Calculating Oven Heat Load Capacity
Q. Please explain how to calculate the heat load capacity of a paint baking oven, using aluminum alloy wheels as an example. H.T.
A. Energy consumption in an oven is primarily related to radiant loss through the oven panels; energy required to raise the product, racks and conveyor to temperature; and exhaust losses. To determine the energy use, you will need to calculate these three factors and then add them to get the total.
To calculate the loss of Btu/h through the oven panels, multiply the total square feet of oven panel surface area by the panel loss factor (see table) and then by the temperature difference between the oven start-up and the controller setting.
Formula: Square feet of oven surface × panel loss factor × temperature rise
Oven Size: 20 × 50 × 10 ft (W × L × H)
Operating Temperature: 300°F
Oven Start-up Temperature: 70°F
Panel Thickness: 4 inches
Oven Surface Area
Sides: 10 × 50 = 500 × 2 sides = 1,000
Ends: 10 × 20 = 200 × 2 ends = 400
Top and bottom: 20 × 50 = 1,000 × 2 = 2,000
Total: 1,000 + 400 + 2,000 = 3,400 sq ft
300°F – 70°F = 230°F
3,400 sq ft surface area × 0.35 panel loss factor × 230°F temperature rise = 273,700 Btu/hr
To calculate the Btu/hr required to support the product loading, multiply the total load (parts, rack, conveyor chain and trolleys) by the specific heat (Btu required per lb °F) by the temperature rise. The factor 0.226 is used for aluminum. Different materials will require a different multiplier, and the table below shows the specific heat values for different metals.
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