VIP 6 - PIPE PROBLEMS Flashcards
Compute the specific volume of an air-vapor mixture in cubic meters per kilogram of dry air when the following conditions prevail. t=30°C, w = 0.015 kg/kg, and P, = 90 ka.
C. 0.79 m°/kg
0.99 m°/kg
D. 0.69 m°/kg
0,89 m°/kg
A. 0.99 m°/kg
Compute the humidity ratio of air considering the density at 3550 and 101 kPa is 1.05 kg/m?.
C. 0.36 kgrapor/kgair
A. 0.036 kgrapor / Kgair
D. 0.63 Kgrapor/ Kgair
B. 0.063 kgvapor / Kgair
A. 0.036 kgrapor / Kgair
B. coll has an Inlet temperature of 60°F and outlet of 909F. If the
mean temperature of the coll is 110°F, find the bypass factor of the
coil.
B. 0.30
C. 0.40
A.0.20
D. 0.50
C. 0.40
compute the pressure drop of 30°C air flowing with a mean velocity or 8 m/s in a circular sheet-metal duct 300 mm in diameter and 15 m
long. Use a friction factor, f = 0.02, and Pair = 1.1644 kg/m
C. 29.34 Pa
A. 37.26 Pa
D. 30.52 Pa
B. 25.27 Pa
A. 37.26 Pa
A pressure difference of 350 Pa is available to force 20°C air through a circular sheet-metal duct 450 mm in diameter and 25 m long. At 20°C, p = 1.204 kg/m? and take friction factor, f = 0.016. Determine
the velocity.
A. 25.57 m/s
C. 28.54 m/S
27.55 m/s
D. 24.85 m/S
A. 25.57 m/s
A duct 0.40 m high and 0.80 m wide suspended from the ceiling in a corridor, makes a right angle turn in the horizontal plane. The inner radius is 0,2 m and the outer radius is 1.0 m measured from the same center. The velocity of air in the duct is 10 m/S. Compute the
pressure drop in this elbow. Assuming ; f = 0.3, p = 1.204 kg/m
and L = 10 m.
A. 341 Pa
C. 143 Pa
B. 441 Pa
D. 144 Pa
A. 341 Pa
A rectangular duct has a dimensions of 0.25 m by 1 m. Determine the equivalent diameter of the duct.
A. 0.40 m
C. 0.70 m
B. 0.80 m
D. 0.30 m
A. 0.40 m
Find the amount of electrical energy expended raising the temperature of 45 liters of water by 75°C. Assume the efficiency of the heating equipment to be 90%?
A. 3.44 kW-hr
C. 4.36 kW-hr
B. 2.45 kW-hr
D. 10.45 kW-hr
C. 4.36 kW-hr
To what height will a barometer column rise if the atmospheric conditions are 13.9 psia and 68°F and barometer fluid is mercury?
A. 28.3 in.
C. 35.6 inches
B. 22.45 n
D. 32.45 inches
A. 28.3 in.
To what height will a barometer column rise if the atmospheric conditions are 13.9 psia and 689F and barometer fluid is ethyl
alcohol? Note: @ 689F ; Pv = 122.4 Ibf/ft? and specific gravity of
0.79 for ethyi alcohol.
A. 457.45 in.
C. 435.6 inches
B, 422.45 n
D. 132.45 inches
A. 457.45 in.
To what height will 68F ethyl alcohol rise in a 0.005 inch internal dameter glass capillary tube? The density of alcohol is 49 ibm/Ft^3.
where: B = 0° = contact angle and surface tension
Ibf/ft @ 68°F.
g = 0.00156
A. 0.3056 ft
B. 0.2504 ft
C. 0.4312 ft
D. 0.2432 ft
A. 0.3056 ft
What is the velocity of sound in 150°F ( 66°C) air at a standard
20
pressure? Note: density of air @ 150°F is 0.064 Ibm/f°
°C
1295 ft/s
B. 3245 ft/s
C. 2345 ft/s
D. 1096 ft/s
1295 ft/s
What is the pressure 8000 ft below the water surface of the ocean?
Neglect compressibility.
A. 512,000 psf
B. 324,500 psf
C. 157,000 psf
D. 213,000 psf
A. 512,000 psf
If atmospheric alr 14.7 psia and 60°F at sea level, what is the pressure at 12000 ft altitude if air is incompressible. Note: @ 60°F;
the density of air is 0.0763 Ibm/f; P, = 14.7 psia
A. 5.467 psia
C. 8.342 psia
B. 9.345 psia
D. 2.346 psia
C. 8.342 psia
If atmospheric air 14.7 psia and 600F at sea level, what is the pressure at 12000 ft altitude if air is incompressible.
Note: @ 60°F; the density of air is 0.0763 Ibm/f; Pi = 14.7 psia
h
e
A. 5.467 psia
C. 8.342 psia
B. 9.53 psia
D. 2.346 psia
C. 8.342 psia
A cylindrical 1 ft diameter, 4 ft high tank contains 3 ft of water.
What rotational speed is required to spin water out the top?
A. 22.7 rad/s
C. 22.7 rad/s
B. 32.5 rad/s
D. 34.5 rad/s
A. 22.7 rad/s
- Water (p = 62.4 lbm/f’) is flowing through a pipe. A pitot-static gage
registers 3.0 inches of mercury. What is the velocity of the water in
the pipe? Note: Prg = 848.6 lbm/ft?
23.
A. 14.24 ft/s
B. 11.24 ft/s
C. 8.24 ft/s
D. 7.45 ft/s
A. 14.24 ft/s
A two-pass surface condenser is to be designed using overall heat transfer coefficient of 480 Btu/°F-ft of outside tube surface. The tubes are to be 1 inch outside diameter with 1/16 in walls (or 7/8 in.
inside diameter). Entering circulating water velocity is to be 6 ft/s. Steam enters the condenser at a rate of 100,000 lb/hr at a pressure of one psia and an enthalpy of 1090 Btu/lb. Condensate leaves at saturated liquid at one psia. Circulating water enters the condenser at 85 deg. F and leaves at 95 deg F. Note: 1 psia condensate has
temperature of 101.7 deg. F. Wet steam entering becomes
condensate at 101.7 deg. F with hf = 69.72 Btu/lb. Calculate the
total number of tubes to be used in each pass.
A. 18,200 tubes
C. 10,450 tubes
B. 15,400 tubes
D. 11,456 tubes
A. 18,200 tubes
A two-pass surface condenser is to be designed using overall heat transfer coefficient of 480 Btu/°F-f? of outside tube surface. The tubes are to be 1 inch outside diameter with 1/16 in walls (or 7/8 in.
Inside diameter). Entering circulating water velocity is to be 6 ft/s.
Steam enters the condenser at a rate of 100,000 lb/hr at a pressure of One psia and an enthalpy of 1090 Btu/b. Condensate leaves at
2
saturated liquid at one psia. Circulating water enters the condenser at 85 deg. F and leaves at 95 deg F. Note: 1 psia condensate hasVIP 06 - PIPE PROBLEMS
temperature of 101.7 deg, F. Wet steam entering becomes
condensate at 101.7 deg. F with hf = 69.72 Btu/lb. Calculate the
total length of the tube to be used in ft.
A,
123,000 ft
C. 742,000 ft
B. 324,000 ft
D. 543,000 ft
C. 742,000 ft
A two-pass surface condenser is to be designed using overall heat transfer coefficient of 480 Btu/°F-ft? of outside tube surface. The tubes are to be 1 inch outside diameter with 1/16 in walls (or 7/8 in. inside diameter), Entering circulating water velocity is to be 6 ft/s.
Steam enters the condenser at a rate of 100,000 lb/hr at a pressure of one psia and an enthalpy of 1090 Btu/lb. Condensate leaves at saturated liquid at one psia. Circulating water enters the condenser at 85 deg. F and leaves at 95 deg F, Note: 1 psla condensate has temperature of 101.7 deg. F. Wet steam entering becomes condensate at 101.7 deg. F with hf m 69.72 Btu/lb. Calculate the total length of the tube to be used in ft per tube.
A. 20.4 At
C. 17.4 ft
B. 80.8 At
D. 15.5 ft
A. 20.4 At
A 0,30 x 0,40 m branch duct leaves a 0.30 × 0,60 main duct at an angle of 60°. The air temperature is 20°C. The dimensions of the main duct remain constant following branch. The flow rate upstream is 2.7 m’/s. What is the pressure downstream in the main duct. Note: at 20°C, p = 1.2041 kg/m?.
A. 346 Pa
C. 634 Pa
B. 436 Pa
D. 643 pa
A. 346 Pa
A sudden enlargement in a circular duct measures 0.20 m diameter upstream and 0.40 m downstream. The upstream pressure is 150 Pa, downstream pressure is 200 Pa. What is the flow rate of 20°C air through the fitting? Use p = 1.02041 kg/m°, B.
0,49 m°/s
C. 0.38 m°/
0,83 m°/s
D. 0.94 m°/s
C. 0.38 m°/
Determine the sensible heat of 5 lb of air having a dry bulb temperature of 70°F and a humidity ratio of 0.0092 lb/Ib, the latter corresponding to a dew point temperature of approximately 55°F.
94 BTU
B. 48 BTU
C. 84 BTU
D. 49 BTU
C. 84 BTU
Determine the approximate load on a cooling tower if the entering and leaving temperatures are 96°F and 88°F, respectively and the flow rate of the water over the tower is 30 gpm.
A. 2500 Btu/min
C. 3000 Btu/min
B. 2000 Btu/min
D 3500 Btu/min
B. 2000 Btu/min
Determine the quantity of water lost. by bleed off If the water flow rate over the tower is 30 gpm and the range is 10°F, Percent bleed-off required is 33%
A. 0.077 gpm
C. 0.099 gpm
B. 0.088 gpm
D. 0,066 gpm
C. 0.099 gpm
The mass of an outside air at 50°C in an air conditioning unit is 60
kg. Ind the temperature after mixing if the outside air mixed with 40 kg with recirculated air at 35°C
A. 44°C
B. 39°C
C. 52°C
D. 47°C
A. 44°C
A creamery must cool 20,000 liters of milk received each day from Initial temperature of 29°C to a final temperature of 2°C in 5 hours. If refrigeration losses amount to 10 percent of the cooling load, what must be the capacity of the refrigerating machine?
Note: Specific heat of milk if 3.9 kJ/kg-K and S.G. = 1.05.
A. 38.5 TOR
C. 37.5 TOR
B. 36.5 TOR
D. 39.5 TOR
A. 38.5 TOR
How many tons of refrigeration are required to produce 10 metric tons of ice per day at - 10°C from raw water at 22°C if miscellaneous losses are 15% of the chilling and freezing load?
A. 17 TOR
C. 15 TOR
B. 20 TOR
D. 24 TOR
A. 17 TOR
Five hundred kilograms of poultry enter a chiller at 8°C and are frozen and chilled to a final temperature of -18°C for storage in 15 hours. The specific heat above and below freezing are 3.18 kJ/kg°C and 1.55 kJ/kg°C respectively. The latent heat is 246 kJ/kg and the freezing temperature is -5°C. Compute the product load.
A. 2.75 kW
B. 2.85 kW
C. 2.95 kW
D. 3.15 kW
B. 2.85 kW
Fish weighing 11,000 kg with a temperature of 20°C is brought to a cold storage and which shall be cooled to -10°C in 11 hours. Find the required plant refrigerating capacity in tons of refrigeration if the specific heat of fish os 0.7 kCal/kg°C above freezing and 0.30 kCal/kg°C below freezing point which Is -3°C. The latent heat of freezing is 55.5 kCal/kg.
A. 25.26
C. 14.38
B. 15.26
D. 24.38
D. 24.38
Mass of ice at -4°C is needed to cool 115 kg of vegetabies in a bunker for 24 hours. The initial temperature of vegetables is assumed to be 30°C. It is also assumed that the average temperature inside the bunker is 7°C within 24 hour period. If the heat gained per hour in the bunker is 30% of the heat removed to cool the vegetable from 30°C to 7°C, what would be the required mass of ice?
Note: Specific heat of ice = 1.935 kJ/kg-K
Specific heat of vegetables = 3.35 kJ/kg-K
Specific heat of water = 4.186 kJ/kg-K
Heat of fusion of ice = 335 kJ/kg
A. 27.86 kg
C. 29.54 kg
B. 26.57 kg
D. 37.48 kg
A. 27.86 kg
A refrigerator is 2 m high, 1.2 m wide and 1 m deep. The over-all heat transfer coefficient is 0.532 W/m? °C. How many kilograms of 0°C ice will melt per hour if the inside temperature is maintained at
10°C while the surrounding air temperature is at 35°C ?
A. 1.60 kg
B,1.80 kg
C. 2.60 kg
D. 2.80 kg
A. 1.60 kg
The power requirement of a Carnot refrigerator in maintaining a low temperature region at 300 K Is 1.5 kW per ton. Find the heat rejected.
A. 4.02 kW
C. 5.02 kW
B. 7.02 kW
D. 6.02 kW
C. 5.02 kW
A vapor compression refrigeration system is designed to have a capacity of 150 tons of refrigeration. It produces chilled water from 22°C to 2°C. Its actual coefficient of performance is 5.86 and 35% of the power supplied to the compressor is lost in the form of friction ME REVIEW COURSE
and cylinder cooling losses. Determine the condenser cooling water required for a temperature rise of 10°C.
A. 14.75 kg/s
C. 18.65 kg/s
B. 15.65 kg/s
D. 13.75 kg/s
A. 14.75 kg/s
Cold salt brine at an initial temperature of 0°C is used in a packing plant to chill beef from 40°C to 5°C in 18 hours. Determine the volume of brine in liters per minute required to cool 1000 beeves of 250 kg each, If the final temperature of brine is 3°C. Specific heat of brine is 3.76 kJ/kg°C and S.G. = 1.05. Specific heat of beef is 3.14 kJ/kg°C.
A. 37.59 kg/s
C. 38.79 kg/s
B. 39.67 kg/s
D. 35.67 kg/s
A. 37.59 kg/s
Four thousand liters per hour of distillates are to be cooled from 21°C
to - 12°C and 12% of wax by weight is separated out at 15°C.
The specific heat of oil is 2 kJ/kg°C and S.G. is 0.87. The specific heat of the wax is 2.5 and the latent heat of fusion is 290 kJ/kg.
Allow 10% for the losses, find the capacity of the refrigerating machine.
A. 20 TOR
C. 40 TOR
B. 51.08 TOR
D. 31.08 TOR
D. 31.08 TOR
Determine the heat extracted from 2000 kg of water from 25°C to ice at - 10°C.
A. 621,150 kJ
B,721,150 kJ
C. 821,150 kJ
D. 921,150 kJ
D. 921,150 kJ
A single acting, twin cylinder, Ammonia compressor with bore equal to stroke is driven by an engine at 250 pm. The machine is installed in a chilling plant to produce 700 kW of refrigeration at -18°C
evaporating temperature. At this temperature the cooling effect per kg mass is 1160 kJ. The specific volume of vapor entering the compressor is 0.592 m per kilogram. Assume 85% volumetric efficiency, determine the bore in mm.
A. 400 mm
C. 450 mm
B. 300 mm
D. 500 mm
A. 400 mm
A cylindrical flash tank mounted with its axis horizontal is used to separate liquid ammonia from ammonia vapor. The ammonia vapor bubbles through the liquid with 70 m/ min leaving the disengaging surface. The disengaging rate is limited to 60 m/min and the liquid level is to operate with the liquid level one-third of the diameter from the top. Determine the diameter if the tank is 1.5 m long.
A. 830 mm
C. 860 mm
B. 730 mm
D. 760 mm
A. 830 mm
A 150 Hp motor is used to drive a compressor. If the heat loss from the compressor is 25 kW and the mass flow rate of the refrigerant entering the compressor is 0.50 kg/s, determine the difference of the enthalpies between the inlet and outlet of the compressor.
A. 143.80 kJ/kg
B. 153.80 kJ/kg
C. 173.80 kJ/kg
D. 183.80 kJ/kg
C. 173.80 kJ/kg
To cool farm products, 300 kg of ice at - 4.4°C are placed in bunker.
Twenty four hours later the ice have melted into water at 7.2°C.
What is the average rate of cooling provided by the ice in kJ/hr?
A. 2679.28 kJ/hr
B. 5679.28 kJ/hr
C. 3679.28 kJ/hr
D. 4679.28 kJ/hr
D. 4679.28 kJ/hr
Determine the estimated condenser load for an open-type compressor having a cooling capacity of 16,500 Btu/hr and a heat rejection factor of 1.32.
A. 22,280 Btu/hr
B.20,780 Btu/hr
C. 21,780 Btu/hr
D. 19,780 Btu/hr
C. 21,780 Btu/hr
If the load on water-cooled condenser In 150,000 Btu/hr and the temperature rise of the water in the condenser is 10°F, what is the quantity of water circulated in gpm?
A. 30
C. 20
B. 40
D, 50
A. 30
The load on a water-cooled condenser is 90,000 Btu/hr. If the 1°C quantity of water circulated through the condenser is 15 gpm,
determine the temperature rise of the water in the condenser.
A. 12°F
B. 14F
C. 16°F
D. 18°F
A. 12°F
The weight of ammonia circulated in a machine is found to be 21.8 b/hr. If the vapor enters the compressor with a specific volume of 9.6 ft/b, calculate the piston displacement, assuming 80% percent volume efficiency.
A. 261.6 A/hr
C. 281.8 ft/hr
B. 271.6 ft/hr
D. 291.6 ft/hr
A. 261.6 A/hr
A single-stage ammonia compressor Is producing 10 tons of refrigeration and the power consumed is 15 Hp. Suction pressure is 25 psi, condensing pressure is 180 psi. Brine temperature is 20°F off brine cooler. Determine the actual coefficient of performance.
A.
10.14
C. 12.14
B.
11.14
D. 13.14
D. 13.14
In an ammonia condensing machine (compressor plus condenser)
the water used for condensing is 55F and the evaporator is at 15°F.
Calculate the ideal COP.
A. 11.875
C. 10.875
B. 12.875
D. 13.875
A. 11.875
How much refrigeration capacity is required to cool 2000 fm of air
from 85°F to 70°F?
A. 2.7 TOR
C. 1.7 TOR
B. 3.7 TOR
D. 4.7 TOR
A. 2.7 TOR
Determine the coil face area required to maintain a face velocity of
400 ft/min if the air flow rate over the coil is 2100 ft/min.
A. 3.25 f
C. 5.25 A?
B. 4.25 f
D. 6.25 f?
C. 5.25 A?
Calculate the heat transfer per hour through a solid brick wall 6 m
long, 2.9 m high, and 225 mm thick, when the outer surface is at 5°C and the inner surface 17°C, the coefficient of thermal
conductivity of the brick being 0.6 W/m-K.
A. 2,004.48 kJ
C. 2,400.48 kJ
B. 3,004.48 kJ
D. 3,400.48 kJ
A. 2,004.48 kJ
A vertical furnace wall is made up of an inner wall of firebrick 20 cm
r.
thick followed by insulating brick 15 cm thick and an outer wall of steel 1 cm thick. The surface temperature of the wall adjacent to the combustion chamber is 1200°C whlle that of the outer surface of steel is 50°C. The thermal conductivities of the wall material in W/m-Kare : firebrick, 10; insulating brick, 0.26; and steel, 45. Neglecting the film resistances and contact resistance of joints, determine the heat loss per sq.m. of wall area.
A. 1.93 W/m?
C. 1.55 W/m?
B. 2.93 W/m?
D. 2.55 W/m?
A. 1.93 W/m?
A composite wall is made up of an external thickness of brickwork
110 mm thick inside which is a layer of fiberglass 75 mm thick. The fiberglass is faced internally by an insulating board 25 mm thick. The coefficient of thermal conductivity for the three are as follows:
Brickwork
1.5 W/m-K
Fiberglass
0.04 W/m-K
Insulating board
0.06 W/m-K
The surface transfer coefficients of the inside wall Is 3.1 W/m?-K while that of the outside wall is 2.5 W/m?-K. Take the Internal ambient temperature as 10°C and the external temperature is 27°C.
Determine the heat loss through such wall 6 m high and 10 m long.
A. 330.10 W
C. 430.10 W
B. 230.10 W
D. 530.10 W
A. 330.10 W
One insulated wall of a cold-storage compartment is 8 m long by 2.5 m high and consists of an outer steel plate 18 mm thick. An inner wood wall 22,5 mm thick, the steel and wood are 90 mm apart to form a cavity which is filled with cork. If the temperature drop across the extreme faces of the composite wall is 15°C. Calculate the heat transfer per hour through the wall and the temperature drop across the thickness of the cork. Take the coefficients of thermal conductivity for steel, cork and wood as 45, 0.045, and 0.18 W/m-K respectively.
A. 408.24 kJ, 12.12°C
C. 608.24 kJ, 13.12°C
B. 708.24 kJ, 11.12°C
D. 508.24 kJ, 14.12°C
D. 508.24 kJ, 14.12°C *
A cubical tank of 2 m sides is constructed of metal plate 12 mm and contains water at 75°C. The surrounding air temperature is 16°C.
Calculate the overall heat transfer coefficient from water to air. Take the coefficient of thermal conductivity of the metal as 48 W/m-K, the coefficient of thermal conductivity of the metal as 48 W/m-K, the coefficient of heat transfer of water is 2.5 kW/m?-K and the coefficient of heat transfer of the air is 16 W/m?-K.
A. 15.84 W/m?oc
C. 16.84 W/moC
B. 14.84 W/m?oC
D. 13.84 W/m~°C
A. 15.84 W/m?oc
A cold storage compartment is 4.5 m long by 4 m wide by 2.5 m
high. The four walls, ceiling and floor are covered to a thickness of 150 mm with insulating material which has a coefficient of thermal conductivity of 5.8 x 10? W/m-K. Calculate the quantity of heat leaking through the insulation per hour when the outside and inside face temperatures of the material is 15°C and -5°C respectively.
A. 2185.44 kJ
C. 3185.44 kJ
B. 1185.44 kJ
D. 4185.44 kJ
A. 2185.44 kJ*
A furnace wall consist of 35 cm firebrick ( k = 1.557 W/m-K), 12 cm
insulating refractory ( k = 0.346 ) and 20 cm common brick ( k =
0.692 ) covered with 7 cm steel plate (k = 45 ) . The temperature
at the inner surface of the firebrick is 1,230°C and at the outer face of the steel plate is 60°C. Atmosphere 27°C. What is the value of the combined coefficient for convection and radiation from the outside wall?
A. 31.13 W/m2-K
C. 41.3 W/m2-K
B. 30.13 W/m-K
D. 40.13 W /m?-K
C. 41.3 W/m2-K *
One side of refrigerated cold chamber is 6 m long by 3.7 m high and consists of 168 mm thickness of cork between outer and inner walls of wood. The outer wood wall is 30 mm thick and its outside faceME REVIEW COURSE
temperature is 20°C, the inner wood wall is 35 mm thick and its inside face temperature is -3°C. Taking the coefficient of thermal conductivity of cork and wood as 0.42 and 0.20 W/m-K respectively,
Calculate the heat transfer per second per sq. m of surface area.
A. 5.138 3
B.4.138 J
C. 6.318 J
D. 3.318 J
A. 5.138 3 *
Hot gases at 280°C flow on one side of a metal plate of 10mm thickness and air at 35°C flows on the other side. The heat transfer coefficient of the gases is 31.5 Wim?.k and that of the air is 32
W/m?-K. Calculate the over-all transfer coeficient.
A. 15.82. W/m?-K
C. 14.82 W/m?-K
B. 16.82 W/m?-K
D. 17.82 W/m?-K
A. 15.82. W/m?-K *
The surface temperature of the hot side of the furnace wall is
1200°C. It is desired to maintain the outside of the wall at 38°C. A
152 mm of refractory silica is used adiacent to the combustion chamber and 10 mm of steel covers the Outside. What thickness of insulating bricks is necessary between refractory and steel, if the
heat loss should be kept at 788 W/m? ? use k = 13.84 W/m-K for
refractory silica; 0.15 for insulating brick, and 45 for steel.
A. 220 mm
C. 260 mm
B. 240 mm
D. 280 mm
A. 220 mm
A hollow sphere has an outside radius of 1 m and is made of polystyrene foam with a thickness of 1 cm. A heat source inside keeps the inner surface 5.20°C hotter than the outside surface. How much power is produced by the heat source? The thermal conductivity of polystyrene foam is 0.033 W/m°C.
A. 200 W
C. 300 W
B. 216 W
D. 316 W
B. 216 W
An insulated steam pipe located where the ambient temperature is
32°C, has an inside diameter of 50 mm with 10 mm thick wall. The outside diameter of the corrugated asbestos insulation is 125 mm
and the surface coefficient of still air, h. = 12 W/m?-k. Inside the
pipe is steam having a temperature of 150°C with film coefficient h: =
6000 W/m?-K. Thermal conductivity of pipe and asbestos insulation are 45 and 0.12 W/m-K respectively. Determine the heat loss per unit length of pipe.
A. 110 W
C. 130 W
B. 120 W
D. 140 W
B. 120 W
A pipe 200 mm outside diameter and 20 m length is covered with a layer, 70 mm thick of insulation having a thermal conductivity of 0.05
W/m-K and a thermal conductance of 10 W/m?-K at the outer surface If the temperature of the pipe is 350°C and the ambient temperature
15°C, calculate the external surface temperature of the lagging.
A. 32.6°C
C. 42.6°C
B. 22.6°C
D. 53.6°C
A. 32.6°C
A copper rod whose diameter is 2 cm and length 50 cm has one end in boiling water, the other end in a jacket cooled by flowing water which enters at 10°C. The thermal conductivity of the copper is 0.102 kCal/m-s-°C. If 0.20 kg of water flows through the jacket in 6 min, by how much does the temperature of the water increase?
A. 10.38°C
C. 11.38°C
B. 9.38°C
D. 12.38°C
A. 10.38°C
How many watts will be radiated from a spherical black body 15 cm
in diameter at a temperature of 800°C?
A. 5.34 kW
C. 6.34 kW
B. 4.34 kW
D. 3.34 kW
A. 5.34 kW *
A surface condenser serving a 50,000 kW steam turbo-generator unit receives exhaust steam at the rate of 196,000 kg/hr. Vacuum in condenser is 702 mm Hg. Sea water for cooling enters at 29.5°C and leaves at 37.5°C. For steam turbine condenser, manufacturers consider 950 Btu/b of steam turbine condensed as heat given up to cooling water.
Calculate the logarithmic mean temperature
difference.
A. 4.57°C
C. 6.57°C
B. 5.57°C
D. 7.57°C
C. 6.57°C *
A wall with an area of 10 m? is made of a 2 cm thickness of white pine (k= 0.113 W/m°C) followed by 10 cm of brick (k = 0.649
W/m°C). The pine is on the inside where the temperature is 30°C while the outside temperature is 10°C. Assuming equilibrium conditions exist, what is the temperature at the interface between the two metals?
A. 15.65°C
C. 18.21°C
B. 17.64°C
D. 19.31°C
D. 19.31°C
A counterfiow heat exchanger is designed to heat fuel oil from 45°C
to 100°C while the heating fluid enters at 150°C and leaves at 115°C.
Calculate the arithmetic mean temperature difference.
A. 40°C
C. 60°C
B. 50°C
D. 70°C
C. 60°C *
A pipe with an outside diameter of 2.5 in. is insulated with a 2 in.
layer of asbestos ( k = 0.396 Btu-in./hr-f-oF), followed by a layer
of cork 1.5 in. thick (k. = 0.30 Btu-in./hr-f-oF). If the temperature
of the outer surface of the cork is 90°F, calculate the heat lost per 100 ft of insulated pipe.
A. 847.64 Btu/hr
C. 2847.42 Btu/hr
B. 3847.51 Btu/hr
D. 1847.14 Btu/hr
C. 2847.42 Btu/hr *
With three different quantities x, y, and z of the same kind of liquid of temperatures 9, 21 and 38°C respectively, it is found that when x and y are mixed together the resultant temperature is 17°C and when y and z are mixed together the resultant temperature is 28°C.
Find the resultant temperature if x and z were mixed.
A. 29.87°C
C. 20.85°C
B. 25.92°C
D. 24.86°C
B. 25.92°C
The journals of a shaft are 380 mm diameter, it runs at 105 pm and the coefficient of friction between journals and bearings is 0.02. If the average load on the bearings is 200 kN, find the heat generated per minute at the bearings,
A.501.375 kJ*
C. 401.375 kJ
B. 505.575 kJ
D. 501.575 kJ
A.501.375 kJ*
A reverse Carnot cycle requires 3 Hp and extracts energy from a lake to heat a house. If the house is kept at 70°F and requires 2000 Btu per minute, what is the temperature of the lake ?
A. 35°F
C. 39°F
B. 36°F
D. 40°F
B. 36°F *
An oxygen cylinder of volume 2.3 ft’ has a pressure of 2200 pig and is at 70°F. Determine the mass of oxygen in the cylinder.
A. 28.66 lbs
C. 26.88 lbs
B. 30.44 Ibs
D. 34.30 Ibs
A. 28.66 lbs
A group of 50 persons attend a secret meeting in room which is 12 m wide by 10 m long and a celling height of 3 m. The room is completely sealed off and insulated. Each person gives off 150 kCal per hour of heat and occupies a volume of 0.20 m°. The room has an initial pressure of 101.3 ka and temperature of 16°C. Calculate the
room temperature after 10 minutes. Use R = 0.287 kJ/kg-K and C, =
0.171 kCal/kg-K.
A. 33.1 °C
C. 38.7 °C
B. 37.7 °C
D. 31.7 °C
A. 33.1 °C
The flow energy of 124 liters per minute of a fluid passing a boundary to system is 108.5 kJ/min. Determine the pressure at this point.
A. 875 kPa
C. 975 kPa
B. 675 kPa
D. 575 kPa
A. 875 kPa
Work done by a substance in reversible nonflow manner in accordance with V = 100/P ft°, where P is in psia. Evaluate the work done on or by the substance as the pressure increases from 10 psia to 100 psia.
A. 33 157.22 ft-Ib
C. 43 157.22 ft-Ib
B. -33 157.22 f-Ib
D. - 43, 157.22 ft-Ib
B. -33 157.22 f-Ib *
The following expressions relate to a particular gaseous mass: PV =
95T, h = 120 + 0.50T where these units obtain in psf, V in #/lb, T
in °R and h in Btu/lb. If the specific heats are temperature dependent only, find Cp and Cv.
A. 0.6 Btu/Ib°R, 0.48 Btu/Ib°R
C. 0.60 Btu/ib°R, 0.7 Btu/lb°R
B.0.5 Btu/Ib°R, 0.50 Btu/Ib°R
D. 0,50 Btu/Ib°R, 0.48 Btu/Ib°R
A. 0.6 Btu/Ib°R, 0.48 Btu/Ib°R *
Calculate the change In enthalpy as 1 kg of nitrogen is heated from
1000 K to 1500 K, assuming the nitrogen is an ideal gas at a constant pressure. The temperature dependent specific heat of nitrogen is Cp = 39.06 - 512.79 Ti5 + 1072.7 T2 - 820.4T where Cp is in kJ/kg-mol, and T is in K.
A. 600 kJ
C. 800 kJ
B. 697.27 kJ
D. 897.27 kJ
B. 697.27 kJ *
One kilogram of wet steam at a pressure of 8 bar ( g = 0.2404
m?/kg, vi = 0.0011148 m°/kg ) and dryness 0.94 is expanded until the pressure is 4 bar ( vg = 0.4625 m°/kg, v = 0.0010836 m /kg ). If
expansion follows the law PV = C, where n = 1.12, find the dryness
fraction of the steam at the lower pressure.
A. 0.9072
C. 0.2260
B.0.4197
D. 0.2404
A. 0.9072 *
2.5 liters of superheated steam at 25 bar and 400°C ( v = 0.1252 m3/kg ) is expanded in an engine to a pressure of 0.1 bar (v, =
13472 mi
14.674 m°/kg, v = 0.0010102 m’/kg) when its dryness fraction is
0.9. Find the final volume of the steam.
A. 163.74 liters
B. 263.74 liters
C. 363.74 liters
D. 463.74 liters
B. 263.74 liters *
A 1.5 kg of wet steam at a pressure of 5 bar (h, = 640 kJ/kg, he =
2109 kJ/kg) dryness 0.95 is blown into 70 liters of water of 12°C (h =
50.4 kJ/kg). Find the final enthalpy of the mixture.
A. 74.80 kJ/kg
C. 94.80 kJ/kg
B. 84.80 kJ/kg
D. 104.80 kJ/kg
D. 104.80 kJ/kg
Wet saturated steam at 16 bar (hr = 859 kJ/kg , Is = 1935 kJ/kg)
reducing valve and is throttled to a pressure of 8 bar ( hr = 721
kJ/kg, he = 2048 kJ/kg ). Find the dryness fraction of the reduced
pressure steam.
A.
0.8833
C. 0.9933
B.0.7733
D. 0.6633
C. 0.9933 *