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coincides with high velocity which make the whole cycle averaged condensation lighter. It can also be seen that the reverse flow induced curve drop is even less sharp. Figure 6.19 In-tube condensation of steady flow, breathing added fluctuating flows under conditions of 4cmH2O, 55°C, 0W, 22°C&80% From these figures above, it can be seen that the deep breathing still does not increase or worsen the condensation even if there is reverse flow. Comparing these three graphs, a trend can be seen. The deep breathing curve turns down sharper when humidity difference between the airflow from humidifier chamber and the exhaled air increases (e.g. when the ambient RH is 20%). If, under some conditions, the exhaled air can drag the curve down enough to outdo the vaporization potentiality, then the deep breathing curve can drop below the normal breathing curve. 6.3.3.2.4 The conditions when reverse flow creates or worsen condensation From Figure 6.20, it can be seen that when the heating element temperature setting is lowered to 45°C and the ambient temperature drops to 21°C, the second section of the deep breathing curve drops below the other two curves. It further drops below 0 in the last few lumps. This means that the condensation worsens and builds up in these lumps. The reason for it is that the condensation increased by the exhaled air outdoes the vaporization potentiality in these lumps. 164
Figure 6.20 In-tube condensation of steady flow, breathing added fluctuating flows under conditions of 4cmH2O, 45°C, 0W, 21°C&50% To summarize, due to the coincidence factor, reverse flow alleviates condensation in the HADT lumps where the exhaled air can not reach. Even for the last few lumps where the exhaled air can reach, reverse flow does not always create or worsen condensation. It creates or worsens condensation only when the humidity of the airflow from the CPAP is much lower than that of the exhaled air and the wall temperature in the last few lumps is low enough for condensation to occur and build up. 165
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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
Page 147 and 148: HADT and connects those upstream se
Page 149 and 150: The experiment was also carried out
Page 151 and 152: air flowing through the elbow, a ce
Page 153 and 154: expansion from the elbow to the mas
Page 155 and 156: Figure 5.12 Environmental control r
Page 157 and 158: Table 5.1 shows the combinations of
Page 159 and 160: Figure 5.17 Comparison of model out
Page 161 and 162: The comparison of experimental resu
Page 167 and 168: 5.3.1.4 Airflow temperature at the
Page 169 and 170: flow rate had been even further inc
Page 171 and 172: Figure 5.31 Comparison of condensat
Page 173 and 174: Table 5.3 Comparison of condensatio
Page 175 and 176: 3. The corrugated grooves on the HA
Page 177 and 178: 5.3.2.1 Validation of evaporation r
Page 179 and 180: The experiment observation showed t
Page 181 and 182: Figure 6.1 Reverse flow under diffe
Page 183 and 184: It can also be seen in Figure 6.2 t
Page 185 and 186: within the same period. However, wh
Page 187 and 188: Figure 6.6 Comparison of evaporatio
Page 189 and 190: Figure 6.8 Airflow velocity in HADT
Page 191 and 192: Figure 6.11 Airflow velocity in HAD
Page 193 and 194: In Figure 6.14 the blue curve repre
Page 195 and 196: 6.3.3.1.2 Comparison when heating e
Page 197: This vaporization potentiality (coi
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
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Figure VIII. 17 Chamber wall 2 and
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Inputs to this subsystem are listed
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Appendix IX. Details of steady stat
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Figure IX. 3 The HADT lump wall out
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Appendix X. Details of HADT lump ai
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2 Absolute value of airflow velocit
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Figure X. 5 HADT lump inlet absolut
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Figure XI. 2 Steady state mask mixi
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Figure XI. 4 Steady state mask wall
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Input port number Input Unit 1 Aver
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Appendix XII. Details of mask air d
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4 Length of the triangular plate in
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8 Length of the triangular plate in
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Appendix XIII. Details of the auxil
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XIII.3 Breath load average subsyste
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Figure XIII. 7 Average evaporation
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XIV.1.2 Under normal ambient temper
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XIV.2.3 Under high ambient temperat
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XIV.4 Airflow temperature at the en
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XIV.5.2 Under normal ambient temper
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XIV.6.3 Under high ambient temperat
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Appendix XVI. Regression of kinetic
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Figure XVII. 2 Condensation/evapora
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Figure XVIII. 2 Condensation/evapor
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at point C. Right after that, here
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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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