P3.43 Water at 20 C flows through a 5-cm-diameter pipe that has a 180 vertical bend, as in Fig. P3.43. The total length of pipe between flanges 1 and 2 is 75 cm. When the weight flow rate is 230 N/s, p1

Respuesta :

Answer:

F_x = 750.7 N

Explanation:

Given:

- Length of the pipe between flanges L = 75 cm

- Weight Flow rate is flow(W) = 230 N/c

- P_1 = 165 KPa

- P_2 = 134 KPa

- P_atm = 101 KPa

- Diameter of pipe D = 0.05 m

Find:

The total force that the flanges must withstand F_x.

Solution:

- Use equation of conservation of momentum.

            (P_1 - P_a)*A + (P_2 - P_a)*A - F_x = flow(m)*( V_2 - V_1)

- From conservation of mass:

                                       A*V_1 = A*V_2

                       V_1 = V_2 ( but opposite in directions)

- Hence,

             (P_1 - P_a)*A + (P_2 - P_a)*A - F_x = - 2*flow(m)*V_1

                                     flow(m) = flow(W) / g

                                     p*A*V_1 = flow(W) / g

                                    V_1 =  flow(W) / g*p*A    

Hence,      

             (P_1 - P_a)*A + (P_2 - P_a)*A - F_x = - 2*flow(W)^2 / g^2*p*A

Hence, compute:

   64*10^3 *pi*0.05^2 /4 + 33*10^3 *pi*0.05^2 /4 - F_x = - 2*(230/9.81)^2 / 997*pi*0.05^2 /4

                            125.6 + 64.7625 - F_x = -560.33

                                        F_x = 750.7 N