Chromalox Big Red Book

Technical

Technical Information Radiant Infrared Heating - Process Applications

Estimating Total Kilowatts for Product Heating

Nomograph for Product Heating — For product heating, the nomograph at the right can be used. The nomograph does not take into account heat energy requirements for air ventilation. To estimate the kW for total product heating: 1. Determine pounds of material per hour to be heated (A) 2. Read across to the specific heat of the material (B) 3. Read up to desired temperature rise in °F (C) 4. Read across to overall efficiency (D). Overall efficiency = Product Absorption Factor x View Factor x Source Efficiency. Determine Product Absorption Factor (surface emissivity) of the work product (ie:  = 0.85 for enamel sheet metal). Determine View Factor (use 0.9 as a view factor for well designed or enclosed ovens). Determine Source efficiency. Typical Source/Reflector efficiencies are: Quartz Lamps 0.70 to 0.80 Quartz Tubes 0.60 to 0.70 Metal Sheath 0.55 to 0.65 5. Read down to Kilowatts required (E). Nomograph for Drying — The nomograph to the right can be used to estimate Kilowatts required to evaporate water from the surfaces of work product. Graph is based on an initial starting product temperature of 70°F. It does not take into account heat energy require- ments for air circulation or ventilation. 1. Determine pounds of water (solvent) per hour to be evaporated (A) 2. Read up to Source/Reflector efficiency (B). Depending on the configuration and cleanliness of the reflector, typical Source/ Reflector efficiencies are: Quartz Lamps 0.70 to 0.80 Quartz Tubes 0.60 to 0.70 Metal Sheath 0.55 to 0.65 3. Read across to Work Product Absorption Factor (C). This value is based on the emissivity of the work product surface (ie:  = 0.85 for enameled sheet metal) and the view factor of the oven or space. Use 0.9 as a view factor for well designed or enclosed ovens. 4. Read down to Kilowatts required (D).

250 300 350 400

100 90 80 70 60 50

40

200

175

Temperature Rise °F

Overall Efficiency

150

30

125

100

20

75

C

D

10

50

25

E

10 30 50 70 90 110 130 150 200 300 500 800 1000 Kilowatts of Infrared Required

Specific Heat of Material

0.8 0.6 0.4 0.3 0.2 1.0

B

2000 3000 5000 8000 10000 Pounds of Material Per Hour

A

.0.05

0.1

Estimating Infrared Kilowatts for Drying

60 55 50

40%

100 90 80 70 60 50% 40

65 70

Source/Reflector Efficiency

Work Product Absorption Factor (Emissivity x View Factor)

30

80

B

C

20

10

A

D

100

80

60

40

20

0 20 40 60 80 100 120 140

Pounds of Water Evaporated Per Hour

Kilowatts of Infrared Energy Required

Note — To evaporate solvents other than water, calculate the energy required to heat the solvent to vaporization temperature using the weight, specific heat and temperature rise. Calculate the latent heat of vaporization and add to the energy required to heat the solvent to vaporization temperature.

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