From ASHRAE (1989), with permission
Conductances given in Btu/(hr·ft2·°F)Values for still air
Position of surface |
Direction of heat flow |
Surface emittance |
|||||
Non-reflective |
Reflective |
||||||
e = 0.90 |
e = 0.20 |
e = 0.05 |
|||||
hi |
R |
hi |
R |
hi |
R |
||
Horizontal |
Upward |
1.63 |
0.61 |
0.91 |
1.10 |
0.76 |
1.32 |
Downward |
1.08 |
0.92 |
0.37 |
2.70 |
0.22 |
4.55 |
|
Sloping at 45° |
Upward |
1.60 |
0.62 |
0.88 |
1.14 |
0.73 |
1.37 |
Downward |
1.32 |
0.76 |
0.60 |
1.67 |
0.45 |
2.22 |
|
Vertical |
Horizontal |
1.46 |
0.68 |
0.74 |
1.35 |
0.59 |
1.70 |
Position of surface |
Direction of heat flow |
hi |
R |
15 mi/h wind (for winter) |
Any |
6.00 |
0.17 |
7.5 mi/h wind (for summer) |
Any |
4.00 |
0.25 |
Notes for both tables: