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4.3 Computational model of thermal dynamic analyses
This model is used to calculate dynamic condensation in HADT when different load of
breath is added and reverse flow occurs. The model also compares the result with the
condensation when breathing is not added and thus flow is steady. Like the fluid and
CO2 model, this thermal dynamic model requires fluid dynamic section and lump-delay
subsystems.
This model consists of three main parts. They are ADU and chamber part, lumped
HADT part and mask part. They are to be described in following sub-sections. As
explained in chapter 3, considering all the wall temperatures are much stable when the
airflow temperature is fluctuating and for shortening the model ramping time, the
Simulink TM model uses steady state calculation for all the wall temperatures and the
chamber water temperature. These steady state (constant) wall temperatures are input to
the dynamic fluctuating subsystems for calculating the fluctuating airflow properties.
Thus, all the chamber part, HADT lump parts and the mask part consist of a steady state
subsystem and a dynamic fluctuating subsystem.
The inputs required are listed in Table 4.11 below:
Table 4.11 Inputs to the thermodynamic model
Input block Unit
Breath magnitude ratio
Mask capacity ratio
Human nose in-mask space occupancy factor
Pressure setting cmH2O
Heat element temperature setting °C
The outputs are listed in Table 4.12 below:
HADT tube heating W
Ambient temperature °C
Ambient relative humidity In decimal
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