Page 250 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.34 CHAPTER FIVE

The thermal ratio TR is calculated from the following formula:

TR = ST (5.13)
AD
where TR = thermal ratio
ST = mean annual site air temperature, °F, minus 32 (The mean annual site air tem-
perature can be obtained from the NOAA publication “Comparative Climatic
Data.” It is available only in tabular form and much too large to be reproduced
in this book.)
AD = average surface temperature differential [This is found by dividing the surface
freezing index (SF) by the number of days in the freezing season.]
The surface freezing index is derived from the formula:
SF = N × AF (5.14)

The number of days in the freezing season, which is defined as the estimated number
of days the temperature will fall to 32°F or below, can be found in Fig. 5.9.
The fusion parameter FP is calculated from the following formula:

FP = AD × volumetric heat capacity (5.15)
f
latent heat of fusion in soil
AD is calculated from Eq. (5.14). Volumetric heat capacity is found in Fig. 5.6. The
latent heat of fusion is found in Fig. 5.7. Table 6.8 gives the soil weight and average value
for moisture content.

FIGURE 5.6 Volumetric heat capacity for soils.

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