Page 22 - HVAC Pump Handbook

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Physical Data for HVAC System Design

Physical Data for HVAC System Design 19

TABLE 2.4 Vapor Pressures and Specific Weights for
Water, for Temperatures of 212 to 450°F

Absolute Specific
Temperature, °F pressure, psia weight , lb/ft 3
212 14.70 59.81
220 17.19 59.63
230 20.78 59.38
240 24.97 59.10
250 29.83 58.82
260 35.43 58.51
270 41.86 58.24
280 49.20 57.94
290 57.56 57.64
300 67.01 57.31
320 89.66 56.66
340 118.01 55.96
360 153.03 55.22
380 195.77 54.47
400 247.31 53.65
420 308.83 52.80
440 381.59 51.92
450 422.6 51.55
SOURCE: Joseph H. Keenan and Frederick G. Keyes,
Thermodynamic Properties of Steam, Wiley, New York, 1936, p. 34;
used with permission.

include these data for the water under consideration. Table 2.2 pro-
vides the absolute viscosity in centipoise and the kinematic viscosity
in square feet per second.

2.4.2 Vapor pressure and specific weight
for water, 32 to 212°F
The vapor pressure of water for temperatures up to 450°F must be in-
cluded, since this information is necessary in evaluating the possibili-
ties of cavitation and in the calculation of net positive suction head
available for pumps, which is included in Chap. 6 on pump perfor-
mance. Vapor pressure is the absolute pressure, psia, at which water
will change from liquid to steam at a specific temperature. For each
temperature of water, there is an absolute pressure at which water
will change from a liquid to a gas. Table 2.3 provides these vapor pres-
sures up to 210°F, as well as the specific weight of water at these tem-
peratures. The vapor pressures are shown in feet of water and not
pounds per square inch at these temperatures for NPSH calculations.
Specific weight is the density in pounds per cubic feet of water at a
particular temperature.

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