A one-dimensional slab of thickness 2L is initially at a uniform temperature T i . Suddenly, electric current is passed through the slab causing uniform volumetric heating q . ( W/m 3 ) . At the same time, both outer surfaces ( x = ± L ) are subjected to a convection process at T ∞ with a heat transfer coefficient h. Write the finite-difference equation expressing conservation of energy for node 0 located on the outersurface at x = − L . Rearrange your equation and identify any important dimensionless coefficients.
A one-dimensional slab of thickness 2L is initially at a uniform temperature T i . Suddenly, electric current is passed through the slab causing uniform volumetric heating q . ( W/m 3 ) . At the same time, both outer surfaces ( x = ± L ) are subjected to a convection process at T ∞ with a heat transfer coefficient h. Write the finite-difference equation expressing conservation of energy for node 0 located on the outersurface at x = − L . Rearrange your equation and identify any important dimensionless coefficients.
Solution Summary: The author explains the finite difference expressing conservation of energy for node 0 in terms of dimensionless numbers.
A one-dimensional slab of thickness 2L is initially at a uniform temperature
T
i
.
Suddenly, electric current is passed through the slab causing uniform volumetric heating
q
.
(
W/m
3
)
.
At the same time, both outer surfaces
(
x
=
±
L
)
are subjected to a convection process at
T
∞
with a heat transfer coefficient h.
Write the finite-difference equation expressing conservation of energy for node 0 located on the outersurface at
x
=
−
L
.
Rearrange your equation and identify any important dimensionless coefficients.
2 A metal block of mass m = 10 kg is sliding along a frictionless surface with an initial speed
Vo, as indicated below. The block then slides above an electromagnetic brake that applies a
force FEB to the block, opposing its motion. The magnitude of the electromagnetic force
varies quadratically with the distance moved along the brake (x):
10
FEB = kx²,
with k
= 5
N
m²
V₁ = 8 m/s
m = 10 kg
FEB
Frictionless surface
Electromagnetic brake
⇒x
Determine how far the block slides along the electromagnetic brake before stopping, in m.
Q1: Determine the length, angle of contact, and width of a 9.75 mm thick
leather belt required to transmit 15 kW from a motor running at 900 r.p.m. The
diameter of the driving pulley of the motor is 300 mm. The driven pulley runs at
300 r.p.m. and the distance between the centers of two pulleys is 3 meters. The
density of the leather is 1000 kg/m³. The maximum allowable stress in the
leather is 2.5 MPa. The coefficient of friction between the leather and pulley is
0.3. Assume open belt drive.
5. A 15 kW and 1200 r.p.m. motor drives a compressor at 300 r.p.m. through a pair of spur gears having
20° stub teeth. The centre to centre distance between the shafts is 400 mm. The motor pinion is made
of forged steel having an allowable static stress as 210 MPa, while the gear is made of cast steel
having allowable static stress as 140 MPa. Assuming that the drive operates 8 to 10 hours per day
under light shock conditions, find from the standpoint of strength,
1. Module; 2. Face width and 3. Number of teeth and pitch circle diameter of each gear.
Check the gears thus designed from the consideration of wear. The surface endurance limit may be
taken as 700 MPa. [Ans. m = 6 mm; b= 60 mm; Tp=24; T=96; Dp = 144mm; DG = 576 mm]
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