Mechanical Measurements

The first edition of this book was co-published by Ane Books India, and CRC Press in 2008. This second edition is an enlarged version of the web course developed by the author at IIT Madras, and also a modified and augmented version of the earlier book.  Major additions/modifications presented are in the treatment of errors in measurement, temperature measurement, measurement of thermo-physical properties, and data manipulation. Many new worked examples have been introduced in this new and updated second edition. 

S.P. Venkateshan, Professor and Head of Department of Mechanical Engineering, Indian Institute of Technology (IIT) Madras, India. Professor Venkateshan obtained his PhD in 1977 from the Indian Institute of Science, Bangalore, India, specializing in heat transfer. He has been teaching a course in "Measurements in Thermal Engineering" for over 30 years to B.Tech. M.Tech. students, and research scholars pursuing M.S. and Ph. D. degrees. He has developed a web based course and a video lecture series on "Mechanical Measurements" under the NPTEL project of IIT Madras. His research interests are in Radiation Heat Transfer, Free Convection Heat Transfer and Interaction with Radiation, Hydrodynamics Studies in Fluidized Beds, and Heat Transfer with Phase Change.

Preface vii

Acknowledgements xi

Nomenclature xiii

Contents xix

I Measurements, Error Analysis and Design of Experiments

1 Measurements and Errors in measurement 3

1.1 Introduction 4

1.2 Errors in measurement 6

1.3 Statistical analysis of experimental data 8

1.4 Propagation of errors 40

1.5 Specifications of instruments and their performance 44

2 Regression analysis 47

2.1 Introduction to regression analysis 48

2.2 Linear regression 49

2.3 Polynomial regression 54

2.4 General non-linear fit 60

2.5 χ2 test of goodness of fit 62

2.6 General discussion on regression analysis including special cases 66

3 Design of experiments 73

3.1 Design of experiments 74

Exercise I 89

I.1 Errors and error distributions 89

I.2 Propagation of errors 92

I.3 Regression analysis 94

I.4 Design of experiments 99

II Measurements of Temperature, Heat Flux and Heat Transfer Coefficient

4 Measurements of Temperature 103

4.1 Introduction 104

4.2 Thermometry or the science and art of temperature measurement 104

4.3 Thermoelectric thermometry 110

4.4 Resistance thermometry 131

4.5 Pyrometry 149

4.6 Other temperature measurement techniques . 162

4.7 Measurement of transient temperature . 171

5 Systematic errors in temperature measurement 183

5.1 Introduction 183

5.2 Examples of temperature measurement 183

5.3 Conduction error in thermocouple temperature measurement 186

5.4 Measurement of temperature of a moving fluid 194

6 Heat flux and Heat Transfer Coefficient 205

6.1 Measurement of heat flux 205

6.2 Measurement of heat transfer coefficient 223

Exercise II 229

II.1 Temperature measurement 229

II.2 Transient temperature measurement 235

II.3 Thermometric error 237

II.4 Heat flux measurement 239

III Measurement of Pressure, Fluid velocity, Volume flow rate, Stagnation and Bulk mean temperatures

7 Measurement of Pressure 243

7.1 Basics of pressure measurement 244

7.2 U - Tube manometer 245

7.3 Bourdon gauge 253

7.4 Pressure transducers 254

7.5 Measurement of pressure transients 269

7.6 Measurement of vacuum 275

8 Measurement of Fluid Velocity 281

8.1 Introduction 282

8.2 Pitot - Pitot static and impact probes 282

8.3 Velocity measurement based on thermal effects 293

8.4 Doppler Velocimeter 303

8.5 Time of Flight Velocimeter 309

9 Volume flow rate 315

9.1 Measurement of volume flow rate 316

9.2 Variable area type flow meters 316

9.3 Rotameter or Drag effect flow meter 330

9.4 Miscellaneous types of flow meters 334

9.5 Factors to be considered in the selection of flow meters 336

9.6 Calibration of flow meters 337

10 Stagnation and Bulk mean temperature 343

10.1 Stagnation temperature measurement 344

10.2 Bulk mean temperature 346

Exercise III 351

III.1 Pressure measurement 351

III.2 Velocity measurement 353

III.3 Volume flow rate 354

IV Thermo-physical properties, Radiation properties of surfaces, Gas concentration, Force/Acceleration, torque and power

11 Measurement of thermo-physical properties 359

11.1 Introduction 360

11.2 Thermal conductivity 360

11.3 Steady state methods 361

11.4 Transient method 369

11.5 Measurement of heat capacity 370

11.6 Measurement of calorific value of fuels 374

11.7 Measurement of viscosity of fluids 380

12 Radiation properties of surfaces 389

12.1 Introduction 390

12.2 Features of radiation measuring instruments 393

12.3 Integrating sphere 394

12.4 Measurement of emissivity 400

13 Gas concentration 409

13.1 Introduction 410

13.2 Non separation methods 413

13.3 Separation methods 419

14 Force/Acceleration, torque and power 429

14.1 Introduction 430

14.2 Force Measurement 430

14.3 Measurement of acceleration 436

14.4 Measurement of torque and power 448

Exercise IV 457

IV.1 Thermo-physical properties 457

IV.2 Radiation properties of surfaces 459

IV.3 Gas concentration 459

IV.4 Force, acceleration, Torque and Power 459

V Data Manipulation and Examples from laboratory practice

15 Data Manipulation 465

15.1 Introduction 466

15.2 Mechanical signal conditioning 466

15.3 Electrical/Electronic signal conditioning 468

16 Examples from laboratory practice 487

16.1 Introduction 488

16.2 Thermocouple calibration using a data logger 489

16.3 Calibration of a digital differential pressure gauge 491

16.4 Signal conditioning for torque measurement using strain gauges 492

16.5 Software 494

Exercise V 497

A Bibliographic Notes and References 499

A.1 Bibliographic Notes 499

A.2 References 501

B Useful tables 505

Index 517

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