Abstracted from ASHRAE (1989), with permission
The effective emittance is E-1 = 1/e1 + 1/e2 - 1 where e1 and e2 are the airspace boundary surface emittancesPosition of airspace |
Direction of heat flow |
Airspace |
1.5 inch airspace |
3.5 inch airspace |
|||||||||
Effective emittance E | Effective emittance E | ||||||||||||
Mean temp., °F |
Temp. diff., °F |
0.03 |
0.05 |
0.2 |
0.5 |
0.82 |
0.03 |
0.05 |
0.2 |
0.5 |
0.82 |
||
Horizontal |
Up |
90 |
10 |
2.55 |
2.41 |
1.71 |
1.08 |
0.77 |
2.84 |
2.66 |
1.83 |
1.13 |
0.80 |
50 |
30 |
1.87 |
1.81 |
1.45 |
1.04 |
0.80 |
2.09 |
2.01 |
1.58 |
1.10 |
0.84 |
||
50 |
10 |
2.50 |
2.40 |
1.81 |
1.21 |
0.89 |
2.8 |
2.66 |
1.95 |
1.28 |
0.93 |
||
0 |
20 |
2.01 |
1.95 |
1.63 |
1.23 |
0.97 |
2.25 |
2.18 |
1.79 |
1.32 |
1.03 |
||
0 |
10 |
2.43 |
2.35 |
1.90 |
1.38 |
1.06 |
2.71 |
2.62 |
2.07 |
1.47 |
1.12 |
||
-50 |
20 |
1.94 |
1.91 |
1.68 |
1.36 |
1.13 |
2.19 |
2.14 |
1.86 |
1.47 |
1.20 |
||
-50 |
10 |
2.37 |
2.31 |
1.99 |
1.55 |
1.26 |
2.65 |
2.58 |
2.18 |
1.67 |
1.33 |
||
Down |
90 |
10 |
6.09 |
5.35 |
2.79 |
1.43 |
0.94 |
10.07 |
8.19 |
3.41 |
1.57 |
1.00 |
|
50 |
30 |
6.27 |
5.63 |
3.18 |
1.70 |
1.14 |
9.60 |
8.17 |
3.86 |
1.88 |
1.22 |
||
150 |
10 |
6.61 |
5.9 |
3.27 |
1.73 |
1.15 |
11.15 |
9.27 |
4.09 |
1.93 |
1.24 |
||
0 |
20 |
7.03 |
6.43 |
3.91 |
2.19 |
1.49 |
10.90 |
9.52 |
4.87 |
2.47 |
1.62 |
||
0 |
10 |
7.31 |
6.66 |
4.00 |
2.22 |
1.51 |
11.97 |
10.32 |
5.08 |
2.52 |
1.64 |
||
-50 |
20 |
7.73 |
7.20 |
4.77 |
2.85 |
1.99 |
11.64 |
10.49 |
6.02 |
3.25 |
2.18 |
||
-50 |
10 |
8.09 |
7.52 |
4.91 |
2.89 |
2.01 |
12.98 |
11.56 |
6.36 |
3.34 |
2.22 |
||
Position of airspace |
Direction of heat flow |
Airspace |
1.5 inch airspace |
3.5 inch airspace |
|||||||||
Effective emittance E | Effective emittance E | ||||||||||||
Mean temp., °F |
Temp. diff., °F |
0.03 |
0.05 |
0.2 |
0.5 |
0.82 |
0.03 |
0.05 |
0.2 |
0.5 |
0.82 |
||
45° slope |
Up |
90 |
10 |
2.92 |
2.73 |
1.86 |
1.14 |
0.80 |
3.18 |
2.96 |
1.97 |
1.18 |
0.82 |
50 |
30 |
2.14 |
2.06 |
1.61 |
1.12 |
0.84 |
2.26 |
2.17 |
1.67 |
1.15 |
0.86 |
||
50 |
10 |
2.88 |
2.74 |
1.99 |
1.29 |
0.94 |
3.12 |
2.95 |
2.10 |
1.34 |
0.96 |
||
0 |
20 |
2.30 |
2.23 |
1.82 |
1.34 |
1.04 |
2.42 |
2.35 |
1.90 |
1.38 |
1.06 |
||
0 |
10 |
2.79 |
2.69 |
2.12 |
1.49 |
1.13 |
2.98 |
2.87 |
2.23 |
1.54 |
1.16 |
||
-50 |
20 |
2.22 |
2.17 |
1.88 |
1.49 |
1.21 |
2.34 |
2.29 |
1.97 |
1.54 |
1.25 |
||
-50 |
10 |
2.71 |
2.64 |
2.23 |
1.69 |
1.35 |
2.87 |
2.79 |
2.33 |
1.75 |
1.39 |
||
Down |
90 |
10 |
5.07 |
4.55 |
2.56 |
1.36 |
0.91 |
4.81 |
4.33 |
2.49 |
1.34 |
0.90 |
|
50 |
30 |
3.58 |
3.36 |
2.31 |
1.42 |
1.00 |
3.51 |
3.30 |
2.28 |
1.40 |
1.00 |
||
50 |
10 |
5.10 |
4.66 |
2.85 |
1.60 |
1.09 |
4.74 |
4.36 |
2.73 |
1.57 |
1.08 |
||
0 |
20 |
3.85 |
3.66 |
2.68 |
1.74 |
1.27 |
3.81 |
3.63 |
2.66 |
1.74 |
1.27 |
||
0 |
10 |
4.92 |
4.62 |
3.16 |
1.94 |
1.37 |
4.59 |
4.32 |
3.02 |
1.88 |
1.34 |
||
-50 |
20 |
3.62 |
3.50 |
2.80 |
2.01 |
1.54 |
3.77 |
3.64 |
2.90 |
2.05 |
1.57 |
||
-50 |
10 |
4.67 |
4.47 |
3.40 |
2.29 |
1.70 |
4.50 |
4.32 |
3.31 |
2.25 |
1.68 |
||
Position of airspace |
Direction of heat flow |
Airspace |
1.5 inch airspace |
3.5 inch airspace |
|||||||||
Effective emittance E | Effective emittance E | ||||||||||||
Mean temp., °F |
Temp. diff., °F |
0.03 |
0.05 |
0.2 |
0.5 |
0.82 |
0.03 |
0.05 |
0.2 |
0.5 |
0.82 |
||
Vertical |
Horizontal |
90 |
10 |
3.99 |
3.66 |
2.25 |
1.27 |
0.87 |
3.69 |
3.40 |
2.15 |
1.24 |
0.85 |
50 |
30 |
2.58 |
2.46 |
1.84 |
1.23 |
0.90 |
2.67 |
2.55 |
1.89 |
1.25 |
0.91 |
||
50 |
10 |
3.79 |
3.55 |
2.39 |
1.45 |
1.02 |
3.63 |
3.40 |
2.32 |
1.42 |
1.01 |
||
0 |
20 |
2.76 |
2.66 |
2.10 |
1.48 |
1.12 |
2.88 |
2.78 |
2.17 |
1.51 |
1.14 |
||
0 |
10 |
3.51 |
3.35 |
2.51 |
1.67 |
1.23 |
3.49 |
3.33 |
2.50 |
1.67 |
1.23 |
||
-50 |
20 |
2.64 |
2.58 |
2.18 |
1.66 |
1.33 |
2.82 |
2.75 |
2.30 |
1.73 |
1.37 |
||
-50 |
10 |
3.31 |
3.21 |
2.62 |
1.91 |
1.48 |
3.40 |
3.30 |
2.67 |
1.94 |
1.50 |