Thermodynamics I ME 20000
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This 53 page Class Notes was uploaded by Kristopher Beahan on Saturday September 19, 2015. The Class Notes belongs to ME 20000 at Purdue University taught by Qingyan Chen in Fall. Since its upload, it has received 93 views. For similar materials see /class/207986/me-20000-purdue-university in Mechanical Engineering at Purdue University.
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Date Created: 09/19/15
1 Syllabus Systems Definitions SyHabus Instructor Yan Chen Office hours MWF 130220 Phone and email 4967562 yanchenpurdueedu Syllabus Cont d Textbook Moran and Shapiro Fundamentals of Engineering Thermodynamics 6th Ed John Wiley 2008 Prerequisite calculus physics chemistry CHEM115 amp 116 PHYS152 and MA261 may be concurrent ThermoNumber 3xxx Syllabus Cont d Preview the text before lecture Attempt to solve homework problems before lecture Solving homework problems by using engineering paper Syllabus Cont d Format of your homework Use 8 12 by 11 inch Engineering paper Only one side of the paper should be used Only one problem should be included per page if more than one page is needed for a problem all pages should be stapled together in order Chen Yan Q 524 7 39957 7 13 Format of your homework At the top of the engineering paper there are 5 boxes Starting from the left Box 1 leave blank Box 2 put your name last first middle Box 3 put the problem number ie Prob 524 Box 4 put your thermo number Le 3000 You can find your thermo number from httpengineeringpurdueeduyanchenme200 Box 5 put the page number of the problemtotal pages for this problem ie 13 or 33 Syllabus Cont d Format of your homework Given Find System sketch Assumptions Basic equations Solution FDP J WN Syllabus Cont d Homework collection You have at least 4 days to work on your homework Homework is due every Friday No late homework is accepted Syllabus Cont d In class quizzes To check your class attendance and to know how well you understand the lecture No prior announcements Syllabus Cont d Three onehour exams and one final exam Course Gradinq Three onehour exams 50 30 Final exam 30 50 Homework 10 10 Class participation amp quizzes 10 10 The exams do not necessarily look like homework assignments or previous exams No makeup exams Prior approval is needed for skipping an exam Use right hand distribution for such a case A note from your doctor is required in case of sickness Syllabus Cont d Help ME 322 Tutorial room Schedule will be posted outside of the room Yan Chen s office hours right after class in ME room 104 Syllabus Cont d Lecture notes to be downloaded httpengineeringpurdueeduyanchenme200 Syllabus Cont d Academic honest A word of warning Thermodynamic Systems What is Thermodynamics Why General Definition Thermal dynamics deals with conversion of energy to different forms Applications of Thermodynamics Power plant FOSSIL HEAT STEAM MECHANICAL ELECTRICAL TRANSMISSION INPUT ENERGY A f 100 LOSS L085 15 Applications of Thermodynamics Air planes 16 Applications of Thermodynamics Air conditioning Emdenser Fan Davdenser Coil Air Inlet Gail Air Duvet Grill mquot Compressor Evaporatm tail G EVAPORATOR COIL INDOORS OUTDOORS 70 F 100 F EXPANSION VALVE FAN FAN I I I I I I I I i 4 5 39 g 00 00 75 100 Figure 1610a A Simpie throughthaws airconditioner unit essentially consists of a compresswe efngeration machine Applications of Thermodynamics Human body NATURAL CONVECTION RADIATION W FUEL 4w EXHALATION 39 39 OF WARM AND MOISTGASES EVAPORATION WARM E 9 0 FORCED CONVECTION AIR CONDUCTION Figure 41b Methods of dISSIanng waste heat from a bmloglcai mamme Closed System or control mass 19 Open System or control volume 20 Example 11 Is this classroom an open or closed system What about an aircraft engine 21 Properties Property ndependent properties A 1 m3 container is fully filled with water Since the water density is 1000 kgm3 the total mass of the water is 1000 kg Among the volume density and mass how many of them are independent properties 22 Properties Extensive properties Intensive properties m 12mE12m V 12V 12V T T ET P p ip P 9 ip State and Equilibrium smm For example in this classroom air temperature T air density p and relative humidity I characterize the state 24 State and Equilibrium Equilibrium eg mechanical forces pressure thermal temperature phase vaporliquid chemical combustion 25 State and Equilibrium State postulate The equilibrium state of a simple compressible substance is completely specified by two independent intensive properties eg For the air in this classroom any two of the following parameters can be used to determine all other intensive properties 26 2 Units Specific Volume Pressure Process 27 Quasistatic quasiequilibrium process System eg room heating up uniformly coffee cooling down uniformly 28 0 State 2 o State1 V 29 Cycle System 2 pM State 2 System 1 State1 V 30 Units Basic quantities Physical quantity SI English mass kg lbm length m ft time s 3 temperature K R amount of matter mol lbmol electric current A A amount of light cd candles 31 Units Derived quantities Force Newton s law of motion SI force unit English force unit 32 Density and Specific Volume 33 Pressure Pressure p normal force area 34 Pressure For a column of fluid Freebody diagram 1 1 U A AL p AL mg p2 l I HI 92A 35 Pressure Atmospheric pressure vacuum fluid T A2 L 36 Pressure System pressure gas fluid 37 Pressure Example 21 Given patm 147 psia g 322 fts2 h 100 ft p 624 Ibmft3 Find pIoumlo Assumptions Basic equations 38 Pressure Absolute gage and vacuum pressure pabs A pgage Atmospheric pressure pvac Zero pressure 39 Pressure SI pressure units 1 Pa 1 Wm2 1bar 105 Pa 100 kPa 1 atm 1013 bars 147 psi 40 3 Temperature Problem Solving Oth law of thermodynamics If objects A and B are separately in contact with a third object C then A and B are in thermal equilibrium with each other if placed in thermal contact 41 Temperature Two objects in thermal equilibrium with each other are at the same temperature Temperature is the property that determines whether or not an object is in equilibrium with other objects A device that is used to measure the temperature of a system is a thermometer which makes use of the temperature dependence of some physical property eg volume length pressure electrical resistance color etc 42 Thermometer Type of Thermometers Physical Property Measured Pressure and volume of dilute gas Expansion or contraction of fluid Difference in expansion of two solid Electrical resistance ldealgas Mercury bulb Bimetallic strip Platinum resis tance Thermocouple Voltage across dissimilar metals Optical Pyrometer Color of emitted light Silicon diode Electrical resistance 43 ConstantVolume Gas Thermometer This is the standard thermometer Temperature is proportional to pressure Tabp 44 Temperature Celsius scale We assign 0 C gt freezing point of water at 1 atm 100 C gt boiling point of water at 1 atm 45 Temperature Lowest possible temperature 0 Kelvin temperature 46 Kelvin Temperature Scale Scale has greater scienti c signi cance Minimum temperature de ned as 0 Kelvin 4731500 Relatinnship between Kelvin Celsius Temperature TKTC27315 339 100 C i Steampeint P 1 1393 K re 3 Icepeint gt 273K 23 C UK C C Celsius Kelvin Celsius and Fahrenheit temperature scales I 100 C 4 Steampeint r 21239 39239 100C J 3 C 1 Ieepeint II QHIIIIIIIIIIIIIIIII 1 M l HIIIIIIIIIIIIIIIII Celsius Fabwhat Temperature Kelvin scale Rankine scale Conversion T C 59 T F 32 T F 95 T C 32 T C 59 T F 40 4o T F 95 T C 40 4o 49 Thermodynamics Problem Solving Problem Setup 1 Sketch process 2 Label known states 3 Identify system i Assumptions 1 Process assumptions 2 Property assumptions Conservation Eqs Performance Indices Boundary Property Evaluat 1 Mass 1 Cycle efficiency 1 Work 1 Enthalpy 2 Energy 2 Process efficiency 2 Heat transfer 2 Entropy 3 3 Flow 3 39 I Determine Unknowns I 50 Solution Format Given State in your own words what is given in the problem statement Example The initial temperature is T130 C Find List what the problem wants you to find Example a the pressure at time 2 or P2 A sketch of your control volume Assumptions Example Ideal gas Basic Equations To be detailed in class Solution This includes correct units 51 Example 31 Refrigerant 22 vapor enters the compressor of a refrigeration system at an absolute pressure of 20 psia A pressure gage at the compressor exit indicates a pressure of 280 psig The atmospheric pressure is 146 psia Determine the change in absolute pressure from inlet to exit in psi 52 53