Air flows through a pipe at a rate of 124 L/s. The pipe consists of two sections of diameters 22 cm and 10 cm with a smooth reducing section that connects them. The pressure difference between the two pipe sections is measured by a water manometer.
Neglecting frictional effects, determine the differential height of water between the two pipe sections. Take the air density to be 1.20 kg/m^3.

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Complete Question

The diagram for this question is shown on the first uploaded image

Answer:

The differential height is  [tex]h= 1.458cm[/tex]

Explanation:

The schematic diagram of the venturimeter is shown on the second uploaded image

   The continuity equation is mathematically given as

              [tex]\r V = Av[/tex]

Where A is the area

           [tex]\r V[/tex] is the flow rate

          [tex]v_1[/tex] is the velocity

At  the inlet making v the subject to obtain the inlet velocity we have

          [tex]v_1 = \frac{\r V}{A_1}[/tex]

Substituting  124 L/s  = [tex]0.124 m^3 /s[/tex] for [tex]\r V[/tex] and  [tex]A_1 = \frac{\pi}{4 } *d^2 = \frac{\pi}{4} * 0.22^2[/tex] given that

    [tex]d =22cm= \frac{22}{100} = 0.22m[/tex]

              So       [tex]v_1 =\frac{0.124}{\frac{\pi}{4} * 0.22^2 }[/tex]

                               [tex]=3.26m/s[/tex]

At the exit point the velocity is  

              [tex]v_2 = \frac{\r V}{A_2}[/tex]

Where [tex]A_ 2 = \frac{\pi}{4}d^2 = \frac{\pi}{4} * 0.10^2[/tex]   given that    [tex]d =10cm= \frac{10}{100} = 0.10m[/tex]

   So              [tex]v_2 = \frac{0.124}{\frac{\pi}{4} *(0.10)^2}[/tex]

                          [tex]= 15.78m/s[/tex]

The Bernoulli's  flow equation between the inlet and exist   is mathematically given as

              [tex]\frac{P_1}{\rho_o } + \frac{v_1^2}{2} = \frac{P_2}{\rho_0} +\frac{v_2^2}{2} +gz_2 ---(1)[/tex]

  And

           [tex]P_1 - P_2 = \rho_o [\frac{v_2^2}{2} + \frac{v_1^2}{2} ] = \rho_{water} gh ---(2)[/tex]

Where [tex]P_1[/tex] is the pressure at inlet

              [tex]P_2[/tex] is the pressure at exist

             [tex]\rho_{water}[/tex] is the density of water with value of [tex]1000kg/m^3[/tex]

             g is acceleration due to gravity

              h is the height of the water column

making h the subject in the equation 2

           [tex]h = \rho _o \frac{v_2^2 - v_1^2}{2g\rho_{water}}[/tex]

where  [tex]\rho _o[/tex] is the density of air given in the question

             

         Substituting value

               [tex]h = (1.20) \frac{15.78^2 - 3.26^2}{2 (9.81 )(1000)}[/tex]

                 [tex]h= 1.458cm[/tex]

                 

               

                         

                 

       

 

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