Environmental Engineering Reference
In-Depth Information
Temperature of gas at
the charging side
Heat exchanger
(a)
Sensible heat of exhaust
gas on the discharging
side
Sensible heat of exhaust
gas on the charging side
Heat recovery rate
(b)
Temperature of exhaust
gas on the discharging
side
RG application rate
Sensible heat of
preheated air
Temperature of
atmosphere
Sensible heat of
atmosphere
(c)
Temperature of
preheated air
FIGURE 5.36
Calcualtion of preheated air temperatures and exhaust gas temperatures.
inputs and program. Therefore, where the equivalent heat transfer coefficient is
concerned, it is necessary to input values that reflect area and adiabatic conditions.
Q
rad
=
h
rad
A
w
(
T
fw
-
T
at
)
(5.1)
Q
rad
= radiation heat of furnace body (I), kW
h
rad
= equivalent heat transfer coefficient (I)
L
= zone length, m
a
= furnace wall area per unit length, m
= furnace wall area, m
2
=
La
A
w
T
fw
= furnace temperature, K
T
at
= atmospheric temperature, K
The heat loss by cooling water of this zone (I) is calculated by the following
formula. Equation 5.2 is also simplified and a linear heat transfer coefficient (I) that
includes the vertical skids has to be input. To obtain the values necessary for
Equations 5.1 and 5.2, support tools shown in
Table 5.4
are programmed and used
in combination.
Q
loss
=
h
rad
Ln
(
T
fw
-
T
wat
)
(5.2)
Q
loss
= heat loss by cooling water, kW
n
= number of skids
T
fw
= furnace temperature, K
T
wat
= water temperature, K
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