UNIVERSITY OF NEVADA-LAS VEGAS
DEPARTMENT OF
MECHANICAL ENGINEERING
Course Objective: Learn to apply the concepts of the First and Second Laws of Thermodynamics to the solution of common engineering problems involving ideal gases, fluids exhibiting liquid/vapor characteristics, and components and systems operating with these substances.Do this in peer groups.
Instructor:R. Boehm, Professor of Mechanical Engineering, Room TBE B364, phone 895-4160e-mail:boehm@me.unlv.edu, Office hours will be held for 10:30-11:30 MWF.If these are not good times for you, please contact Instructor to make other arrangements.
In Class Procedures: Starting with the second day of the term, the following will take place each typical day.The Instructor will say a few words related to the concepts to be covered.Then four-person groups will work together on the problem(s) assigned for that day.Each person should write out the solution(s) and turn this in at the end of the period.Note that answers are given in the back of the book for most of these problems.If more than one problem is noted for a given day, the group should determine an appropriate schedule so that all problems can be addressed, even if they are not completed.This work will not be graded per se.Instead it will be used by the Instructor to make a general assessment of class progress and to record class participation.Periodically during the semester, the groups will be reconstituted as noted on the syllabus.At these points, each student should join in a totally new group of four people.
Homework:Homework is due on the day assigned, at the beginning of class.This can be done individually or in groups, but a separate, self-written submittal is required for each student. No late homework will be accepted.At least 30% of the homework must be successfully accomplished to pass the course.
Exams:One week prior to each exam an announcement will be made regarding the type of exam to be given.In general they will be one of two types:either closed book and notes, or open book, closed notes.It is recommended that any items brought out in class that may not be in the book should be noted in the book.
Grading: In-class participation at 10%, homework at 15%, 3 one-hour exams at 15% each (total of 45%), and final at 30%.
Text:Moran and Shapiro, Fundamentals of Engineering Thermodynamics, 4th Ed.,Wiley, 2000.
Syllabus
(The right is reserved to change assignments up to class before
day due):
1Aug 28IntroductionChapter 1----
2Concepts & UnitsChapter 11.20, 27, 46A
3Work2.1-2.22.10, 32
Sep 4Labor Day Recess, No Class
4First Law2.3-2.62.66, 68
5First Law2.3-2.62.691.23, 42, 57
2.12, 33, 67
6Sep 11First Law2.3-2.62.75
7Properties3.1-3.33.1, 15, 43
8Properties3.1-3.33.48, 632.70, 84; 3.17
9Sep 18Ideal Gas3.4-3.83.81, 106
10Control Volume4.1-4.24.3, 10
11Control Volume4.1-4.34.22, 253.55, 100, 108; 4.13B
(Continued on the other side of this sheet)
Syllabus
(Continued from other side):
12Sep 25Steady Flow4.1-4.34.36, 62
13Transient Analysis4.44.88, 92a
14Transient Analysis4.44.97, 1014.31, 60, 77, 100
15Oct 2First Law Review.Instructor lecture.
16EXAM I (Through Chapter 4)
172nd Law5.1-5.45.26, 34
18Oct 92nd Law5.1-5.75.41, 49
19Entropy6.1-6.36.21, 24(a, b)5.17, 56
20Process 2nd Law6.1-6.56.27, 35
21Oct 16Process 2nd Law6.3-6.76.43, 47C
22Process 2nd Law6.3-6.76.54, 666.22, 29, 52
23Entropy Generation6.5-6.66.91, 127
24Oct 23Isentropic Efficiency6.86.149, 156(a, c)
25Reversible, Steady6.96.161, 1736.61, 103, 121, 145
Nevada Day Recess, No Class
26Oct 302nd Law Review.Instructor lecture.
27EXAM 2, through Chapter 6
28Vapor Power Syst8.1-8.28.1
Note: November 3 (Day 29) is the last day to drop the class.
29Nov 6Rankine Cycle8.1-8.38.26
30Rankine Cycle8.1-8.58.356.171, 175; 8.9, 27
Veterans Day Recess, No Class
31Nov 13Air-Standard Cycles9.1-9.39.11D
32Brayton Cycles9.1-9.69.42
33Brayton Cycles9.6-9.99.618.19, 45; 9.21
34Nov 20Refrigeration10.1-10.310.6
35Gas Mixtures12.1-12.412.2, 16
Thanksgiving Recess, No Class
36Nov 27Air/Water Mixtures12.1-12,512.479.48(a-c), 84; 10.15
37EXAM 3, through section 12.4
38Air/Water
Mixtures12.5-12.712.47
39Dec 4Air/Water Mixtures12.5-12.812.67
40Psychrometric Chart12.5-12.912.7312.35, 59, 62
41Psychrometric Appls.12.5-12.912.83
December 15 (Friday), Final Exam, 8:00 am – 10:00 am.Comprehensive.Covers complete course.
If
you have a documented disability that may require assistance, you
will need to contact the Disability Resource Center (DRC) for
coordination in your academic accommodations.The DRC is located
in the Reynolds Student Services Complex room 137.Their phone
number is 895-0866 TDD 895-0652.
MEG
311
Thermodynamics
1
Prerequisites:PHY
182, 182L.
Learning
Objectives
At the
conclusion of this course, the student should:
1.Be able to
identify which substances typically used in engineering systems
can be analyzed with ideal gas assumptions and which
require the use of liquid/vapor tables.The student should
show competency applying both of these concepts and the
appropriate properties in the solution of problems.
2.Recognize the
differences between thermodynamic cycles and processes,
and be able to perform basic analyses of both.
3.Comprehend
the differences between work, heat, internal energy,
potential energy, and kinetic energy as they apply to typical
engineering systems.As part of this understanding the distinction
between concepts of path functions (inexact differentials)
and point functions (exact differentials) should be clear.
4.Be able to
express and apply the First Law of Thermodynamics
(Conservation of Energy) for closed systems and open
systems of the steady-state steady-flow (ss-sf) and
uniform-state uniform-flow (us-uf) types.Understand the
concept of conservation of mass as it applies to flow systems.Realize
the basis and application of the property enthalpy.
5.Have a basic
understanding of the Second Law of Thermodynamics and how
it applies to cycles.Particularly appreciate the
implications and applications of the Carnot Cycle
idealization.
6.Understand
the applications of the Second Law of Thermodynamics and
how it applies to processes.Recognize the influence of heat
transfer and irreversibilities on the entropy
change.Be able to apply this law to situations that involve
ideal gases or liquid/vapor substances.
7.Be able to
analyze basic Rankine (steam power), Brayton (gas
turbines and jet engines), and Vapor-Compression
(refrigeration) cycles to determine component and overall
performance.
8.Develop an
understanding of the basic ideas of psychrometrics (air/water
vapor mixtures) and apply them to elementary concepts related
to heating, ventilating, and air conditioning (HVAC)
systems.Be aware of the simplicity afforded by the Psychrometric
Chart in solving practical problems, as well as realize its
limitations.
UNIVERSITY OF NEVADA-LAS VEGAS
DEPARTMENT OF MECHANICAL ENGINEERING
MEG 311Exam I SolutionsFALL 2000
Average of all scores:approximately 76%.Highest grade:97%.
1.
|
|
|
|||
PT
Conclude
the state is superheated.
 |
 |
 |
 |
vv
2.The keys to the solution are the First Law for a closed system:?U=Q-W and the fact that internal energy is a point function.The latter can be written for a cycle as the summation of the process values: S?U = 0.Apply the First Law individually to all but the first process to fill in those blanks.Then use the point function aspect to find the internal energy in the first process.Then apply the First Law for the first process to find the Q.
Process?UQW
1-2560 -50 -610
2-3670900 230
3-4-920 0920
4-1-310-310 0
3.For throttling, this is a special case of SS-SF, no changes in KE, PE, no work, no heat transfer, and one flow in, one flow out.Thus First Law becomes h1 = h2.
Looking up T1 = 38°C, P1 = 12 bar from the R134a saturated table indicates that the state is compressed liquid.Use the temperature to find the corresponding hf value and assume that this is close to the enthalpy for the compressed liquid state.So h1 = h2 = 103.21 kJ/kg.At 2.4 bar, use the saturated values to find the quality
x = (h - hf)/ hfg = (103.21-42.95)/201.14 = 0.30
4.There is more than one way to work this
problem.But they are all equivalent overall.First, the work can
be determined from W = mòP(v) dv = P m (v2
– v1) which can be written as m (P2v2-P1v1).When
the First Law is applied to this constant pressure process, the
following results for the heat transfer:Q = W + ?U = m (P2v2-P1v1)
+ m (u2 – u1)
= m (h2 - h1).This
last step follows from the definition of enthalpy.For ideal gases
the enthalpy and internal energy can be found using the
temperature difference times the constant pressure specific heat
or the constant volume specific heat, respectively.Hence W = m
cp ?T, ?U = m cv
?T, and Q = W + ?U.Using specific heat values from
Table A-20 (300K values are close enough), find ?U = 21.54
kJ, Q = 30.15 kJ, and W = 8.7 kJ.Suggestion:Even if
you calculate work explicitly, you do not have to go through
determination of volume for this ideal gas.In this case use Pv
= RT, and use RT instead of the Pv product.Going
all the way through calculating volumes should still give the
same results, but the calculations are lengthy, and I am prone to
making errors doing that.
UNIVERSITY OF NEVADA-LAS VEGAS
DEPARTMENT OF MECHANICAL ENGINEERING
MEG 311Preliminary Course FeedbackFALL 2000
Please fill out and return to the instructor.Use back if necessary.Do not list your name. Thanks.
1. Comment on your feelings about the objectives related to the way the class is being instructed (group work on problems).How does this compare to “conventional” instructional approaches you have had in similar classes for attempting to master the material covered?How well or how poorly does the group interaction work for you?Indicate any problems with the group.How could any or all of this be improved to aid your learning ability?
New and effective, fine (14)
First group better than second…less
communicative (2)
Good and some other classes are using this
approach (1)
Doesn’t work…only one person does
work…uses outside groups of own selection(2)
I
work more slowly than some people, so the group approach is not
good for me (1)
2.Comment on the instructor’s lectures: too long, too short, boring, not relevant, hard to follow or…
Perhaps too short (4)
3.Comment on the midterm exam: totally unexpected types of problems, too long, differed greatly from other topics addressed in the course, inaccurately graded?Please be as specific as possible.
Reasonable, fair (18)
Kind of easy (1)
Inaccurately graded (2)
4.Comment on the homework: too much, too little, poorly graded, or any other aspects.
Reasonable (17)
Give more (1)
Tough or poor grading (4)
Some problems too hard (1)
5.Comment on the problem assignments in class: too long, too short, too difficult, not relevant…
Should have looked at before class,
sometimes too long or difficult (9)
Would like solutions to in-class problems at end of hour (1)
6.Make any other comments here that you feel would improve the learning experience in this class.
More instructor examples, more lecture
(50/50?)(2)
Classroom should be larger…countertops
needed. (2).
Group works if everyone wants to be part of
it.Would like at least one full lecture a week (1)
Need more feedback on if doing the work correctly (1)