Answer:B
Explanation:
Given
For motor A
Characteristic life(r)=4100 hr
MTTF=4650 hrs
shape factor(B )=0.8
For motor B
Characteristic life(r)=336 hr
MTTF=300 hr
Shape Factor (B)=3
Reliability for 100 hours
For B
B is better for 100 hours
(b)For 750 hours
So here B is more Reliable.
Answer:
The total tube surface area in m² required to achieve an air outlet temperature of 850 K is 192.3 m²
Explanation:
Here we have the heat Q given as follows;
Q = 15 × 1075 × (1100 - ) = 10 × 1075 × (850 - 300) = 5912500 J
∴ 1100 - = 1100/3
= 733.33 K
Where
= Arithmetic mean temperature difference
= Inlet temperature of the gas = 1100 K
= Outlet temperature of the gas = 733.33 K
= Inlet temperature of the air = 300 K
= Outlet temperature of the air = 850 K
Hence, plugging in the values, we have;
Hence, from;
, we have
5912500 = 90 × A × 341.67
Hence, the total tube surface area in m² required to achieve an air outlet temperature of 850 K = 192.3 m².