Question

A vacuum gage attached to a power plant condenser gives a reading of 27.86 in. of mercury. The surrounding atmospheric pressure is 14.66 lbf/in. Determine the absolute pressure inside the condenser, in lbf/in. The density of mercury is 848 lb/ft and the acceleration of gravity is g = 32.0 ft/s?.

Answer 1

absolute pressure = 1.07 lbft/in^2

Step-by-step explanation:

given data:

vaccum gauge reading h = 27.86 inch = 2.32 ft

we know that

gauge pressure p is given as

`p = \rho gh`

`p = 848 \ lb/ft^3 * 32 \ ft/s^2 *2.32 ft  = 62955.52 \ lbft/s^2 * 1/ft^2`

we know that
`1\  lb ft\s^2 = (1)/(32.174)\  lbft`

1 ft = 12 inch

therefore
`p = 62955.52 * (1)/(32.174) * (1)/(12^2)\ lbf/in^2`

`p = 13.59\  lbft/in^2`

`P_(atm) = 14.66\  lbf/in^2`

so absolute pressure =
`P_(atm) - p`

= 14.66 - 13.59 = 1.07 lbft/in^2