Solar Thermal Information

9
the average water temperature in the tubing
exceeds room air temperature. Thus, if the ceiling
operated with an average water temperature of
110ºF in a room with 70ºF air temperature, each
square foot of wall would release about 0.71 x
(110 - 70) = 28.4 Btu/hr/ft
2
. This performance
makes the radiant ceiling well suited for use in a
solar combisystem.
PANEL RADIATORS:
Generously sized panel radiators can also provide
good performance when used as part of a solar
combisystem. Again, the suggested guideline is
to size panels so they can deliver design space
heating output using a supply water temperature
no higher than 120ºF.
Manufacturers provide output
ratings for their panel radiators
in either graphical or tabular
form. In many cases, “reference”
heat output ratings for a
given size panel are stated
along with corresponding
water temperature and room
air temperatures. Correction
factors are then given, which,
when multiplied by the reference
heat output, give the actual heat
output for specific water and
room air temperatures.
Figure 3-6 shows a typical
fluted water panel radiator.
Figure 3-7 gives reference heat
output ratings for this type of
panel based on an average
panel water temperature of
180ºF and room air temperature
of 68ºF. Figure 3-8 gives
correction factor to modify the
reference heat output ratings
based on different average
water temperatures and room
air temperatures. The formula
on the graph in figure 3-8 can
also be used to calculate these
correction factors.
For example: Figure 3-7
indicates that a panel with a
1/2" drywall
3/4" foil-faced polyisocyanurate foam strips
aluminum heat transfer plate
tube 7/16" oriented strand board
top side insulation
ceiling framing
Btu
hr • ft
2
= 0.71
( )
× T
water
− T
room
( )
finished radiant wall thermal image of ceiling in operation
figure 3-5
figure 3-6
Courtesy H. Youker