Name :_________________ Quiz: No. 3 Time: 15 minutes Student ID# : ____________ Course: ME 5160, Fall 2021
--- The exam is closed book and closed notes.
Water at 20°C (ρ=998 kg/m
3) flows through the elbow and waterjet exits to the atmosphere. The diameter of pipe is 𝐷
1= 10𝑐𝑚, while 𝐷
2= 3𝑐𝑚. At a flow rate of 0.0153 m
3/s, the pressure p
1= 2.3atm (gage). Neglecting the weight of water and elbow, estimate x component of the force on the flange bolts at section 1.
{2.3atm = 233kPa}
Continuity Equation:
− 𝑑
𝑑𝑡∫ 𝜌𝑑∀𝐶𝑉 = ∫ 𝜌𝑉𝐶𝑆 𝑅. 𝑛 𝑑𝐴 Momentum Equation:
∑ 𝐹 = 𝑑
𝑑𝑡∫ 𝑉𝜌𝑑∀𝐶𝑉 + ∫ 𝑉𝜌𝑉𝐶𝑆 𝑅. 𝑛 𝑑𝐴
Name :_________________ Quiz: No. 3 Time: 15 minutes Student ID# : ____________ Course: ME 5160, Fall 2021
---
Solution:
a) Continuity:
Q = V
1A
1= V
2A
2𝑉
1=
𝑄𝐴1
=
0.0153(𝜋4)(0.1)2
= 1.95 𝑚/𝑠
𝑉
2=
𝑄𝐴2
=
0.0153(𝜋4)(0.03)2
= 21.64 𝑚/𝑠 x – Momentum:
∑ 𝐹
𝑥= 𝑚̇𝑢
2− 𝑚̇𝑢
1−𝐹
𝑥,𝑏𝑜𝑙𝑡𝑠+ 𝑝
1𝐴
1= 𝜌𝑄(−𝑉
2cos 40° − 𝑉
1) 𝐹
𝑥,𝑏𝑜𝑙𝑡𝑠= (233 × 10
3)
𝜋4
(0.1)
2+ (998)(0.0153)(21.64 cos 40° + 1.95) = 2113 𝑁
(+1)
(+3) (+2)
(+1)
(+1) (+2)