Applications manual
| 19
Panel Radiator
Design Manual
Panel Radiator Design Manual | 12.2009
Technical specifications are subject to change without prior notice
If tables 7 and 8 do not match a system‘s requirements,
the following guidelines provide means to calculate the
effects of ambient room temperature, supply water
temperature and temperature drop through the radiator
on the radiator output.
Ambient room temperature effect:
The (adjusted)
output of a radiator at any room temperature (∆T room)
can be computed from the output listed at a room
temperature of 68°F (20°C) as:
Adjusted Output = Listed Output x [1+
α
x (68-Troom)]
(Troom in °F) where
α
is a correction factor computed as:
α
= 1.385 / (ΔT supply - 75) with ΔT supply in °F.
Note:
The listed radiator output depends on the supply
temperature.
Example:
Select the proper radiator to heat a porch
which is to be kept at 55°F (13°C) during the winter.
Maximum heat loss is 8,750 Btu/hr. Assume supply
temperature equal to 194°F (90°C).
Solution:
The larger temperature difference between the
radiator and the porch increases the radiator output. To
find the proper size radiator, we must compute the listed
output at 68°F (20°C).
Adjusted Output = 8,750 Btu/hr at 194°F (90°C) and 55°F
(13°C). (∆T room).
Compute correction factor
α
as:
α
= 1.385 / (194 - 75) = 0.0116
Listed Output = 8,750 / [1 + (0.0116 x (68 - 55)] =
7,560 Btu/hr
From Table 8: Use Model 22 20” x 48” x 4“ instead of
Model 22 24” x 48” x 4“ (listed output = 7,500 Btu/hr).
This ambient room temperature effect is generally small
and need only be considered in system design if desired
room temperatures are well beyond the typical 68 - 72°F
(20 - 22°C) range.
Supply water temperature effect:
The effect of different
supply temperatures on the output of panel radiators is
computed using the conversion factors of Table 9 or read
directly from the Performance Curves in Figure 10.
Table 9 contains conversion factors needed to compute
the adjusted radiator output from the listed ratings. The
∆T factor is computed as the difference between the
average water temperature and room temperature.
Fig. 10 Performance Curves Model 22 Radiators
Conversion Factors Table 9
∆ T in ºF (°C)
Conversion Factor
10 (6)
0.045
20 (11)
0.112
30 (17)
0.198
40 (22)
0.275
50 (28)
0.367
60 (33)
0.466
70 (39)
0.569
80 (44)
0.677
90 (50)
0.789
100 (56)
0.905
108 (60)
1.000
110 (61)
1.024
120 (67)
1.147
130 (72)
1.272
140 (78)
1.401
150 (83)
1.535
