Page 246 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

HEAT TRANSFER, INSULATION, AND FREEZE PROTECTION

5.30 CHAPTER FIVE

Equation (5.9) has been used to create Fig. 5.4, which is a nomogram that shows the
temperature drop of flowing water in a pipeline. Before Fig. 5.4 can be entered, the follow-
ing values must be known:
V = velocity of flow, ft/s
H = heat-transfer coefficient (By field experience, a value of 6 has been found to be an
average value.)
S = length of pipe run, ft
r = radius of pipe, ft
TI = inlet water temperature, °F
TO = outlet water temperature, °F (It is recommended that a minimum temperature
of 35°F be used to provide a safety factor to allow for variations in the thermal
properties of soil along the run, intermittent flow in the pipe, and temperature
fluctuations of both the air and ground.)
TS = ambient temperature of either air or soil around pipe (Soil temperature can be
approximated by adding 5°F to the lowest monthly mean temperature.)

FIGURE 5.4 Temperature drop of flowing water in a pipeline.

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