Understanding Infrared Thermography Reading 3

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Heat Capacity The heat capacity of a malerial or a structure describes its ability to store heat. It is the product of the specific thermal energy C p and the density ρ of the material. When thermal energy is stored in a structure and then the structure is placed in a cooler environment, the sections of the structure that have low heat capacity will change temperature more rapidly because less thermal energy is stored in them. Consequently, these sections will reach thermal equilibrium with their surroundings sooner than those sections with higher heat capacity, The term thermal capacitance is used to describe heat capacity in terms of an electrical analog. where loss of heat is analogous to loss of charge on a capacitor. Structures with low thermal capacitance reach equilibrium sooner when placed in a cooler environmcnt than those with high thermal capacitance. This phenomenon is exploited when performing unstimulated nondestructive testing of structures, specifically when locating water saturated sections on flat roofs. This is discussed in greater detail in Chapter 5, Charlie Chong/ Fion Zhang
Thermal Diffusivity As in emissivity Ɛ. the heat conducting properties of materials may vary from sample to sample. depending on variables in the fabrication process and other factors. Thermal diffusivity α is the 3D expansion of thermal conductivity in any given material sample. Diffusivily relates more to transient heat flow, whereas conductivity relates to steady state heat flow. It takes into account the thermal conductivity k of the sample, its specific heat C p , and its density ρ. Its equation is α = k/ρ C p cm 2 s -1 . Because thermal diffusivity of a sample can be measured directly using infrared thermography, it is used extensively by the materials flaw evaluation community as an assessment of a test sample's ability to carry heat away, in all directions, from a heat injection site. Table 2.1 lists thermal diffusivities for several common materials in increasing order of thermal diffusivity. Several protocols for measuring the thermal diffusivity of a test sample are described by Maldague. Charlie Chong/ Fion Zhang
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Infrared Thermal Testing Reading II
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Infrared Thermography ~-- ... ... .
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Infrared Thermography Charlie Chong
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See Through & Fun Thermal Camera Ex
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How to see through clothing 2 I'
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Apache IR Thermal Weaponry ■ http
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Charlie Chong/ Fion Zhang
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Greek alphabet Letter Name Sound An
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Greek letter l fl 0 I1 p u w Charli
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SGuide-IRT Content Part 1 of 2 ■
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1.1 Introduction to Principles & Th
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The infrared thermal imaging equipm
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The three modes of heat transfer ar
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The three modes of heat transfer ar
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Temperature and Temperature Scales
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Boston Tea Party - New governances
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The Mighty Fahrenheit & ⅝”, Eng
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Absolute zero is equal to - 273.16
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The Fourier conduction Law expresse
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The Fourier conduction Law ( One di
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Convective Heat Transfer Convective
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Figure 1.2: Convective heat flow T
Page 45 and 46: Newton's cooling law defines the co
Page 47 and 48: Radiative Heat Transfer Radiative h
Page 49 and 50: Figure 1.4: Infrared radiation leav
Page 51 and 52: Thermal infrared radiation impingin
Page 53 and 54: Reflections off Specular and Diffus
Page 55 and 56: Reflections off Specular and Diffus
Page 57 and 58: Radiant Energy Related to Target Su
Page 59 and 60: The Stefan-Boltzmann law: W= σƐT
Page 61 and 62: Figure 1.6: Typical blackbody distr
Page 63 and 64: 1.4 Practical Infrared Measurements
Page 65 and 66: Characteristics of the Target Surfa
Page 67 and 68: Referring back to Figure 1.5, the t
Page 69 and 70: Characteristics of the Transmitting
Page 71 and 72: Figure 1.10; Transmission of 10m (3
Page 73 and 74: Figure 1.11: Transmission, absorpti
Page 75 and 76: Figure 1.12: Transmission curves of
Page 77 and 78: Chapter 1 Review Questions Q&A 1. b
Page 79 and 80: Q4. Heat can only flow in the direc
Page 81 and 82: Q10. The follow ing spectral band i
Page 83 and 84: Q16. In forced convection, the boun
Page 85 and 86: Q22. In the 8 to 14 μm spectral re
Page 87 and 88: 2.1 Materials Characteristics A kno
Page 89 and 90: For an emissivity reference table t
Page 91 and 92: Errors because of point source refl
Page 93 and 94: View Angle The angle between the in
Page 95: Thermal Conductivity Thermal conduc
Page 99 and 100: Partial 2.1 Table 2.1: d i'ffusivit
Page 101 and 102: Partial Table 2.2 Table 2.2: Normal
Page 103 and 104: Chapter 2 Review Questions Q&A 1. c
Page 105 and 106: 4. When measuring the temperature o
Page 107 and 108: 10. A highly textured surface is sa
Page 109 and 110: 3.1 Thermal Instrumentation Overvie
Page 111 and 112: Thermopile- Thermoelectric Seebeck
Page 113 and 114: What is a IR Thermopile? (non-conta
Page 115 and 116: IR Thermopile Quad Sensor (non-cont
Page 117 and 118: Thermocouple A thermocouple is a te
Page 119 and 120: Bourdon Gas Thermometers 5 f\G.3 0
Page 121 and 122: Liquid Crystal Thermometer A liquid
Page 123 and 124: Bimetallic Thermometers Dial Spiral
Page 125 and 126: In RTD devices; Copper, Nickel and
Page 127 and 128: Platinum Resistance Thermometer Cha
Page 129 and 130: RTD Materials Different materials u
Page 131 and 132: Operations of RTD An RTD takes a me
Page 133 and 134: Benefits of Thin Film RTD There are
Page 135 and 136: Thermistor +V r===~ Op A p V to A I
Page 137 and 138: 3.2 Contacting Thermal Measuring De
Page 139 and 140: ■ Thermocouple Thermocouples are
Page 141 and 142: ■ Thermistors Thermistors arc als
Page 143 and 144: 3.3 Optical Pyrometers Optical pyro
Page 145 and 146: Pyrometer A pyrometer is a type of
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Brightness Pyrometers -Wien’s Law
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The processing electronics unit amp
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Infrared Detector An infrared detec
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Figure 3.2: Response Curves of Vari
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The mercury cadmium telluride (HgCd
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Infrared Optics - Lenses, Mirrors a
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Field of View (FOV) A field of view
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What is IFOV? A measure of the spat
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Instantaneous Field of View (IFOV)
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3.5 Scanning and Imaging When probl
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Line Scanning When the measurement
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Two-dimensional Scanning - Thermal
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Figure 3.5: Optomechanlcally scanne
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Pyroelectric Vidicon Thermal Imager
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Figure 3.6: Typical uncooled infrar
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IRFPA Charlie Chong/ Fion Zhang htt
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3.6 Performance Parameters of Infra
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Performance parameters of qualitati
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Temperature Range Temperature range
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Temperature Sensitivity Temperature
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Speed of Response Speed of response
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Figure 3.7: Instrument speed to res
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Figure 3.8: Instrument field-of-vie
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D ≡ αd D = spot size (approximat
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Output Requirements Output requirem
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Spectral Range Spectral range denot
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Spectrall y selective instrumems us
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Figure 3.9: Spectral response of an
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3.7 Performance Characteristics of
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The total field of view for a line
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Instantaneous Field of View IFOV In
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Recalling! Temperature sensitivity
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IFOV - MTF The 0.35 MTF refers to:
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Fig. 2a. Slit Response Function. Ca
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Minimum Resolvable Temperature Diff
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EXAM score! D=σ∙d IFOV ratio = d
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Charlie Chong/ Fion Zhang
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Answer: D= σ•d, IFOV ration= 1/
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Break Time - Kenya Coffee Picker Ch
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Portable Handheld Devices Charlie C
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Temperature sensitivity and readabi
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Hand Held Infrared Module Charlie C
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Note that the laser beam docs not r
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Emissivity set controls, located in
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IR Sensor Module Charlie Chong/ Fio
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IR Sensor Module Charlie Chong/ Fio
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Two-color Pyrometers or Ratio Pyrom
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Phenomena which are non-dynamic in
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Some ratio thermometers use more th
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Infrared Radiometric Microscopes Ch
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Line Scanners Line scanners are div
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Special Purpose Devices Special pur
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FLIR- Forward Looking Infrared Char
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Typically, the total field of view
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Pyroelectric devices have no direct
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Figure 3.12: Infrared focal plane a
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Infrared focal plane array imager C
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Infrared focal plane array imager C
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On-board capabilities include isoth
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ccc Electron Microscope Image of mi
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Platinum Silicide IrFPA 19 t«lU 98
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Quantitative IR Image Charlie Chong
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Quantitative Thermal Measurements S
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In addition to the spot measurement
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Stored images can be retrieved, dis
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Calibration Accessories Infrared ra
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Online printers and plotters are re
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Q1. The thermal resolution of an in
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Q7. The 3 to 5 μm spectral region
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Q13. A line scanner can be used to
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Q19. For which of the following app
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Q25. Two-color (ratio) pyrometers m
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Chapter 4 Operating Equipment and U
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■ Emissivity Differences ∆τ Em
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Causes of Real Temperature Changes
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Mass Transport Differences (Fluid F
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Figure 4.1: An indication of water
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Thermal Capacitance Differences ∆
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■ Induced Heating Differences (by
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Induced Heating Differences Charlie
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■ Energy Conversion Differences E
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Figure 4.3: Catalytic reformer vess
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Infrared Thermogram Energy Conversi
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Infrared Thermogram Energy Conversi
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■ Combination of Heat Transfer Me
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Infrared Thermogram of a running mo
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■ Spectral Considerations in Prod
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Infrared Thermogram Charlie Chong/
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Infrared Thermogram ..... " I Charl
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Figure 4.5: Spectral selectivity fo
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Figure 4.7: temperature thermogram
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Figure 4.8 shows the transmission s
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Figure 4.9: Measuring temperature o
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IR Filter Charlie Chong/ Fion Zhang
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Figure 4.10: Line scanner for conti
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Preparation of Equipment for Operat
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If the instrument is out of cal ibr
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The batteries mentioned on the miss
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Comments: ■ ■ ■ Thermal resol
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Figure 4.11 : Test configuration fo
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3. Reduce the ΔT until the image i
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■ Imaging Spatial Resolution Imag
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A sample setup is illustrated in Fi
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5. If the modulation transfer funct
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Figure 4.13: Test configuration for
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4. Open slit until V meas = V max .
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■ Learning the Startup Procedure
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■ Setting the Correct Effective E
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Figure 4.14: Test configuration for
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■ Measuring and Reporting Tempera
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■ Recognizing and Avoiding Reflec
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■ Measuring the Appropriate Backg
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■ Temperature Differences Between
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■ Liquid and Compressed Gases Som
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Dewar Flask for LN Loosely fitting
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■ Electrical Safety Failure to re
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Table 4.1: Electric shock current t
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4.4 Record Keeping Keeping thorough
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Easily accessible and easily unders
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Q1. Apparent but not real temperatu
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Q5. The higher the temperature of a
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Q9. Differential thermography can b
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5.1 Overview of Applications Becaus
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Electrical Applications Electrical
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High electrical resistance is the m
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Excessive heating due to a defectiv
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Inductive currents flowing with in
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Moisture in Airframes The detection
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Process Control and Product Monitor
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The differences produced by this co
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Night Vision, Seareh, Surveillance,
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Thermogram of helicopter taken at n
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Aircraft Under IR Trap Charlie Chon
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Instruments used for these applicat
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8 to 12 μm spectral region over wh
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Animal Studies Body heat allows inf
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Injured equine foreleg (left) appea
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Work energy is expended by friction
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5.4 Fluid Flow Investigations For s
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Figure 1.7: Thermographs of valve (
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■ Building Insulation and Other F
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Figures 5.8 and 5.9 illustrate thes
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Figure 5.9: Example of air exfiltra
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Example of air exfiltration Charlie
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■ Refractory Systems Industrial s
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Refractory Thermogram Charlie Chong
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■ Subsurface Discontinuity Detect
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Figure 5.11: An example of passive
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The equipment necessary to perform
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Figure 5.12: Example of active (hea
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Typical failure modes of the materi
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Figure 5.13: Test of aircraft deici
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DC - 9 Charlie Chong/ Fion Zhang
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Figure 5.14: Conceptual sketch of t
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In this case. however, the heat pul
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Figure 5.15: Erosion/corrosion dama
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737 aircraft Charlie Chong/ Fion Zh
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When there has been adequate solar
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Liquid Level Detection Thermal capa
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Unstimulated and Stimulated Approac
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Subsurface Discontinuity Detection
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1. A major area of infrared nondest
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5. The diagnostics involved in dete
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9. Thermography has been successful
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Appendix A Glossary The following a
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Ambient temperature - Temperature o
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Figure A-1 Apparent ambient tempera
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13.Blackbody, blackbody radiator -
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Alas! Heat Capacity Volumetric = C
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27.Detector, infrared - A transduce
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Thermal Effusivity In Thermodynamic
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Alas! Exitance = Rodiosity for my A
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45.Frame repetition rate - The time
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Thermal Inertia Thermal inertia is
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Instantaneous field of View (lFOV)
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Laser pyrometer - Laser pyrometer -
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Figure 3.2: Response Curves of Vari
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Compare: Minimum resolvable tempera
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86.Radiation rererenee source - A b
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101. Sector - For a line scanner, a
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113. Subtense, angular - The angula
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121. Thermal wave imaging - A term
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125. Thermogram - A thermal map or
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Appendix B Cost Benefit Determinati
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Although the calculations are quite
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96 ASNT Level Ill Study Guide: Infr
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Appendix C, Commonly Used Infrared
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Appendix C, Commonly Used Infrared
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Peach - 我爱桃子 Charlie Cho
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Good Luck Charlie Chong/ Fion Zhang
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