The equations are based on the following assumptions
1) The bar is straight and of uniform section
2) The material of the bar is has uniform properties.
3) The only loading is the applied torque which is applied normal to the axis of the bar.
4) The bar is stressed within its elastic limit.
Nomenclature
T = torque (Nm)
l = length of bar (m)
J = Polar moment of inertia.(Circular Sections) ( m^4)
J' = Polar moment of inertia.(Non circluar sections) ( m^4 )
K = Factor replacing J for non-circular sections.( m^4)
r = radial distance of point from center of section (m)
ro = radius of section OD (m)
τ = shear stress (N/m^2)
G Modulus of rigidity (N/m^2)
θ = angle of twist (radians)
Answer:
14.52 minutes
<u>OR</u>
14 minutes and 31 seconds
Explanation:
Let's first start by mentioning the specific heat of air at constant volume. We consider constant volume and NOT constant pressure because the volume of the room remains constant while pressure may vary.
Specific heat at constant volume at 27°C = 0.718 kJ/kg*K
Initial temperature of room (in kelvin) = 283.15 K
Final temperature (required) of room = 293.15 K
Mass of air in room= volume * density= (4 * 5 * 7) * (1.204 kg/m3) = 168.56kg
Heat required at constant volume: 0.718 * (change in temp) * (mass of air)
Heat required = 0.718 * (293.15 - 283.15) * (168.56) = 1,210.26 kJ
Time taken for temperature rise: heat required / (rate of heat change)
Where rate of heat change = 10000 - 5000 = 5000 kJ/hr
Time taken = 1210.26 / 5000 = 0.24205 hours
Converted to minutes = 0.24205 * 60 = 14.52 minutes
Answer:
a) 75%
b) 82%
Explanation:
Assumptions:
Properties: The density of water
Conversions:
Analysis:
Note that the bottom of the lake is the reference level. The potential energy of water at the surface becomes gh. Consider that kinetic energy of water at the lake surface & the turbine exit is negligible and the pressure at both locations is the atmospheric pressure and change in the mechanical energy of water between lake surface & turbine exit are:
Then;
gh = 0.491 kJ/kg
= 1559 kW
Therefore; the overall efficiency is:
= 0.75
= 75%
b) mechanical efficiency of the turbine:
thus;
![\eta_{turbine} = \dfrac{\eta_{[turbine- generator]} }{\eta_{generator}} \\ \\ \eta_{turbine} = \dfrac{0.75}{0.92} \\ \\ \eta_{turbine} = 0.82 \\ \\ \eta_{turbine} = 82\%](https://tex.z-dn.net/?f=%5Ceta_%7Bturbine%7D%20%3D%20%5Cdfrac%7B%5Ceta_%7B%5Bturbine-%20generator%5D%7D%20%7D%7B%5Ceta_%7Bgenerator%7D%7D%20%5C%5C%20%5C%5C%20%5Ceta_%7Bturbine%7D%20%3D%20%5Cdfrac%7B0.75%7D%7B0.92%7D%20%5C%5C%20%5C%5C%20%5Ceta_%7Bturbine%7D%20%3D%200.82%20%5C%5C%20%5C%5C%20%5Ceta_%7Bturbine%7D%20%3D%2082%5C%25)
Answer:
The GMAW process commonly uses a constant voltage power source (GMAW-CV) that allows for a relatively constant welding voltage output over a range of welding currents. For GMAW-CV the welder selects the wire feed speed (WFS) on the wire feeder unit and an appropriate voltage on the welding power supply.