CHE 322 Process & Engineering Thermodynamics Fall 2016

Transcription

1 CHE 322 Process & Engineering Thermodynamics Fall 2016 Instructor JENNIFER MAYNARD W 2:30-4 pm, CPE Teaching Assistants KRITI MISHRA Th 3-4:30 pm, CPE 3.448; office Grader EMILY BOLYARD Lecture T/Th 11:00 am 12:15 pm RLM Recitation F 9:00 9:50 am RLM #14960 NOTE: HW will be due Friday at the beginning of recitation NOTE: quizzes will be conducted during recitation most weeks Text: Engineering & Chemical Thermodynamics, 2 nd ed., Milo D. Koretsky, Wiley. 1

2 Course Description: Thermodynamics relates work, heat, temperature and states of matter to each other. From a surprisingly small set of empirically based laws, an enormous amount of information about the relationships among equilibrium parameters for a system can be deduced. This information can then be applied to physical, chemical and biological systems including engine design, materials processing and cellular processes. Amazingly, thermodynamics is independent of any molecular model of matter, but molecular interpretations of various aspects of the subject (e.g., entropy and temperature) will be discussed in the course to broaden understanding. The focus of this course is the further development of thermodynamics based on the Ch353 Physical Chemistry pre-requisite and the application of the subject to practical systems. Goals: The objective of this course is to introduce students to the principles of thermodynamics as they apply to physical and chemical processes. Knowledge, Abilities, and Skills Students Should Have Entering This Course: 1. Units, material and energy balances, the use of steam tables and P-H charts (ChE 317). 2. The first law of thermodynamics, enthalpy, and heat capacity (ChE 317) 3. Ideal gas and real fluid behavior (ChE 317). 4. Solution of simple chemical engineering process problems (ChE 317). 5. The first and second laws of thermodynamics (Ch 353). 6. State functions and path-dependent functions in the solution of chemical problems (ChE 353). 7. The theoretical aspects of thermodynamics and the treatment of ideal and real fluids (Ch 353). 8. Deviations from ideality by use of various equations of state (Ch 353). 9. Solution thermodynamics (Ch 353). Knowledge, Abilities, and Skills Students Should Gain Form This Course: 1. The student should be able to apply energy and entropy balances to open and closed systems and to evaluate the thermodynamic efficiency of compressors, turbines, Rankine cycles and refrigeration cycles. They should be comfortable using steam tables, P-H, T-S, and H-S charts and calculating residual properties with equations of state. They should be able to derive property relationships using multivariable calculus. 2. The student should be able to solve phase equilibria problems involving vapor, liquid and solid phases. They should know how to use experimental data to evaluate the constants for various empirical equations, e.g. Van Laar, Margulies, and to use these equations to construct binary phase diagrams. 3. The student should be able to set up and calculate yields from homogeneous and heterogeneous reaction equilibria (useful for 372). 2

3 Impact on Subsequent Courses in Curriculum: Thermodynamic properties, phase equilibrium and chemical reaction equilibrium play an important role throughout chemical engineering, e.g. in ChE 360, ChE 363, ChE 372 and ChE 473K. Thermodynamics is one of the main pillars of chemical engineering; others include transport phenomena and reaction kinetics. Course procedure Attendance in lecture or discussions is encouraged but not required. If you do attend any class, please arrive promptly, attentive and ready to work. No electronics are permitted without permission; unauthorized use may result in temporary confiscation. Lecture hours will be used to introduce new material, provide detailed examples, conduct some quizes, conduct three hourly exams. Recitation hours will be used to conduct quizzes, work example problems, provide extra time on difficult topics. Canvas will be used to post homework assignments and solutions, assignment grades and any announcements. Please check Canvas at least weekly. Grading Homework 10% Typically posted Fri on Canvas, due the.following Fri in recitation. No late HW accepted. Quizes 10% Based on the prior weeks lecture, reading & HW, most Fridays during recitation. These are designed to be a check that you are keeping up with and understanding the material. No quizzes on Exam weeks. Lowest quiz score will be dropped; if you miss a quiz, this will be your dropped quiz. If you are late to class, you will not get extra time for your quiz. If you present your explanation of a short problem to the class, this can replace your second lowest quiz score (optional). Exams (3) 20% each In-class exam dates and sections covered are noted in the schedule. There will be no make-up exams. Final 20% Time and room determined by the college. Registration for this course includes the University-scheduled final exam date; there will be no make-up final. The final will be cumulative. Total 100% Bbbbbbbbbbbbbbbbbbbbbbbbbbbb Please show the detailed steps/ logic you follow in solving a problem (ie, a diagram of the problem, define variables, analytical approach and equations used/ derived) grading will be based primarily upon these steps, not upon a correct final answer. We want to give you credit for your work, but there needs to be something on page to justify this. Reading assingments are required and you are responsible for the concepts and examples contained therein. Content may be covered in the reading that is not covered in lecture or recitation. The reading is most valuable if you complete it before the relevant class period. 3

4 Homework problems are for you to practice using the concepts and equations and are representative of those on exams. The way to learn is to struggle with the problems, to understand why a certain approach is chosen and the details of each step. For some homework problems, class will prepare you to complete them; for some you will need to refer to the text. Quizes will be conducted most Thursdays during recitation and will consist of one to two problems. These will be based on material covered in the classroom, reading assignments and homework. You may have unannounced quizzes if it does not appear that students are keeping up with the class. Your lowest quiz score will be dropped. Exams will be based upon material covered in lecture, recitation, reading and in the homework; reading assignments complement lecture and provide additional examples for practice. During exams, you may bring one 3x5 inch cheat sheet to help you. The exam will be closed notes, closed book. All required equations and other key information will be provided. Practice exams with solutions will be provided on Canvas. Exams will be conducted during the normal class period and will be a combination of simpler problems (i.e., knowledge-based or those similar to HW and class examples) and more challenging problems (i.e., in which you apply the concepts in a slightly different way; e.g. you have seen distillation columns with one feed now you have two feeds or you have only seen total condensers now you have a partial condenser). These are not intended to be tricky but to probe the depths of your understanding. Re-grades will be accepted up to one week after the assignment s return and must be accompanied by a written explanation of the request. A regrade request may trigger a re-grade of the entire assignment. In class descriptions You will have the opportunity to present problems (examples from the handouts) to the class in 5-10 minutes. This is optional but will replace your lowest quiz score; grading will reflect the accuracy, clarity and depth of your solution as well as your ability to handle questions about the problem. Final grades will be assigned based on the overall grade distribution using the class mean and standard deviation. If you are consistently more than one standard deviation below the mean, we should discuss the situation and/ or adjust your study strategies. Students with disabilities The University of Texas at Austin provides upon request appropriate academic adjustments for qualified students with disabilities. For more information, contact the Office of the Dean of Students at , TTY or the College of Engineering Director of Students with Disabilities at Division of Diversity and Community Engagement, Services for Students with Disabilities, , 4

5 Academic dishonesty UT Honor Code (or statement of ethics) and an explanation or example of what constitutes plagiarism (Link to University Honor Code: Religious holidays By UT Austin policy, you must notify the instructor of your pending absence at least fourteen days p rior to the date of observance of a religious holy day. If you must miss a class, an examination, a work assignment, or a project in order to observe a religious holy day, you will be given an opportunity to complete the missed work within a reasonable time after the absence. ) Emergency evacuations Recommendations regarding emergency evacuation are available from the Office of Campus Safety and Security, , For CPE specifically, in the event of an emergency, we egress from CPE and assemble on the south side of the pedestrian bridge until the all-clear notifcaiton. You can sign up to receive emergency text alerts here: How to succeed in this class Diagram the problem make sure you understand what is being asked, choose your system, label variables and flow streams, identify unknowns, etc. Do the homework preferably not just the night before it s due and try to understand the steps. Working in groups is great as long as all members understand the problem solutions. Do more than the HW periodically, look over and try to understand your notes, always read the assigned text before class, explain things to your roommate. Often it helps to turn off all electronics in order to focus high quality effort on the task at hand. Ask questions help us to help you! Lecture Outline: The course is composed of the following lectures. Please read the assigned sections of the text before attending the lecture. Date Topic Read before lecture* 1. The first law Th 8/25 Course overview First Law of Thermodynamics Energy balance for closed systems (liquids, steam) R1, 8/26 R1: energy balance boot camp HW1 due T 8/30 Energy balance for closed systems, un-steady-state (liquids, steam) Review ChE 317 MB, Chapter 1, Sections 2.1, 2.4 Section

6 Th 9/1 Open systems - Mass and Energy Balances for Open Systems; Enthalpy and Heat Capacity R2, 9/2 R2: cycles, leaking tank examples; steam table review 2. Equations of state T 9/6 Ideal gases: PVT Behavior of Pure Substances, Ideal Gas Law & Energy Balances Th 9/8 Real gases I: Generalized Correlations for Gases & Liquids; Compressibility, corresponding states R3, 9/9 R3: T 9/13 Real gases II: cubic equations of state Section 2.7, Sections The second law Th 9/15 Second Law of Thermodynamics: Origins in heat engines Sections R4, 9/16 Aspen module to work with real gases T 9/20 Review for Exam 1 Th 9/22 Midterm Exam 1 R5, 9/23 Entropy and the Second Law of Thermodynamics Sections T 9/27 Entropy Balance for Closed Systems Section 3.5 Th 9/29 Entropy Balance for Open Systems Section 3.6 R6, 9/30 Entropy balance problems Section Thermodynamic cycles T 10/4 Thermodynamic Network: Variables & Property Tables, Section calculating delta H for real gases from PVT data Th 10/6 Unit operations: nozzle, throttle, turbine, compressor, boiler, Section 2.8 condenser, pump R7, 10/7 T 10/11 Introduction to thermodynamic cycles, Carnot & Rankine cycles Th 10/13 Variations on power cycles Section 2.9, handout from another book R8, 10/14 T 10/18 Refrigeration cycles; exam review Th 10/20 Midterm Exam 2 R9, 10/21 No class 5. Phase equilibrium T 10/25 Ideal VLE I: Qualitative behavior: phase diagrams; thermo Section requirements for equilibrium and stability; one component/two phase systems Clausius-Clapeyron; Clapeyron; Antoine Th 10/27 Ideal VLE II: Raoult & Henry s Laws; K-values Section 8.1 6

7 R10, 10/28 T 11/1 Ideal VLE practice Non-ideal VLE I: one component/ two phase systems: derive fugacity, calculate fugacity of a pure gas and pure liquid, using vdw and PR Th 11/3 Non-ideal VLE II: two component/ two phase systems: azeotropes; partial molar properties, Gibbs-Duhem eqn, mixing in gases R11, 11/4 T 11/8 Section 7.2 Section 6.3 Non-ideal VLE III: two phases/ two component systems: mixing Section 7.4 in liquids - correlations to get activity coefficients Th 11/10 Non-ideal VLE IV: Liquid-Liquid Equilibrium: immiscible, partially Section 8.2 miscible; stability R12, 11/11 Osmotic pressure & Boiling point elevation Section 8.5 T 11/15 Non-ideal VLE V: Liquid-Liquid-Vapor Equilibrium: phase Section 8.3 diagrams, calculate phase composition Th 11/17 Midterm Exam 3 R13, 11/18 6. Chemical reaction equilibrium T 11/22 Chemical Reaction Equilibrium I: Introduction, derive K a = exp (- Sections 2.6, G/RT) eqn, gas example /24-25 Thanksgiving holidays T 11/29 Chemical Reaction Equilibrium II: Temperature effects; Multiple Section 9.4, 9.7 Reactions Th 12/1 Chemical Reaction Equilibrium III: Reactions with liquids and solids; rxns with coupled phase equilibria or heat transfer R14, 12/2 Non-stoicheometric feed, effect of inerts Section 9.5 Mon 12/12 FINAL EXAM (comprehensive) 2 pm 5 pm, Room TBD *all reading assignments from Koretsky, 2 nd edition Essential Thermo 322 Vocab Sheet System: any part of the universe we choose to study; it may have real (eg, a capped test tube) or imaginary boundaries and these boundaries may be rigid or mobile (as in a piston). Careful choice of your system can make the problem much easier (eg, choose a closed system if poss.). 7

8 State: the condition in which the system exists (eg, temp, pressure, number of moles of substance); in thermodynamics, this will often refer to the state at which equilibrium exists. a condition which is time-invariant and reproducible. Surroundings: once you choose the system and its boundaries, everything else becomes the surroundings. Realistically, this may be the part of the universe that is affected by changes in the system. Closed system: this system does not exchange mass with its surroundings, but may exchange work and heat. Thus the energy, P, T, V may change but the mass of the system remains fixed. Open system: this system does exchange mass with its surroundings. Here, the boundaries may be defined as a specific volume in space through which mass may enter and leave, or an actual container, say a length of pipe with reactants flowing in and products flowing out. Isothermal system: a process which occurs at constant temperature (T 1 = T 2) and can apply to both open and closed systems. To maintain an isothermal state, it is usually necessary to exchange heat with the surroundings. Adiabatic system: a process occurs in either an open or closed system without exchanging heat with its surroundings (Q = 0). Commonly also termed perfectly insulated. Isolated system: a system that exchanges neither heat nor mass nor work with its surroundings; eg, a chemical reaction occurring in an insulated vessel of constant volume. State variable: the terms state variable, state property, property are used interchangeably and refer to a variable whose value depends on the state in which the system exists. Between two states, the change in a state variable is always the same, regardless of the path taken. Temp, pressure, volume & internal energy are all state variables. Path variable: properties whose value depends on the path travelled by the system. This only has meaning when applied to a process in which the path taken is specified; key path variables are work (W) and heat (Q). Extensive property: the value depends on the size of the system and are additive. For example, volume: if you double the number of particles, keeping T and P constant, the volume of an ideal gas will double; if a system has multiple parts, the volume of each part can be added to determine the total system volume. Intensive property: these properties do not depend on the size of the system, for instance, T, P, specific volume (=V/n), density (=m/v). When the system is homogeneous, extensive variables will often be rendered intensive by dividing by the size of the system (eg, number of moles); this is indicated by a bar over the variable. Work (W): work can the energy used to move an object over a specified distance (W = F*d = mad), PV work used to maintain or change the volume of a system [W = (PV)], but also shaft (mechanical) or electrical work. Our convention is that work done by a system on its surroundings will decrease the energy of the system, while work done by the surroundings on the system will increase the energy of the system. Heat (Q): heat is transferred when two bodies of different temperature are in constant (see 0 law of thermo). Common calculations: Q = m*c p*t or Q/t = h*a*t (ChE 353). Reversible process: a reversible process can proceed forward or backwards with no energy input and S=0; this does not actually occur in real life but is an approximation. 8