The pressure guage on the steam condenser for a turbine indicates 26.2 in. Hg of vacuum. The barometer reading is 30.4 in. What the absolute pressure in the condenser in psia?
To calculate the absolute pressure in the condenser, we need to understand the concept of vacuum and how it relates to pressure measurements.
In pressure measurements, vacuum refers to pressure lower than atmospheric pressure. It is commonly expressed in inches of mercury (in. Hg). Positive pressure is measured as inches of mercury above vacuum, while negative pressure or vacuum is measured as inches of mercury below atmospheric pressure.
Given the pressure gauge reading of 26.2 in. Hg of vacuum and the barometer reading of 30.4 in., we can calculate the absolute pressure in the condenser using the following equation:
Absolute Pressure = Atmospheric Pressure + Vacuum Pressure
To convert the barometer reading into absolute pressure, we need to add the vacuum pressure to it. However, since we have the vacuum pressure in inches of mercury below atmospheric pressure, we need to subtract it instead.
Step-by-step calculation:
1. Subtract the vacuum pressure from the barometer reading to obtain the absolute pressure:
Absolute Pressure = 30.4 in. - 26.2 in.
Absolute Pressure = 4.2 in.
2. Convert the absolute pressure from inches of mercury to pounds per square inch (psi):
To convert inches of mercury to psi, we can divide the value by 2.036:
Absolute Pressure in psi = Absolute Pressure / 2.036
Absolute Pressure in psi = 4.2 in. / 2.036
Absolute Pressure in psi ≈ 2.06 psi
3. Convert the pressure from psi to pounds per square inch absolute (psia):
Absolute Pressure in psia = Absolute Pressure in psi + Atmospheric Pressure
Atmospheric Pressure is usually around 14.7 psi.
Absolute Pressure in psia = 2.06 psi + 14.7 psi
Absolute Pressure in psia ≈ 16.76 psia
Therefore, the absolute pressure in the condenser is approximately 16.76 psia.