Iran University of Science & Technology
School of Mechanical Engineering
Fluid Mechanics I
Problems # 6
1. SAE 30 oil at 20°C flows in the 3 cm diameter pipe in Fig.1, which slopes at 37°. For
the pressure measurements shown, determine (a) whether the flow is up or down and
(b) the flow rate in m3/h.
Fig.1
2. The pipe flow in Fig.2 is driven by pressurized air in the tank. What gage pressure p1 is
needed to provide a 20°C water flow rate Q = 60 m3/h?
Fig.2
4. Water at 20°C is to be pumped through 2000 ft of pipe from reservoir 1 to 2 at a rate of
3 ft3/s, as shown in Fig.3. If the pipe is cast iron of diameter 6 in and the pump is 75
percent efficient, what horsepower pump is needed?
Fig.3
Iran University of Science & Technology
School of Mechanical Engineering
Fluid Mechanics I
Problems # 6
4. Heat exchangers often consist of many triangular passages. Typical is Fig.4, with L =
60 cm and an isosceles-triangle cross section of side length a = 2 cm and included
angle  = 80°. If the average velocity is V = 2 m/s and the fluid is SAE 10 oil at 20°C,
estimate the pressure drop.
Fig.4
5. A rectangular heat exchanger is to be divided into smaller sections using sheets of
commercial steel 0.4 mm thick, as sketched in Fig.6. The flow rate is 20 kg/s of water
at 20°C. Basic dimensions are L = 1 m, W = 20 cm, and H = 10 cm. What is the proper
number of square sections if the overall pressure drop is to be no more than 1600 Pa?
Fig.5
6. The reservoirs in Fig.6 are connected by cast iron pipes joined abruptly, with sharpedged entrance and exit. Including minor losses, estimate the flow of water at 20°C if
the surface of reservoir 1 is 45 ft higher than that of reservoir 2.
Fig.6
Iran University of Science & Technology
School of Mechanical Engineering
Fluid Mechanics I
Problems # 6
7. The system in Fig.7 consists of 1200 m of 5 cm cast iron pipe, two 45° and four 90°
flanged long-radius elbows, a fully open flanged globe valve, and a sharp exit into a
reservoir. If the elevation at point 1 is 400 m, what gage pressure is required at point 1
to deliver 0.005 m3/s of water at 20°C into the reservoir?
Fig.7
8. For the series-parallel system of Fig.8, all pipes are 8 cm diameter asphalted cast iron.
If the total pressure drop p1 = p2 = 750 kPa, find the resulting flow rate Q m3/h for
water at 20°C. Neglect minor losses.
Fig.8
9. In Fig.9 all four horizontal cast-iron pipes are 45 m long and 8 cm in diameter and
meet at junction a, delivering water at 20°C. The pressures are known at four points as
shown: p1 = 950 kPa, p2 = 350 kPa, p3 = 675 kPa and p4 = 100 kPa. Neglecting minor
losses, determine the flow rate in each pipe.
Fig. 9
Iran University of Science & Technology
School of Mechanical Engineering
Fluid Mechanics I
Problems # 6
10. In Fig.10 lengths AB and BD are 2000 and 1500 ft, respectively. The friction factor is
0.022 everywhere, and pA = 90 lbf/in2 gage. All pipes have a diameter of 6 in. For
water at 20°C, determine the flow rate in all pipes and the pressures at points B, C, and
D.
Fig.10