Water at 60.0°F (p =62.4 lb/ft2) is flowing through a pipe at steady state. A differential manometer attached to the pipe the height of the manometer fluid is 48 inches. measures a pressure drop of 3.55 lb/in2 when (17 pts.) What is the specific gravity (60.0°F/60.0°F) of the manometer fluid? а. b. (6 pts.) What is the pressure drop in millimeters of mercury (SG=13.6)?

Respuesta :

Explanation:

The given data is as follows.

       Temperature = [tex]10^{o}F[/tex]

        Density ([tex]\rho[/tex]) = 62.4 [tex]lb/ft^{2}[/tex]

        Pressure drop = 3.55 [tex]lb/in^{2}[/tex]

                                 = 511.6 [tex]lb/ft^{2}[/tex]       (as 1 [tex]lb/in^{2} = 144 lb/ft^{2}[/tex])

        Height of manometer = 48 inch = 4 ft     (as 1 inch = 0.0833)

              g = 9.81 [tex]m/s^{2}[/tex]

                  = 32.18 [tex]ft/s^{2}[/tex]        (as 1 [tex]m/s^{2}m = 3.280 ft/s^{2}[/tex])

(a)    Specific gravity of monometric fluid [tex](S_{G})[/tex] will be calculated as follows.

              [tex]S_{G} = \frac{\rho_{m}}{\rho_{soln}}[/tex]

where,     [tex]\rho_{m}[/tex] = density of manometric fluid

               [tex]\rho_{soln}[/tex] = density of standard fluid (water) = 1000 g/ml

So,        [tex]S_{G} = \frac{\rho_{m}}{1000}[/tex]

          [tex]\Delta P = \rho_{m} \times g \times h_{m}[/tex]

where,    [tex]h_{m}[/tex] = height of manometric fluid

               [tex]\rho_{m}[/tex] = density of manometric fluid

Now, putting the given values into the above formula as follows.

               [tex]\Delta P = \rho_{m} \times g \times h_{m}[/tex]

            511.6 [tex]lb/ft^{2}[/tex] = [tex]\rho_{m} \times 32.18ft/s^{2} \times 4 ft[/tex]          

                   [tex]\rho_{m}[/tex] = 3.97 [tex]lb/ft^{3}[/tex]

Therefore, calculate the value of [tex]S_{G}[/tex] as follows.

                      [tex]S_{G} = \frac{\rho_{m}}{1000}[/tex]

                                = [tex]\frac{3.97 lb/ft^{3}}{1000}[/tex]

                                = [tex]3.97 \times 10^{-3}[/tex]

And, for mercury   [tex]\Delta P = \rho_{m}gh[/tex]

               [tex]\Delta P[/tex] = [tex]849 lb/ft^{3} \times 32.18 ft/s^{2} \times 4 ft[/tex]

                              = 109283.28 [tex]lb/ft^{2}[/tex]

                              = 39246.99 mm Hg       (1 [tex]lb/ft^{2}[/tex] = 0.3591 mm Hg)

Thus, we can conclude that the pressure drop in millimeters of mercury is 39246.99 mm Hg.