Fluid Mechanics Ppt

FLUID MECHANICS

Problem 6

What is the enthalpy enthalpy of steam at 15 150 0 psi psia and 400˚F

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Problem 7

Ap pum ump p del deliv iver erss 40 40 gpm gpm of water with a total head of 40 ft. The efficiency efficiency of the pump is 65%. What is its BHP?

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Problem 8 

When the ID of the pipe through which a fluid flows is doubled, the pressure loss due to friction per unit length of pipe and for the same volumetric flow rate is changed by approximately a factor of

Problem 9

When two centrifugal pumps are connected in series, the discharge changes by a factor of

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Problem 10

When two reciprocating pumps are connected in parallel, the volumetric capacity of the system changes by a factor of

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Problem 11

The pressure drop in a pipeline changes by a factor of ___ when the velocity of the flowing fluid is doubled.

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Problem 12

Oil with a viscosity of 30 cP 3 and a density of 60 lb/ft flows through a 1/2-inch inside diameter pipe. Determine the velocity in ft/s below which flow will be laminar.

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Problem 13

Water at 80˚F flows at 10 ft per second through a 6-inch Sch. 40 steel pipe with length of 1000 ft. The Reynolds number is

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Problem 14 

A cylindrical tank 1 ft in diameter discharges through a nozzle connected to the base. Find the time needed for the water level in the tank to drop from 4 ft to 2 ft above the nozzle. The diameter of the nozzle is 1 inch and its discharge coefficient may be taken as unity.

Problem 15 

A pitot tube with U-tube water manometer is attached to a horizontal oil pipe of 4 in. inside diameter. If the manometer reading is 15 in., deter mine the volumetric flow rate, in gpm, of oil in the pipe. The pitot opening is placed at the center of the pipe. The oil has a specific gravity of 0.84 and a viscosity of 0.0336 lb/ft-s.

Problem 16 

A sharp edged orifice is to be fabricated to measure water flowing at a rate not to exceed 1,200 cu.ft per hour, with a differential head of 10 ft. What orifice diameter in inches is required if D2/D1 is made 1/5.

Problem 17 

A sharp edged orifice with diameter of 0.0566 m is installed in a 0.1541 m pipe thru which oil with density of 878 kg/m3 and viscosity of 4.1 cP is flowing. The measured pressure difference across the orifice is 93.2 kN/m2. What is the power requirement for this meter?

Problem 18 

The pressure after the pump in a 6-inch inside diameter smooth pipe conducting water is 20 psia. The water is discharged at an open tank 100 ft. from the pump. Calculate the rate of discharge of water in ft3/s.

Problem 19 

Water at 40 deg F is to flow thru 1000 ft horizontal iron pipe at 150 gpm. A head of 20 ft is available. The pipe to be used is A) 1” SCH 40 B) 2” SCH 40 C) 3” SCH 40 D) 4” SCH 40

Problem 20 

Calculate the radius of the capillary tube in mm, such that it is a flow of a viscous fluid

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Kinematic Viscosity = 0.000043 m2/s

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Length of tube = 50.2 cm

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Mass flow rate = 0.003 kg/s

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Density of fluid = 955 kg/m3

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Pressure drop = 4.77 atm

Problem 21 Predict ΔP/100m [bar] of the 10” steam line below. Assume 25 mm/1 inch for inside diameter determination (nominal pipe size).

Fluid Flow Predict ΔP/100m [bar] of the Cooling water line after increasing the capacity. Assume 25 mm/1 inch for inside diameter determination (nominal pipe size). 

Original Design

24”, 2,700 t/h, 998 kg/m^3, ΔP/100m = 0.0746 bar 

Capacity Up

24”, 3,200 t/h, 998 kg/m^3, ΔP/100m =?

Problem 22 

Calculate the fluid velocity [m/s] inside pipe.

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Steam

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P = 7 bar, T = 180 deg C

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Flow = 12500 kg/h

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Density = 4.052 kg/m^3

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Pipe is 10” SCH 40

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Outside diameter of 10” pipe = 273.1 mm

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Tube wall thickness of 10” SCH 40 = 9.3 mm

NPSH 

Net Positive Suction Head (NPSH): is the excess pressure (in terms of liquid height) at the pump suction nozzle over the vapor pressure of the liquid being pumped. Two values of NPSH must be considered; i.e., NPSHA and NPSHR described as follows.

NPSHA 

NPSH available (NPSHA): is the NPSH given by actual system characteristics such as height of equipment, friction heads, and physical properties. In order to avoid cavitation and damage of pump, NPSHA must always be equal to or exceed the NPSHR for the particular pump at the desired flow rate.

NPSHR 

NPSH required (NPSHR): Each pump impeller design has a characteristic suction head requirement over the vapor pressure of the liquid. This characteristic, termed NPSHR is given on manufacturers’ performance curves for each pump.

Problem 23 You are in the field-piping area of a refinery, without a calculator or friction factor chart, doing an inspection with your manager. The flow through pipe A is always fully turbulent. While you are watching the gauges on pipe A, which read pressure drop through the length of the pipe, the pressure increases by a factor of two. Your manager wants to know what is happening. You know that no valves are closed downstream, and the density and viscosity remain unchanged. In five seconds you figure out the flow rate increase. What do you tell your manager? a) Tell your manager, “The flow increased by 20%.” b) Tell your manager, “The flow increased by 40%.” c) Tell your manager, “The flow increased by 80%.” d) Tell your manager, “The flow increased by 100%.”

Problem 24 Water is flowing under fully turbulent flow in a pipe. If the diameter of the pipe is lowered by 10%, what will be the effect on pressure drop for the same flow rate? a) Increase by 10%

c) Increase by 59.05%

b) Increase by 21%

d) Increase by 69.35%

Problem 25 

In an effort to increase the flow rate of a Newtonian liquid, the supply pressure is increased by 40% in a pipe. Assuming fully turbulent flow before and after the increase of pressure, and no change in density or viscosity, what will be the % increase in flow?

a)12

b) 18

c) 24

d) 30

Problem 26 

Calculate the head loss in a pipe 1/4 in. in diameter and 16 ft long, when the water flows at half the critical velocity. The critical velocity occurs when the Reynolds number is 2500. Take viscosity = 0.679 x 10^(-3) lbm/ft-s and density = 62.4 lbm/ft3. Express answer in feet of water (in 2 decimal places).

a)0.26

b)0.36

c) 0.46

d) 0.56

Problem 27 

Honey flows through a pipe with Reynolds Number < 10. The honey is heated to a temperature at which its viscosity decreases to one-half its original value. What effect will the heating have on the friction pressure drop in the pipe?

a) The pressure drop decreases by one-half. b) The pressure drop increases by one-half. c) The pressure drop decreases by one-fourth. d) The pressure drop increases by one-fourth.

Problem 28 

Water at 68˚F is pumped at a constant rate of 5 cubic feet per minute from a supply tank resting on the floor to the top of an experimental absorber. The point of discharge is 15’ above the floor, and the frictional loss in the 2” schedule-40 pipe are estimated to be 0.8’. At what height in the supply tank must the water level be kept if the pump can develop only 1/8 net horsepower.

For SCH-40 2-inch pipe, 1 ft/s = 10.45 gpm I.D. = 2.067 in. A = 0.0233 ft^2 a) 1.8 ft

b) 2.8 ft

c) 3.8 ft

d) 4.8 ft

Problem 29 Calculate the steam velocity (m/s) inside pipe. Pipe is 10” SCH 40. Outside diameter of 10” pipe = 273.1 mm Tube wall thickness of 10” SCH 40 = 9.3 mm Pressure = 7.00 bar Temperature = 180˚C Density = 4.052 kg/m^3 Flow rate = 12,500 kg/h a) 15 b) 16 c) 17 d) 18 

Problem 30 

A 1” diameter smooth tube 1000’ long is carrying a product with a viscosity of 25 centipoise and a density of 55 pcf at an average velocity of 7.33’ per second. Due to a production change, the product viscosity will be decreased to 12.5 centipoise with no change in density. What will be the percentage change in the pump horsepower needed to overcome the friction losses in the smooth tube for the same flow? Hint: the increase in horsepower is proportional to f.

Problem 31 Fluid is flowing through a 5-mile length of 4” schedule-40 (I.D. = 4.026 in.) steel pipe with an average linear velocity of 10’ per second. Assume that the pipeline is well insulated to prevent heat loss from the surroundings. The constant liquid properties are density = 62.4 pounds per cubic foot; viscosity = 4.35 centipoise; and specific heat = 0.2 BTU/lbm-˚F.

Problem 31 

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Calculate the Reynolds number a) 51,600 b) 61,600

c) 71,600

d) 81,600

Calculate the fanning friction factor a) 5.2786 x 10^-3 b) 6.2786 x 10^-3 c) 7.2786 x 10^-3 d)8.2786 x 10^-3 Calculate the head loss due to skin friction a) 5580 ft c) 3580 ft b) 4580 ft d) 2580 ft

Problem 31 

Calculate the heat lost in BTU/lbm

a) 7.17 

b) 5.89

c)3.32

d)4.60

Calculate the temperature rise of the liquid over the 5-mile section

a)16.6˚F

b)29.45˚F c)35.9˚F

d)23˚F

Problem 32 

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Calculate the Friction Factor (f) with two methods under the below conditions using f = 0.0637*NRe^(-0.21) Fluid: Steam Temperature = 170 deg C Inlet Pressure: P1 = 4.00 kg/m^3 Flow Rate = 10,000 kg/h Density = 2.503 kg/m^3 Viscosity = 0.0148 x 10^(-3) Pa-s Wall thickness = 9.5 mm Pipe: 12” SCH 40 (tube OD = 323.9 mm) Surface Roughness e = 0.100 mm