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Heat loss by radiation, convection, and leak through the supports is minimised in order to let the conduction through the gas be the dominant transfer mechanism of heat from the filament to the surroundings. Changes in gas composition in a chamber lead to temperature changes of the filament and thus to accompanying changes in resistance which are measured with the completed Wheatstone bridge. The heat lost from the filament will depend on both the thermal conductivity of the gas and its specific heat. Both these parameters will change in the presence of a different gas or solute vapor and as a result the temperature of the filament changes, causing a change in potential across the filament. This potential change is amplified and either fed to a suitable recorder or passed to an appropriate data acquisition system. As the detector filament is in thermal equilibrium with its surroundings and the device actually responds to the heat lost from the filament, the detector is extremely flow and pressure sensitive. Consequently, all katharometer detectors must be carefully thermostated and must be fitted with reference cells to help compensate for changes in pressure or flow rate. Usually, one of the spirals of the katharometer is sealed permanently in air and the resistance readings are the reference readings. Other filament is connected with the gas as analyze reading. The katharometer has the advantage that its open cell can form part of the diffusion cell, and so it can indicate continuously the changes in composition as diffusion and thermal diffusion proceeds without sampling. 1.5.2 From the variation of viscosity Van Itterbeek and van Paemel (1938, 1940) ([101, 102], see also [50]) have developed a method of measurement based on the damping of an oscillating-disk viscometers. The oscillating disk itself is a part of the top bulb of the thermal diffusion cells. The change in the composition of the upper part due to thermal diffusion, changes the viscosity of the mixture and then corresponding change in composition is found from calibration curve. This method has a precision of the same as the conductivity detector. 1.5.3 Gas Chromatography (GC) In a Gas Chromatograph the sample is injected into a heated inlet where it is vaporized, and then transferred into a chromatographic column. Different compounds are separated in the column, primarily through their physical interaction with the walls of the column. Once 16
separated, the compounds are fed into a detector. There are two types of the detector: Flame Ionization Detector (FID) and Electron Capture Detector (ECD). Schematic of a gas chromatograph flame ionization detector is illustrated in Fig. 1-7. As we can see in this figure, GC-FID uses a flame ionization detector for identification of compounds. The flame ionization detector responds to compounds that create ions when combusted in a hydrogen-air flame. These ions pass into a detector and are converted to an electrical signal. This method of analysis can be used for the detection of compounds such as ethanol, acetaldehyde, ethyl acetate, and higher alcohols. Fig. 1-7. Schematics of a Gas Chromatograph Flame Ionization Detector (GC-FID) The ECD or electron capture detector (Fig. 1-8) measures electron capturing compounds (usually halogenated) by creating an electrical field in which molecules exiting a GC column can be detected by the drop in current in the field. Fig. 1-8. Schematics of a Gas Chromatograph Electron Capture Detector (GC-ECD) The ECD works by directing the gas phase output from the column across an electrical field applied across two electrodes, either using a constant DC potential or a pulsed potential. The electrical field is produced using a thermally stable 63Ni source that ionizes 17
Page 1: ��
Page 4 and 5: while the effective thermal conduct
Page 6 and 7: propriétés thermiques, sont ainsi
Page 8 and 9: Remerciements Ma thèse, comme bien
Page 10: Toute mon amitié à Yohan Davit (l
Page 13 and 14: 2.5 Transient conduction and convec
Page 15 and 16: List of tables Table 1-1. Flux-forc
Page 17 and 18: Fig. 2-11. Comparison of closure va
Page 19 and 20: Fig. 4-15. Composition-time history
Page 21 and 22: Chapter 1 General Introduction
Page 23 and 24: interested in the upscaling of mass
Page 25 and 26: possible to ignore the important ve
Page 27 and 28: • mesoscopic or macroscopic scale
Page 29 and 30: macroscopic scale. In these macrosc
Page 31 and 32: different temperatures. A temperatu
Page 33 and 34: 1.4.3 Thermal Field-Flow Fractionat
Page 35: 1.5.1 From the variation of thermal
Page 39 and 40: 1.6 Conclusion From the discussion
Page 41 and 42: 2. Theoretical predictions of the e
Page 43 and 44: g Gravitational acceleration, m 2 /
Page 45 and 46: 2.1 Introduction It is well establi
Page 47 and 48: However, for all these models many
Page 49 and 50: At the fluid-solid interfaces there
Page 51 and 52: 2.4 Darcy’s law If we assume that
Page 53 and 54: where F is the Forchheimer correcti
Page 55 and 56: ε β ∂ β ( ρc ) T + ( ρc ) p
Page 57 and 58: Finally, we postulate the functiona
Page 59 and 60: ⎛ ⎜ k ~ . βσ ⎜ p ⎝ β Aβ
Page 61 and 62: − ε V −1 σ ∫ Aβσ n βσ 2
Page 63 and 64: ( ε + ε k ) ( k − k ) ( ρcp )
Page 65 and 66: We see on these figures a very good
Page 67 and 68: If the local equilibrium assumption
Page 69 and 70: epresentation of these coefficients
Page 71 and 72: 2.6 Transient diffusion and convect
Page 73 and 74: ε ε −1 β −1 β ⎛ ⎜ Dβ
Page 75 and 76: Problem I for Chang’s unit cell 2
Page 77 and 78: 1 ∫ Vβ A βσ n βσ b Sβ dA =
Page 79 and 80: 2.7 Results In order to illustrate
Page 81 and 82: Problem IIa ( k ≈ 0 ): closure pr
Page 83 and 84: We have therefore found that the ef
Page 85 and 86: a b c d β D * β D β xx * β ε
Page 87 and 88:
2.7.2 Conductive solid-phase ( k
Page 89 and 90:
diffusion. Fig. 2-13 shows the effe
Page 91 and 92:
β ϕ ϕ * 1.6 1.4 1.2 1.0 0.8 0.6
Page 93 and 94:
Unfortunately we cannot use this ty
Page 95 and 96:
a) κ = 0. 001 , b Tβ b Sβ b) κ
Page 97 and 98:
Chapter 3 Microscopic simulation an
Page 99 and 100:
3.1 Microscopic geometry and bounda
Page 101 and 102:
in the dimensionless system, for th
Page 103 and 104:
Fig. 3-2b and Fig. 3-2c show the di
Page 105 and 106:
3.3 Conductive solid-phase ( k ≠
Page 107 and 108:
Temperature Concentration 1 0.9 0.8
Page 109 and 110:
a b k * = 1. 72ε k . Fig. 3-7a and
Page 111 and 112:
c a Volume averaged temperature. Vo
Page 113 and 114:
c a Volume averaged concentration.
Page 115 and 116:
If we define a new parameter, A S ,
Page 117 and 118:
3.4 Conclusion In order to validate
Page 119 and 120:
4. A new experimental setup to dete
Page 121 and 122:
N N i n The number of chemical spec
Page 123 and 124:
The main purpose of this part is to
Page 125 and 126:
Table 4-1. Thermal conductivity and
Page 127 and 128:
Two vessels containing gases with d
Page 129 and 130:
4.2.2 Two-bulb apparatus end correc
Page 131 and 132:
then the thermal diffusion factor
Page 133 and 134:
4.3 Experimental setup for porous m
Page 135 and 136:
Table 4-2. The properties of CO2, N
Page 137 and 138:
Table 4-3. Molecular weight and Len
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Glass spheres d= 700-1000 μm ε=42
Page 141 and 142:
Concentration of CO2 in bottom bulb
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increases with increasing concentra
Page 145 and 146:
Concentration of CO 2 in bottom bul
Page 147 and 148:
Concentration of N2 in bottom bulb
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convection between the two bulbs th
Page 151 and 152:
Table 4-11. The solid (spheres) and
Page 153 and 154:
Table 4-12. Porous medium tortuosit
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in Fig. 2-6. In this system, the ef
Page 157 and 158:
4.6 Conclusion In this chapter, we
Page 159 and 160:
5. General conclusions and perspect
Page 161 and 162:
this model. Therefore, the next ste
Page 163 and 164:
Temperature Concentration 1 0.8 0.6
Page 165 and 166:
moyennes sont comparées avec les p
Page 167 and 168:
dispositif expérimental avec une c
Page 169 and 170:
Appendix B. Estimation of the therm
Page 171 and 172:
References [1] A. Ahmadi, A. Aiguep
Page 173 and 174:
porous media. Lecture Notes of the
Page 175 and 176:
[51] B. Lacabanne, S. Blancher, R.
Page 177 and 178:
[80] M. Quintard, L. Bletzaker, D.
Page 179:
[106] H. Watts. Diffusion of krypto
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