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3.3.2 Heat flow from chamber water into ambient air via wall 1, QC1i
Figure 3.10 Temperature at wall 1
Due to the water high temperature, heat from the chamber water dissipates toward
ambient through chamber wall (Figure 3.10). The chamber wall under water level is a
vertical cylinder (wall 1). Based on Eq.(3.22), the chamber inner wall can be simplified
as a vertical flat plate. On the inner surface there is only natural convection from water
to the chamber wall. On its outer surface, since the chamber, specifically the lower
hotter part, is well surrounded by the CPAP case, the radiation dissipation is neglected
for simplification. Thus it is assumed that there is only natural convection on the
chamber outer surfaces. The heat balance at wall 1 may be written as:
Q Q Q
(3.27)
C1i C1st C1o However, since the water temperature and the ambient air temperature are simplified as
constant during operation. Thus QC1st is neglected and Eq. (3.27) can be changed to:
Tw TC 1i TC1o T
(3.28)
R R
C1i C1o The heat dissipation into the ambient at the outer surface also equals to the conductive
heat flow through the chamber wall. Thus:
T T T T
R R R
C1i C1o
C1cyl C1o C1o 49
(3.29)