What is the duct surface area in square feet of a 38 foot run of 20" diameter pipe?

To determine the duct surface area of a cylindrical pipe, you can use the formula for the lateral surface area of a cylinder:

[ \text{Surface Area} = \pi \times \text{Diameter} \times \text{Length} ]

In this case, the diameter of the pipe is 20 inches, and the run length is 38 feet.

First, convert the diameter from inches to feet:

[ \text{Diameter in feet} = \frac{20 \text{ inches}}{12 \text{ inches/foot}} = \frac{20}{12} = 1.67 \text{ feet} ]

Now, substitute the diameter (in feet) and the length (38 feet) into the surface area formula:

[ \text{Surface Area} = \pi \times 1.67 \text{ ft} \times 38 \text{ ft} ]

Calculating this gives:

[ \text{Surface Area} \approx 3.14 \times 1.67 \times 38 ]

Doing the multiplication:

[ \text{Surface Area} \approx 3.14 \times 63.46 \approx 199.75 \text{ square