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STUDY OF PERFORMANCE CHARACTERISTICS OF VAPOUR PUMPS

BY

DESH RAJ SHARMA

NATIONAL PHYSICAL LABORATORY NEW DELHI-110012

THESIS SUBMITTED TO DEPARTMENT OF PHYSICS, INDIAN INSTITUTE OF TECHNOLOGY, DELHI FOR PARTIAL FULFILMENT OF THE DEGREE OF

DOCTOR OF PHILOSOPHY APRIL, 1984

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THESIS SUPLEVISORS

Xi ti oo SHA MA. D *PHIL OXON) HEWN ir

TACMDI

LID

tRESSURE ST

AND

Allik3 HAT

ID

NAL PH IS I0 AL LABOR CORY.

NEW HEIR LA I 001 2

••'-' PRO L.L. CHO Alp PROPESSO OP PHYSI AID HEAD, ENERGY MITRE

MIAS MISTIME OP TECHEOI004 HAUZ ERAS*

MEW DELHI.110016.

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ACKNOWLEDGEMEBTS ABSTRACT

CHAPTER I MEASUREMENT OF LOW PRKSSURE 1.1 Introduction

1.2 Basic Principle of McLeod

5

Gauge

1.3 The Chief Sources of Errors 6 and Their Elimination

1.4 The Bakeable McLeod Gauge 9

1.5

Details of Experimental System 12 1.6 Experimental Procedure 14 1.7 Study of Capillary Depreseion 16

Phenomena

1.7.1 Correction due to Capillarity 19 in Wide Bore Reference Arm Tube

las

Study of Mercury Vapour Drag 27 Effect

1.8.1 Theoretical Treatment

30

1.8.2 Experimental Results and 35 Discussion

1.9 Conclusion 39

Reforencee 41

CHAPT;!R II ilL;ASUREMENT 01 THROUGHPUT

45

2.1 Concept of Throughput 45 2.2 A Survey of Different Types

47

of Flovmeters

(a)Constant Pressure rimester

48

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iJAM.A2A (b )Constant Vol.um Ploemeter 49 (o ):Liquid Displacement llowmeter 49 2.3 A Modified Stevenson Type 53

Flommeter

2.3.1 Operation 54

2.4 Investigation of a *s Type of 57 Relative Flowmeter

2.4.1 Design and Operation 58

2.4.2

Calibration Characteristics 60

2.4.3 Discussion 61

References 64

CHAFTidi III MEASUREMENT OF INTRINSIC SPEED AND 66 CRITICAL BACKING PRESSURE

SECTION As Measurement of Intrinsic 66 Speed

3.1 Introduot ion 66 3.1.1 Use of the Same Diameter Test Dome 69 3.2 Theoretical Aspects 72 3.3 Experimental Details and 74

Procedures

3.3.1 Test Dome Method 75 3.3.2 Conductance Tube Method 77 3.3.2.1 Measurement Procedure 79 3.4 Results and Discussion 81 SECTION Bs Study of Critical Backing 85

Pressure

3.5 Concept of Critical Backing 85 Pressure

3.6 Experimental Set-Up 88

3.6.1 Measuring Procedure 89 3.7 Calibration of Pirani Clues 92

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Page No.

3.8 Results and Discussion

92

References

95

CHAPTER IV STUDY OF GAO BEAMING EFFi:CT INSIDE THI

TEST DOME 98

4.1 Introduction 98

4.2 Theoretical Consideration 104 4.2.1 Tabulated Gauge Connection 104 4.2.2 Orifice Gauge Connection 108 4.3 location of Pressure Gauge 111

for Sax: • S

(a) Tubulated Gauge 111 (b) Orifice Osage 112 4.4 Effect of Gauge Inlet Orientation 114 4.4.1 Values of LA for the Orientations 119

A and C

4.5 Details of Experimental set.up 121 and Procedure

4.6

Results 126

4.6.1 Comparison of Measured old 126 Experimentally Computed Throughput

4.6.2 A New Approach to Intrinsio 128 Speed Measurement

4.6.3 Measurement of Molecular Conductance 130 4.6.4 Number of Gas Molecules/Sec 131

Crossing the Orifice of the Test Dome at any Position

4.6.5 Comparison of Experimentally 134 Measured and Theoretically

Determined Speeds

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4.6.6 Effective Conductance and the Test 139 Dome Constant

4.6.7 Pressure Distribution in Axial 143 Direction

4.7 Discussions 144

4.8 Conclusion 148

References 152

References

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