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Figure 4.6 – Reverse flow Calculation Subsystem<br />

4.2.3 Varying transport delay subsystem<br />

Transport of fluid mass and its properties from one lump to another takes time. Figure<br />

4.7 shows the varying transport delay subsystem created from Eq. (2.32). Enlarged part<br />

in the right upper corner of Figure 4.7 is the inside algorithm in one of the ten<br />

s<br />

subsystems. The algorithm represents t and ten of such together consists of a<br />

v ( t)<br />

“one lump delay subsystem” which gives the fluctuating time of air flowing through a<br />

lump.<br />

Input one is the signal input. For this fluid dynamic and CO2 model, it is the exhaled air<br />

concentration level in fluid flow from neighbouring lump. Input two is fluid flow<br />

velocity. The fluid flow velocity is used to calculate the amount of time delay which<br />

will be put into the variable transport delay block to suspend the input signal such<br />

amount of time. Output is the delayed signal which will be delivered to the next lump as<br />

signal input.<br />

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