Fluid Flow 58c7

FLOW OF FLUIDS

NATURE OF FLUIDS

Question No.1 A fluid is one which a. cannot remain at rest under the action of shear force b. continuously expands till it fills any container c. is incompressible d. permanently resists distortion

A

Question No.2 In an incompressible fluid density a. is greatly affected by moderate changes in pressure b. is greatly affected only by moderate changes in temperature c. remains unaffected with moderate change in temperature and pressure d. is sensible to changes in both temperature and pressure

C

VISCOSITY

Question No.3 Dimension of viscosity is a. ML-1T-1 b. MLT-1 c. MLT-1T d. MLT

A

Question No.4 Poise is converted into stoke by a. multiplying with density (g/cc) b. dividing with density (g/cc) c. multiplying with specific gravity d. dividing with specific gravity

A

Question No.5 Dimension of kinematic viscosity is a. ML-2 b. L2T-1 c. L2T d. L2T2

C

Question No.6 With increase in the temperature viscosity of a liquid a. increase b. decreases c. remains constant d. first decreases and then increases

B

Question No.7 For water, when the pressure increases the viscosity a. also increases b. decreases c. remains constant d. first decreases and then increases

D

Question No.8 A certain oil is 100 times more viscous than water at 25 0C. Its viscosity is a. 0.001 Pa-s b. 0.01 Pa-s c. 0.10 Pa-s d. 1 Pa-s

C

PRESSURE

Question No.9 Choose the set of pressure intensities that are equivalent a. 4.33 psi, 10 ft. of water, 8.83 inches of Hg. b. 4.33 psi, 10 ft. of water, 20.7 inches of Hg. c. 10 psi, 19.7 ft. of water, 23.3 inches of Hg. d. 10 psi, 19.7 ft of water, 5.3 inches of Hg.

A

Question No.10 The absolute pressure exerted by water 2 m below the surface of a swimming pool is a. 20 kPa b. 200 kPa c. 150 kPa d. none of these

D

LAMINAR AND TURBULENT FLOW

Question No.11 The dimensionless number that characterizes the flows of fluid in a conduit a. Nusselt number b. Grashof number c. Peclet number d. Reynolds number

D

Question No.12 Turbulent flow generally occurs for cases involving a. very viscous fluid b. very narrow ages for capillary tube c. very slow motions d. none of these

D

Question No.13 Oil with a viscosity of 30 and a density of 60 lb/ft3 flows through a 1/2 inch inside diameter pipe. Determine the velocity in ft/s below which flow will be laminar. a. 87.20 b. 13.10 c. 0.63 d. 16.90

D

Question No.14 The value of critical Reynolds number for pipe flow is a. 1300 b. 10,000 c. 100,000 d. none of these

A

Question No.15 Reynolds number flow of water at room temperature through 2 cm diameter pipe at average velocity of 5 cm/sec is around a. 2000 b. 10 c. 100 d. 1000

D

Question No.16 Water at 80 0F is flowing through a straight 4 inch SCH 40 pipe at a rate of 1 gpm. The length of the pipe is 10 ft. What is the maximum velocity of water in the pipe? a. 0.0504 fps b. 0.0354 fps c. 0.0454 fps d. 0.0254 fps

CONTINUITY EQUATION

Question No.17 A fluid flowing at a rate of 25 cubic meters per hour in a 60 mm inside diameter pipe has an average velocity in m/s equals to a. 5.9 b. 1.5 c. 2.5 d. 0.6

C

Question No.18 What is the hydraulic diameter of a rectangular duct with dimensions 6 inches by 12 inches? a. 8 inches b. 10.63 inches c. 10 inches d. 11.86 inches

A

Question No.19 Benzene flows through a 100 mm-diameter pipe at a mean velocity of 3 m/s. Find the (a) volume flow rate (b) weight flow rate, and (c) mass flow rate. ρ=879 kg/m3

0.0236 m3/s, 203.17 N/s and 20.71 kg/s

Question No.20 Water at 20 0C flows steadily through the nozzle at 50 kg/s. The diameters are D1 = 20 cm and D2 = 6 cm. compute the average velocities at sections 1 and 2. Density of water at 20 0C is 998 kg/m3.

1.59 m/s and 17.72 m/s

Question No.21 In an air pipeline, the flow has the following conditions at section 1: 25 0C, 1.8 bar, 15 m/s velocity, and 50 mm inside diameter of pipe. At section 2 the conditions are: 25 0C, 1.3 bar, and 75 mm inside diameter of pipe. Calculate the mass flow rate of air and the velocity at section 2.

OVER-ALL ENERGY BALANCE

Question No.22 What is the enthalpy of the steam at 150 psia and 400 0F? a. 1275 BTU/lb b. 1195.2 BTU/lb c. 1250 BTU/lb d. 1220 BTU/lb

Question No.23 Air expands adiabatically through a nozzle from a negligible initial velocity to a final velocity of 325 m/s. What is the temperature drop of the air if air is assumed to be ideal gas for which = 7/2 R?

Question No.24 Steam enters a turbine operating at steady state at 600 0F and 200 psia (H = 1322.1 BTU/lb). The inlet velocity is 80 fps and leaves as saturated vapor at 5 psia and velocity = 300 fps. The power developed by the turbine is 200 hp. Heat loss to the surroundings is 50000 BTU/hr. What is the mass flowrate of steam in kg/s?

Question No.25 A small steam turbine delivers 100 hp at the turbine shaft when the steam flows is 3600 lb/hr. The steam enters the turbine at 150 psia and 440 0F with a velocity of 100 ft/s. Steam leaves the turbine as wet steam 2 in Hg abs with a quality of 92% and at a velocity of 300 ft/s. Calculate the heat loss from the turbine in kW.

Question No.26 Air is flowing at a steady rate of 0.0232 lb/s through a straight line having an inside diameter of 0.902 in. At the first section the air has a temperature of 0.902 0F and is under an absolute pressure of 0.2 atm. The tube is heated, and the net input of power, between the first and second section, is 174 watts. The air at the second section is under an absolute pressure of 0.1 atm. The average specific heat of the air is 0.24 BTU/lb-0F. Calculate the temperature of the air leaving the second section.

MECHANICAL ENERGY BALANCE

Question No.27 Which of the following statement is not true? a. Potential flow is a flow of compressible fluids with no shear. b. Boundary layers are formed when moving fluid is influenced by solid boundaries. c. There are 8 schedule numbers in use for standard pipes. d. Roughness has no appreciable effect on the friction factor when flow is laminar.

C

Question No.28 Frictional losses through valves, fittings, bends and contractors are commonly regarded as proportional to a. pressure drop b. velocity head c. static head d. potential head

B

Question No.29 The differential height between two points where a fluid has to be transferred is the a. potential head b. velocity head c. pressure head d. dynamic head

A

Question No.30 A viscous fluid flows through a pipe with Re<100. If this liquid is heated to a temperature at which is viscosity decreases to 1/2 its original value, what will be the effect of pressure drop in the pipe? a. the pressure drop increases by 50 % b. the pressure drop increase by 100 % c. the pressure drop decreases by 50 % d. the pressure drop decreases by 100 %

C

Question No.31 When the flow is laminar a. the pressure drop is proportional to the first power of the velocity. b. the pressure drop is proportional to the square of the velocity. c. the pressure drop is inversely proportional to the velocity. d. the pressure drop is not affected by the velocity.

A

Question No.32 When the ID of the pipe through which a fluid flows is doubled, the pressure loss due to friction per unit length of pipe for the same volumetric flow rate is changed by approximately a factor of a. 1/8 b. 1/32 c. 1/16 d. 1/64

Question No.33 The pressure drop of a pipeline increase by a factor of ___ when the velocity of the flowing fluid is doubled. a. 1/2 b. 2 c. 1 d. 4

Question No.34 Water at 60 0F is flowing through a 3 inch inside diameter smooth pipe. If the Reynolds number is 3.5 x104, the pressure drop in psi per foot length of pipe is a. 1.17 b. 0.017 c. 0.17 d. 0.0017

Question No.35 In a certain chemical plant, the carbonate solution used in the absorption tower is pump continuously from the bottom of the lye storage tank through a standard 4 in pipe and then through the spray head at the top of the scrubber. The depth of solution in the tank is 5 ft and the vertical distance from the bottom of the tank to the spray head is 105 ft. In a test on this equipment the following data were obtained; Rate of flow = 200 gpm, Specific gravity = 1.10; Friction drop from tank to spray head = 15 ftlb/lb; Gage pressure on spray head =5 psi; Power input to the pump= 15 hp. Calculate the efficiency of the pump.

Question No.36 A steel pipe having an inside diameter of 13.25 inches is to be designed to carry 48 bbl of oil per 24 hr day from a mid-continent field to a refinery located 578 miles from the source. The difference in elevation of the two ends of the line is negligible. Calculate the horsepower theoretically required to overcome friction in the pipeline. Since the maximum allowable pressure in any section of the line is 650 lb/in2, it will be necessary to insert additional pumping stations at suitable intervals along the pipeline. What is the smallest number of pumping stations required? At the average temperature involved, the oil has an absolute viscosity of 50 and a specific gravity of 0.87.

Question No.37 A town derives its water supply from a lake nearby, pumping it up to a standpipe on the highest hill. The intake to the system is 10 ft below the lake surface, the inlet to the pump is 15 deep above the lake surface, and the water level in the tower is kept constant 310 ft above the pump discharge. The friction loss is 140 ft-lb/lb of water through the 6000 feet of 4-inch pipe line which includes the total equivalent length of all piping from the lake to the water tower. If the pump capacity is 6000 gph and the water pump set is 85% efficient, what would be the hourly pumping cost if electric power is 1 cent per kilowatt-hour?

COMPRESSIBLE FLUIDS

Question No. A natural gas at 600F is flowing at a steady mass rate through a steel main having an inside diameter of 12 inches. The absolute pressure drops from 40 to 20 atm, in a length of 500 miles of substantially horizontal pipe, the gas has an average molecular weight of 17.3 and a viscosity of 0.011 . Calculate the hourly rate of flow expressed as ft3measured at 600F and normal barometric pressure.

PUMPS AND COMPRESSOR

Question No. A pump delivers 40 gpm of water with a total head of 40 ft. The efficiency of the pump is 65 %. What is its BHP? a. 0.62 b. 2.00 c. 0.70 d. 5.50

0.62

Question No. If the suction pressure is less than or is only slighter greater than the vapor pressure of the liquid being pumped, some of the liquid may be flash inside the pump. This phenomenon is called a. flash vaporization b. condensation c. cavitation d. evaporation

C

Question No. Pumps used in pumping moderately viscous and viscous fluids. a. centrifugal pumps b. piston pumps c. gear pumps d. diaphragm pumps

C

Question No. The head developed by an ideal centrifugal pump is directly proportional to the a. square of the impeller speed b. square root of the impeller speed c. volumetric flowrate d. cube of the volumetric flowrate

B

Question No. A pump delivering 500 GPM at 1150 RPM and 50 ft head requires 10 hp. What will be its capacity if its speed is increased to 1750 RPM?

760 GPM

Question No. Calculate the theoretical horsepower required to compress 100 cfm of carbon dioxide at -60 0F and 1 atm to 10 atm in a single stage adiabatic compressor. Use /Cv = 1.3

Question No. A water storage tank supplies water into a factory. Water is supplied to the tank through a booster pump installed in the water line. The theoretical pump horsepower required is 3.25 hp. What is the monthly operating cost of the pump, if electrical power cost on the average is P 3.73/kWh? The pump is 65% efficient and operates for 12 hours a day. a. P 3300 b. P 5000 c. P 7000 d. none of these

B

METERING OF FLUIDS

Question No. Which valve is used accurately to regulate the flow of liquids and gases at low flowrates? a. Check valve b. Needle Valve c. Ball valve d. Globe valve

C