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the working temperature range thus Eq. (3.62) is simplified as a constant value of 0.2205°C /W for the conductive thermal resistance R C 23 . Figure VIII. 19 Chamber wall 2 and 3 conductive and outer surface resistance subsystem VIII.4 In-chamber air specific humidity calculation subsystem This subsystem is created for calculating the specific humidity of air in the chamber. It is actually a calculation of the mixing of the inlet and the evaporated water vapour. It is d m m C ev based on Eq. (3.66) i.e. Ca m C d . However, when the flow rate is near zero, the calculated specific humidity level from Eq. (3.66) is extraordinarily high. This makes the result unreal and the model stuck. In fact the change of total vapour amount in the chamber is far from so significant as the calculated result since the extremity occurs only when flow rate is very small. To get rid of the influence of such unreal calculated result, a saturation-control subsystem is placed after this subsystem to curb the result no more than saturation level. Thus this subsystem contains two subsystems. One is for calculating the specific humidity of in-chamber air after such mixing and another following this is the humidity-level curbing subsystem using saturation controlling. They are shown below. Figure VIII. 20 In-chamber air specific humidity calculation subsystem 216
Inputs to this subsystem are listed below. Input port number Input Unit 1 Specific humidity of chamber inlet In decimal 2 Dynamic evaporation rate kg/s 3 Velocity of air flowing into the chamber m/s 4 In-chamber air temperature °C VIII.4.1 In-chamber air mixing for specific humidity subsystem This sub-subsystem is based on Eq. (3.66). Figure VIII. 21 In-chamber air mixing for specific humidity subsystem VIII.4.2 In-chamber air specific humidity curbing subsystem This subsystem is for curbing the unreal high specific humidity level from calculation when air flow velocity is near zero (see Appendix VI for calculation details). Output from this subsystem is the in-chamber air specific humidity curbed by the chamber air temperature. 217
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The Effects of CPAP Tube Reverse Fl
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Acknowledgement First of all, I wou
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When deep breathing induced reverse
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2.4.1 Reverse flow calculation ....
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5.3.1 Thermal dynamic model under s
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XI.3 Steady state mask thermal bala
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List of Figures Figure 1.1 Obstruct
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Figure 5.10 Comparison between expe
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Figure 6.13 Fluctuation of airflow
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Table 5.3 Comparison of condensatio
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Nomenclature Symbol Meaning of the
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CMFeO CMFet C O C t Concentration o
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m C 23 m Ca m cv m Cw m store m i m
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Nu Cp Nu dir Nu Ti Nu To Nuwsn Nuws
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QMor QMwst QTastn QTicn QTin Q
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R Mic R Moc R Ticn R Toc R Torn Mas
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V Capacity of the container m 3 V C
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1.1 Background Chapter 1 Introducti
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The MRD is worn in user’s mouth w
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Figure 1.4 CPAP machine Figure 1.5
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1.3 Literature survey A literature
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CPAP fluid dynamic performance with
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Chapter 2 Mathematical Modelling of
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2.3 Fluid dynamic analysis This sec
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If there are minor pressure drops,
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Figure 2.6 Pressure sensor - Honeyw
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The pressure readings were taken af
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Figure 2.12 Experimental set up for
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2.3.4 Chamber air space mass balanc
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From the above analysis, the pressu
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Figure 2.18 Full face mask and the
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Inserting Eq. (2.26) and Eq. (2.27)
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Where n( ) t is the airflow proper
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However in reality, mixing turns ou
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Chapter 3 Mathematical Modelling of
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An Environment Control Chamber (Vö
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Figure 3.4 Thermal enthalpy gain of
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Figure 3.6 Heating element beneath
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Figure 3.8 Chamber water heat balan
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Table 3.1 Thermal resistance from h
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3.3.1.2 Heat balance at the outer s
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3.3.2 Heat flow from chamber water
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through ADU which is a function of
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It is assumed that the direct impac
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Sc a a (3.47) Dwa Analogous to th
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and keep them in gaseous status. On
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through the walls and natural conve
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Where d Ca is the specific humidity
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TTa ( n1) is also considered as inl
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R Torn 2 2 ATlor ( TTWn T )( TTWn
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condensation severity but cannot ca
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condensation has occurred at all or
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The inlet is the air from HADT duri
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3.9 Average temperature of inhaled
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Table 4.1 Inputs to the fluid dynam
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Figure 4.2 Simulink TM model for fl
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Table 4.4 Outputs from the overall
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Gain block after input 1 is to conv
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Figure 4.7 Varying Transport Delay
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4.2.5 Mask mixing calculation subsy
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4.3 Computational model of thermal
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Figure 4.11 Block diagram of CPAP t
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Figure 4.13 Simulink TM model for t
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The outputs are listed in Table 4.1
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Figure 4.16 Dynamic chamber-air the
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Figure 4.17 HADT lump thermal balan
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Figure 4.18 Steady state HADT lump
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Figure 4.19 HADT lump air dynamic f
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Figure 4.21Steady state mask full t
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4 Temperature of airflow from HADT
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Average evaporation rate subsystem
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HADT and connects those upstream se
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The experiment was also carried out
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air flowing through the elbow, a ce
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expansion from the elbow to the mas
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Figure 5.12 Environmental control r
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Table 5.1 shows the combinations of
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Figure 5.17 Comparison of model out
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The comparison of experimental resu
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5.3.1.4 Airflow temperature at the
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flow rate had been even further inc
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Figure 5.31 Comparison of condensat
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Table 5.3 Comparison of condensatio
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3. The corrugated grooves on the HA
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5.3.2.1 Validation of evaporation r
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The experiment observation showed t
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Figure 6.1 Reverse flow under diffe
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It can also be seen in Figure 6.2 t
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within the same period. However, wh
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Figure 6.6 Comparison of evaporatio
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Figure 6.8 Airflow velocity in HADT
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Figure 6.11 Airflow velocity in HAD
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In Figure 6.14 the blue curve repre
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6.3.3.1.2 Comparison when heating e
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This vaporization potentiality (coi
Page 199 and 200: Figure 6.20 In-tube condensation of
Page 201 and 202: When using different sized masks, t
Page 203 and 204: Figure 6.23 Average specific humidi
Page 205 and 206: The average specific humidity in an
Page 207 and 208: Table 6.5 Comparison of average spe
Page 209 and 210: 6. The deep breathing and reverse f
Page 211 and 212: Appendices Appendix I Regression of
Page 213 and 214: Appendix I. Regression of the press
Page 215 and 216: Figure I. 1 Tested results and the
Page 217 and 218: Appendix II. Regression of the pres
Page 219 and 220: Table III. 2 Airflow temperature an
Page 221 and 222: Appendix IV. The corrugated HADT ou
Page 223 and 224: The total area of the complicated c
Page 225 and 226: Figure V. 1 Regression of saturated
Page 227 and 228: This ratio can be regressed against
Page 229 and 230: Appendix VII. Details of the CPAP f
Page 231 and 232: VII.4 The mask pressure subsystem F
Page 233 and 234: Inputs to this water-centred subsys
Page 235 and 236: Input port number Input Unit 1 Heat
Page 237 and 238: input 4 is the portion of impact ar
Page 239 and 240: VIII.2.3 Water surface mass transfe
Page 241 and 242: This subsystem also contains two su
Page 243 and 244: VIII.2.5 Chamber wall 1 heat transf
Page 245 and 246: Figure VIII. 13 Wall 1 outer surfac
Page 247 and 248: Wall 2 and 3 inner surface temperat
Page 249: Figure VIII. 17 Chamber wall 2 and
Page 253 and 254: Appendix IX. Details of steady stat
Page 255 and 256: Figure IX. 3 The HADT lump wall out
Page 257 and 258: Appendix X. Details of HADT lump ai
Page 259 and 260: 2 Absolute value of airflow velocit
Page 261 and 262: Figure X. 5 HADT lump inlet absolut
Page 263 and 264: Figure XI. 2 Steady state mask mixi
Page 265 and 266: Figure XI. 4 Steady state mask wall
Page 267 and 268: Input port number Input Unit 1 Aver
Page 269 and 270: Appendix XII. Details of mask air d
Page 271 and 272: 4 Length of the triangular plate in
Page 273 and 274: 8 Length of the triangular plate in
Page 275 and 276: Appendix XIII. Details of the auxil
Page 277 and 278: XIII.3 Breath load average subsyste
Page 279 and 280: Figure XIII. 7 Average evaporation
Page 281 and 282: XIV.1.2 Under normal ambient temper
Page 283 and 284: XIV.2.3 Under high ambient temperat
Page 285 and 286: XIV.4 Airflow temperature at the en
Page 287 and 288: XIV.5.2 Under normal ambient temper
Page 289 and 290: XIV.6.3 Under high ambient temperat
Page 291 and 292: Appendix XVI. Regression of kinetic
Page 293 and 294: Figure XVII. 2 Condensation/evapora
Page 295 and 296: Figure XVIII. 2 Condensation/evapor
Page 297 and 298: at point C. Right after that, here
Page 299 and 300: Appendix XIX. Coefficient and param
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Average water thermal conductivity
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Appendix XXI. Fluid dynamic and the
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The lung simulator drives the air.
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Appendix XXII. Model user instructi
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The input blocks and their values a
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Dynamically fluctuating air tempera
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References [1] Good sleep advice. W
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[28] Schettino GPP, Chatmongkolchar
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[60] Marek R, Straub J. Analysis of
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