Watlow Heater Catalog

Reference Data (Imperial Unit)

Power Calculations Heat Loss Curves

Ref. 5

Heat Losses from Vertical Insulated Surfaces

1. Based upon combined natural convection and radiation losses into 70°F environment. 2. Insulation characteristics k = 0.67 @ 200°F k = 0.83 @ 1000°F 3. For molded ceramic fiber products and packed or tightly packed insulation, losses will be lower than values shown. For 2 or 3 inches insulation multiply by 0.84. For 4 or 5 inches insulation multiply by 0.81. For 6 inches insulation multiply by 0.79.

2600 2400 2200 2000 1800 1600 1400 1200 1000

4 in. Insulation

5 in. Insulation

6 in. Insulation

3 in. Insulation

2 in. Insulation

1 in. Insulation

800 600 400 200 Temperature of Insulated Surface—°F

0 in. Insulation

0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Losses—W/in 2

Ref. 6

Heat Losses from Horizontal Metal Surfaces

1400 1300 1200 1100 1000

*For losses of molten metal surfaces, use the curve e=0.40.

e = 0 . 2 0

n d R a d i a t i o n o n v e c t i o n a n d

N a t u r a l C o n v e c t i o n

R a d i a t i o n e = 0 . 4 0 *

t i o n a

o n v e c

n e d C

a d i a t i o n e = 1 . 0

900 800 700 600 500

C o m b i

C o m b i n e d C

n v e c t i o n a n d R

C o m b i n e d C o

Temperature of Surface—°F

Losses—W/in 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0

*For losses of molten metal surfaces, use the curve e=0.40.

Ref. 7

Combined Convection and Radiation—Losses from Oil or Paraffin Surfaces

600

500

400

300

200

100

Temperature of Surface—°F

0 0

Losses—W/ft 2 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300

526