A piston-cylinder assembly contains 2 lb of air at a temperature of 540 °R and a pressure of 1 atm. The air compressed to a stat
e where the temperature is 840 °R and the pressure is 6 atm. During the compression, there is a heat transfer from the air to the surroundings equal to 20 Btu.
1. Using the ideal gas model for air, determine the work during the process in Btu.
1. Using the ideal gas model for air, determine the work during the process in Btu.
1 answer:
Answer:
123.9 Btu
Explanation:
The energy balance on the air is:
∆E = E2 − E1 = ∆KE + ∆PE + ∆U = Q + W
ignore ∆KE and ∆PE,
W = ∆U − Q = m(u2 − u1) − Q; (u2 − u1 = 51.94 Btu/lb)
ideal gas properties is attached
W = (2 lb)(143.98 − 92.04) Btu/lb − (− 20 Btu) = 123.9 Btu
u2 − u1 ≈ cv(T2 − T1) = (0.173 Btu/lb°R)(840 − 540) °R = 51.9 Btu/lb
You might be interested in
Answer:
The heat is transferred is at the rate of 752.33 kW
Solution:
As per the question:
Temperature at inlet, = 273 + 20 = 293 K
Temperature at the outlet, = 273 + 200 = 473 K
Pressure at inlet,
Pressure at outlet,
Speed at the outlet,
Diameter of the tube,
Input power,
Now,
To calculate the heat transfer, , we make use of the steady flow eqn:
where
= specific enthalpy at inlet
= specific enthalpy at outlet
= air speed at inlet
= specific power input
H and H' = Elevation of inlet and outlet
Now, if
and H = H'
Then the above eqn reduces to:
(1)
Also,
Area of cross-section, A =
Specific Volume at outlet,
From the eqn:
Now,
Also,
Now, using these values in eqn (1):
Now, rate of heat transfer, q:
q = mQ =