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humidity. Because of the high velocity, the dry portion coincides with high velocity in most of the lumps in this case. This vaporization potentiality (coincidence factor) overcomes the condensation-to-evaporation coefficient factor. This can explain why the first section of the deep breathing condensation/evaporation curve is significantly above the normal breathing curve and the steady flow curve. The graph also shows that the second section of the deep breathing curve drops sharply. This is because the exhaled air with higher humidity reaches these lumps and flows through these lumps twice. This high humidity reverse flow crosses off some of the vaporization potentiality. More details about the real-time condensation are explained below. Figure XVIII. 4 Condensation/evaporation rate in lump 1 under conditions of deep breathing, 4cmH2O pressure setting, 55°C heating element setting, ambient temperature and relative humidity of 22°C&20% and no tube heating The real-time situation related to condensation is more complicated when there is reverse flow. Figure XVIII. 4 shows the condensation rate in lump 1. During inhalation, the high velocity coincides with the dry portion of air provides a very high peak of vaporization potentiality (point A in the graph). Around point B, certain amount of the air just flew through (some of the portion of A) flows back from bigger-numbered lumps because of reverse flow. The reverse flow is at a comparatively much lower velocity thus low convection rate therefore the B point is much lower than point A. When the reverse flow stops and positive flow resumes, the very short portion of air between the chamber and lump 1 flows through lump 1 again and forms the small peak 262
at point C. Right after that, here comes the very highly humidified portion of air which has flown over the water surface for three times because of the reverse flow. This portion flows on with a very high humidity but at a quite low velocity and forms the trough D (means condensation). Following this highly humid portion is the air the first time entering the chamber from the blower and ambient. This portion is drier and makes the curve returns back to above zero again. Then the next inhalation starts and the high velocity along with dry air makes a high peak of vaporization potentiality again (replica of point A). From the graph, it is clear that the overwhelming factor is the vaporization potentiality created by the coincidence of dry air and high velocity. This can explain why the first section of the deep breathing condensation/evaporation curve is significantly above the normal breathing curve and the steady curve. Figure XVIII. 5 Condensation/evaporation rate in lump 30 under conditions of deep breathing, 4cmH2O pressure setting, 55°C heating element setting, ambient temperature and relative humidity of 22°C&20% and no tube heating Figure XVIII. 5 shows the condensation rate in lump 30. At the beginning of a breath cycle, inhalation drags the drier portion of air flowing through very fast and makes a high peak of vaporization potentiality. Within this peak, there is a steep gorge (point B) which represents the very humid three-times-over-water portion travelling through this lump at a very high velocity. Reverse flow starts right before point C, the small peak of point C represents the fresh air stayed in the mask now being pushed back into the HADT. After this “maskful” of fresh air comes the exhaled air with very high humidity 263
Page 1 and 2:
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
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Figure 6.20 In-tube condensation of
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When using different sized masks, t
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Figure 6.23 Average specific humidi
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The average specific humidity in an
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Table 6.5 Comparison of average spe
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6. The deep breathing and reverse f
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Appendices Appendix I Regression of
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Appendix I. Regression of the press
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Figure I. 1 Tested results and the
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Appendix II. Regression of the pres
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Table III. 2 Airflow temperature an
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Appendix IV. The corrugated HADT ou
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The total area of the complicated c
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Figure V. 1 Regression of saturated
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This ratio can be regressed against
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Appendix VII. Details of the CPAP f
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VII.4 The mask pressure subsystem F
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Inputs to this water-centred subsys
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Input port number Input Unit 1 Heat
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input 4 is the portion of impact ar
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VIII.2.3 Water surface mass transfe
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This subsystem also contains two su
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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 and 250: Figure VIII. 17 Chamber wall 2 and
Page 251 and 252: Inputs to this subsystem are listed
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: Figure XVIII. 2 Condensation/evapor
Page 299 and 300: Appendix XIX. Coefficient and param
Page 301 and 302: Average water thermal conductivity
Page 303 and 304: Appendix XXI. Fluid dynamic and the
Page 305 and 306: The lung simulator drives the air.
Page 307 and 308: Appendix XXII. Model user instructi
Page 309 and 310: The input blocks and their values a
Page 311 and 312: Dynamically fluctuating air tempera
Page 313 and 314: References [1] Good sleep advice. W
Page 315 and 316: [28] Schettino GPP, Chatmongkolchar
Page 317: [60] Marek R, Straub J. Analysis of
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