A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. Air enters a 1200-W hair dryer at 100 kPa and 22°C and leaves at 47°C. The cross-sectional area of the hair dryer at the exit is 60 cm 2 . Neglecting the power consumed by the fan and the heat losses through the walls of the hair dryer, determine ( a ) the volume flow rate of air at the inlet and ( b ) the velocity of the air at the exit. FIGURE P5–108 5–109 Reconsider Prob. 5–108. Using appropriate software, investigate the effect of the exit cross-sectional area of the hair dryer on the exit velocity. Let the exit area vary from 25 to 75 cm 2 . Plot the exit velocity against the exit cross-sectional area, and discuss the results. Include the effect of the flow kinetic energy in the analysis.
A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. Air enters a 1200-W hair dryer at 100 kPa and 22°C and leaves at 47°C. The cross-sectional area of the hair dryer at the exit is 60 cm 2 . Neglecting the power consumed by the fan and the heat losses through the walls of the hair dryer, determine ( a ) the volume flow rate of air at the inlet and ( b ) the velocity of the air at the exit. FIGURE P5–108 5–109 Reconsider Prob. 5–108. Using appropriate software, investigate the effect of the exit cross-sectional area of the hair dryer on the exit velocity. Let the exit area vary from 25 to 75 cm 2 . Plot the exit velocity against the exit cross-sectional area, and discuss the results. Include the effect of the flow kinetic energy in the analysis.
Solution Summary: The author plots the exit velocity against exit cross-sectional area based on the energy rate balance equation for one inlet and one outlet system.
A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. Air enters a 1200-W hair dryer at 100 kPa and 22°C and leaves at 47°C. The cross-sectional area of the hair dryer at the exit is 60 cm2. Neglecting the power consumed by the fan and the heat losses through the walls of the hair dryer, determine (a) the volume flow rate of air at the inlet and (b) the velocity of the air at the exit.
FIGURE P5–108
5–109 Reconsider Prob. 5–108. Using appropriate software, investigate the effect of the exit cross-sectional area of the hair dryer on the exit velocity. Let the exit area vary from 25 to 75 cm2. Plot the exit velocity against the exit cross-sectional area, and discuss the results. Include the effect of the flow kinetic energy in the analysis.
The single degree of freedom (SDOF) system that you studied under free vibration in Assignment #3 - Laboratory Component has been subjected to a strong ground motion. The acceleration at the base (excitation) and the acceleration at the roof (response) of the SDOF system was recorded with sampling rate 50 Hz (50 samples per second, or dt= 0.02 seconds). The file ElCentro.txt includes the two columns of acceleration data. The first column lists the acceleration at the base of the SDOF system. The second column lists the acceleration at the roof of the SDOF system. (a) Plot the time histories of the recorded accelerations at the base and at the roof of the SDOF system. (b) Compute the acceleration, velocity and displacement time histories of the roof of the SDOF system subjected to the recorded base acceleration using the Central Difference method. Plot the accel- eration, velocity and displacement time histories. Plot the restoring force, the damping force, and the inertia force time…
The single degree of freedom (SDOF) system that you studied under free vibration in Assignment #3 - Laboratory Component has been subjected to a strong ground motion. The acceleration at the base (excitation) and the acceleration at the roof (response) of the SDOF system was recorded with sampling rate 50 Hz (50 samples per second, or dt= 0.02 seconds). The file ElCentro.txt includes the two columns of acceleration data. The first column lists the acceleration at the base of the SDOF system. The second column lists the acceleration at the roof of the SDOF system. (a) Plot the time histories of the recorded accelerations at the base and at the roof of the SDOF system. (b) Compute the acceleration, velocity and displacement time histories of the roof of the SDOF system subjected to the recorded base acceleration using the Central Difference method. Plot the accel- eration, velocity and displacement time histories. Plot the restoring force, the damping force, and the inertia force time…
A tensile specimen made of hot-rolled AISI 1020 steel is loaded to point corresponding to a strain of 43%.
60
Su = 66 ksi
Stress σ (ksi)
40 B
20
0
0
0
T
H
Sy = 39 ksi
Se = 36 ksi
Hot-rolled 1020 steel
F
10 20 30 40
50 60 70 80 90 100 110 120 130 140 150 160
Strain € (%)
T
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6
Area ratio R
0.1
0.2
0.3
0.4
0.5
Area reduction A,
What value of strain is applicable to this location?
0.6
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