, and 1 week on Real Gases. 1
Tutorials Each student in the course has a one- hour tutorial each week, at a time and place indicated on his/her schedule. Please ensure that you come to the correct tutorial. Each tutorial involves a 30 minute quiz on the previous week’s lecture material. These will be graded and returned the following week. Quizzes are compulsory, and at least 9 must be completed (unless satisfactorily excused). The remaining tutorial time will be devoted to a discussion and illustration of lecture material. Engineering Communication Laboratory: CPH 1346 (See Dr. Michael Fowler) Lecture Assignments Assignments are posted on UW-ACE every Wednesday and they are usually due Friday by noon the following week. They must be submitted in the mailbox outside Room DWE-2518 under the appropriate section number. These will be graded and returned to the shelves outside DWE-2518, usually within one week. Important note related to privacy law: In order to respect privacy law the returned marked assignments placed on the shelves (public area) should not give direct information as to whom it belongs. As such, when you submit assignments you are asked to staple a short paper where you indicate both your name and ID#. This paper will be ripped out before the assignment is returned to you. On the assignment, however, you will only indicate your ID# on each page. Failure to do so (e.g. writing your name directly on the assignment) will result in 5 points subtracted from the assignment mark. Lecture assignments are compulsory, and a minimum of 8 of the 10 assignments must be submitted. The average grade for the assignment will be based on the 8th best assignment marks. If less than 8 assignments are submitted, the difference between 8 and the # of assignments submitted will be subtracted to the final mark. E.g., hand in 6 assignments, then 8-6 = 2 pts to be subtracted from the final mark! Each question on an assignment will be graded as follows: 2 - the solution is correct or very nearly correct 1 - the solution is partially correct 0 - the solution is incorrect or nearly incorrect You should plan to spend about five hours per week outside classes on this course. Examinations There will be a 2-hour mid-term test on Wednesday, October 21st from 7:00-9:00 p.m. There will be a 2.5-hour final examination (covering the entire course) scheduled by the Registrar during the final examination period. Course Grading The “normal” course grade will be computed as follows: Communication Laboratory Assignments: Co-op/PDENG Midterm Final Examination Assignments Quizzes
18% 2% 20% 50% 5% 5%
Note that if the average of the Midterm and Final exams (with weights of 35% and 65%, respectively) is less than 50, then this average will become your course grade, resulting in a failed course. 2
ChE 100 Chemical Engineering Concepts 1 PROBLEM SOLVING IN ENGINEERING Engineers are persons who not only are competent to originate, plan, design, construct, and operate, but also to direct others effectively in such activities. Engineers are able to coordinate the contribution of many sciences, some arts, business procedures, sound economics, and enlightened social policies, to the attainment of the desired end. In short, engineers are problem solvers. To be a competent engineer, therefore, you must become a competent problem solver. Effective problem solvers may be born, but experience has shown that most of them are made! A function of problem assignments in chemical engineering is to help you gain the skills necessary for the achievement of competency in problem solving, in addition to their traditional role of enhancing understanding of basic concepts. Problem Scope Real world problems, of course, vary greatly in both scope and complexity. While the type of approach to solving a particular problem depends on, for example, 1. the nature of the problem itself: is it (and the perceived goals) well defined or is it open ended (multiple possible solutions)? 2. imposed constraints (time, money, availability of information, solution techniques), There are generalized guidelines which have been found to be very useful in solving any type of engineering problem, including sub-parts of very complex problems. In ChE 100/101, the assignments largely consist of closely prescribed problems which serve to illustrate, and to increase the student’s comprehension of the underlying concepts. In later years, the curriculum provides opportunities for dealing with more extensive and open-ended problems, building on the techniques developed in ChE 100/101. Methods of Problem Solving In engineering, problems may often be designated as belonging to one of two general classifications. First, those in which rather precise answers (for which accurate data, system models and computations procedures are obviously required) are either necessary, e.g., process control stability, or desirable, e.g., design optimization of established technologies. On the other hand, where the direction or magnitude of the solution(s) is not readily perceived beforehand, e.g., development of new technologies, or where economic, environmental or other constraints dictate, we often seek a preliminary description of the results by applying the principle of successive approximation (fine tuning the input on each go-around in view of the initial results) or by doing order-of magnitude calculations. The trick is recognizing which of these approaches is required in order to get a useful (meaningful) solution. How does one do this? The approach to be taken often depends on the degree of definition of the problem and the end use of the solution obtained. This is termed the “Principle of optimal sloppiness”. In textbooks, the nature of the problem (what information is sought) is, usually, clearly stated; on the other hand, the major difficulty with many real-world problems lies in expressing clearly the actual problem required to be solved (often the problem description given you by others merely serves to hide the true nature of the problem!). Experience is the best instructor here.
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Regardless of the specific approach to be taken, complex engineering computations involve translation of the physical problem into “abstract” terms, i.e., into a mathematical MODEL of the real world, manipulation of the model to achieve a mathematical solution, and, finally, translation of the abstract results into terms of physical significance. Such a process is illustrated below.
MATHEMATICS (abstract world)
STEP 2 solution of the mathematical problem
Step 1
Step 3
translation of abstract results into terms of physical significance
translation of the physical problem into abstract terms
THE PROBLEM (real world)
MATHEMATICAL SOLUTION (abstract terms)
(direct route not feasible in complex situation)
THE ANSWER (real world)
The physicochemical principles are of prime importance. The language (mathematical model) in which we express them and manipulate the relationship between them is of secondary importance, but the ability to choose the appropriate mathematical tools is an important attribute of an engineer. Although translation of the problem into mathematics has the disadvantage that we may lose our intuitive feel for cause and effect, this procedure is essential in complex situations and produces useful results as long as the model reproduces the essential features of the real world. It is also important to recognize that in order to achieve a solution when there are complex or ill-defined relationships, it often is necessary to make one or more ASSUMPTIONS about the physicochemical behaviour of the system under study. The resulting model will then be subject to the constraints imposed by the assumption(s) and its use in situations in which the original assumptions are not valid can lead to serious error. The problem solver must ensure that SIMPLIFYING ASSUMPTIONS ARE CONSISTENT WITH THE PHYSICOCHEMICAL REALITY OF THE SYSTEM UNDER INVESTIGATION.
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