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accurate and real flow pattern analysis may be helpful for future design. I.e. a design which can also compensate for the influence of water level change on evaporation rate. 4. It will be helpful to develop a scheme which would be able to adjust the humidifier heating inputs so to compensate for the airflow humidity change due to the change of the pressure setting and the water level drop. 5. It will also be beneficial to develop a scheme which will be able to adjust the heating element setting to offset the breath load induced inhaled air humidity change. 6. A scheme may also be needed for the tube heating adjustment to alleviate the condensation induced by the above-mentioned humidifier heating adjustments and reverse flow. This means a higher humidifier heating and a higher tube heating to cooperatively provide an ideal humidity level without increasing condensation. 7. Usually, the inhaled air has a lower humidity than the average humidity of airflow from the chamber. This means the majority of the water evaporated is not utilized but may only increase the possibility of downstream condensation. It would be ideal to find a way to reduce the humidity fluctuation from the chamber which could increase the inhaled air humidity without increasing condensation. 176
Appendices Appendix I Regression of the pressure at air delivery unit blower outlet Appendix II Regression of the pressure drop on the connecting duct Appendix III Regression of the air temperature increase after flowing through the blower Appendix IV The corrugated HADT outer surface area Appendix V Regression of dew point Appendix VI Relationship regressions between relative humidity, specific humidity and absolute humidity Appendix VII Details of the CPAP fluid dynamic section after ADU outlet Appendix VIII Details of whole chamber steady state subsystem Appendix IX Details of steady state HADT lump full thermal balance subsystem Appendix X Details of HADT lump air dynamic fluctuating thermal balance and condensation subsystem Appendix XI Details of steady state mask full thermal balance subsystem Appendix XII Details of mask air dynamic fluctuating thermal balance and condensation subsystem Appendix XIII Details of the auxiliary subsystems Appendix XIV Steady state thermal-validation experiment result and model output comparison Appendix XV Regression of temperature related water properties for Grashof number - 177 -
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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
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 and 198: 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: 6. The deep breathing and reverse f
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 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
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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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