The air-release flap on a hot-air balloon is used to release hot air from the balloon when appropriate. On one hot-air balloon, the air release opening has an area of 0.5 m 2 , and the filling opening has an area of 1 m 2 . During a two-minute adiabatic flight maneuver, hot air enters the balloon at 100 kPa and 35°C with a velocity of 2 m/s; the air in the balloon remains at 100 kPa and 35°C; and air leaves the balloon through the air-release flap at velocity 1 m/s. At the start of this maneuver, the volume of the balloon is 75 m 3 . Determine the final volume of the balloon and the work produced by the air inside the balloon as it expands the balloon skin. FIGURE P5–126
The air-release flap on a hot-air balloon is used to release hot air from the balloon when appropriate. On one hot-air balloon, the air release opening has an area of 0.5 m 2 , and the filling opening has an area of 1 m 2 . During a two-minute adiabatic flight maneuver, hot air enters the balloon at 100 kPa and 35°C with a velocity of 2 m/s; the air in the balloon remains at 100 kPa and 35°C; and air leaves the balloon through the air-release flap at velocity 1 m/s. At the start of this maneuver, the volume of the balloon is 75 m 3 . Determine the final volume of the balloon and the work produced by the air inside the balloon as it expands the balloon skin. FIGURE P5–126
Solution Summary: The author analyzes the final volume of the balloon and the work produced by the air inside it as it expands its skin.
The air-release flap on a hot-air balloon is used to release hot air from the balloon when appropriate. On one hot-air balloon, the air release opening has an area of 0.5 m2, and the filling opening has an area of 1 m2. During a two-minute adiabatic flight maneuver, hot air enters the balloon at 100 kPa and 35°C with a velocity of 2 m/s; the air in the balloon remains at 100 kPa and 35°C; and air leaves the balloon through the air-release flap at velocity 1 m/s. At the start of this maneuver, the volume of the balloon is 75 m3. Determine the final volume of the balloon and the work produced by the air inside the balloon as it expands the balloon skin.
motor supplies 200 kW at 6 Hz to flange A of the shaft shown in Figure. Gear B transfers 125 W of power to operating machinery in the factory, and the remaining power in the shaft is mansferred by gear D. Shafts (1) and (2) are solid aluminum (G = 28 GPa) shafts that have the same diameter and an allowable shear stress of t= 40 MPa. Shaft (3) is a solid steel (G = 80 GPa) shaft with an allowable shear stress of t = 55 MPa. Determine:
a) the minimum permissible diameter for aluminum shafts (1) and (2)
b) the minimum permissible diameter for steel shaft (3).
c) the rotation angle of gear D with respect to flange A if the shafts have the minimum permissible diameters as determined in (a) and (b).
First monthly exam
Gas dynamics
Third stage
Q1/Water at 15° C flow through a 300 mm diameter riveted steel pipe, E-3 mm with a head loss of 6 m in
300 m length. Determine the flow rate in pipe. Use moody chart.
Q2/ Assume a car's exhaust system can be approximated as 14 ft long and 0.125 ft-diameter cast-iron pipe (
= 0.00085 ft) with the equivalent of (6) regular 90° flanged elbows (KL = 0.3) and a muffler. The
muffler acts as a resistor with a loss coefficient of KL= 8.5. Determine the pressure at the beginning of the
exhaust system (pl) if the flowrate is 0.10 cfs, and the exhaust has the same properties as air.(p = 1.74 ×
10-3 slug/ft³, u= 4.7 x 10-7 lb.s/ft²) Use moody chart
(1)
MIDAS
Kel=0.3
Q3/Liquid ammonia at -20°C is flowing through a 30 m long section of a 5 mm diameter copper tube(e =
1.5 × 10-6 m) at a rate of 0.15 kg/s. Determine the pressure drop and the head losses.
.μ= 2.36 × 10-4 kg/m.s)p = 665.1 kg/m³
2/Y
Y+1
2Cp
Q1/ Show that
Cda
Az x
P1
mactual
Cdf
Af
R/T₁
2pf(P1-P2-zxgxpf)
Q2/ A simple jet carburetor has to supply 5 Kg of air per minute. The air is at a pressure of 1.013 bar
and a temperature of 27 °C. Calculate the throat diameter of the choke for air flow velocity of 90 m/sec.
Take velocity coefficient to be 0.8. Assume isentropic flow and the flow to be compressible.
Quiz/ Determine the air-fuel ratio supplied at 5000 m altitude by a carburetor which is adjusted to give
an air-fuel ratio of 14:1 at sea level where air temperature is 27 °C and pressure is 1.013 bar. The
temperature of air decreases with altitude as given by the expression
The air pressure decreases with altitude as per relation h = 19200 log10 (1.013), where P is in bar. State
any assumptions made.
t = ts
P
0.0065h
Chapter 5 Solutions
Thermodynamics: An Engineering Approach ( 9th International Edition ) ISBN:9781260092684
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