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

Answer:

absolute pressure =  1.07 lbft/in^2

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  $1\ lb ft\s^2 = \frac{1}{32.174}\ lbft$

1 ft = 12 inch

therefore $p = 62955.52 * \frac{1}{32.174} * \frac{1}{12^2}\ lbf/in^2$

               $p = 13.59\ lbft/in^2$

$P_{atm} = 14.66\ lbf/in^2$

so absolute pressure = $P_{atm} - p$

                                   = 14.66 - 13.59 = 1.07 lbft/in^2