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eventually beneficial to the users by reducing condensation and carbon dioxide inhalation. The model should be able to cope with changes within a certain range of variations of ambient conditions, settings and coefficients. The main objectives of this research are to Quantify the reverse flow under combinations of pressure setting and breathe load The influence of the reverse flow on carbon dioxide re-breathing, delivered humidity to the patient and condensation in the HADT. To accomplish this, the following tasks will be undertaken: 1. Understand the CPAP system, its working principles and working conditions. 2. Use laws of physics to mathematically model the relevant components of the CPAP system. 3. Based on the mathematical model, build a software model of the CPAP system on Simulink in the Matlab environment. 4. Validate the Simulink model simulation through experiments. 5. Use the validated model(s) to study the factors which influence the fluid dynamics and thermodynamics of the CPAP system, the reverse flow and the consequential influences on exhaled air inhalation, delivered humidity and condensation. 10
Chapter 2 Mathematical Modelling of Fluid Dynamics 2.1 Introduction The CPAP machine type chosen for analyse is CPAP HC600 manufactured by Fisher & Paykel Healthcare Co. Ltd. (Figure 2.1). This chapter is to analyse and understand the physics of the machine’s operation then build up a mathematical model to simulate its working and predict the required outputs. Geometry and physical characteristics of the machine components will be used to obtain correct values of parameters. Physical laws, mainly of fluid mechanics, will be used to develop differential equations to describe the relationships and simulate the dynamic situation. The machine’s components will be analysed sequentially. The model’s inputs include machine settings and patient’s breathe load. Figure 2.1 CPAP HC600 by Fisher and Paykel Healthcare Co. Ltd. 11
Page 1 and 2: The Effects of CPAP Tube Reverse Fl
Page 3 and 4: Acknowledgement First of all, I wou
Page 5 and 6: When deep breathing induced reverse
Page 7 and 8: 2.4.1 Reverse flow calculation ....
Page 9 and 10: 5.3.1 Thermal dynamic model under s
Page 11 and 12: XI.3 Steady state mask thermal bala
Page 13 and 14: List of Figures Figure 1.1 Obstruct
Page 15 and 16: Figure 5.10 Comparison between expe
Page 17 and 18: Figure 6.13 Fluctuation of airflow
Page 19 and 20: Table 5.3 Comparison of condensatio
Page 21 and 22: Nomenclature Symbol Meaning of the
Page 23 and 24: CMFeO CMFet C O C t Concentration o
Page 25 and 26: m C 23 m Ca m cv m Cw m store m i m
Page 27 and 28: Nu Cp Nu dir Nu Ti Nu To Nuwsn Nuws
Page 29 and 30: QMor QMwst QTastn QTicn QTin Q
Page 31 and 32: R Mic R Moc R Ticn R Toc R Torn Mas
Page 33 and 34: V Capacity of the container m 3 V C
Page 35 and 36: 1.1 Background Chapter 1 Introducti
Page 37 and 38: The MRD is worn in user’s mouth w
Page 39 and 40: Figure 1.4 CPAP machine Figure 1.5
Page 41 and 42: 1.3 Literature survey A literature
Page 43: CPAP fluid dynamic performance with
Page 47 and 48: 2.3 Fluid dynamic analysis This sec
Page 49 and 50: If there are minor pressure drops,
Page 51 and 52: Figure 2.6 Pressure sensor - Honeyw
Page 53 and 54: The pressure readings were taken af
Page 55 and 56: Figure 2.12 Experimental set up for
Page 57 and 58: 2.3.4 Chamber air space mass balanc
Page 59 and 60: From the above analysis, the pressu
Page 61 and 62: Figure 2.18 Full face mask and the
Page 63 and 64: Inserting Eq. (2.26) and Eq. (2.27)
Page 65 and 66: Where n( ) t is the airflow proper
Page 67 and 68: However in reality, mixing turns ou
Page 69 and 70: Chapter 3 Mathematical Modelling of
Page 71 and 72: An Environment Control Chamber (Vö
Page 73 and 74: Figure 3.4 Thermal enthalpy gain of
Page 75 and 76: Figure 3.6 Heating element beneath
Page 77 and 78: Figure 3.8 Chamber water heat balan
Page 79 and 80: Table 3.1 Thermal resistance from h
Page 81 and 82: 3.3.1.2 Heat balance at the outer s
Page 83 and 84: 3.3.2 Heat flow from chamber water
Page 85 and 86: through ADU which is a function of
Page 87 and 88: It is assumed that the direct impac
Page 89 and 90: Sc a a (3.47) Dwa Analogous to th
Page 91 and 92: and keep them in gaseous status. On
Page 93 and 94: through the walls and natural conve
Page 95 and 96:
Where d Ca is the specific humidity
Page 97 and 98:
TTa ( n1) is also considered as inl
Page 99 and 100:
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
Page 109 and 110:
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
Page 125 and 126:
Figure 4.13 Simulink TM model for t
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The outputs are listed in Table 4.1
Page 129 and 130:
Page 131 and 132:
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
Page 139 and 140:
Page 141 and 142:
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
Page 161 and 162:
The comparison of experimental resu
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Page 165 and 166:
Page 167 and 168:
5.3.1.4 Airflow temperature at the
Page 169 and 170:
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
Page 179 and 180:
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
Page 201 and 202:
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
Page 211 and 212:
Appendices Appendix I Regression of
Page 213 and 214:
Appendix I. Regression of the press
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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
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The total area of the complicated c
Page 225 and 226:
Figure V. 1 Regression of saturated
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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
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Input port number Input Unit 1 Heat
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input 4 is the portion of impact ar
Page 239 and 240:
VIII.2.3 Water surface mass transfe
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This subsystem also contains two su
Page 243 and 244:
VIII.2.5 Chamber wall 1 heat transf
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Figure VIII. 13 Wall 1 outer surfac
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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
Page 253 and 254:
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
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
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at point C. Right after that, here
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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