Thermodynamics
TEMPERATURE AND PRESSURE MEASUREMENTS
Example 2: Pressure Relationships
What is the absolute pressure at the bottom of a swimming pool 6 feet deep that is filled
with fresh water? Patm = 14.7 psia
Solution:
Pabs
= Patm + Pgauge
= 14.7 + rH
= 14.7 + [(62.4 lbm/ft3)(6 ft)/(144 in.2/ft2)]
= 14.7 + 2.6
Pabs
= 17.3 psia
In addition to pounds per square inch, pressure can be measured with reference to the force that
exists in a column of fluid at a certain height. The most common of these are inches of water,
inches of mercury, millimeters of mercury, and microns of mercury. Conversion factors are listed
below.
14.7 psia = 408 inches of water
14.7 psia = 29.9 inches of mercury
1 inch of mercury = 25.4 millimeters of mercury
1 millimeter of mercury = 103 microns of mercury
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