Answer:
79 kW.
Explanation:
The equation for enthalpy is:
H2 = H1 + Q - L
Enthalpy is defined as:
H = G*(Cv*T + p*v)
This is specific volume.
The gas state equation is:
p*v = R*T (with specific volume)
The specific gas constant for air is:
287 K/(kg*K)
Then:
T1 = 60 + 273 = 333 K
T2 = 200 + 273 = 473 K
p1*v1 = 287 * 333 = 95.6 kJ/kg
p2*v2 = 287 * 473 = 135.7 kJ/kg
The Cv for air is:
Cv = 720 J/(kg*K)
So the enthalpies are:
H1 = 0.8*(0.72 * 333 + 95.6) = 268 kW
H2 = 0.8*(0.72 * 473 + 135.7) = 381 kW
Ang the heat is:
Q = 34 kW
Then:
H2 = H1 + Q - L
381 = 268 + 34 - L
L = 268 + 34 - 381 = -79 kW
This is the work from the point of view of the air, that's why it is negative.
From the point of view of the machine it is positive.
Answer:
Option C
Both A and B
Explanation:
Both technicians are right about what they say about wire brushes. wire brushes are usually made up of steel wire bristles. however, when high RPMs are involved, it is better to get some special types of brushes for that purpose. This is because the heat generated at high RPMs is great, and most times, damages the brush after prolonged use if it is not specially built for such speeds.
In addition that, some wire brushes have plastic hubs which help support the bristles and is usually attached to the motor.
Considering these, we can say that the Two technicians are right
Answer:
A soldering process
Explanation:
Given that ,The filler metal's melting point temperature is less than 450 ° C.
Usually, the brazing material has the liquid temperature of the melting point, the full melting point of the filler material approaching 450 degrees centigrade, while the filler material is less than 450 degrees centigrade in the case of soldering.
Therefore the answer is "A soldering process".
