Environmental Engineering Reference
In-Depth Information
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