Solution :
Characteristic length = thickness / 2
= 0.02 m
Thermal conductivity for steel is 42.5 W/m.K
= 0.014
Since the Biot number is less than 0.01, the lumped system analysis is applicable.
Where,
T = temperature after t time
= surrounding temperature
= initial temperature
t = time
We calculate B:
= 0.000416
Thus,
t = 5281.78 second
= 88.02 minutes
Thus the time taken for reaching 100 degree Celsius is 88.02 minutes.
I think it’s A
Hope I helped
The three load contacts connected between the three-phase power line and the motor close to connect the motor to the line. The normally open auxiliary contact connected in parallel with the two Start buttons closes to maintain the circuit to M coil when the Start button is released.
Answer:
T surface = 3.9°C
Explanation:
given data
emissivity 0.6
absorptivity = 0.2
solar radiation is incident rate = 1200 W/m²
solution
we get here surface temperature by equality of emitted and absorbed heat rate that is
Q (absorbed) = Q (heat ) .................1
α Qinc =
T surface = ..........................2
put here value and we get
T surface =
T surface = 276.9 K
T surface = 3.9°C
Answer:
Head loss = 28.03 m
Explanation:
According to Bernoulli's theorem for fluids we have
Applying this between the 2 given points we have
Here is the head loss that occurs
Since the pipe is horizantal we have
Applying contunity equation between the 2 sections we get
Since the cross sectional area of the both the sections is same thus the speed
is also same
Using this information in the above equation of head loss we obtain
Applying values we get