SAMPLE PROBLEMS: Fluid Mechanics Taken From: Taken From: Richardson, J. H., et al, COULSON & RICHARDSON: CHEMICAL ENGINEERING, Volumes 1 & 3, 5th edition, Butterworth-Heinemann ©2002
PART 1 _____ 1. Water is contained in the basket of a centrifuge of 0.5 m internal diameter, rotating at 50 revolutions per second. If the inner radius of the liquid is 0.15 m, what is the pressure at the walls of the basket? a. 4.94 x 105 Pa b. 1.97 x 106 Pa c. 11.2 x 106 Pa d. none of these _____ 2. A free vortex exists in the following excepta. Outside the impeller of a centrifugal pump b. In a cyclone separator or hydrocyclone c. Inside the region of the agitator in a stirred tank d. In liquid flowing round a bend in a pipe _____ 3. The angular velocity of the liquid in a ____ vortex is maintained constant by mechanical means, like in an agitator rotating in the liquid or by rotation in the basket of a centrifuge. a. Forced b. free c. impulsive d. none of these _____ 4. Which of the following is true? a. The forced vortex tends to decay into a free vortex. b. The free vortex tends to decay into a forced vertex. c. Forced vortex occurs in the flow of liquid into a drain, as in a sink or bath d. All of these _____ 5. It is characterized by the rapid movement of fluid as eddies in random directions across a tube. a. Laminar flow b. streamline flow c. turbulent flow d. boundary layer flow _____ 6. In a turbulent layer, there is a thin region near the surface where the flow remains laminar, and this is known asa. turbulent sub-layer b. laminar sub-layer c. boundary flow sub-layer d. none of these _____ 7. Ninety-eight per cent sulfuric acid (viscosity = 25 x 10-3 N s/m2, density = 1840 kg/m3) is pumped at 1.25 kg/s through a 25 mm diameter pipe, 30 m long, to a reservoir 12 m higher than the feed point. Calculate the pressure drop in the pipeline. Use mild steel pipe as the pipe. a. 320 kPa b. 240 kPa c. 480 kPa d. 560 kPa _____ 8. Water flows in a 50 mm pipe, 100 m long, whose relative roughness is equal to 0.013 mm. If the pressure drop across this length of pipe is not to exceed 50 kPa, what is the maximum allowable water velocity? The density and viscosity of water is 1000 kg/m3 and 1 cP, respectively. a. 1.0 m/s b. 1.6 m/s c. 0.1 m/s d. 6.1 m/s _____ 9. The velocity at any point in the cross-section is proportional to the one-seventh power of the distance from the walls if the shear stress is in accordance to Blasius equation. This equation is also known asa. Blausius one-seventh power rule c. Prandtl one-seventh power rule b. Moody one-seventh power rule d. none of these
_____ 10. Water flows at 7.2 m3/hr through a sudden enlargement from a 40 mm to a 50 mm diameter pipe. What is the loss in head? a. 759 mm b. 165 mm c. 561 mm d. 957 mm _____ 11. Ninety eight percent of sulfuric acid of viscosity 0.025 N s/m2 and density 1840 kg/m3 is pumped at 685 cm3/s through a 25 mm line. Calculate the value of the Reynolds number. a. 2572 b. 2752 c. 7522 d. 5272 _____ 12. Calculate the ideal available energy produced by the discharge to atmosphere through a nozzle of air stored in a cylinder of capacity 0.1 m3 at a pressure of 5 MN/m2. The initial temperature of the air is 290 K and the ratio of the specific heats is 1.4. a. -480 kJ b. +480 kJ c. -840 kJ d. +840 kJ _____ 13. Calculate the energy stored in 1000 cm3 of gas at 80 MN/m2 at 290 K using STP as the datum. a. +47.7 kJ b. -47.7 kJ c. -74.4 kJ d. +74.4 kJ _____ 14. Calculate the hydraulic mean diameter of the annular space between a 40 mm and a 50 mm tube. a. 10 mm b. 45 mm c. 40 mm d. 22.5 mm _____ 15. 0.015 m3/s of acetic acid is pumped through a 75 mm diameter horizontal pipe 70 m long. What is the pressure drop in the pipe? Viscosity of acid = 2.5mNs/m2, density of acid = 1060 kg/m3, and roughness of pipe surface = 6x10-5 m. a. 511 kPa b. 115 kPa c. 246 kPa d. 426 kPa _____ 16. Find the drop in pressure due to friction in a glazed porcelain pipe 300 m long and 150 mm diameter when water is flowing at the rate of 0.05 m3/s. a. 1 MPa b. 2 MPa c. 3 MPa d. 4 MPa _____ 17. Calculate the pressure drop when 3 kg/s of sulphuric acid flows through 60 m of 25 mm pipe (density = 1840 kg/m3, viscosity 0.025 N s/m2). a. 500 kPa b. 700 kPa c. 800 kPa d. 900 kPa _____ 18. A heat exchanger is to consist of a number of tubes each 25 mm diameter and 5 m long arranged in parallel. The exchanger is to be used as a cooler with a rating of 4 MW and the temperature rise in the water feed to the tubes is to be 20 deg K. If the pressure drop over the tubes is not to exceed 2 kN/m2, calculate the minimum number of tubes that are required. Assume that the tube walls are smooth and that entrance and exit effects can be neglected. Viscosity of water = 1mNs/m2. a. 20 tubes b. 42 tubes c. 84 tubes d. 116 tubes ______ 19. Sulfuric acid is pumped at 3 kg/s through a 60 m length of smooth 25 mm pipe. Calculate the drop in pressure. Density of acid = 1840 kg/m3. Viscosity of acid = 25 mN s/m2. a. 480 kPa b. 840 kPa c. 620 kPa d. 260 kPa
______ 20. In problem # 19, If the pressure drop falls by one half, what will be the new flow rate? a. 8.61 kg/s b. 1.68 kg/s c. 1.86 kg/s d. 16.8 kg/s ______ 21. Oil with a viscosity of 10 mNs/m2 and density 900 kg/m3 is flowing through a 500 mm diameter pipe 10 km long. The pressure difference between the two ends of the pipe is 106 N/m2. What will the pressure drop be at the same flow rate if it is necessary to replace the pipe by one only 300 mm in diameter? Assume the pipe surface to be smooth. a. 9.11 x 107 Pa b. 11.9 x 107 Pa c. 1.19 x 107 Pa d. 91.1 x 107 Pa ______ 22. A pipeline 0.5 m diameter and 1200 m long is used for transporting an oil of density 950 kg/m3 and of viscosity 0.01 Ns/m2 at 0.4m3/s. If the roughness of the pipe surface is 0.5 mm, what is the pressure drop? a. 1.3 x 105 Pa b. 3.1 x 105 Pa c. 7.2 x 105 Pa d. 2.7 x 105 Pa _____ 23. With the same pressure drop, what will be the flow rate of a second oil of density 980 kg/m3 and of viscosity 0.02 Ns/m2? a. 0.34 m3/s b. 4.30 m3/s c. 3.4 m3/s d. 0.43 m3/s _____ 24. A venturi meter with a 50 mm throat is used to measure a flow of slightly salt water in a pipe of inside diameter 100 mm. The meter is checked by adding 20 cm3/s of normal sodium chloride solution above the meter and analyzing a sample of water downstream from the meter. Before addition of the salt, 1000 cm3 of water requires 10 cm3 of 0.1 M silver nitrate solution in a titration. 1000 cm3 of the downstream sample required 23.5cm3 of 0.1 M silver nitrate. If a mercury-under-water manometer connected to the meter gives a reading of 221 mm, what is the discharge coefficient of the meter? Assume that the density of the liquid is not appreciably affected by the salt. a. 0.982 b. 0.289 c. 0.829 d. 0.928 _____ 25. Air, at 1500 kN/m2 and 370 K, flows through an orifice of 30 mm2 to atmospheric pressure. If the coefficient of discharge is 0.65, the critical pressure ratio 0.527, and the ratio of the specific heats is 1.4, calculate the mass flow rate in kilograms per second. a. 0.015 b. 0.061 c. 0.512 d. 1.060 _____ 26. In the rotational motion of a fluid, the angular velocity is a constant and is independent of the radius of the vortex formation is described asa. Forced b. free c. impulsive d. none of these _____ 27. Which of the following is NOT a result of the formation of forced vortex? a. The movement of liquid within the impeller of a centrifugal pump when there is no flow as, for example, when the outlet valve is closed. b. The rotation of liquid within the confines of a stirrer in an agitated tank. c. The rotation of liquid in the basket of a centrifuge. d. None of these _____ 28. Shear thinning liquids. a. pseudoplastic b. Bingham plastic
c. dilatants liquid
d. Newtonian
_____ 29. Shear thickening liquids. a. pseudoplastic b. Bingham plastic
c. dilatants liquid
d. Newtonian
_____ 30. A model used to describe the viscosity of non-Newtonian liquids. a. Newton’s Law of viscosity c. Ostwald de Waele Law b. Martina’s Law of consistency d. none of these _____ 31. A pump is designed to be driven at 10 Hz and to operate at a maximum efficiency when delivering 0.4 m3/s of water against a head of 20 m. Calculate the specific speed. a. 0.211 b. 0.121 c. 0.112 d. none of these _____ 32. In problem #31, what type of pump does this value suggest? a. centrifugal pump c. positive-displacement pump b. radial pump d. none of these _____ 33. In problem #31, a pump built for these operating conditions has a measured overall efficiency of 70%. The same pump is now required to deliver water at 30 m head. At what speed should the pump be driven if it is to operate at maximum efficiency? a. 12.24 Hz b. 24.21 Hz c. 42.12 Hz d. 14.22 Hz _____ 34. In problem #33, What will be the power required? a. 260 W b. 62 W c. 620 W
d. 206 W
_____ 35. A centrifugal pump is to be used to extract water from a condenser in which the vacuum is 640 mm of mercury. At the rated discharge, the net positive suction head must be at least 3 m above the cavitation vapor pressure of 710 mm mercury vacuum. If losses in the suction pipe account for a head of 1.5 m, what must be the least height of the liquid level in the condenser above the pump inlet? a. 5.33 m b. 3.55 m c. 1.77m d. 7.17 m _____ 36. 1250 cm3/s of water is to be pumped through a steel pipe, 25 mm diameter and 30 m long, to a tank 12 m higher than its reservoir. Calculate the approximate power required. Viscosity of water = 1.30 mN s/m2. Density of water = 1000 kg/m3. a. 752 W b. 275 W c. 496 W d. 649 W _____ 37. 60% sulfuric acid is to be pumped at the rate of 4000 cm3/s through a lead pipe 25 mm diameter and raised to a height of 25 m. The pipe is 30 m long and includes two rightangled bends. Calculate the theoretical power required. The density of the acid is 1531 kg/m3 and its kinematic viscosity is 4.25 x 10-5 m2/s. The density of water may be taken as 1000 kg/m3. a. 11 kW b. 22 kW c. 33 kW d. 44 kW _____ 38. In a stationary fluid the pressure is exerted equally in all directions and is referred to asa. gauge pressure b. static pressure c. absolute pressure d. may pressure _____ 39. In a moving fluid, the ____ is exerted on any plane parallel to the direction of motion. a. gauge pressure b. static pressure c. absolute pressure d. may pressure
_____ 40. With this instrument, a small element of fluid is brought to rest at an orifice situated at right angles to the direction of flow. The velocity measured here is a small filament of fluid. a. Nozzle b. pitot tube c. orifice meter d. venturi meter _____ 41. With this instrument, the fluid is accelerated at a sudden constriction, known as the orifice, and the pressure developed is then measured. This is a relatively cheap and reliable instrument though the overall pressure drop is high because most of the kinetic energy of the fluid at the orifice is wasted. a. Nozzle b. pitot tube c. orifice meter d. venturi meter _____ 42. With this instrument, the fluid is gradually accelerated to a throat and gradually retarded as the flow channel is expanded to the pipe size. A high proportion of the kinetic energy is thus recovered but the instrument is expensive and bulky. a. Nozzle b. pitot tube c. orifice meter d. venturi meter _____ 43. With this instrument, the fluid is gradually accelerated up to the throat of the instrument but expansion to pipe diameter is sudden as with an orifice. This instrument is again expensive because of the accuracy required over the inlet section. a. Nozzle b. weir c. orifice meter d. venturi meter _____ 44. With this instrument, the fluid flows over it so that its kinetic energy is measured by determining the head of the fluid flowing above it. This instrument is used in open-channel flow and extensively in tray towers where its height is adjusted to provide the necessary liquid depth for a given flow. a. Nozzle b. weir c. orifice meter d. venturi meter _____ 45. Water flows through an orifice of 25 mm diameter situated in a 75 mm diameter pipe, at a rate of 300 cm3/s. What will be the difference in level on a water manometer connected across the meter? The viscosity of water is 1 cP. a. 51 mm water c. 15 mm water b. 26 mm water d. 62 mm water _____ 46. The rate of flow of water in a 150 mm diameter pipe is measured with a venturi meter with a 50 mm diameter throat. When the pressure drop over the converging section is 121 mm of water, the flow rate is 2.91 kg/s. What is the coefficient for the converging cone of the meter at this flow rate? a. 0.986 b. 0.786 c. 0.985 d. 0.785 _____ 47. An instrument wherein the tube contains a freely moving float which rests on a stop at the base of the tube. a. Venturi meter b. Bourdon gauge c. rotameter d. viscometer _____ 48. A rotameter tube is 0.3 m long with an internal diameter of 25 mm at the top and 20 mm at the bottom. The diameter of the float is 20 mm, its density is 4800 kg/m3 and its volume is 6.0 cm3. If the coefficient of discharge is 0.7, what is the flow rate of water (density 1000 kg/m3) when the float is halfway up the tube? a. 0.072 kg/s b. 0.502 kg/s c. 0.027 kg/s d. 0.205 kg/s
______ 49. Water flows in an open channel across a weir which occupies the full width of the channel. The length of the weir is 0.5 m and the height of water over the weir is 100 mm. What is the volumetric flow rate of water? a. 0.01 m3/s b. 0.02 m3/s c. 0.03 m3/s d. 0.04 m3/s ______ 50. An organic liquid flows across a distillation tray and over a weir at the rate of 15 kg/s. The weir is 2 m long and the liquid density is 650 kg/m3. What is the height of liquid flowing over the weir? a. 22 mm b. 33 mm c. 44 mm d. 55 mm PART 2 ____ 1. Water leaves the 25 mm diameter nozzle of a fire hose at a velocity of 25 m/s. What will be the reaction force at the nozzle which the fireman will need to counterbalance? a. 307 N b. 703 N c. 902 N d. 209 N ____ 2. Water is flowing at 5 m/s in a 50 mm diameter pipe which incorporates a 90° bend, as shown. What is the additional force to which a retaining bracket will be subjected, as a result of the momentum changes in the liquid, if it is arranged symmetrically in the pipe bend? a. 49.6 N b. 69.4 N c. 46.9 N d. 64.9 N _____ 3. ChE Board Exam, Nov. 2011. Water at a rate of 2.27 m3/h and at 320 K is pumped in a 40 mm inside diameter pipe through a distance of 150 m in a horizontal direction and then up through a vertical height of 10m. In the pipe there is a control valve for which the friction loss may be taken as equivalent to 200 pipe diameters and also other pipe fittings equivalent to 60 pipe diameters. Also in the line is a heat exchanger across which there is a loss in head of 1.5 m of water. If the main pipe has a roughness of 0.2 mm, what power must be supplied to the pump if it is 60 per cent efficient? a. 0.136 kW b. 0.245 kW c. 0.527 kW d. 2.27 kW _____ 4. This represents the work which must be done in order to introduce the fluid, without change in volume, into the system. It is therefore given by the product Pv, where P is the pressure of the system and v is the volume of unit mass of fluid. a. pressure energy b. internal energy c. potential energy d. kinetic energy _____ 5. Water flows from a tap at a pressure of 250 kN/m2 above atmospheric. What is the velocity of the jet if frictional effects are neglected? a. 10.3 m/s b. 15.6 m/s c. 22.4 m/s d. 24.7 m/s ____ 6. ChE Board Exam, Nov. 2012. Six thousand liters per second (600 L/s) of water at 320 K is pumped in a 40 mm inside diameter pipe through a length of 150 m in a horizontal direction and up through a vertical height of 10 m. In the pipe there is a control valve which may be taken as equivalent to 200 pipe diameters and other pipe fittings equivalent to 60 pipe diameters. Also in the line there is a heat exchanger across which there is a loss in head of 1.5 m of water. If the main pipe has a roughness of 0.0002 m, what power must be delivered to the pump if the unit is 60% efficient? a. 218 W b. 128 W c. 521 W d. 512 W
____ 7. Crude oil is pumped from a terminal to a refinery through a 0.3 m diameter pipeline. As a result of frictional heating, the temperature of the oil is 20 deg K higher at the refinery end than at the terminal end of the pipe and the viscosity has fallen to one half its original value. What is the ratio of the pressure gradient in the pipeline at the refinery end to that at the terminal end? Viscosity of oil at terminal = 90 mNs/m2. Density of oil (approximately constant) = 960 kg/m3. Flow rate of oil = 20,000 tonne/day. a. 0.50 b. 0.60 c. 0.70 d. 0.80 ____ 8. It is defined as the ratio of the increase of stress within the fluid and the resulting volumetric strain. a. Young’s modulus b. Poisson’s ratio c. Bulk’s modulus d. compressibility ____ 9. ChE Board Exam, Nov. 2012. Hydrogen is pumped from a reservoir at 2 MN/m2 pressure through a clean horizontal mild steel pipe 50 mm diameter and 500 m long. The downstream pressure is also 2 MN/m2 and the pressure of this gas is raised to 2.6 MN/m2 by a pump at the upstream end of the pipe. The conditions of flow are isothermal and the temperature of the gas is 293 K. What is the flowrate? Viscosity of hydrogen = 0.009 mN s/m2 at 293 K. a. 0.312 kg/s b. 0.456 kg/s c. 0.213 kg/s d. 0.564 kg/s ____ 10. ChE Board Exam, Nov. 2012. In Problem #9, what is the effective rate of working of the pump? a. 113 W b. 311 W c. 133 W d. 331 W ____ 11. Lazal nozzles are famous to be called as ____. a. converging-diverging nozzles c. converging nozzles b. diverging nozzles d. none of these ____ 12. A vacuum distillation plant operating at 7 kN/m2 pressure at the top has a boil-up rate of 0.125 kg/s of xylene. Calculate the pressure drop along a 150 mm bore vapor pipe used to connect the column to the condenser. The pipe length may be taken as equivalent to 6 m, e/d = 0.002 and absolute viscosity = 0.01 mN s/m2. a. 70 Pa b. 80 Pa c. 90 Pa d. 100 Pa ____ 13. Sulfuric acid of density 1300 kg/m3 is flowing through a pipe of 50 mm, internal diameter. A thin-lipped orifice, 10 mm in diameter is fitted in the pipe and the differential pressure shown on mercury manometer is 0.1 m. Assuming that the leads to the manometer are filled with the acid, calculate the mass flow rate of acid. The coefficient of discharge of the orifice may be taken as 0.61, the density of mercury as 13,550 kg/m3 and the density of the water as 1000 kg/m3. a. 0.268 kg/s b. 0.862 kg/s c. 0.682 kg/s d. 0.286 kg/s ____ 14. In problem #13, find the approximate drop in pressure caused by the orifice. a. 10 kPa b. 12 kPa c. 14 kPa d. 16 kPa ____ 15. The rate of flow of water in a 150 mm diameter pipe is measured with a venturi meter with a 50 mm diameter throat. When the pressure drop over the converging section is 121 mm of water, the flow rate is 2.91 kg/s. What is the coefficient for the converging cone of the meter at this flow rate? a. 0.895 b. 0.598 c. 0.859 d. 0.985
____ 16. Air, at 1500 kN/m2 and 370 K, flows through an orifice of 30 mm2 to atmospheric pressure. If the coefficient of discharge is 0.65, the critical pressure ratio 0.527, and the ratio of the specific heats is 1.4, calculate the mass flow rate in kg/s. a. 0.061 b. 0.160 c. 0.016 d. 0.610 ____ 17. Water flowing at 1.5 L/s in a 50 mm diameter pipe is metered by means of a simple orifice of diameter 25 mm. What is the Reynolds number for the flow in the pipe? Density of water = 1000 kg/m3. Viscosity of water = 1 mN s/m2. a. 3.83 x 103 b. 3.83 x 104 c. 3.83 x 105 d. 3.83 x 106 ____ 18. From problem #17, if the coefficient of discharge of the meter is 0.62, what will be the reading on a mercury-under-water manometer connected to the meter? a. 29 mmHg b. 37 mmHg c. 73 mmHg d. 92 mmHg ____ 19. What size of orifice would give a pressure difference of 0.3 m water gauge for the flow of a petroleum product of density 900 kg/m3 at 0.05 m3/s in a 150 mm diameter pipe? (Assume CD = 0.6) a. 0.20 m b. 0.14 m c. 0.16 m d. 0.18 m ____ 20. A gas of molecular weight 44 kg/kmol, temperature 373 K and pressure 202.6 kN/m2 is flowing in a duct. A pitot tube is located at the centre of the duct and is connected to a differential manometer containing water. If the differential reading is 38.1 mm water, what is the velocity at the center of the duct? The volume occupied by 1 kmol at 273 K and 101.3 kN/m2 is 22.4 m3. a. 11.6 m/s b. 16.1 m/s c. 6.11 m/s d. 0.61 m/s ____ 21. A single-acting reciprocating pump has a cylinder diameter of 110 mm and a stroke of 230 mm. The suction line is 6 m long and 50 mm in diameter and the level of the water in the suction tank is 3 m below the cylinder of the pump. What is the maximum speed at which the pump can run without an air vessel if separation is not to occur in the suction line? The piston undergoes approximately simple harmonic motion. Atmospheric pressure is equivalent to a head of 10.36 m of water and separation occurs at an absolute pressure corresponding to a head of 1.20 m of water a. 0.765 Hz b. 0.675 Hz c. 0.567 Hz d. 1.567 Hz ____ 22. Which of the following is false about the advantages of using a centrifugal pump? a. It is simple in construction and can, therefore, be made in a wide range of materials. b. There is a complete absence of valves. c. It operates at low speed (up to 100 Hz) and, therefore, can be coupled directly to an electric motor. In general, the higher the speed the smaller the pump and motor for a given duty. d. It gives a steady delivery. ____ 23. Which of the following is FALSE about the disadvantages of using a centrifugal pump? a. It operates at a high efficiency over only a limited range of conditions: this applies especially to turbine pumps. b. It is not usually self-priming.
c. If a non-return valve is not incorporated in the delivery or suction line, the liquid will run back into the suction tank as soon as the pump stops. d. Very viscous liquids can be handled efficiently. ____ 24. A centrifugal pump is required to circulate a liquid of density 800 kg/m3 and viscosity 0.5 x 10-3 Ns/m2 from the reboiler of a distillation column through a vaporizer at the rate of 0.004 m3/s, and to introduce the superheated vapor above the vapor space in the reboiler which contains a 0.07 m depth of liquid. If smooth-bore 25 mm diameter pipe is to be used, the pressure of vapor in the reboiler is 1 kN/m2 and the Net Positive Suction Head required by the pump is 2 m of liquid, what is the minimum height required between the liquid level in the reboiler and the pump? a. 0.03 m b. 2.0 m c. 2.3 m d. 1.5 m ____ 25. The volume remaining in the cylinder after the forward stroke of the piston. a. clearance volume b. swept volume c. piston volume d. compressed volume ____ 26. A single-acting air compressor supplies 0.1 m3/s of air measured at, 273 K and 101.3 kN/m2 which is compressed to 380 kN/m2 from 101.3 kN/m2. If the suction temperature is 289 K, the stroke is 0.25 m, and the speed is 4.0 Hz, what is the cylinder diameter? Assuming the cylinder clearance is 4 per cent and compression and re-expansion are isentropic (y = 1.4). a. 0.113 m b. 0.0283 m c. 0.38 m d. 0.0264 m ____ 27. From problem #26, what are the theoretical power requirements for the compression? a. 17.1 kW b. 11.7 kW c. 7.11 kW d. 71.1 kW For numbers 28-31, Air at 290 K is compressed from 101.3 kN/m2 to 2065 kN/m2 in a two-stage compressor operating with a mechanical efficiency of 85 per cent. The relation between pressure and volume during the compression stroke and expansion of the clearance gas is PV1.25 = constant. The compression ratio in each of the two cylinders is the same, and the interstage cooler may be assumed 100 per cent efficient. If the clearances in the two cylinders are 4 per cent and 5 per cent respectively, calculate the following: _____ 28. the work of compression per kg of air compressed (kJ/kg) a. 345.5 b. 20.4 c. 293.7 _____ 29. isothermal efficiency a. 37% b. 20.4% 66.2% _____ 30. isentropic efficiency (y = 1.4). a. 110 % b. 115% d. 125% _____ 31. the ratio of the swept volumes in the two cylinders. a. 1.14 b. 4.41 c. 3.25
d. 252.3
c. 73%
d.
c. 120%
d. 2.35
_____ 32. An air-lift pump is used for raising 7.5 x 10-4 m3/s of a liquid of density 1200 kg/m3 to a height of 20 m. Air is available at a pressure of 450 kN/m2. Assuming isentropic compression of the air, what is the power requirement of the pump its efficiency is 30 per cent? (y = 1.4). Take the volume of 1 kmol of an ideal gas at 273 K and 101.3 kN/m2 as 22.4 m3. a. 0.733 kW b. 0.377 kW c. 0.844 kW d. 0.488 kW _____ 33. 2.16 m3/h (600 x 10-6 m3/s) water at 320 K is pumped through a 40 mm i.d. pipe, through a length of 150 m in a horizontal direction, and up through a vertical height of 10 m. In the pipe there are a control valve, equivalent to 200 pipe diameters, and other pipe fittings equivalent to 60 pipe diameters. Also in the line is a heat exchanger across which the head lost is 2 m water. Assuming the main pipe has a roughness of 0.0002 m. what power must be supplied to the pump if it is 60 per cent efficient? a. 135 W b. 315 W c. 425 W d. 524 W _____ 34. A twin-cylinder, single-acting compressor, working at 5 Hz, delivers air at 515 kN/m2 at the rate of 0.2 m3/s. If the diameter of the cylinder is 20 cm, the cylinder clearance ratio 5%, and the temperature of the inlet air 283 K, calculate the delivery temperature. a. 400 K b. 450 K c. 500 K d. 550 K _____ 35. In problem #34, calculate the length of stroke of the piston. a. 0.40 m b. 0.45 m c. 0.50 m
d. 0.55 m
_____ 36. A single-stage double-acting compressor running at 3 Hz is used to compress air from 110 kN/m2 and 282 K to 1150 kN/m2. If the internal diameter of the cylinder is 20 cm, the length of stroke 25 cm, and the piston clearance 5%, calculate the maximum capacity of the machine, referred to air at the initial temperature and pressure. a. 0.047 m3/s b. 0.074 m3/s c. 0.024 m3/s d. 0.042 m3/s _____ 37. From problem #36, calculate the theoretical power requirements under isentropic conditions. a. 17.3 kW b. 13.7 kW c. 31.7 kW d. 71.3 kW
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