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200.5°F. Then find a new k = 0.26, which gives a new RI = 2/126 = 7.69.

STEP 8. Return to step 4 with the new RI and proceed. This example shows the insensitivity of heat loss to changes in surface temperature since the new Q = 22 Btu/hr ft2.

For pipe insulation, the same procedure is followed except that RI is calculated using the equivalent thickness. Also, conversion to heat loss per linear foot must be done separately after the square-foot loss is determined.

Thickness for a Specified Heat Loss

Again, a surface temperature ts must first be assumed ad then checked for accuracy at the end of the calculation.

From Section 15.4.2,

Ri tk/k

Determine k from appendix Figure 15.A3 at 210°F. k = 0.27.

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