2

Since k at 504°F = k at 495°F (assumed) = 0.53, the assumption is okay. A check on Rs can also be made based on the calculated surface temperature.

STEP 7. If the assumption is not okay, recalculate using a new k value based on the new tm.

The Qf used above is for flat surfaces. In determining heat flow from a pipe, the same equations are used with Eq tk substituted for tk in the Rj calculation as discussed in Section 15.4.2. Often, it is desired to express pipe heat losses in terms of Btu/hr-lin.-ft rather than

Table 15.6 Fiberglass pipe insulation: minimum thickness to prevent condensation0.

8O0F and 9O% RH 8O0F and 7O% RH 8O0F and 5O% RH

Operating Pipe

Table 15.6 Fiberglass pipe insulation: minimum thickness to prevent condensation0.

Operating Pipe

Temperature

Pipe Size

Thickness

Pipe Size

Thickness

Pipe Size

Thickness

(0F)

(in.)

(in.)

(in.)

(in.)

(in.)

(in.)

0 0

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