Environmental Engineering Reference
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Figure 3.15 Cylindrical Hot Water Tank with Spherical Ends
inner diameter d i of the heat insulation of the cylindrical part define the heat
transition coefficient:
(3.40)
Linearly interpolated values between 10 W/(m 2 K) for k' = 0.2 W/(m K)
and 15.5 W/(m 2 K) for k' = 0.5 W/(m K) are used to estimate the surface
coefficient of heat transfer
.
With the temperature difference between the storage medium and ambient
air, the coefficient of heat transfer k and the surface A sphere of the spherical
caps, the heat losses of the spherical caps become:
α
(3.41)
With the surface coefficient of heat transfer
α 1
from the tank wall to the
insulation and
α 2 from the insulation to the ambient air, the insulation
thickness s , the heat conductivity
of the insulation, and assuming that the
temperature of the tank wall is equal to the storage temperature
λ
ϑ S , the
coefficient of heat transfer becomes:
(3.42)
The surface coefficient of heat transfer from the tank wall to the insulation
can be estimated as
= 300 W/(m 2
α 1
K). The surface coefficient of heat
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