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Page 6
Problemas del Tema 2
Problemas 6.2, 6.5 y 8.4 del McCabe 7ª. Edición.
6.2 Natural gas consisting essentially of methane is to be transported through a 20-in-ID pipeline over
flat terrain. Each pumping station increases the pressure to 100 lb/in2 abs, and the pressure drops to
25 lbf/in2 abs at the inlet to the next pumping station 50 mi away. What is the gas flow rate in cubic
feet per hour measured at 60ºF and 30 in-Hg pressure?
Respuesta:1,484,000 ft3/h.
6.5 Air at 25ºC enters a section of 2-in. Schedule 40 steel pipe at a gauge pressure of 310 kN/m2 and a
flow rate of 1,200 kg/h. Assuming isothermal flow, what is the pressure drop in 60 m of pipe?
Respuesta: 0.583 atm.
8.4 Air entering at 70ºF and atmospheric pressure is to be compressed to 4,000 lbf/in2 gauge in a
reciprocating compressor at the rate of 125 std ft3/min. If the compression ratio is the same in each
stage, how many stages should be used? What is the theoretical shaft work per standard cubic foot
for frictionless adiabatic compression? What is the brake horsepower if the efficiency of each stage is
85 percent? For air, γ = 1.40
Respuesta: 4 (why?), 14,888 lbf-ft/ft3STD
Problema 1
Calcular la velocidad másica de aire en kg/(m2-s) que puede transportar una tubería horizontal de acero
Cédula 40 de ½” y 300 m de largo. El aire fluye isotérmicamente a 40oC a través del tubo. La presión
disminuye desde 50 hasta 5 psig.
Respuesta: 62 kg/(m2-s).
Problema 2
Supón ahora que las condiciones del problema (1) son para flujo adiabático de aire. Si la velocidad
másica es de 60 (kg/m2 s), calcula Lmáx, T*, * y P*. Supón un valor de = 1.40.
Respuesta: 331.6m; 261 K.
Problema 3
Para los casos de los problemas 1 y 2 calcula la potencia del compresor si = 0.40.
Respuesta: 4.32 HP; 5.0 HP.
Problema 4
Monóxido de Carbono fluye adiabáticamente a través de una tubería de acero de 3” cédula 40. La
temperatura de entrada es de 25oC. Considera un valor de = 1.40. Para un valor de fL/rH = 280.0
calcula:
a. ¿Cual debe ser el NMa a la entrada si se desea un NMa a la salida 10 veces mayor que el NMa a
la entrada?
Page 10
Problemas del Tema 4
Problema 9.1, Mc Cabe, 7ª. Edición.
A tank 1.2 m in diameter and 2 m high is filled to a depth of 1.2 m with latex having a viscosity of 10 P
and a density of 800 kg/m3. The tank is not baffled. A three-blade 360-mm-diameter propeller is installed
in the tank 360 mm from the bottom. The pitch is 1:1 (pitch equals diameter) The motor available
develops 8kW. Is the motor adequate to drive this agitator at a speed of 800 rpm?
Respuesta: No, ¿por qué?
Problema 9.2, Mc Cabe, 7ª. Edición.
What is the maximum speed at which the agitator described in Problem 9.1 may be driven if the liquid is
replaced by one having a viscosity of 1 P and the same density?
Respuesta: 841 rpm.
Problema 9.3, Mc Cabe, 7ª. Edición.
What power is required for the mixing operation of Problem 9.1 if a propeller 360 mm in diameter
turning at 15 rps is used and four baffles, each 120 mm wide, are installed?
Respuesta:14.7 kW.
Problema 9.5, Mc Cabe, 7ª. Edición.
A mixing time of 29 s was measured for a 4.5-ft baffled tank with a 1.5-ft six-blade turbine and a liquid
depth of 4.8 ft. The turbine speed was 75 rpm, and the fluid has a viscosity of 3 cP and a density of 65
lb/ft3. Estimate the mixing times if an impeller one-quarter or one-half the tank diameter were used with
the speeds chosen to give the same power per unit volume.
Respuesta: 35.7 s; 21.6 s.
Problema 9.6, Mc Cabe, 7ª. Edición.
A pilot-plant reactor, a scale model of a production unit, is such size that 1 g charged to the pilot-plant
reactor is equivalent to 500 g of the same material charged to the production unit. The production unit is
2 m in diameter and 2 m deep and contains a six-blade turbine agitator 0.6 m in diameter. The optimum
agitator speed in the pilot plant reactor is found by experiment to be 330 rpm. (a) What are the
significant dimensions of the pilot-plant reactor? (b) If the reaction mass has the properties of water at
70oC and the power input per unit of volume is to be constant, at what speed should the impeller turn in
the large reactor? (c) At what speed should it turn if the mixing time is to kept constant? (d) At what
speed should it turn if the Reynolds number is held constant? (e) Which basis would you recommend for
scale-up? Why?
Respuesta: Da = 0.076m; 82.9 rpm; 330 rpm; 5.24 rpm.
Problema 9.10, Mc Cabe, 6ª. Edición.
A 15 percent slurry of 20-to-28-mesh limestone in water is to be kept in suspension in a 20-ft-diameter
tank using a six-blade 45ºC turbine. (a) If Da/Dt = ⅓ and W/ Da = 0.2, what stirrer speed is required? (b)
Calculate the stirrer speed and power requirement if Da/Dt = 0.4
Respuesta:61 rpm; 45 rpm, 232 HP.
Problemas del Tema 2
Problemas 6.2, 6.5 y 8.4 del McCabe 7ª. Edición.
6.2 Natural gas consisting essentially of methane is to be transported through a 20-in-ID pipeline over
flat terrain. Each pumping station increases the pressure to 100 lb/in2 abs, and the pressure drops to
25 lbf/in2 abs at the inlet to the next pumping station 50 mi away. What is the gas flow rate in cubic
feet per hour measured at 60ºF and 30 in-Hg pressure?
Respuesta:1,484,000 ft3/h.
6.5 Air at 25ºC enters a section of 2-in. Schedule 40 steel pipe at a gauge pressure of 310 kN/m2 and a
flow rate of 1,200 kg/h. Assuming isothermal flow, what is the pressure drop in 60 m of pipe?
Respuesta: 0.583 atm.
8.4 Air entering at 70ºF and atmospheric pressure is to be compressed to 4,000 lbf/in2 gauge in a
reciprocating compressor at the rate of 125 std ft3/min. If the compression ratio is the same in each
stage, how many stages should be used? What is the theoretical shaft work per standard cubic foot
for frictionless adiabatic compression? What is the brake horsepower if the efficiency of each stage is
85 percent? For air, γ = 1.40
Respuesta: 4 (why?), 14,888 lbf-ft/ft3STD
Problema 1
Calcular la velocidad másica de aire en kg/(m2-s) que puede transportar una tubería horizontal de acero
Cédula 40 de ½” y 300 m de largo. El aire fluye isotérmicamente a 40oC a través del tubo. La presión
disminuye desde 50 hasta 5 psig.
Respuesta: 62 kg/(m2-s).
Problema 2
Supón ahora que las condiciones del problema (1) son para flujo adiabático de aire. Si la velocidad
másica es de 60 (kg/m2 s), calcula Lmáx, T*, * y P*. Supón un valor de = 1.40.
Respuesta: 331.6m; 261 K.
Problema 3
Para los casos de los problemas 1 y 2 calcula la potencia del compresor si = 0.40.
Respuesta: 4.32 HP; 5.0 HP.
Problema 4
Monóxido de Carbono fluye adiabáticamente a través de una tubería de acero de 3” cédula 40. La
temperatura de entrada es de 25oC. Considera un valor de = 1.40. Para un valor de fL/rH = 280.0
calcula:
a. ¿Cual debe ser el NMa a la entrada si se desea un NMa a la salida 10 veces mayor que el NMa a
la entrada?
Page 10
Problemas del Tema 4
Problema 9.1, Mc Cabe, 7ª. Edición.
A tank 1.2 m in diameter and 2 m high is filled to a depth of 1.2 m with latex having a viscosity of 10 P
and a density of 800 kg/m3. The tank is not baffled. A three-blade 360-mm-diameter propeller is installed
in the tank 360 mm from the bottom. The pitch is 1:1 (pitch equals diameter) The motor available
develops 8kW. Is the motor adequate to drive this agitator at a speed of 800 rpm?
Respuesta: No, ¿por qué?
Problema 9.2, Mc Cabe, 7ª. Edición.
What is the maximum speed at which the agitator described in Problem 9.1 may be driven if the liquid is
replaced by one having a viscosity of 1 P and the same density?
Respuesta: 841 rpm.
Problema 9.3, Mc Cabe, 7ª. Edición.
What power is required for the mixing operation of Problem 9.1 if a propeller 360 mm in diameter
turning at 15 rps is used and four baffles, each 120 mm wide, are installed?
Respuesta:14.7 kW.
Problema 9.5, Mc Cabe, 7ª. Edición.
A mixing time of 29 s was measured for a 4.5-ft baffled tank with a 1.5-ft six-blade turbine and a liquid
depth of 4.8 ft. The turbine speed was 75 rpm, and the fluid has a viscosity of 3 cP and a density of 65
lb/ft3. Estimate the mixing times if an impeller one-quarter or one-half the tank diameter were used with
the speeds chosen to give the same power per unit volume.
Respuesta: 35.7 s; 21.6 s.
Problema 9.6, Mc Cabe, 7ª. Edición.
A pilot-plant reactor, a scale model of a production unit, is such size that 1 g charged to the pilot-plant
reactor is equivalent to 500 g of the same material charged to the production unit. The production unit is
2 m in diameter and 2 m deep and contains a six-blade turbine agitator 0.6 m in diameter. The optimum
agitator speed in the pilot plant reactor is found by experiment to be 330 rpm. (a) What are the
significant dimensions of the pilot-plant reactor? (b) If the reaction mass has the properties of water at
70oC and the power input per unit of volume is to be constant, at what speed should the impeller turn in
the large reactor? (c) At what speed should it turn if the mixing time is to kept constant? (d) At what
speed should it turn if the Reynolds number is held constant? (e) Which basis would you recommend for
scale-up? Why?
Respuesta: Da = 0.076m; 82.9 rpm; 330 rpm; 5.24 rpm.
Problema 9.10, Mc Cabe, 6ª. Edición.
A 15 percent slurry of 20-to-28-mesh limestone in water is to be kept in suspension in a 20-ft-diameter
tank using a six-blade 45ºC turbine. (a) If Da/Dt = ⅓ and W/ Da = 0.2, what stirrer speed is required? (b)
Calculate the stirrer speed and power requirement if Da/Dt = 0.4
Respuesta:61 rpm; 45 rpm, 232 HP.
