Question

What is the absolute pressure of a gas in PSIA if a pressure gauge indicates a vacuum pressure of 60 mm of Hg?

A pressure difference of 20 PSID is equivalent to what pressure in kPA units.

Water at 50F flows through a pipe at average velocity 1 m/s. What is the equivalent PSI units of pressure for this flow where pressure = (1/2) velocity squared * density?

Answer 1

The pressure given is 60 mmHg in gauge

Hence absolute pressure = 760+60 = 820 mmHg

now

1 atm = 14.69 psi = 760 mmHg

Hence 820 mmHg = (820*14.69)/760 =15.85 PSIA

NOW Difference in pressure is actually independent of units as . when converting from one unit to another we multiply it by a factor. When we take the different both will have the factor as result the difference we will remain the same

Hence 20 psia will be equal to 20 KPa

Density of water = 1000 Kg/m3

V = 1 m/s

Pressure = (1/2) * (1)*1000 = 500 Kg /m*s2 = 500 Pa

now

101325 Pa = 14.69 PSIA

Hence, 500 Pa = 0.07248 PSIA