Thermodynamics: An Interactive Approach · PDF fileChapter 5 Mass, Energy, and Entropy ... 5.4 Thermodynamic Cycle as a Closed Process 241 5.4.1 Origin of Internal Energy 242 ... 7.4

Thermodynamics: An Interactive Approach

Subrata Bhattacharjee

San Diego State University

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10 9 8 7 6 5 4 3 2 1

Library of Congress Cataloging-in-Publication Data

Bhattacharjee, Subrata, 1961- Thermodynamics : an interactive approach : a text based on webware / Subrata (Sooby) Bhattacharjee, San Diego State University. — First edition. pages cm ISBN-13: 978-0-13-035117-3 ISBN-10: 0-13-035117-2 1. Thermodynamics—Textbooks. 2. Machinery, Dynamics of—Textbooks. 3. Thermodynamics—Computer-assisted instruction. I. Title. TJ265.B58 2014 621.402'1—dc23 2013039655

ISBN-13: 978-0-13-035117-3ISBN-10: 0-13-035117-2


TAble of conTenTs

Preface xvii

Introduction Thermodynamic System and Its Interactions with the Surroundings 1 0.1 Thermodynamic Systems 1

0.2 Test and Animations 3

0.3 Examples of Thermodynamic Systems 3

0.4 Interactions Between the System and Its Surroundings 5

0.5 Mass Interaction 5

0.6 Test and the TESTcalcs 7

0.7 Energy, Work, and Heat 7

0.7.1 Heat and Heating Rate (Q, Q#) 10

0.7.2 Work and Power (W, W#

) 12

0.8 Work Transfer Mechanisms 13

0.8.1 Mechanical Work (WM, W#

M) 13

0.8.2 Shaft Work (Wsh, W#

sh) 15

0.8.3 Electrical Work (Wel, Wel#

) 15

0.8.4 Boundary Work (WB, W#B) 16

0.8.5 Flow Work (W#

F) 18

0.8.6 Net Work Transfer (W#, Wext) 19

0.8.7 Other Interactions 21

0.9 Closure 21

Chapter 1 Description of a System: States and Properties 34 1.1 Consequences of Interactions 34

1.2 States 34

1.3 Macroscopic vs. Microscopic Thermodynamics 36

1.4 An Image Analogy 37

1.5 Properties of State 38

1.5.1 Property Evaluation by State TESTcalcs 38

1.5.2 Properties Related to System Size (V, A, m, n, m#, V

#, n#) 40

1.5.3 Density and Specific Volume (r, n) 42

1.5.4 Velocity and Elevation (V, z) 43

1.5.5 Pressure (p) 43

1.5.6 Temperature (T ) 47

1.5.7 Stored Energy (E, KE, PE, U, e, ke, pe, u, E#) 49

1.5.8 Flow Energy and Enthalpy (j, J#, h, H

# ) 52

1.5.9 Entropy (S, s, S#) 54

1.5.10 Exergy (f, c) 56

1.6 Property Classification 57

1.7 Evaluation of Extended State 58

1.8 Closure 61

iii


Chapter 2 Development of Balance Equations for Mass, Energy, and Entropy: Application to Closed-Steady Systems 69

2.1 Balance Equations 69

2.1.1 Mass Balance Equation 70

2.1.2 Energy Balance Equation 72

2.1.3 Entropy Balance Equation 77

2.1.4 Entropy and Reversibility 80

2.2 Closed-Steady Systems 85

2.3 Cycles—a Special Case of Closed-Steady Systems 88

2.3.1 Heat Engine 88

2.3.2 Refrigerator and Heat Pump 91

2.3.3 The Carnot Cycle 93

2.3.4 The Kelvin Temperature Scale 97

2.4 Closure 98

Chapter 3 Evaluation of Properties: Material Models 113 3.1 Thermodynamic Equilibrium and States 113

3.1.1 Equilibrium and LTE (Local Thermodynamic Equilibrium) 113

3.1.2 The State Postulate 114

3.1.3 Differential Thermodynamic Relations 116

3.2 Material Models 118

3.2.1 State TESTcalcs and TEST-Codes 119

3.3 The SL (Solid/Liquid) Model 119

3.3.1 SL Model Assumptions 120

3.3.2 Equations of State 120

3.3.3 Model Summary: SL Model 121

3.4 The PC (Phase-Change) Model 123

3.4.1 A New Pair of Properties—Qualities x and y 124

3.4.2 Numerical Simulation 125

3.4.3 Property Diagrams 126

3.4.4 Extending the Diagrams: The Solid Phase 128

3.4.5 Thermodynamic Property Tables 129

3.4.6 Evaluation of Phase Composition 131

3.4.7 Properties of Saturated Mixture 133

3.4.8 Subcooled or Compressed Liquid 136

3.4.9 Supercritical Vapor or Liquid 138

3.4.10 Sublimation States 138

3.4.11 Model Summary—PC Model 138

3.5 GAS MODELS 139

3.5.1 The IG (Ideal Gas) and PG (Perfect Gas) Models 139

3.5.2 IG and PG Model Assumptions 139

3.5.3 Equations of State 140

3.5.4 Model Summary: PG and IG Models 145

3.5.5 The RG (Real Gas) Model 149

3.5.6 RG Model Assumptions 150

3.5.7 Compressibility Charts 151

3.5.8 Other Equations of State 152

3.5.9 Model Summary: RG Model 153

iv Table of Contents


3.6 Mixture Models 154

3.6.1 Vacuum 154

3.7 Standard Reference State and Reference Values 155

3.8 Selection of a Model 155

3.9 Closure 157

Chapter 4 Mass, Energy, and Entropy Analysis of Open-Steady Systems 169 4.1 Governing Equations and Device Efficiencies 169

4.1.1 TEST and the Open-Steady TESTcalcs 170

4.1.2 Energetic Efficiency 171

4.1.3 Internally Reversible System 172

4.1.4 Isentropic Efficiency 174

4.2 Comprehensive Analysis 175

4.2.1 Pipes, Ducts, or Tubes 175

4.2.2 Nozzles and Diffusers 178

4.2.3 Turbines 183

4.2.4 Compressors, Fans, and Pumps 187

4.2.5 Throttling Valves 190

4.2.6 Heat Exchangers 192

4.2.7 TEST and the Multi-Flow, Non-Mixing TESTcalcs 192

4.2.8 Mixing Chambers and Separators 194

4.2.9 TEST and the Multi-Flow, Mixing TESTcalcs 194

4.3 Closure 197

Chapter 5 Mass, Energy, and Entropy Analysis of Unsteady Systems 209 5.1 Unsteady Processes 209

5.1.1 Closed Processes 210

5.1.2 TEST and the Closed-Process TESTcalcs 211

5.1.3 Energetic Efficiency and Reversibility 211

5.1.4 Uniform Closed Processes 214

5.1.5 Non-Uniform Systems 226

5.1.6 TEST and the Non-Uniform Closed-Process TESTcalcs 226

5.1.7 Open Processes 230

5.1.8 TEST and Open-Process TESTcalcs 232

5.2 Transient Analysis 235

5.2.1 Closed-Transient Systems 235

5.2.2 Isolated Systems 236

5.2.3 Mechanical Systems 237

5.2.4 Open-Transient Systems 238

5.3 Differential Processes 240

5.4 Thermodynamic Cycle as a Closed Process 241

5.4.1 Origin of Internal Energy 242

5.4.2 Clausius Inequality and Entropy 242

5.5 Closure 243

Chapter 6 Exergy Balance Equation: Application to Steady and Unsteady Systems 253 6.1 Exergy Balance Equation 253

6.1.1 Exergy, Reversible Work, and Irreversibility 256

6.1.2 TESTcalcs for Exergy Analysis 259

Table of Contents v


6.2 Closed-Steady Systems 260

6.2.1 Exergy Analysis of Cycles 261

6.3 Open-Steady Systems 263

6.4 Closed Processes 268

6.5 Open Processes 271

6.6 Closure 273

Chapter 7 Reciprocating Closed Power Cycles 280 7.1 The Closed Carnot Heat Engine 280

7.1.1 Significance of the Carnot Engine 282

7.2 IC Engine Terminology 282

7.3 Air-Standard Cycles 285

7.3.1 TEST and the Reciprocating Cycle TESTcalcs 286

7.4 Otto Cycle 286

7.4.1 Cycle Analysis 287

7.4.2 Qualitative Performance Predictions 288

7.4.3 Fuel Consideration 288

7.5 Diesel Cycle 291

7.5.1 Cycle Analysis 292


7.6 Dual Cycle 295

7.7 Atkinson and Miller Cycles 296

7.8 Stirling Cycle 297

7.9 Two-Stroke Cycle 300

7.10 Fuels 300

7.11 Closure 301

Chapter 8 Open Gas Power Cycle 309 8.1 The Gas Turbine 309

8.2 The Air-Standard Brayton Cycle 311

8.2.1 TEST and the Open Gas Power Cycle TESTcalcs 313



8.2.4 Irreversibilities in an Actual Cycle 317

8.2.5 Exergy Accounting of Brayton Cycle 319

8.3 Gas Turbine with Regeneration 321

8.4 Gas Turbine with Reheat 322

8.5 Gas Turbine with Intercooling and Reheat 324

8.6 Regenerative Gas Turbine with Reheat and Intercooling 325

8.7 Gas Turbines For Jet Propulsion 327

8.7.1 The Momentum Balance Equation 327

8.7.2 Jet Engine Performance 329

8.7.3 Air-Standard Cycle for Turbojet Analysis 332

8.8 Other Forms of Jet Propulsion 334

8.9 Closure 334

Chapter 9 Open Vapor Power Cycles 345 9.1 The Steam Power Plant 345

9.2 The Rankine Cycle 346

vi Table of Contents


9.2.1 Carbon Footprint 348

9.2.2 TEST and the Open Vapor Power Cycle TESTcalcs 348


9.2.4 Parametric Study of the Rankine Cycle 352

9.2.5 Irreversibilities in an Actual Cycle 353

9.2.6 Exergy Accounting of Rankine Cycle 355

9.3 Modification of Rankine Cycle 356

9.3.1 Reheat Rankine Cycle 356

9.3.2 Regenerative Rankine Cycle 358

9.4 Cogeneration 363

9.5 Binary Vapor Cycle 366

9.6 Combined Cycle 367

9.7 Closure 369

Chapter 10 Refrigeration Cycles 383 10.1 Refrigerators and Heat Pump 383

10.2 Test and the Refrigeration Cycle TESTcalcs 384

10.3 Vapor-Refrigeration Cycles 384

10.3.1 Carnot Refrigeration Cycle 385

10.3.2 Vapor Compression Cycle 385

10.3.3 Analysis of an Ideal Vapor-Compression Refrigeration Cycle 386


10.3.5 Actual Vapor-Compression Cycle 388

10.3.6 Components of a Vapor-Compression Plant 391

10.3.7 Exergy Accounting of Vapor Compression Cycle 391

10.3.8 Refrigerant Selection 393

10.3.9 Cascade Refrigeration Systems 394

10.3.10 Multistage Refrigeration with Flash Chamber 396

10.4 Absorption Refrigeration Cycle 397

10.5 Gas Refrigeration Cycles 399

10.5.1 Reversed Brayton Cycle 399

10.5.2 Linde-Hampson Cycle 402

10.6 Heat Pump Systems 403

10.7 Closure 404

Chapter 11 Evaluation of Properties: Thermodynamic Relations 417 11.1 Thermodynamic Relations 417

11.1.1 The Tds Relations 417

11.1.2 Partial Differential Relations 419

11.1.3 The Maxwell Relations 421

11.1.4 The Clapeyron Equation 424

11.1.5 The Clapeyron-Clausius Equation 425

11.2 Evaluation of Properties 426

11.2.1 Internal Energy 426

11.2.2 Enthalpy 428

11.2.3 Entropy 429

11.2.4 Volume Expansivity and Compressibility 430

Table of Contents vii


11.2.5 Specific Heats 430

11.2.6 Joule-Thompson Coefficient 433

11.3 The Real Gas (RG) Model 434

11.4 Mixture Models 438

11.4.1 Mixture Composition 438

11.4.2 Mixture TESTcalcs 440

11.4.3 PG and IG Mixture Models 442

11.4.4 Mass, Energy, and Entropy Equations for IG-Mixtures 446

11.4.5 Real Gas Mixture Model 450

11.5 Closure 452

Chapter 12 Psychrometry 459 12.1 The Moist Air Model 459

12.1.1 Model Assumptions 459

12.1.2 Saturation Processes 460

12.1.3 Absolute and Relative Humidity 461

12.1.4 Dry- and Wet-Bulb Temperatures 462

12.1.5 Moist Air (MA) TESTcalcs 462

12.1.6 More properties of Moist Air 463

12.2 Mass and Energy Balance Equations 466

12.2.1 Open-Steady Device 466

12.2.2 Closed Process 468

12.3 Adiabatic Saturation and Wet-Bulb Temperature 469

12.4 Psychrometric Chart 471

12.5 Air-Conditioning Processes 473

12.5.1 Simple Heating or Cooling 473

12.5.2 Heating with Humidification 474

12.5.3 Cooling with Dehumidification 476

12.5.4 Evaporative Cooling 477

12.5.5 Adiabatic Mixing 479

12.5.6 Wet Cooling Tower 480

12.6 Closure 483

Chapter 13 Combustion 489 13.1 Combustion Reaction 489

13.1.1 Combustion TESTcalcs 490

13.1.2 Fuels 492

13.1.3 Air 493

13.1.4 Combustion Products 496

13.2 System Analysis 498

13.3 Open-Steady Device 498

13.3.1 Enthalpy of Formation 500

13.3.2 Energy Analysis 502

13.3.3 Entropy Analysis 507

13.3.4 Exergy Analysis 510

13.3.5 Isothermal Combustion—Fuel Cells 515

13.3.6 Adiabatic Combustion—Power Plants 516

viii Table of Contents


13.4 Closed Process 518

13.5 Combustion Efficiencies 520

13.6 Closure 522

Chapter 14 Equilibrium 529 14.1 Criteria for Equilibrium 529

14.2 Equilibrium of Gas Mixtures 534

14.3 Phase Equilibrium 538

14.3.1 Osmotic Pressure and Desalination 543

14.4 Chemical Equilibrium 546

14.4.1 Equilibrium TESTcalcs 549

14.4.2 Equilibrium Composition 550

14.4.3 Significance of Equilibrium Constant 554

14.5 Closure 560

Chapter 15 Gas Dynamics 567 15.1 One-Dimensional Flow 567

15.1.1 Static, Stagnation and Total Properties 568

15.1.2 The Gas Dynamics TESTcalc 569

15.2 Isentropic Flow of a Perfect Gas 571

15.3 Mach Number 572

15.4 Shape of an Isentropic Duct 575

15.5 Isentropic Table for Perfect Gases 577

15.6 Effect of Back Pressure: Converging Nozzle 580

15.7 Effect of Back Pressure: Converging-Diverging Nozzle 582

15.7.1 Normal Shock 584

15.7.2 Normal Shock in a Nozzle 587

15.8 Nozzle and Diffuser Coefficients 590

15.9 Closure 595Appendix A 603

Appendix B 674

Answers to Key Problems 680

Index 684

Table of Contents ix



With this new textbook, Subrata Bhattacharjee offers a new perspective on thermodynamic engineering by integrating his “ layered approach” with online technological resources. Students are introduced to new terminology and integral applications, then called upon to apply these concepts in mul-tiple scenarios throughout the text.

40 Chapter1 • DescriptionofaSystem:States and Properties

global control panel to update all calculated states. Likewise, to use the working substance as a parameter, simply select a new substance and click Super-Calculate.

Just as a state number stores the properties of a state, a case is used to preserve a set of states. The calculated states are automatically preserved as Case-0. To repeat a set of calculations with a different fluid, for instance, select a new case, say, Case-1, and then change the fluid type and click Super-Calculate. Selecting a calculated state or a calculated case (identified by an © sign in front of the state or case number), loads the state or the entire case. The Super-Calculate button also is used to convert the unit system of an entire solution, to produce a detailed output of the solution including spreadsheet-friendly tables in the I/O panel, and generating TEST-code (discussed later) for storing and reproducing the solution.

The flow-state TESTcalcs, which calculate extended flow states, are quite similar to the system-state TESTcalcs. As an exercise, launch the flow-state TESTcalc with the SL-model in a new browser window next to the system-state TESTcalc of Figure 1.12. The extensive total properties (marked in black) are replaced by the corresponding rate of transport: mass (m) by the mass flow rate (mdot); volume (Vol) by the volume flow rate (Voldot). However, all the intensive properties (marked in red, green, and blue colors) remain the same. Suppose we would like to evaluate the pipe diameter for a water flow identified by State-2 under the following conditions: p2 = 10 atm, T2 = 50 deg@C, Vel2 = 2 m/s, and Voldot2 = 100 gallons/hr. In the SL flow-state TESTcalc, select Water (L) from the working substance menu, select State-2, and enter the given properties. To change the default value of the velocity, you must de-select the Vel2 checkbox and then select it again to trigger the input mode. Click Calculate and the area is displayed as 0.5257 cm^2.

1.5.2 properties related to system size (V- , A, m, n, m#, V-

#, n

#)

We begin the discussion of individual properties with extensive properties that are directly related to the extent or amount of matter in the system. While volume V- and mass m are exten-sive properties of a system state, the flow area A, volume flow rate V-

#, and mass flow rate m

# are

extensive properties of a flow state.Although mass measures the quantity of matter in a system in kg (SI) or in lbm

(English units), when we say a system is massive or heavy, we usually mean that the weight (the force with which the Earth pulls on the system) is large. Unlike weight, the mass of a closed system stays the same regardless of elevation. It is easier to intuitively understand force; hence, mass can be operationally defined by Newton’s second law in terms of force, F and acceleration, a:

F =ma

(1000 N/kN); c kN = kg. m

s2 kN

Nd (1.2)

The weight w of a mass, m, that is, the force with which the Earth pulls on an object of mass m, can be related to acceleration during free fall or the acceleration due to gravity, g, as:

w =mg

(1000 N/kN); c kN = kg.m

s2 kN

Nd (1.3)

To prevent a free fall, an upward force, w, proportional to the mass of the body, must be exerted on the body. This gives us an appreciation for the mass of the body (Fig. 1.14). In space, mass can be viewed as attempting to alter the inertia of a body—the more massive the body, the greater the force that is necessary to affect the magnitude or direction of the body’s velocity (think about how we can distinguish two identical looking baseballs that have different masses in the absence of gravity).

The acceleration due to gravity g can be regarded as a proportionality constant between the weight and mass of a system, which can be expressed by Newton’s law of universal gravitation in the gravitational constant and the distance of the system from the Earth’s center. The local value of g, therefore, is a function of the elevation, z, of a system. For example, at 45-degrees latitude and at sea level (z = 0), g has a value of 9.807 m/s2. Most engineering problems involve only minor changes in elevation when compared with the Earth’s radius, and a constant value of 9.81 m/s2 for g, called the standard gravity, provides acceptable accuracy. In this book, we will assume standard gravity value for g unless mentioned otherwise.

w = mg

fIgure 1.14 Although equal

and opposite forces act on the

apple and Earth, the acceleration

of Earth is negligible while

that of the apple is g (see

Anim. 0.A.weight).

DiD you know?

• Thedensestnaturallyoccurringsubstance on Earth is Iridium, at about 22,650 kg/m3.

• Density of water is about1000 kg/m3.

• Densityofairatsealevelisabout 1.229 kg/m3.

M01_BHAT1173_01_SE_C01.indd 40 02/09/14 12:41 PM

Did You Know? offers Interesting and helpful facts about materials and engineering.

Key terms are emphasized in bold as they are introduced

400 Chapter10 • RefrigerationCycles

examPle 10-7 Analysis of an Ideal Reversed-Brayton Cycle

An ideal gas refrigeration, based on the reversed-Brayton cycle, is used to maintain a cold region at 10°C while rejecting heat to a warm region at 40°C. The minimum temperature difference between the working fluid, air, and the cold or warm region is 5°C. Air enters the compressor, which has a compression ratio of 3, at 101 kPa with a volumetric flow rate of 100 m3/min. Using the PG model, determine (a) the cooling capacity in ton, (b) the net power input, and (c) the COP. What-if scenario: (d) What would the COP be if the IG model were used?

SOlutiOn

Use the PG model to evaluate the temperature of each principal state. Use an energy balance on the open-steady components to evaluate the desired answers.

Assumptions

Ideal reversed-Brayton cycle assumptions.

Analysis

Use the PG model to evaluate the following states. It can be deduced from Figure 10.21 that T1 = 278 K and T3 = 318 K.

State-1 (given p1, T1, V#1): m

#1 =

V#1

v1=

Mp1V#1

RT1=

(29)(101)(100/60)

(8.314)(273 + 5)= 2.11 kg/s;

State-2 (given p2 = 3p1, s2 = s1): Use of isentropic relation gives us T2 = (278)3(1.4 - 1)/1.4 = 380.8 K;

State-3 (given p3 = p2, T3 = 318 K);

State-4 (given p4 = p3/3, s4 = s3): T4 = (318)/3(1.4 - 1)/1.4 = 232.4 K

An energy analysis is carried out for the following devices:

Heat Exchanger (4-1): Q#C = Q

#= m

#(h1 - h4) = m

#cp(T1 - T4)

= (2.11)(1.00)(278.0 - 232.4) = 96.9 kW = 27.5 ton

Compressor (1-2): W#C = -W

#ext = m

#(h2 - h1) = m

#cp(T2 - T1)

= (2.11)(1.00)(380.8 - 278.0) = 217.3 kW

Turbine (3-4): W#T = W

#ext = m

#(h3 - h4) = m

#cp(T3 - T4)

= (2.11)(1.00)(318.0 - 232.4) = 181.5 kW

Therefore, the COP is obtained as:

COPR =Q#C

W#net

=96.9

217.3 - 181.5= 2.71

Also, using Eq. (10.23), we can directly obtain COPRPG =

1

3(1.4 - 1)/1.4 - 1= 2.71

test Analysis

Evaluate the principal states and analyze all the four devices as described in the TEST-code (TEST 7 TEST@codes) using the PG refrigeration cycle TESTcalc. Click Super-Calculate and obtain the overall results in the cycle panel.

What-if scenario

Click Super-Calculate to produce the TEST codes in the I/O panel. Launch the IG refrigeration cycle TESTcalc in a separate browser tab. Paste the TEST codes on the I/O panel of the new TESTcalc. Use the Load button and the new COP is calculated as 2.72.

s

T

4

3

2

1

5 K

5 K

TC = 283 K

TH = 313 K

QH

QC

p = c

p = c

figuRe 10.21 T @s diagram for the refrigeration

cycle of Ex. 10-7.

M10_BHAT1173_01_SE_C10.indd 400 02/09/14 10:16 AM

Examples present opportunities to apply analysis, offer detailed solutions, and What-If scenarios.

x



Property Tables allow for quick reference of material properties, as well as saturation and vapor tables, for many elements and compounds.

Figures illustrate the textbook concepts and accompany examples.

6 Introduction • ThermodynamicSystemandItsInteractionswiththeSurroundings

that element are given by A∆x and rA∆x, respectively, where A is the cross-sectional area and ∆x is the element’s length. The corresponding flow rates, therefore, are given by the following transport equations:

V#= lim

∆tS0

A∆x

∆t= A lim

∆tS0

∆x

∆t= AV; c m3

s= m2

msd (0.1)

m# = lim

∆tS0

r(A∆x)

∆t; 1 m

# = rAV = rV#; c kg

s=

kg

m3 m3

sd (0.2)

These equations express the instantaneous values of volume and mass flow rates, V# and m

#,

at a given cross section in terms of flow properties A, V , and r. Implicit in this derivation is the assumption that V and r do not change across the flow area, and are allowed to vary only along the axial direction. This assumption is called the bulk flow or one-dimensional flow approxi-mation, which restricts any change in flow properties only in the direction of the flow. In situa-tions where the flow is not uniform, the average values (see Fig. 0.9) of V and r can be used in Eqs. (0.1) and (0.2) without much sacrifice in accuracy.

One way to remember these important formulas is to visualize a solid rod moving with a velocity V past a reference mark as shown in Figure 0.10. Every second AV m3 of solid volume and rAV kg of solid mass moves past that mark, which are the volume flow rate V

# and mass flow

rate m# of the solid flow respectively.Mass transfer, or the lack of it, introduces the most basic classification of thermodynamic

systems: those with no significant mass interactions are called closed systems and those with significant mass transfer with their surroundings are called open systems. Always assume a sys-tem is open unless established otherwise. The advantage to this assumption is that any equation derived for a general open system can be simplified for a closed system by setting terms involv-ing mass transfer, called the transport terms, to zero.

A simple inspection of the system’s boundary can reveal if a system is open or closed. Open systems usually have inlet and/or exit ports carrying the mass in or out of the system. As a simple exercise, classify each system shown in Figure 0.5 as an open or closed system. Also, see animations in Sec. 0.C again, this time inspecting the system boundaries for any possible mass transfer. Select the Mass, Heat, or Work radio-button to identify the locations of a specific inter-action. Sometimes the same physical system can be treated as an open or closed system depend-ing on how its boundary is drawn. The system shown in Figure 0.11, in which air is charged into an empty cylinder, can be analyzed based on the open system, marked by the red boundary, or the closed system marked by the black boundary constructed around the fixed mass of air that passes through the valve into the cylinder.

example 0-2 Mass Flow Rate

A pipe of diameter 10 cm carries water at a velocity of 5 m/s. Determine (a) the volume flow rate in m3/min and (b) the mass flow rate in kg/min. Assume the density of water to be 997 kg/m3.

Solution

Apply the volume and mass transport equations: Eqs. (0.1) and (0.2).

Assumptions

Assume the flow to be uniform across the cross-sectional area of the pipe with a uniform velocity of 5 m/s (see Fig. 0.12).

Analysis

The volume flow rate is calculated using Eq. (0.1):

V#= AV =

p(0.12)

4 (5) = 0.0393

m3

s= 2.356

m3

min

V

(a) Actual pro�les

V

V

(b) Average pro�les

V

Figure 0.9 Different types of

actual profiles (a) (parabolic

and top-hat profiles) and the

corresponding average velocity

profiles (b) at two different

locations in a channel flow.

Volume: AV

Mass: rAV

V

Figure 0.10 Every second

V#= AV m3 and m

# = rAV kg

cross the red mark.

Closedsystem

Opensystem

Figure 0.11 The black boundary

tracks a closed system while the

red boundary defines an open

system.

5 m/s 10 cm

Figure 0.12 Schematic used in

Ex. 0-2.

M00_BHAT1173_01_SE_C00.indd 6 9/16/14 8:59 AM

620 Appendix A

Superheated Table (PC Model), R-134a

°C m3/kg kJ/kg kJ/kg kJ/kg·K m3/kg kJ/kg kJ/kg kJ/kg·K m3/kg kJ/kg kJ/kg kJ/kg·K

Tp=0.06 MPa (Tsat=−37.07°C) p=0.10 MPa (Tsat=−26.43°C) p=0.14 MPa (Tsat=−18.80°C)

v u h s v u h s v u h s

Sat. 0.31003 206.12 224.72 0.9520 0.19170 212.18 231.35 0.9395 0.13945 216.52 236.04 0.9322

-20 0.33536 217.86 237.98 1.0062 0.19770 216.77 236.54 0.9602 0.14549 223.03 243.40 0.9606

-10 0.34992 224.97 245.96 1.0371 0.20686 224.01 244.70 0.9918 0.15219 230.55 251.86 0.9922

0 0.36433 232.24 254.10 1.0675 0.21587 231.41 252.99 1.0227 0.15875 238.32 260.43 1.0230

10 0.37861 239.69 262.41 1.0973 0.22473 238.96 261.43 1.0531 0.16520 246.01 269.13 1.0532

20 0.39279 247.32 270.89 1.1267 0.23349 246.67 270.02 1.0829 0.17155 253.96 277.97 1.0828

30 0.40688 255.12 279.53 1.1557 0.24216 254.54 278.76 1.1122 0.17783 262.06 286.96 1.1120

40 0.42091 263.10 288.35 1.1844 0.25076 262.58 287.66 1.1411 0.18404 270.32 296.09 1.1407

50 0.43487 271.25 297.34 1.2126 0.59300 270.79 296.72 1.1696 0.19020 278.74 305.37 1.1690

60 0.44879 279.58 306.51 1.2405 0.26779 279.16 305.94 1.1977 0.19633 287.32 314.80 1.1969

70 0.46266 288.08 315.84 1.2681 0.27623 287.70 315.32 1.2254 0.20241 296.06 324.39 1.2244

80 0.47650 296.75 325.34 1.2954 0.28464 296.40 324.87 1.2528 0.20846 304.95 334.14 1.2516

90 0.49031 305.58 335.00 1.3224 0.29302 305.27 344.57 1.2799 0.21449 314.01 344.04 1.2785

Tp=0.18 MPa (Tsat=−12.73°C) p=0.20 MPa (Tsat=−10.09°C) p=0.24 MPa (Tsat=−5.37°C)


Sat. 0.10983 219.94 239.71 0.9273 0.09933 221.43 241.30 0.9253 0.08343 224.07 244.09 0.9222

-10 0.11135 222.02 242.06 0.9362 0.09938 221.50 241.38 0.9256 – – – –

0 0.11678 229.67 250.69 0.9684 0.10438 229.23 250.10 0.9582 0.08574 228.31 248.89 0.9399

10 0.12207 237.44 259.41 0.9998 0.10922 237.05 258.89 0.9898 0.08993 236.26 257.84 0.9721

20 0.12723 245.33 268.23 1.0304 0.11394 244.99 267.78 1.0206 0.09339 244.30 266.85 1.0034

30 0.13230 253.36 277.17 1.0604 0.11856 253.06 276.77 1.0508 0.09794 252.45 275.95 1.0339

40 0.13730 261.53 286.24 1.0898 0.12311 261.26 285.88 1.0804 0.10181 260.72 285.16 1.0637

50 0.14222 269.85 295.45 1.1187 0.12758 269.61 295.12 1.1094 0.10562 269.12 294.47 1.0930

60 0.14710 278.31 304.79 1.1472 0.13201 278.10 304.50 1.1380 0.10937 277.67 303.91 1.1218

70 0.15193 286.93 314.28 1.1753 0.13639 286.74 314.02 1.1661 0.11307 286.35 313.49 1.1501

80 0.15672 295.71 323.92 1.2030 0.14073 295.53 323.68 1.1939 0.11674 295.18 323.19 1.1780

90 0.16148 304.63 333.70 1.2303 0.14504 304.47 333.48 1.2212 0.12037 304.15 333.04 1.2055

100 0.16622 313.72 343.69 1.2573 0.14932 313.57 343.43 1.2483 0.12398 313.27 343.03 1.2326

Tp=0.28 MPa (Tsat=−1.23°C) p=0.32 MPa (Tsat=2.48°C) p=0.40 MPa (Tsat=8.93°C)


Sat. 0.07193 226.38 246.52 0.9197 0.06322 228.43 248.66 0.9177 0.05089 231.97 252.32 0.9145

0 0.07240 227.37 247.64 0.9238 – – – – – – – –

10 0.07613 235.44 256.76 0.9566 0.06576 234.61 255.65 0.9427 0.05119 232.87 253.35 0.9182

20 0.07972 243.59 265.91 0.9883 0.06901 242.87 264.95 0.9749 0.05397 241.37 262.96 0.9515

30 0.08320 251.83 275.12 1.0192 0.07214 251.19 274.28 1.0062 0.05662 249.89 272.54 0.9837

40 0.08660 260.17 284.42 1.0494 0.07518 259.61 283.67 1.0367 0.05917 258.47 282.14 1.0148

50 0.08992 268.64 293.81 1.0789 0.07815 268.14 293.15 1.0665 0.06164 267.13 291.79 1.0452

60 0.09319 277.23 303.32 1.1079 0.08106 276.79 302.72 1.0957 0.06405 275.89 301.51 1.0748

70 0.09641 285.96 312.95 1.1364 0.08392 285.56 312.41 1.1243 0.06641 284.75 311.32 1.1038

80 0.09960 294.82 322.71 1.1644 0.08674 294.46 322.22 1.1525 0.06873 293.73 321.23 1.1322

Table B-7 PC Model: Superheated Vapor Table, R-134a

Z01_BHAT1173_01_SE_APPA.indd 620 31/08/14 6:10 PM

302 Chapter7 • ReciprocatingClosedPowerCycles

Stroke

BDC

TDC

PROBlEmS

SECtion 7-1: EnginE tErminology

7-1-1 A four-cylinder four-stroke engine operates at 4000 rpm. The bore and stroke are 100 mm each, the MEP is measured as 0.6 MPa, and the thermal efficiency is 35%. Determine (a) the power produced (W

.net) by the engine in kW, (b) the waste heat in kW, (c) and the volumetric air intake per

cylinder in L/s.

7-1-2 A six-cylinder four-stroke engine operating at 3000 rpm produces 200 kW of total brake power. If the cylinder displacement is 1 L, determine (a) the net work output in kJ per cylinder per cycle, (b) the MEP and (c) the fuel consumption rate in kg/h. Assume the heat release per kg of fuel to be 30 MJ and the thermal efficiency to be 40%.

7-1-3 A four-cylinder two-stroke engine operating at 2000 rpm produces 50 kW of total brake power. If the cyclinder displacement is 1 L, determine (a) the net work output in kJ per cylinder per cycle, (b) the MEP and (c) the fuel consumption rate in kg/h. Assume the heat release per kg of fuel to be 35 MJ and the thermal efficiency to be 30%.

7-1-4 A six-cylinder engine with a volumetric efficiency of 90% and a thermal efficiency of 38% pro-duces 200 kW of power at 3000 rpm. The cylinder bore and stroke are 100 mm and 200 mm respectively. If the condition of air in the intake manifold is 95 kPa and 300 K, determine (a) the mass flow rate (m

#) of air in kg/s, (b) the fuel consumption rate in kg/s and (c) the specific fuel

consumption in kg/kWh. Assume the heating value of the fuel to be 35 MJ/kg of fuel.

SECtion 7-2: CArnot CyClES

7-2-1 A Carnot cycle running on a closed system has 1.5 kg of air. The temperature limits are 300 K and 1000 K, and the pressure limits are 20 kPa and 1900 kPa. Determine (a) the efficiency and (b) thenetworkoutput.UsethePGmodel.(c)What-if scenario: How would the answer in part (b) change if the IG model were used intead?

7-2-2 Consider a Carnot cycle executed in a closed system with 0.003 kg of air. The temperature limits are 25°C and 730°C, and the pressure limits are 15 kPa and 1700 kPa. Determine (a) the efficiency and(b)thenetworkoutputpercycle.UsethePGmodelforair.

7-2-3 An air standard Carnot cycle is executed in a closed system between the temperature limits of 300 K and 1000 K. The pressure before and after the isothermal compression are 100 kPa and 300 kPa, respectively. If the net work output per cycle is 0.22 kJ, determine (a) the maximum pres-sureinthecycle,(b)theheattransfertoair,and(c)themassofair.UsethePGmodel.(d)What-if scenario: What would the mass of air be if the IG model were used?

7-2-4 An air standard Carnot cycle is executed in a closed system between the temperature limits of 350 K and 1200 K. The pressure before and after the isothermal compression are 150 kPa and 300 kPa respectively. If the net work output per cycle is 0.5 kJ, determine (a) the maximum pres-sureinthecycle,(b)theheattransfertoairand(c)themassofair.UsetheIGmodelforair.

SECtion 7-3: otto CyClES

7-3-1 An ideal Otto cycle has a compression ratio of 9. At the beginning of compression, air is at 14.4 psia and 80°F. During constant-volume heat addition 450 Btu/lbm of heat is transferred. Calculate(a)themaximumtemperature,(b)efficiencyand(c)thenetworkoutput.UsetheIGmodel. (d) What-if scenario: What would the efficiency be if the air were at 100°F at the begin-ning of compression?

7-3-2 An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The minimum and maximum temperatures in the cycle are 25°C and 1000°Crespectively.UsingtheIGmodel,determine (a) the amount of heat transferred per unit mass of air during the heat addition process, (b) the thermal efficiency and (c) the mean effective pressure.

3

41

2T

TH

TC

s

3

4

v = c

v = c

1

2

T

s

M07_BHAT1173_01_SE_C07.indd 302 16/09/14 10:46 AM

Problems at the end of each chapter apply concepts and refine engineering analysis.

xi


TesT: The expert system for Thermodynamics

TEST is an online platform focusing on visualization and problem solving of complicated Thermodynamics topics. TEST was designed specifically to complement Thermodynamics: An Interactive Approach and using them together will greatly improve the learning experience.

TEST can be accessed at: www.pearsonhighered.com/bhattacharjee

0.7 Energy, Work, and Heat 7

The mass flow rate is calculated using Eq. (0.2):

m# = rAV = (997)

p(0.12)

4 (5) = 39.15

kg

s= 2349

kg

min

tESt Analysis

Although the manual solution is simple, a TEST analysis still can be useful in verifying results. To calculate the flow rates:

1. Navigate to the TESTcalcs 7 States 7 Flow page; 2. Select the SL-Model (representing a pure solid or liquid working substance) to launch the

SL flow-state TESTcalc; 3. Choose Water (L) from the working substance menu, enter the velocity (click the check

box to activate input mode) and area (use the expression ‘=PI*0.1^2/4’ with the appropri-ate units), and press Enter. The mass flow rate (mdot1) and volume flow rate (Voldot1) are displayed along with other flow variables;

4. Now select a different working substance and click Calculate to observe how the flow rate adjusts according to the new material’s density.

Discussion

Densities of solids and liquids often are assumed constant in thermodynamic analysis and are listed in Tables A-1 and A-2. Density and many other properties of working substances are dis-cussed in Chapter 1.

0.6 TeST and The TeSTcalcs

tEStcalcs, such as the one used in Example 0-2, are dedicated thermodynamic calculators that can help us verify a solution, visualize calculations in thermodynamic plots, and pursue “what-if ” studies. Go through My First Solution in the Tutorial for a step-by-step introduction to a TESTcalc. Although there are a large number of TESTcalcs, they are organized in a tree-like structure (visit the TESTcalcs module) much like thermodynamic systems (e.g., open, closed, etc.). Each TESTcalc is labeled with its hierarchical location (see Fig. 0.13), which is a sequence of simplifying assumptions. For example, a page address x 7 y 7 z means that assumptions x, y, and z in sequence lead one into that particular branch of TESTcalcs to analyze the corresponding thermodynamic systems. To launch the SL flow-state TESTcalc click the Flow State node of the TESTcalcs, states, flow state branch to display all available models, and then the SL model icon.

Launch a few TESTcalcs and you will realize that they look strikingly similar, sometimes making it hard to distinguish one from another. Once you learn how to use one TESTcalc, you can use any other TESTcalc, without much of a learning curve. The I/O panel of each TESTcalc also doubles as a built-in calculator that recognizes property symbols. To evaluate any arithmetic expression, simply type it into the I/O panel beginning with an equal sign—use the syntax as in: exp(-2)*sin(30) = PI*(15/100)^2/4, etc.—and press Enter to evaluate the expression. In the TEST solution of Example 0-2, you can use the expression ‘= rho1*Vel1*A1’ to calculate the mass flow rate at State-1 in the I/O panel.

0.7 energy, work, and heaT

Recall that there are only three types of possible interactions between a system and its surroundings: mass, heat, and work. In physics, heat and work are treated as different forms of energy, but in engineering thermodynamics, an important dis-tinction is made between energy stored in a system and energy in transit. Heat and work are energies in transit—they lose their individual identity and become part of stored energy as soon as they enter or leave a system (see Fig. 0.14). Therefore, an understanding of energy is crucial.

Like mass, energy is difficult to define. In mechanics, energy is defined as the measure of a system’s capacity to do work, that is, how much work a system is capable of delivering. Then again, we need a definition for work, a precise definition

Figure 0.13 Each page in TEST has a hierarchical

address.

Figure 0.14 The battery possesses stored

energy as evident from its ability to raise a

weight (also see Anim. 0.D.uConstructive).

M00_BHAT1173_01_SE_C00.indd 7 9/16/14 8:59 AM

Throughout the text, examples, problems, and figures reference TEST to supplement and illustrate their content.

xii



TESTcalcs are thermodynamic calculators that correspond to specific states, systems, and processes in the book.

The TESTcalc Map allows for quick navigation to referenced TESTcalcs.

TESTcalcs contain many options, panels, and data entry points to verify manual solutions and check calculations.

xiii


Interactives are presented in a map in which the animations are organized by types of process and system.

Each Interactive includes illustrative animated elements and graphs, while allowing for data entry to model a range of complex calculations.


xiv


TEST contains more than 400 custom Animation assets that complement the figures and provide visual illustrations of many problems.

Property Tables are organized by model and feature links to corresponding TESTcalc assets

Property Tables display properties of elements and compounds, and allow the units to be toggled between SI Units and English Units.


xv



PrefAce

It is hard to justify writing yet another textbook on Engineering Thermodynamics. Even when you compare the most popular textbooks in use today, you will notice striking similarities in content, organization, and the style of engaging stu-dents. Even after repeated attempts by different authors to integrate software (such as EES, IT, etc.) with thermodynamics, use of tables and charts are still the norm and parametric studies are still a thing of the future. The Internet revolution has not changed much in the way thermodynamics is taught or learned.

Based on a belief that if software is truly user friendly and easily accessible like a web page, and that students will wel-come it is as a true learning tool, I started working on the web application TEST (www.pearsonhighered.com/bhattacharjee). TEST has proven to be a very popular resource with more than two thousand educators around the world using it in their classrooms, as well as among today’s students, who enjoy learning from multiple sources, not just from a single textbook. This textbook is a result of melding the web-based resources of TEST with the traditional content of thermodynamics to create a rich learning environment. It differs from other textbooks in a number of ways:

1. A Layered Approach: Following the tradition of mechanics, most textbooks use a “spiral approach”, where the concepts of mass, energy, and entropy are introduced sequentially. As a result, an analysis of a device—a turbine, for example—is carried out twice; once with the help of the energy equation, and later, more comprehensively, after the entropy balance equation is developed. By decoupling energy analysis from a comprehensive analysis in this manner, students are encouraged to ask the wrong question, “Is this an energy problem or is this an entropy prob-lem? ” Moreover, entropy is introduced so late in the semester that many students do not have sufficient time to fully appreciate the role entropy plays in practical problem solving, let alone the significance of entropy as a profound property. This textbook adopts a “layered approach”, in which important concepts are introduced early based on physical arguments and numerical experiments, and progressively refined in subsequent chapters as the underly-ing theories unfold. The equation, for example, is first alluded to in Chapter 2, introduced in Chapter 3, derived in Chapter 5, and again revisited in Chapter 11 for a more complete discussion.

2. Organization: The layered approach requires a restructuring of the first few chapters, giving each chapter its distinc-tive theme. The first chapter, the Introduction, introduces a system, its surroundings, and their interactions. Energy, heat, and work are discussed in depth, borrowing concepts from mechanics. Chapter 1 is devoted to the descrip-tion of a thermodynamic system through system and flow states. The concept of local thermodynamic equilibrium (LTE), a hypothesis that establishes thermodynamics as a practical subject, is discussed, and properties including entropy and exergy are introduced and classified, with the TESTcalcs serving as numerical laboratories. Chapter 2 consolidates the development of mass, energy, and entropy balance equations by exploiting their similarities. Closed steady systems, of which heat engines, refrigerators, and heat pumps are special cases, are analyzed. Chapter 3 centralizes evaluation of properties of all pure substances, divided into several material models. Emphasis is placed on thoughtful selection of the model before looking for the correct equation of state or the right chart in evaluating properties. TESTcalcs are used to verify manual calculations and compare competing models. It is a lengthy chapter and an instructor may cover just a single model and move on to Chapters 4 and 5 before coming back iteratively for additional models. Chapters 4 and 5 are dedicated to comprehensive mass, energy, and entropy analysis of steady and unsteady systems respectively. Every analysis, regardless the type of the system, begins with the same set of governing balance equations. TESTcalcs are used to verify manual solution and pursue “what-if” scenarios. The rest of the chapters, 6 through 15, follow a similar organization to that of most textbooks.

3. Tables and Charts: The Tables module of TEST organizes various property tables and charts into easily accessible web pages according to the underlying material model. Projecting a superheated table in the classroom alongside the constant-pressure lines produced by the PC state TESTcalc for example, can create a powerful visual connection between a series of dull numbers and coordinates in a thermodynamic plot.

4. Animations: TEST provides a huge library of animations, which are referenced throughout the book to explain almost every concept, device, and process discussed in this book. Whether it is the derivation of the energy balance equation, explaining the psychrometric chart, or the operation of a combined gas and vapor power cycle, a suitable animation can be used in the classroom to save time and visually connect operation of a device to its depiction in a thermodynamic plot, say, a T–s diagram. A slide bar under an animation can be used to go back and forth over a particular region of interest. A three-node address (chapter number followed by a section letter and a label—9.B.CombinedCycle—for example) is used to identify animations, which are organized according to the structure of this book.

5. Interactives: While an animation can be a good place to be introduced to the operation of a device, say, a turbine, an Interactive can go much further in establishing the parametric behavior. Simulating a system has never been easier. Simply launch an Interactive, for instance the IG turbine simulator, and you will notice that all the input parameters are already set to reasonable default values. To explore how the turbine power changes with inlet temperature, for

xvii


example, simply click the Parametric Study button, select inlet temperature T1 as the independent variable, and click Analyze. Once the plot appears, you can change the dependent variable and redo the plot instantly. Some of the advanced Interactives, such as the Combustion Chamber Simulator, can perform quite sophisticated equilibrium analyses of a large set of fuels and also, for example, plot how the equilibrium flame temperature and emissions would change with the equivalence ratio.

6. TESTcalcs: These thermodynamic calculators are the workhorses of TEST. The TESTcalc can be used to verify manual solutions, create thermodynamic plots, analyze a system or a process, and run “what-if” scenarios. But first and foremost, TESTcalc is a learning tool. To launch TESTcalc, one must make a successive series of assumptions and watch in real time how the governing equations simplify along with the system animation. Just hovering the pointer over a property brings up its definition and relation to other properties. It produces a comprehensive solu-tion in a visual spreadsheet. For example, when calculating a property, it displays the entire state; when analyzing a device it calculates and displays each term of the energy, entropy, and exergy balance equations. Throughout the textbook, TESTcalcs are used to check manual calculations and gain further insight by performing “what-if” stud-ies. Although using the TESTcalcs does not require any programming, a solution can be stored by generating what is called the TEST-code; a few statements about what is known about the analysis. TEST-code for a wide range of problems is posted in the TEST-code module. Parametric studies of complex systems, say, a modified Rankine cycle with reheat and regeneration, can be jump started by loading suitable TEST-code into the appropriate TESTcalc.

7. Examples and Problems: Examples are presented within the main text of every chapter. After presenting a com-plete manual solution, most Examples step students through a TEST solution for verification of manually calculated results. What-if Scenarios in the examples offer another opportunity to further explore the problem. At the end of each chapter, Problems are grouped by section to help students relate the questions to major sections of the chapter. Using the skills demonstrated in the Examples, students can now use TEST to verify the solutions their own. Many of the problems also include What-if Scenarios, which should be solved using TEST for further insight.

8. Thermodynamic Diagrams: When states are calculated by a state TESTcalc, they can be instantly visualized on a thermodynamic plot such as the T–s or the p–v diagram. Constant-property lines can be added by simply clicking the appropriate buttons. Another type of diagram called the flow diagram is introduced in this book, to graphically describe the inventory of energy, entropy, and exergy of a system or a process.

9. “What-if” Studies: Many problems have an extra section called “What-if” Scenario, which asks for evaluation of the effect of changing an input variable on the analysis. It is assumed that TESTcalcs will be used to explore such questions. Once a manual solution is verified through a TEST solution, a “What-if” study is almost effort-less; simply change a parameter and click the Super-Calculate button to see its effect on the entire solution. The Interactives come with built-in parametric study tools. The effect of any input variable on the device can be studied with a few clicks.

10. Consistent Terminologies and Symbols: Thermodynamic textbooks are replete with conflicting use of symbols (for example, use of x as mass or mole fraction, V for velocity or volume, etc.). In Chapter 1, we develop a consistent nota-tion: use of lowercase symbols for intensive properties and uppercase symbols for extensive properties, temperature (T), mass (m), and velocity (V) being the notable exceptions. Thus, pressure, an intensive property, is represented by p and not by P. Molar specific (per unit kmol) properties are expressed with a bar on top of a symbol, molar mass M included. The terms specific stored energy (e), stored exergy (f), flow energy ( j), and flow exergy (c) are consistently used in a standardized manner. Some textbooks use terms such as closed system exergy or fixed mass exergy to mean stored exergy while using the term total energy to mean stored energy. A few new terminolo-gies, such as the SL model for incompressible solids and liquids and PC model to mean possible phase change by a pure substance, are introduced to parallel other standard models such as the IG or the RG model. Similarly, descrip-tion of a system and description of a flow are distinguished through the terms system state and flow state.

11. Benchmarking: Ask a student of mechanics to estimate the kinetic energy of a truck moving at freeway speed, and you will probably see him or her reaching for the calculator. Throughout this book, topics selected in the “Did you know?” boxes are intended not only to grow curiosity but also to instill a sense of benchmarking. Students will not only learn to estimate how much fuel will be needed to accelerate a truck to its freeway kinetic energy, but to com-pare entropy of water vapor with liquid water without consulting any tables or charts.

12. Physics Based Arguments: Throughout this book physical arguments are used to simplify concepts, support math-ematical arguments, and explain numerically derived conclusions. The lake analogy to explain the relations between energy, heat, and work in the Introduction, discussion of the mechanism of entropy generation in Chapter 2, expla-nation of the meaning of partial derivative using animations in Chapter 3, or understanding why compressing a vapor is more costly than compressing a liquid in Chapter 4 are examples of such physics based argument. To understand the effect of different modifications to a Rankine or Brayton cycle, the concept of an equivalent Carnot cycle with effective temperatures of heat addition and rejection is introduced in Chapter 7 and used in the subsequent chapters. Results of parametric studies are explained by evaluating the effect of the parameter change on the effec-tive temperatures. In Chapter 14, the equilibrium criterion is derived not by mathematical manipulation, but from

xviii Preface


physical arguments that a system in equilibrium has no internal differences to exploit to extract useful work. The discussion in Chapter 14 to demystify the chemical potential and understand it as a special thermodynamic property that determines the direction of movement of mass, just as temperature gradient decides the direction of heat trans-fer, is another case in point.

This book is written in such a manner that an instructor is free to decide to what extent TEST should be integrated. For instance, someone following the traditional approach may not use TEST much, but students may find this resource quite complementary, using some of the animations or on-line tables and charts in the classroom, or asking students to explore some of the devices simulated by the Interactives are a few ways to gradually incorporate TEST resources. Using the TESTcalc to verify homework solutions could be the next logical step. This will build confidence as students spend less time tracking down petty errors in interpolating properties from tables. Some educators have completely dispensed with manual evaluation of state properties in favor of TEST solution. Finally, parametric studies can be made part of the home-work where students display their curiosity by pursuing different “what-if ” scenarios on a given analysis.

I would greatly appreciate any suggestion for increasing the synergy between the textbook and the courseware TEST. Educators can access the professional TEST site and other instructor resources via the Pearson Instructor Resource Center at www.pearsonhighered.com. The professional site allows the instructor to use the full featured TESTcalcs, to quickly develop or customize new problems, leave a comment for the author, and to see what is next for TEST.

Finally, I must acknowledge the contribution from my students, who have helped me throughout the development of TEST and the manuscript. Even the mnemonic WinHip for the sign convention is their creation. I would be remiss if I do not mention at least a few names—Christopher Paolini, Grayson Lange, Luca Carmignani, Wynn Tran, Gaurav Patel, Shan Liang, Crosby Jhonson, Matt Patterson, Tommy Lin, Chris Ederer, Matt Smiley, Etanto Wijayanto, Jyoti Bhattacharjee, Kushagra Gupta, Deepa Gopal, Animesh Agrawal, and Jin Xing as the representatives of a large group I have been fortunate enough to befriend. I must also thank my children, Robi, Sarah, and Neil, who have helped me with the accuracy check and have been my biggest cheerleaders while sacrificing so much of their time with me.

— Subrata Bhattacharjee

Preface xix


your work... your answer specifi c feedback


your work... your answer specifi c feedback


Resources for Instructors

MasteringEngineering. This online Tutorial Homework program allows you to integrate dynamic homework with auto-matic grading and adaptive tutoring. MasteringEngineering allows you to easily track the performance of your entire class on an assignment-by-assignment basis, or the detailed work of an individual student.

Instructor’s Resource. Visual resources to accompany the text are located on the Pearson Higher Education website: www.pearsonhighered.com. If you are in need of a login and password for this site, please contact your local Pearson representative. Visual resources include:

• Allartfromthetext,availableinPowerPointslideandJPEGformat.• Instructor’s Solutions Manual. This supplement provides complete solutions.

Video Solutions. Located on the TEST website, at www.pearsonhighered.com/bhattacharjee, as well as, MasteringEngineering, the Video Solutions offer step-by-step solution walkthroughs of select homework problems from the text. Make efficient use of class time and office hours by showing students the complete and concise problem-solving approaches that they can access any time and view at their own pace. The videos are designed to be a flexible resource to be used however each instructor and student prefers. A valuable tutorial resource, the videos are also helpful for student self-evaluation as students can pause the videos to check their understanding and work alongside the video.

Resources for Students

MasteringEngineering. Tutorial homework problems emulate the instructor’s office-hour environment, guiding students through engineering concepts with self-paced individualized coaching. These in-depth tutorial homework problems are designed to coach students with feedback specific to their errors and optional hints that break problems down into simpler steps.

TEST Website. TEST, The Expert System for Thermodynamics, the Companion Website, located at www.pearsonhighered .com/bhattacharjee, includes:

• TESTcalc: A first of its kind thermodynamics calculator for students and professors to check their work, help create new problems, and analyze thermofluids problems.

• Interactives: Interactive models in which students can manipulate the inputs to help visualize the content while learning the theory.

• Animations: Models to help students visualize and conceptualize the theory they are learning.• Online Thermodynamic Tables: Easily accessible and searchable thermodynamics tables. Tables are in both US

and SI units and supplement TESTcalcs to verify interpolated data.

Video Solutions. Complete, step-by-step solution walkthroughs of select homework problems. Video Solutions offer fully worked solutions that show every step of how to solve and verify hand calculations using TESTcalcs—this helps students make vital connections between concepts.

xxii


Documents

Thermodynamics: An Interactive Approach · PDF fileChapter 5 Mass, Energy, and Entropy ... 5.4 Thermodynamic Cycle as a Closed Process 241 5.4.1 Origin of Internal Energy 242 ... 7.4