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Inside Surface Temperature Performance of Two Aluminum Windows
with Different Heating Arrangements
Sasaki, J. R.; Brown, W. P.
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DOI ci-dessous.
Publisher’s version / Version de l'éditeur:
http://doi.org/10.4224/20386777
Internal Report (National Research Council Canada. Division of Building
Research), 1968-12-01
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NATIONAL RESEARCH COUNCIL OF CANADA
DIVISION OF BUILDING RESEARCH
INSIDE SURFACE TEMPERATURE PERFORMANCE OF
TWO ALUMINUM WINDOWS WITH DIFFERENT
HEATING ARRANGEMENTS
by
J. R. Sasaki and W. P. Brown
ANA!.. YZED
Internal Report No. 366
of the
Division of Building Research
OTTAWA
December 1968
PREFACE
Windows have been the subj e ct of extensive investigation by the
Division. They are critical elements in the enclosure of a building,
particularly in winter when they present cold condensing surfaces to the
interior. They become a limiting factor in the relative humidity which
can be carried, and better information is often required in order to be able
to design for improved performance in this respect. The work now reported includes studies of the thermal performance of two common window
arrangements. The emphasis in this work was on the influence of the
arrangement of heating outlets under the window.
The work was carried out mainly by W. P. Brown, a mechanical
engineer, while he was a research officer on the staff of the Building
Services Section. He was not able to complete the work before leaving
the Division and it is now reported by J. R. Sasaki, also a mechanical
engineer and a research officer having an interest in the technical aspects
of windows.
Ottawa
December 1968
N. B. Hutcheon
Associate Director
INSIDE SURFACE TEMPERATURE PERFORMANCE OF
TWO ALUMINUM WINDOWS WITH DIFFERENT
HEATING ARRANGEMENTS
by
J. R. Sasaki and W. P. Brown
Of all the elements comprising the building enclosure, the
window normally has the lowest resistance to heat flow and the lowest
inside surface temperature s in cold weather. Because of its low
surface temperatures the window experiences condensation more
readily than the other enclosure surfaces. Low inside window surface
temperatures also contribute to discomfort which is partially determined by the radiant heat lost by occupants located near windows.
Effort should, therefore, be made to maintain high temperatures on
the inside window surfaces in cold weather in order to minimize
condensation and occupant discomfort. The thermal requirement in
the aluminum window specifications of the Canadian Government
Specifications Board attempts to do just this by promoting window
designs that ensure relatively high inside surface temperatures.
Inside surface temperatures of a window installed in a building
are determined not only by the window design but also by the type and
location of the terminal units of the building's heating system. The
purpose of the present study is to determine the effect of heater type
and configuration on the inside surface temperature performance
of two aluminum windows. One window was representative of a double
window having an adequate thermal separation between inside and
outside metal members; the other window was representative of a
double-glazed window having an inadequate thermal separation.
The foregoing discussion stresses the need to provide high
inside surface temperature s for satisfactory window thermal performance
in cold weather with regards to condensation and comfort. There is one
special problem, however, that may be aggravated by attempts to raise
inside window surface temperatures. This is the problem of thermal
breakage of factory-sealed double-glazing units.
The construction of sealed double -glazing units is such that the
heat los s through the edge is much greater than that acros s the air space
between the panes of glass. The temperature at the edge of the inner
- 2 -
pane will, therefore, be lower than that of the central portion. When
heated air is directed against the inside surface s of the window the
temperature of the central portion of the inner pane is increased more
than that of the edge which is buried in a metal surround and is isolated
from the heated air. If the temperature difference between the central
portion and the edge becomes very large, breakage of the inner pane
due to thermally-induced tensile stress may result. Window installations
incorporating sealed double -glazing units, therefore, require more care
in the design and location of the heating units near windows to ensure
that the highest inside surface temperatures are obtained without creating
a potential breakage problem.
This report describes a series of thermal tests performed on
two aluminum windows with different heating arrangements on the warm
side of the windows. The tests were conducted in the DBRjNRC coldroom facility with air temperatures of -lO°F and 72°F on the cold and
warm sides of the windows, respectively. The inside surface temperatures of the windows were measured with the following heater arrangements
on the warm side: a baseboard electric heater located remote from the
windows providing natural-convection air flow down the inside window
surface; electric heaters located beneath the windows providing naturalconvection air flow up the inside window surfaces; and electric heaters
located beneath the windows providing forced-convection air flow up
the inside window surfaces. An additional test was conducted with the
last heater arrangement using augmented heat input. Forced-convection
air flow conditions were provided on the cold side of the windows in
all tests.
The determination of the over-all heat transmission coefficients
for the two windows is described in Appendix I.
2.
2.1
DESCRIPTION OF WINDOWS
Window A
Window A was a double aluminum window consisting of two upper
and two lower sashes, as shown in Figure 1. The upper prime and storm
sashes were openable for cleaning purposes only; they pivoted independently about vertical side hinges and were locked to the frame by tab
locks. The lower prime and storm sashes were bottom-hinged and
linked to operate together; the prime sash was locked to the frame by
a three -point lock. The upper and lower air space s between prime
and storm sashes were separated by the muntin frame members and an
- 3 -
aluminum separator. The joints between frame and sash were sealed
with vinyl and stainless steel weatherstripping.. The frame was
constructed in three sections separated from each other by wood thermal
breaks.
The over-all frame dimensions were 39-% in. wide by 60-3/4 in.
high; the upper sash, 36-% in. wide by 42-% in. high; the upper glazed
area, 33 in. wide by 39 -% in. high; the lower sash, 36 -% in. wide by
15 in. high; the lower glazed area, 33 in. wide by 12-% in. high. The
air space thickness for both upper and lower assemblies was 4-7/8 in.
2.2 Window B
Window B, shown in Figure 2, was an aluminum window with
an upper and lower sash, each containing a factory-sealed double -glazing
unit with a nominal air space thickne s s of %in. The upper sash pivoted
about vertical side hinges and was locked to the frame by a two -point lock.
The lower sash was bottom-hinged and locked to the frame by a threepoint lock. The joints between frame and sash were sealed with vinyl
weatherstripping. The frame and sash members were constructed in
two sections which were separated by a wood thermal break.
The over-all frame dimensions were 36-% in. wide by 59-% in.
high; the upper sash, 35 in. wide by 39
in. high; the upper glazed
area, 30 in. wide by 34-1/4 in. high; the lower sash, 35 in. wide by
17 in. high; the lower glazed area, 30 in. wide by 12 in. high.
-1
3.
DESCRIPTION OF TEST APPARATUS
The two windows were installed in the DBR/NRC cold room
facility (Figure 3) described in NRC 6887. The windows were mounted
in the partition with their inside face flush with the inside of the partition. The outside face of Window A protruded past the outer face
of the partition by approximately 4 in. ; the outside face of Window B
was nearly flush with the outer face of the partition. The windows
were thermally isolated from the wooden partition.
The cold-room air flow conditions remained unchanged for
all tests (including the heat transmission tests described in Appendix
A). The cold room was maintained at test temperature with only the
main refrigeration unit operating. The main-unit fan operated at
high speed and discharged refrigerated air against the partition and
test windows in such a way that forced-convection air flow occurred
down the cold surface of the windows. The average surface conductance
on the cold face of the windows was approximately 4 Btu per (hr) (sq it)
( OF).
- 4 -
Temperatures were measured with 30-gauge copper-constantan
thermocouples in conjunction with an electronic temperature indicator.
Glass-surface temperature measurements were made with junctions
fabricated by soldering i-in. lengths of copper and constantan wire
laid side by side with the leads opposed. The junction, with 2 in. of
lead wire on both sides, was taped onto the glass surface. Metal surface temperatures were measured with twisted soldered junctions
taped in place with 2 in. of lead wire.
Air temperatures were measured with unshielded thermocouples having twisted soldered junctions. On the warm side,
vertical strings of thermocouples measured air temperature
gradients 11 in. from the glas s and opposite the vertical centreline
of each window. The average of these values was taken as the
reference warm-room air temperature, two On the cold side, a
vertical string of thermocouples measured the cold-air temperature
gradient 6 in. from the plane of the windows. The mid-height thermocouple on this string measured the reference cold-room air temperature,
tc '
The locations of surface thermocouple s on windows A and B
are shown in Figure 4.
The conditions on the warm side of the windows were changed
for each test and are described in the following section.
4.
4.1
DESCRIPTION OF TEST CONFIGURATIONS AND TEST PROCEDURE
Remote Baseboard Convector (Test 1)
The convector was located at the base of the warm room wall
opposite and 7 ft away from the test windows. The convector contained
18 electric heater elements installed end to end acros s the width of
the room. Alternate elements were wired together, forming two separate
circuits, one supplying 1250 watts and the other 1000 watts at 115 VAC.
The air temperature in the warm room was controlled by
regulating the input voltage to the convector with a temperature
controller. The thermostat for the controller was located 4 ft above
the floor on the centre of the end warm-room wall. The heat input
to the warm room was measured with a calibrated watt-hour meter.
- 5 -
The baseboard heating arrangement provided natural-convection
air flow down the warm face of the windows. The average surface conductance value provided over the inside window surfaces was approximately 1. 5 Btu per (hr) (sq ft ) (0 F).
Air and window surface temperatures were measured with the
warm room controlled to 72°F and the cold room to _10°F. These
temperatures were used for all subsequent tests.
The measured surface temperatures, t, were converted to
non-dimensional temperature indices,
t - t
c
1=--t - t
w
c
where t = measured surface temperature, OF
t w = reference warm-air temperature, OF
t
c
= reference cold-air temperature, of.
The advantage of expressing the thermal characteristics of a
window in terms of temperature index rather than temperature is that,
for any particular configuration, the index is practically independent
of test air temperatures over the temperature range of interest. For
the present test series, a change in the index at a given point, from
te st to te st , indicate s the effect of different heating arrangements
on the window thermal performance.
4.2 Under-Window Convector Natural Convection (Te sts 2 to 5)
The baseboard convector was disconnected and a portable
convector was placed beneath each window to simulate an underwindow heating arrangement (Figure 5). The blast heater and diffusion
box shown in the figure were not incorporated. Four heating elements
in each convector were wired together to provide 1000 watts at 115
VAC. Baffles were located in the convector outlet to give a uniform
discharge temperature.
The air temperature in the warm room was controlled by regulating the input voltage to the two under-window convectors; the
control and heat-metering equipment described in 4. 1 were used.
Each convector provided half the total heat requirement of the warm
room.
- 6 The geometry of the convector beneath the window is shown in
Figure 6. The location of the outlet with respect to the bottom edge of
the window is described by X and Y, the outlet width is W, and the
deflector angle. 8. A sheet metal stool covered the gap between the
convector and partition.
Tests 2 to 5 were performed with two settings each of X, Y
and W, and with the deflector folded down in the open position.
4. 3 Under - Window Convector Forced Convection (Tests 6 to 13)
The heating arrangement described in 4.2 was used for these
tests with the following modifications: removal of baffles in convector
outlet; connection of blast heater and diffuser to convector inlet.
Each blast heater consisted of a blower with a capacity of 250 cfm
at 3/4 in. of water, and an external heater. The external heater
contained four heating elements wired to provide lOOO watts at 115
VAC.
The air temperature in the warm room was controlled by
regulating the input voltage to the two under-window convectors and
their blast heaters; control was the same as in the previous tests.
The total heat input to the convectors, external heaters and blowers
was metered. Each convector assembly provided half the total
heat requirement of the warm room.
The discharge air velocity was measured at the convector
outlet with a hot-wire anemometer at low velocities and a deflectingvane anemometer at high velocities. The geometry of the convector
is shown in Figure 6.
Four tests (7. 9, 12 and 13) were performed with two settings
each of X, Y and W, and with the deflector plate vertical. Two tests
(6 and 8) were performed with the geometry of test 7 but with different
discharge velocities. Test 10 was performed with the deflector adjusted
at 45 to direct the discharge against the window sill. Test 11 was
performed with augmented heat input; cold air was bled into the warm
room to increase the heating load.
0
5.
DISCUSSION OF TEST RESULTS
The test conditions and surface temperature indices for all
te sts are listed in Table s I to IV.
- 7 -
5. 1 Inside -Surface Temperature
Performance - Baseboard Convector
The inside surface temperature performance s of windows A
and B obtained with the remote baseboard heater configuration are
compared in Figure 7. The minimum inside surface temperature
indices for window A were: glass, 0.55; sash, 0.525; frame, 0.505.
The minimum indices for window B were: glass, 0.485; sash, 0.42;
frame, 0.305. The minimum glass temperatures measured would
have been lower for both windows had the thermocouples been
located closer to the exposed edge of the inside glass; at the edge
of the sealed unit in window B, the glass temperature would have
been still lower.
The minimum frame and sash temperatures of Window B were lower
than those of window A because the thermal separation in the frame
and sash members of window B was not as effective in reducing heat
loss as the separation and air space of window A. The minimum glass
temperature of window B was lower than that of window A because of
the highly conductive heat flow path occurring around the edge of the
sealed double -glazing unit in
indow B.
The low surface temperatures of window B are a reflection
of the high heat transmission coefficient for this window; the over-all
heat transmission coefficient of window B was 0.72 Btu per (hr) (sq ft)
(OF) while that of window A was 0.56 (See Appendix 1).
5.2 Under - Window Convector Natural Convection
The vertical temperature profiles obtained for the four natural
convection tests are compared with that for baseboard heating in Figure
8.
The inside surface temperatures obtained with the under-window
heater arrangements were significantly higher than the temperatures
obtained with the remote baseboard heater. The bottom half of the
windows showed the largest increase in temperature.
The highest surface temperatures were obtained with the convector
outlet closest to the bottom edge of the window (tests 3 and 4). The
surface temperature s obtained with a large value of Y and a small value
of X (test 2) were higher than those obtained with large X and small Y
(test 5).
- 8 -
Because the size of the convector outlet in test 4 was twice
that in test 3. the discharge air flow rate was higher and the surface
temperatures in test 4 should have been higher than those in test 3.
The mean discharge air temperature with the larger opening. however.
was lower than that for te st 3. This reduction in discharge temperature nullified to some extent the effect of the higher flow rate; and the
surface temperatures with the larger outlet (test 4) were higher on the
upper portion of the windows but lower near the sill than those of te st 3.
Test 3 gave the most uniformly high surface temperature
profile s. The se are shown in Figure 11 compared with the optimum
temperature profiles obtained with under-window heater and forcedconvection air flow.
5. 3 Under - Window Convector - Forced Convection
5. 3. 1 Convector Geometry
The vertical temperature profiles obtained with five convector
geometries in the forced convection tests are shown in Figure 9.
The dependence of surface temperature on convector geometry
was similar to that for the natural convection tests; the highest surface
temperatures were obtained with the convector outlet nearest the
bottom edge of the window (tests 9 and 10). The highest temperatures
on the lower regions of the window occurred when the discharge air
stream was deflected against the window (test 10). The temperature
profiles obtained in this test are shown in Figure 11 compared with
the optimum profiles of the other test configurations.
5.3.2 Discharge Air Velocity
The vertical temperature profiles obtained with three discharge
velocities are shown in Figure 10; the velocity varied from 50 to 300
ft/min. These values of discharge velocity are not unlike the normal
velocities used in building heating systems.
The window surface temperature increased with discharge
velocity because of the increase in surface conductance value. The
drop in mean discharge air temperature with increasing velocity did
not significantly affect the inside surface temperature. The temperature profiles obtained with the highest discharge velocity (test 8) are
shown in Figure 11 compared with the optimum profiles of the other
te st configurations.
- 9 5. 3. 3 High Heat Input
The temperature profiles obtained in test 11 with a high heat
input rate are shown in Figure 11, in comparison with the optimum
profiles of the other test configurations. This test gave the highest
surface temperatures of all the tests.
Calculations have shown that the heat input rate in re sidential
buildings varies between 750 and 1400 Btuj(hr) (ft of window width)
whereas the input rate in commercial buildings is normally less than
400 Btuj(hr) (ft of window width). The heat input rate in test 11 was
approximately 1450 Btuj(hr) (ft of window width) which was not unlike the
higher rates used in residential buildings. The heat input rate of
approximately 450 Btu/(hr) (ft of window width) used in all the other
tests was similar to that used in commercial buildings.
6.
CONCLUSIONS
1.
The inside surface temperatures of a window can be increased
over that obtained with remote baseboard heating by using an
under -window heating arrangement and forced or natural
convection air flow.
2.
With under-window heater and natural-convection air flow, the
highest surface temperatures are obtained with a heater outlet
of small opening located close to the bottom edge of the window.
3.
With under-window heater and forced-convection air flow, the
highest surface temperatures are obtained with the heater
outlet located close to the bottom edge of the window; with the
convector discharge deflected towards the window; with a high
discharge air velocity; and with a high rate of heat input in the
convector.
4.
With few exceptions, window A which has the higher inside
surface temperature s appeared to be more sensitive to
change in performance with changing heater and convection
conditions than window B.
5.
The results of the tests on window B did not permit an accurate
estimation of the variation in thermal-breakage potential of
sealed double -glazing units with changing heater and convection
conditions. The estimation of the breakage potential, or temperature difference between edge and central portton of the inner
- 10 -
pane, was poor because the thermocouple closest to the edge of
the sealed unit was approximately 1 in. away. Subsequent work
on sealed double -glazing units has shown that the temperature
at this point behaves more like that in the central portion of the
inner pane than that at the edge.
I..6ll.!&.l
TEST CONDITIONS - WINDOW A
1
Test Number
W - in.
9 - -«: degrees
Velocity. V - It/min.
d
Volume flow - ft 3/ m i n .
Convector Air Temperature, t
d
Btu/hr
61
7
81
91
10
I
I
II
12
13
Forced Convection
23/4
6
153/41
2 3/4
I
6
T
14 174
2
I 51.
,
1
2
180'
90'
45·
90·
---
15
15
15
15
55
105
310
105
105
110
105
100
---
5
5
10
10
20
35
105
35
35
40
35
65
88
Ｑ Ｔ Ｐ ｾ Ｐ Ｐ
85
81
--1260
1370
1400
1400
1350
1380 1400 1560 1440 1500
4580
1460 1400
73.3
-9.0
72.3
-9.5
72.6
-9.3
72.5
-9.6
72.8 73.4 73.7 73.3 73.7
-9.2 -9.3 -9.2 -9.3 -8.9
73.6
-10.6
73.7 73.4
-8.8 -8.5
4
5
Warm room, 1:w
Cold room, t c
Air Temperature, ·F
5
Ｑ Ｒ Ｕ ｾ Ｐ Ｐ
Maximum/Minimum - ·F
Heat Input pe r Window
ｾ ･ ｦ ･ ｲ ･ ｮ ｣
I
Natural Convection
--- -- ----
X - in.
Air Flow
4
Under the Window
Natural
y . in ..
Convector Discharge
l
3
Baseboard
Heater Location
Air Flow Condition Over Window Surface
Configuration of
Convector Outlet
(Figure 6)
I
2
73.2
-9.5
1
-
IＳ Ｕ
05
2
120/
90
120/
90
3
88
6
87
81
7
-',-
86
8
9
10
11
7
8
9
10
12
13
TABLE 11
TEST CONDITIONS - WINDOW B
I
Test Number
X - in.
Y - In.
W - in.
e - .,:. des eee e
Convector Discharge
Velocity. Vd - it/min.
Air Flow
Volume flow - ft3/m in .
Convector Air Temperature. t d
Heat Input per Window
Reference Air Temperature.
Maximum/Minimum - -F
Btu/hr
·F
4
5
Baseboard
Heater Location
Air Flow Condition Over Window Surface
Configuration of
Convector Outlet
(Figure 6)
3
2
Warm room, t w
Cold room. t c
Natural Convection
3
161/4
--
Forced Convection
6
3
6
14 I Z
1
Z
2
I
180·
--
---
,3
Z
Under the Window
Natural
----
6
Z
Z
qO·
QO·
45·
10
10
15
18
45
95
305
95
95
95
100
90
3.5
3.5
10
IZ
15
35
105
35
35
35
35
65
ｉ ｚ Ｕ ｾ
ｉ ｚ ｏ ｾ
89
86
80
84
89
85
81
Ｑ Ｒ Ｕ ｾ Ｐ
ｉ ｚ ｏ ｾ ｉ
Ｑ Ｓ Ｐ ｾ Ｐ Ｐ
Iz60
1370
1400
1400
1350
1380 1400 1560 1440 1500
4580
1460 1400
73.2
-8.9
73.3
-9.0
n.3
-9.5
ra.a
n.6
-9.6
ra.e
-9.3
73.6
-10.6
73.7 73.4
-8.8 -8.5
1
2
3
4
5
6
73.5 73.7 73.3 73.7
-9. Z -9.3 -9. Z -9.3 -8.9
7
8
9
10
11
IZ
13
TABLE 1lI
TEMPERATURE INDICES ON VERTICAL CENTRE-LINE OF INSIDE WINDOW SURFACE - WINDOW A
I
Test Number
Heater Location &: Air Flow Condition
r arne - head member
3
4
5
6
7
8
9
10
II
12
13
ｕ ｮ ､ ･ ｲ ｾ ｗ ｩ ｮ ､ ｯ
Heating
Forced Convection
Under-Window Heating
Natural Convection
A I
.635
.68
.695
.70
.695
.665
.675
.725
.675
.67
.755
.665
.685
l5 a s h
- top rail
A 2
.675
.72
.725
.73
.725
.69
.705
.75
.70
.695
.78
.695
.71
blass
- ! in.
A 3
A4
A 5
A 6
A7
A8
A 9
.70
.705
.685
.63
.61
.59
.55
.74
.72
.71
.685
.71
.68
.62
.745
.73
.72
.695
.725
.715
.655
.745
.73
.725
:695
.74
.715
.65
.745
.73
.72
.695
.705
.69
.63
.72
.71
.695
.665
.64
.615
.575
.73
.725
.705
.67
.665
.64
.60
.755
.74
.74
.725
.745
.735
.685
.73
.725
.705
.68
.72
.695
.635
.73
.725
.705
.675
.705
.68
.64
.78
.765
.76
.745
.82
.82
.765
.725
.725
.705
.68
.715
.71
.665
.71
.685
.68
65
.61
A 10
.56
.65
.69
.675
.65
.595
.64
.745
.685
.70
.83
.67
.635
Frame - muntin
A II
.505
.60
.64
.625
.595
.535
.59
.695
.635
.65
.785
.605
.56
Sash
A 12
.605
.76
.80
.79
.75
.655
.74
.83
.785
.795
.94
.745
.685
- zl
. zt in.
A
A
A
A
A
.745
.745
.76
.785
.725
.77
.77
.775
.80
.79
.775
.785
.80
.815
.765
.745
.725
.70
.655
.615
.685
.69
.675
.66
.61
.735
.73
.74
.755
.68
.80
.785
.81
.83
.805
.79
.83
.825
.71
.645
.78
.79
.83
.875
.93
.895
15
16
17
.63
.65
.63
.595
.555
.985
.935
.84
.77
.735
.685
.635
.59
.675
.68
.655
.61
.565
- bottom rail
A 18
.525
.67
.735
.69
.595
.585
.645
.765
.615
.86
.795
.565
.545
A 19
.505
.665
.74
.675
.58
.575
.635
.76
.595
.86
.79
.545
.525
12
13
from top sash rail
in. from top sash rail
- S! in. from top sash rail
- ｚ
ｾ
Baseboard
Natural
2
ｾ
<fJ
- centre
in. from bottom sash rail
Ｒ
in. from bottom sash rail
51
"0
...
- Iz .In.
Sa ah
.; Glass
ｾ
<fJ
E
0
11
- top rail
I
- 1" in. {rom top sash rail
in. from top sash rail
- centre
-!
/Xl
Sa ah
from bottom sash rail
- bottom rail
from bottom sash rail
in. from bottom sash rail
Frame -sill me mbe r
13
14
.94
.735
.n
TABLEly
TEMPERATURE INDICES ON VERTICAL CENTRE-LINE OF INSIDE WINDOW SURFACE - WINDOW B
I
Test Number
Heater Location
&a:
Air Flow Condition
3
4
5
6
7
8
Under- Window Heating
Natural Convection
9
10
II
Under - Window Heating
Forced Convection
Frame .. head member
B 1
.41
.42
.435
.44
.44
.42
.405
.49
.44
.425
.54
.445
.44
Sash
- top rail
B 2
.475
.495
.505
.515
.51
.49
.485
.58
.515
.50
.625
.515
.455
- t in. from top sash rail
ｾ zt in. from top saah rail
. 5t in. from top sash rail
. t
.56
.64
.635
.635
.645
.61
.485
.595
.67
.67
.68
.665
.62
.495
.605
.68
.67
.685
.75
.71
.56
.615
.68
.675
.695
.76
.71
.55
.61
- centre
in. from bottom sash rail
.. 2;a in. from bottom sash rail
in. from bottom sash rail
B 3
B4
B 5
B 6
B7
B8
B9
.675
.69
.70
.645
.50
.575
.655
.65
.665
.665
.625
.495
.575
.655
.655
.655
.65
.61
.49
.65
.69
.70
.74
.795
.765
.625
.62
.68
.68
.695
.695
.645
.515
.595
.67
.67
.685
.70
.645
.51
.715
.75
.755
.785
.865
.865
.76
.615
.68
.675
.68
.72
.68
.535
.605
.67
.67
.685
.715
.675
.53
- bottom rail
B 10
.42
.445
.515
.515
.44
.43
.44
.605
.475
.465
.715
.47
.465
B II
.31
.35
.40
.395
.29
.33
.35
.44
.375
.375
.635
.365
.36
.. 2! in. from bottom sash rail
- t in. from bottom sash rail
- centre
B
B
B
B
B
12
13
14
15
16
.605
.68
.66
.61
.485
.70
.745
.79
.775
.60
.73
.74
.805
.825
.68
.735
.76
.785
.775
.65
.69
.75
.75
.70
.555
.645
.70
.695
.65
.515
.69
.745
.755
.70
.545
.775
.80
.84
.815
.645
.72
.79
.805
.74
.575
.71
.745
.83
.875
.735
.875
.87
.95
.98
.81
.67
.72
.70
.65
.52
.645
.695
.68
.635
.51
.. bottom rail
B 17
.425
.535
.61
.545
.455
.445
.50
.64
.485
.72
.68
.435
.43
B 18
.305
.355
.41
.36
.30
.305
.335
.425
.315
.51
.445
.285
.28
-; Glas8
ｾ
<fJ
g
...
-st
Sash
Frame - muntin
Gta e e
ｾ
Baseboard
Natural
2
ｾ
<fJ
E
0
l::
.. ! in. from top sash rail
.. 21 in. from top sash rail
.68
0
lQSash
Frame .. sill member
0UT'SIDr
HEAD SECTION
STAINLESS STEEL
WEATHERSTRIPPING
\
INSIDE
//
""-//
VINYL
ｗ
ｅ
ａ
ｔ
ｈ
,
ｅ
ｒ
ｓ
ｔ
ｒ
ｉ
ｐ
ｐ
ｉ
ｎ
ｇ
MUNTIN
HORIZONTAL SECTION THROUGH UPPER CASEMENT
-......
3-POINT LOCK
/
I
/
OUTSIDE
SILL SECTION
Fill INSULATION
FIGURE I DETAILS OF WINDOW A AND TEST MOUNTING
'''___I"," PlYWOOO
8"
BR 3724-1
FILL INSULATION
CAULKING
SEALED DOUBLE - GLAZING UNIT
(
IJ \
j
HEAD SECTION
I
\
\-r- MUNTIN
---
INSIDE
HORIZONTAL SECTION THROUGH UPPER CASEMENT
ｾ ］ Ｎ
SEPARATOR
.., :
LOWER HOPPfR
tu..···0!l/I
SILL SECTION
/
INSIDE
VINYL
WEATHERSTRIPPING
FIGURE 2 DETAILS OF WINDOW B AND TEST MOUNTING
'4. PLYWOOD
I.
Ｔｾ
.
..I
BR3724-2
LTHERMOSTAT
..---"
MAIN
REFRIGERATING
UNIT
l_ ---
..
n
---..
I I
0
WINDOW
I0
B
I
0
•Ie
J
;r
-- _J
•I.
LOCATIONS OF
PORTABLE CONVECTOR
WINOOWA
AUXILIARY
REFRIGERATING
UNIT
,0
0
I
0
I
,
.J
COLD ROOM
WARM ROOM
14'-4". 15'-1"
7'-4".15'-1"
IASEBOAROCONVEC1OIl
I
DOOR
I
I
I
DOOR
PLAN VIEW
M
AIR FlOW
I
..
t%
WINDOW
MAIN
REFRIGERATING
UNIT
B
•Ie
•
I•
•
CEILING HEIGHT· 10'-0"
I
f1PORTABLE CONVECTOR
\ LOCATION OF
INLET
---
LJ
Ｘ ａ ｓ ｅ Ｘ Ｐ ａ ｒ
CONVECTOR
(
ｾ
VERTICAL SECTION
FIGURE 3 COLD- ROOM FACILITY SHOWING LOCATION OF WINDOWS
BR 3124-3
AI
•
A3
-)IOA4
I
oA5
n
I
l
,.
ｾ
LEGEND
Ｎｾｾ
1i:'. l ""'-1"
...
I
.
• ALUMINUM - SURFACE TIC
o GLASS-SURFACE TIC
• AIR TIC
:::-N
____
..,
'"
ｊｾ
I
1-
I
0.!!6_
I!II
I
In! ｾ
ｾ
r
I
-
I
I
5
...
I
ｾ
oB7
I
oA7
I
OAB
bA9
i;. ｾ ｉ ａ ｉ
.
:::'
!::!
___
•
I
&:::I
Ｂ
lAI5
1AI6
WINDOW
A
I
-
L-
ｾ
...--0BI2
bBI3
''''L __
.
OAI4
=
Lr"
ｾ
'.:I?
I
I
-
IoAI7
J
oBB
bB9
JIDL__
!::!
lBI5
,
°I BI6
--.J
-B17
+BI8-
WINDOW
FIGURE 4 LOCATION OF THERMOCOUPLES ON WARM SIDE OF WINDOWS
8R 3724-4
8
J
ｾ
I
DIFFUSER (FORCED CONVECTION TESTS ONLY)
- ,-
Ｍ Ｍ ｩ ｩ Ｍ ｩ Ｓ Ｍ ｩ ｪ Ｍ Ｍ ｅ ｾ Ｍ ｦ ｽ Ｍ Ｍ ｦ ｽ Ｍ ｦ ｴ Ｍ Ｍ ｆ ｲ Ｍ ｦ ｪ Ｍ Ｍ ｅ ｽ Ｍ ｴ ｪ Ｍ ｾ Ｍ ｦ ｲ Ｍ ｩ Ｓ Ｍ Ｍ ｴ ｴ Ｍ ｴ ｪ Ｍ Ｍ Ｕ ｾ Ｍ ｅ ｪ ｾ ｾ ｩ
A
l--It=
E
r--------------------------,
a WINDOW :
I LOCATION OF PARTITION
ｾ
B
I
_J
PLAN VIEW
I
I
,
!ｾ
, 0,
8
----1
I z'
ｲ Ｎ ｌ Ｎ Ｎ ｾ Ｍ ｌ Ｎ
,-.L._. __
,,
,
00
.:»
ca
Z
o
!::
...
a:
ｾ
...
o
Z
o
ｾ
I
,
I
I
'
I
,
I
I
I
Cl
..,
I
I
I
,,
ｾ
,
,,
,
1
END VIEW (SECTION B-B)
/\/\/\/
I
I
,l
...
o...J
BAFFLES (REMOVED FOR FORCED CONVECTION TESTS I
,,
I.
0
0
0
0
0
0
0
0
0
0
0
000 000
0
.I
50·
FRONT VIEW (SECTION A - A)
FIGURE 5 DETAILS OF UNDER-WINDOW CONVECTOR
1113124 -5
N
W
x
DEFLECTOR
PARTITION
SEPARATION
SHEET
UNDER -WINDOW
PORTABLE CONVECTOR
e• DEFLECTOR
ANGLE
FIGURE 6
GEOMETRY OF UNDER -WI NDOW PORTABLE CONVECTOR
BR 3724-6
•
0
0
ｯ ｾ ｾ
GLASS HEIGHT IIN.I
A
UPPER GLASS
LOWER GLASS
-----7
•
fRAMt.
SASH
\
B
39lit 34'4
121fa 12
WINDOW
8
WINDOW A
I
_ _ _ _ MID-HEIG.!tT
----- -----
\
II
,,
I
It
t)
ｯＭＭＭＭＭＭＭＮ
0
•
•
0
•
ｾ
MID -HEIGHT
1----
0
0.30
0.40
ｾ
ｗｾｎｯｯｷｩｊＧｾｏｏｗ
/,/
___
ｯＭＭＭＭＭＭＭＺｾＬ
•
0
..
SASH
MUNTIN
SASH
•
0.50
0.60
__
SASH
FRAME
0.70
0.80
I - Ie
1=Iw-I e
FIGURE 7
INSIDE - SURFACE TEMPERATURE INDEX PROFILES WITH
REMOTE BASEBOARD CONVECTOR a NATURAL CONVECTION
AIR FLOW
BR 3124-7
._
FRAM
H
DEFLECTOR
(FOLDED BACKI
TEST
X Y W 'd
(IN) (IN.) (IN.) I(OFl
•
1
BASEBOARD
0
2
2\ Ｑ Ｕ ｾ
X
3
2\
2
o
4
ｾ
2
A
5
6
WINDOW
1 110
105
ｉ
2
105
•
lC
Ｏ ｾ ｾ ｾ
d
'-,>
,/
,.,/'
SASH
FRAM
0·20
/
0----'::::
0·60
0·50
\ ｾ
n
A
•
0-40
0·30
A
1 120
ｉ
.---
SASH
MUNTI
H
0
0-70
0'80
1·00
0·90
ｾ
I'" lw-1c
• ..0 xA_
---.- 0-100
FRAME
SASH
--Ｎ
｟
Ｍ
Ｍ
Ｎ
Ｎ
ｯ
｟
--
Xl'
III
I
't
W)I(!d
x liN.)
Y
TEST I'IN)
(IN.) °FI
§
......,
% •
",I.. %
"''''
"'W
... %
•
I
0
2
3
ＱＶｾ
1
115
X
3
3
2
1
115
C
4
3
2
ｉｾ
A
5
6
2
1\ 110
0. '"
0.'"
:::I".....
ｾ
BASEBOARD
ｾｾｾ
110
.0
A
__...ｮ ｾ Ｂ Ｂ Ｂ Ｚ Ｚ Ｂ Ｇ Ｍ Ｍ ｟
SASH
MUNTIN
SASH
__.--16
A .-----0
ｾ
_:0-
ex-
ﾷ Ｍ Ｍ Ｍ ｾ Ｗ ｾ Ｌ
ｾ
.. X
Ｂ Ｇ
",'"
",x
.'"
ｾ
-:
............
0'"
｟ Ｍ Ｍ Ｍ Ｍ Ｍ Ｍ ｾ
ｾ
0·20
B
.-. nA=--'-c..;-:=--
% 0
",I-
SASH
FRAME
WINDOW
Ｎ Ｍ Ｍ Ｎ Ｍ Ｍ Ｍ Ｍ ﾷ Ｍ Ｍ Ｍ Ｍ Ｍ ｾ Ｍ ｯ
__ .--- A
A. -
0·30
c:::;F::::::=S
ｾ ｃ
_x
n n
Ｍ Ｍ Ｍ ｾ
0·40
0·50
0·70
0·80
1·00
0·90
FIGURE 8
INSIDE - SURFACE TEMPERATURE INDEX PROFILES WITH NATURAL
CONVECTION - EFFECT OF CONVECTOR DISCHARGE GEOMETRY
BR3124-8
FRAME
SASH
TEST
X
Y
W 9
liN.) liN.! liN.! (OEG
•
I
0
7
2\ '4'4
X
9
Ｒｾ
c
10 2\
...
12
IJ.
13
WINDOW
8ASE90ARO (N.CJ
1
90
ｾ
I
90
1\
1
45
6
ｾ
I
90
6
1\
ｉｾ
90
A
Vd • 100 FPM
Id. 85 OF
A
M NT
SASH
.---
SASH
FRAME
..- '"
•
c
0·30
0·20
'"
.l
.l
0·50
0040
0·70
0·60
0·80
0·90
1·00
t -Ic
I .. r---'!'
'w-tc
·c._ n
ｆ ｒ ａ ｍ
......
SASH
-",--.Ｍ
Ｍ
Ｍ
...
x '"
•
"'."x
"''''
a:w
•
I
BASEBOARD (N.CJ
0
7
3
14\
I
90
X
9
3
1
2 fe
I
90
1
45
I
90
....
x
e,
C
10
3
21/e
:::>'"
.l
12
6
2'11
'"
13
6
Z'/e
.
Cl.'"
. .J
ｾ
ｉｾ
X
WINDOW
0
B
ｾ
1
90
｟ Ｂ Ｍ Ｍ ｲ Ａ ｘ ［ Ｚ ［ Ｇ Ｖ ａ Ｍ Ｍ Ｍ
_ -.-"'1l
SASH
MUNTIN
SASH
｜
Ｍ Ｍ Ｍ Ｍ Ｍ Ｍ Ｎ ｾ ｾ
.In(-
.--- -O"'.llJX-
ｾ Ｍ Ｍ Ｍ Ｍ ｴ ｱ
N
::r-;
"'."x
Ｂ Ｇ
a: ....
.. s
/'Z/
.... x
ｾ..J ｾ . .
'"
｟ Ｍ Ｍ Ｍ Ｍ ｾ Ｗ ＾ ］ Ｍ Ｍ Ｍ Ｍ Ｍ Ｍ ｾ
..J
ｾ
0·20
Ｍ Ｎ ｯ
-------.-
\
Vd .. 95 FPM
Id .. 85 OF
SASH
FRAME
Ｎ
ｊｊ
Y W,b:(
TEST X
liN.) liN.! (INJ
Gl
$!
Ｍ
_ • __e-tfJ{---
"'4
.·x· .-
0·30
ｾ Ｍ ｲ ｲ
0
/
-.
_:_ _ _ _0
o
0
0040
0'50
0·70
0·80
0·90
FIGURE 9
INSIDE -SURFACE TEMPERATURE INDEX PROFILES WITH FORCED
CONVECTION - EFFECT OF CONVECTOR DISCHARGE GEOMETRY
BR3724-e
1·00
.,0
FRAME
SASH
Q
>l.
"ec-o:'x...
"'1:
.0
-. »X
\.0'>!.
TEST ｾ
0>
:z:'"
......
"'"
"':z:
a:!!!
......
...
...
I
0
6
57
7
107 87
8
308 81
0
... %
ｾ
ｾ
ｾ
s
IH.cJ
X
=Ｒ
y
=Ｑ Ｔ ｾ Ｔ
W
e
/
I
BASEBOARO
•
x
:-r-
0
// /
.0 X
ｾ ｴ ('f!
WINDOW
88
A
ｾ
="
= 90'
/.//x
Ｌ
Ｏ
Ｅ
.' 0
-_-.
SASH
M NTIN
SASH
.--- 0 -
ｾ
ｾ
ｾ
..
SASH
FRAME
'
(}40
0·30
0·20
Ｎ
TEST ［
_-......
:z:.
ｾ
"' ...
:z:
ｾ ｉ ｴ
-
ｾ Ｇ
ｾ
ｾ
!!!
ｾ
v
0
6
47
89
X
7
95
87
a
8
303 80
ﾷ
-cr'.
.,..=-
__
Ｎ
｟
ｾ
｟
ｏ
Ｚ
ｾ
ｩ
ｬ
'" w
'"
a:
... :z:
eo-4(
0·30
___... Ｍ
0 .-
.--- -0·40
B
a
ｾ
ｾ
WINDOW
O
O_'
-Gy0 Orr
....
...
0·20
ｾ
/0
. =:..-------0
N
SASH
FRAME
100
il \
14\'
:z:i
c:z:
ｾ
0·90
8t,
w- c
[1 \
.ｾｾ ｾ
0:80
-t
IN.CJ
_..->.
",
......0.
8ASEBOARO
ｾ
•
r'\
0·70
ｾ
-0_
w= "
e = 90'
SASH
MUNTIN
SASH
7
0"':"'Ｎ
Ｍ
I
=
{
0
('f)
•
Y
Ｇ ｾ
ey)',
0·60
X = 3'
... :z:
y
r{
a:",
ｾ
0
y
0·50
ｯ
.....0
a-
,.- .,_--.. .. /o.. .x
1=
FRAME
SASH
ｯ
":::?c
•
':-1"
N
a:iAi
ｾ
>c
0
V-
ﾷ
ｾ
Ｌ Ｇ Ｎ
___Ｎ Ｏ Ｏ Ｏ ｾ x/
ｏ
ｾ
ｾ
.v--"
0·50
0·60
0·70
0·80
0·90
t-tc
1=tw-t c
FIGURE 10
INSIDE - SURFACE TEMPERATURE INDEX PROFILES WITH FORCED
CONVECTION - EFFECT OF CONVECTOR DISCHARGE VELOCITY
OR3124-10
1·00
FRAME
SASH
Ｇ
y
Vd Td
TEST (I N.) (DEGl FPM ('F)
ｾ
•
I
o
3-
,..,en
X
B
141(a 90' 30B 81
o
10
Ｑｾ
4S' 107 88
•
ｉ
1\
90' 109 120
2
IBOO 14 122
:Z:II
ｾ ｾ
en",
a:l;;
"':z:
R:en
Ｂ Ｇ
ｾ
..J
X
no x
•
II/!!
BASEBOARD (N.C.!
.-
P?,.X / •
•
/ // I /
e
BASEBOARD)
I
=ＲｾＴ
0
A
WINDOW
ｾ
0
4S·(FC.!
I
W = I"
- NATURAL CONVECTION
(Unde'- Window Heated
•• TRIPLED HEAT LOAD
I
I
I
NATURAL
CONVECTION
.:
.--
SASH
MUNTIN
SASH
ｯ
.,/
ｾ
AUGMENTED HEATING (F.CJ
HIGH
VELOCITY
Ｈ ｾ ｾ
0/ f 1
ｾ
•
!
.s-:'
sc
10
....
<,
ｸ Ｚ ｾ ｸ
NATURAL
CONVECTION
ｾ ｾｾＧＨｆＧｃＮ
ａｕｇｍｅｎ
HEATING (F.9/'
HIGH VELOCITY
/
ｯ
I
ｾ
_' X _ . - - - SASH
FRAME
....
0·20
0·40
0·30
0·50
._ o.;
FRAME
SASH
0)(
0·60
X.!...
- - - . __ 0 0 _
.-
0·70
-:x_
-A_
-
Ｎ Ｚ
•
0
3-
2
•,..,
T
8
14Stl 90- 303 80
･ ｮ
0
10
Ｒ Ｑ
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•
II" 2 1/
8 90'
.. '"
",'"
"'.
en>-
I
I
I
I
I
I
I
I
I
ｾ ｾ
..J
4S'
94
I
89
I
I
•,,
BASEBOARD ｾ
X = 3'
W= I'
NATURAL CONVECTION
(Under -Window Heater)
TRIPLED HEAT LOAD
..
\,
4S·(F.C.!
\
I
.>
Ｌ Ｎ ｾ
.-
____-eD)(..
o-v·
_0
-4<'
.- _.- 0
._--------,
N
.",,,,'"
･
ｾ
,/
ｮ
",,,,
BASEBOARO __' /
,/
;JI:en
°en
--'et
--'
ｾ
SASH
FRAME
0·20
o
l
'" II
en>-
.----0·30
-----.-
_-•..e---- -------
-----.'
ｯ
0'40
0·50
0·60
AUGMENTED HEATING
Ｈ ｾ ｃ
HIGH
VELOCITY
/0
_--.-,;..-c=- . . . - 0 - . ) ( -
--
B
•
/' _ _ _•I
-=-2....--X_
____ - - __.-:::::0
SASH
MUNTIN
SASH
ｾ ｣ ｲ
t
•
WINDOW
Ｎｾ
CD
I
97 liS
\
\ \.
I
I
X
ｾ
I
180' 10 liS
",II
1·00
.--........
I
CD
f
ｾ ｊ ｦ ｖ
Id
TEST Y
(IN.! DE FPM (OF)
BASEBOARD (N.C.)
0·90
0·80
t -tc
1=tw-tc
Ｍ Ｍ Ｍ ﾷ Ｍ Ｍ ｾ ｾ ｾ ｾ
I
>0
.,
...-.
x
ｾ ｈ D
ｉ ｇ
NATURAL
CONVECTION
t
Ｎ ｾ ｔ HEATING
ｅ (F.C.)
VELOCITY
ＨｾｃＮ
4S·(F.CJ
•
ｾ
ｾ ｏ ］ ｏ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ Ｚ ［
.=-0
0·70
o.so
-
0·90
t - tc
1=
tw-t-c
FIGURE II
INSIDE - SURFACE TEMPERATURE INDEX PROFILES WITH NATURAL
AND FORCED CONVECTION - OPTIMUM CONFIGURATIONS
BR3724-11
1·00
APPENDIX A
MEASUREMENT OF HEAT TRANSMISSION COEFFICIENTS
FOR WINDOWS A AND B
The over-all heat transmission coefficients or "U" values for
windows A and B were measured using the guarded hot box and the
cold-room facility which are described in NRC 6887. The air flow
conditions imposed on the warm and cold sides of the test windows
are also described. The air temperatures used in the guarded hotbox tests were approximately O°F and 72°F on the cold and warm
sides, respectively.
The metered te st area of 32 sq ft consisted of window and
supporting wall. The heat flow through the supporting wall was
obtained from an auxiliary hot-box test using a specimen of known
conductivity in place of the window.
Surface temperatures on the window were measured with
copper -constantan thermocouple s fabricated and attached as described
in Section 3 of this report. The surface temperatures in the auxiliary
test were measured with twisted-junction thermocouples fabricated
from 30-gauge copper and constantan wires.
The values listed in Table Al for the two windows were
obtained in the following manner.
(a) Heat Transmis sion Coefficient
for Supporting Wall, U
sw
A rigid-insulation panel of area, A
thickness, x , and
p'
conductivity, k , was located in the supportmg wall in place of the
test window. The panel area was approximately equal to that of
the test window. The conductivity of the panel material was determined
previously in a guarded hot-plate test.
U sing air temperature s approximately equal to those used in
the window test, the total heat flow through the wall and panel, Qt!,
was obtained with the guarded hot box. The mean temperature
difference across the surfaces of the insulation panel, 6t p ' and the
mean air temperature difference, btl t were also measured.
The heat flow through the supporting wall, Q s I, of area,
(32 - A p)' was the difference between the total measured heat flow,
Qt!' and the heat flow calculated for the panel, Q • Thus,
P
A - 2
k , A • 6t
.p
P
x
The heat transmission coefficient for the supporting wall, U sw?
was then;
Usw
=
(32 - A ) • 6t
p
1
(b) Window Heat Transmission Coefficient, U
w
With the window of area, A w' installed in the supporting
wall, the total heat flow through the window and wall, Qt2' was determined
with the guarded hot box. The mean air temperature difference acros s
the specimen, M 2 , and the mean temperature difference between the
window surface and air on the cold and warm sides, M o and Mi' were
also measured.
The heat flow through the supporting wall, Qs2' of area,
(32 - A w), was approximated by
=
(32 - A
w
)
U
sw
The above expre s sion as sume s identical surface conductance
values for the window test and the panel test; and does not account
for the difference in heat flow conditions existing at the connection
between panel and su pporting wall and between window and supporting
wall.
The window heat flow, Qw, was the difference between Q t 2 and
Qs2' and the over-all heat transmission coefficient, U w ' was calculated
as
U
w
=
U
(c)
Window Application Factor, --..::!!.U
as
The over -all heat transmis sion coefficient for an idealized
glas s -enclosed air space, Uas' was calculated using the air - space
A - 3
conductance value given in the 1960 ASHRAE Guide and Data Book
for an air-space thickness equal to that of the test window, and using
the te rnpe r atur e s and surface conductance values obtained in the
present test.
The mean surface conductance values for the warm and cold
surfaces of the window, f i and f o, were calculated from the window
heat flow, Ow' the window area, A w ' and the mean temperature
difference between the window surface and air on the wa r rn and cold
sides, M i and .6.t o' as follows:
f.
1
=
ow
A
w
• M.
and
f
1
The application factor,
uw
o
=
cw
A
w
• .6.t
0
is a rne a sur e of the heat
as
los s attributable to the metal sash and f r arrie rne mb e r s that, with
the glass -enclosed air space, form an integral part of a window.
U
TABLE A-I
RESULTS OF U-VALUE TESTS FOR WINDOWS A AND B
Test
A
B
14.5
14.1
Ap
-
area of rigid insulation panel
sq ft
X
-
mean panel thickness
in.
4.07
4.06
k
-
thermal conductivity of rigid insulation
Btu
(hr) (sqft) (OF/in.)
0.'1.77
0.'1.77
total heat flow, insulation panel and wall
Btu
hr
149.3
169.8
-
mean panel-surface temperature difference
of
65.6
64.9
mean air temperature difference across specimen
of
69.9
69.9
-
heat flow, rigid-insulation panel
Btu
hr
64.7
6'1..4
heat flow, supporting wall
Btu
hr
84.6
107.4
...
III
QJ
E-t
....
QJ
s::
nl
at l -
o,
e tit
0
......
p
nl
:;.,
tI t
.......
a
l
.s
"Cl
bO
ｾ
p
a sl sw
-
heat transmission coefficient, supporting wall
Btu
(hr) (sq ft) (OF)
w
-
area of window
sq ft
15.6
14.6
at Z
-
heat flow, window and wall
Btu
hr
666.
804.
tI t
z
-
mean air temperature difference across specimen
of
67.6
66.'1.
- mean temperature difference, cold window surface to cold air
of
0
8.
10.8
i
-
U
A
tit
tI t
mean temperature difference, warm air to warrr window surface °F
0.069
0.086
23.8
'1.8.
...., a sZ
heat flow, supporting wall
Btu
hr
77•
99.
ｾ
589.
705.
QJ
E-t
-e
.s
;t
W
-
heat flow, window
Btu
hr
w
-
heat transmission coefficient, window
Btu
(hr) (sq ft) (OF)
0.56
0.73
i
-
inside surface conductance
Btu
(hr) (sq ft) (OF)
1.6
1.7
0
-
outside surface conductance
Btu
(hr) (sq ft) (OF)
4.7
4.5
-
heat transmis sion coefficient, idealized
Btu
(hr) (sq ft) (OF)
0.54
0.55
-
window application factor
1.04
1. 31
a
U
f
f
U
as
U
w
-U
as