Question

1. A tank of air contains 100 ft^3. The pressure and temperature
are 1000 F and 100 psia. The air

is cooled to 100 F.

a. Find the mass of the air

b. Find the initial energy of the tank (Btu)

c. Find the final energy of the tank (Btu)

d. Compute the heat (Btu)

2. Water is contained inside a constant pressure piston cylinder
device. The initial temperature

and quality of the water are x=0 and T=300 F. The water is heated
to 500 F. The mass of the

water is 2 lbm. The cross-sectional area of the piston is 10
in^2.

a. Find the initial energy of the water (Btu)

b. Find the final energy of the water (Btu)

c. Determine how much work crossed the boundary (Btu). Hint use
integral of Fdx

d. Determine how much heat crossed the boundary (Btu). Hint use an
energy balance

Answer #1

A piston cylinder contains 2 lbm of air and operates at a
constant pressure of 400 psia. The initial volume is 1 ft.3 and the
initial temperature is 100°F. The final volume is 4 ft.3 and the
final temperature is 1780°F. Determine the work and its direction
(in or out) and the heat transfer and its direction, in
Btu/lbm.

A closed, rigid steel tank contains 1 lbm of water, initially at
260 F and a quality of 60%. The tank is fitted with a paddle wheel
and the water is stirred until the temperature is 350 F. The tank
is well insulated on the outside and the steel is in thermal
equilibrium with the water. The mass of the steel tank itself (not
including water) is 60 lbm and the specific heat of the tank is
0.115 Btu/lbm·R. Changes...

A closed, rigid steel tank contains 1 lbm of water, initially at
260F and a quality of 60%. The tank is fitted with a paddle wheel
and the water is stirred until the temperature is 350F. The tank
is well insulated on the outside and the steel is in thermal
equilibrium with the water. The mass of the steel tank itself (not
including water) is 60 lbm and the specific heat of the tank is
0.115 Btu/lbm·R. Changes in kinetic...

A rigid tank contains 20lbm of air at 80ºF and 35
psig. Heat is added until the pressure doubles to 70 psig.
Rair = 0.3704 psia-ft3/lbm-R
Draw the P-v and T-v diagrams for the problem.
What is the volume of the tank ft3?
What is final temperature of the air in ºF?
How much heat is transferred in the process in Btu?

Problem 17-2: Determine the heat transfer required to cause a
tank initially pressurized with air to discharge isenthalpically.
The initial state inside the tank is 1500 psia, 100 F, 10 lbm. The
final state is 14.7 psia and .098 lbm. Assume ideal gas
behavior.

A compressed air tank has a volume of 0.81 ft3. The
temperature is 70 °F and the atmospheric pressure is 14.7 psia.
When the tank is filled with air at a pressure of 46 psig,
determine the density of the air and the weight of air in the
tank.
Answer in lb

An industrial facility needs a flow of 100 gpm of hot water at
180°F, 50 psia. Two designs are being considered to make the hot
water. In Design 1, the hot water is produced by injecting steam
into an insulated mixing chamber through which the water passes.
The water enters the chamber at 50°F, 50 psia. Steam is injected
into the chamber at 325°F, 50 psia. The hot water leaves at the
required flow rate and temperature. For this system...

Atmospheric pressure is 100 kPa in a system of cylinders and pistons.The mass of the piston is 4 kg and the area of the piston is 4.0 cm2. The following process takes place by external heat transfer. (Gravity acceleration is 10 m / s2).
1. Calculate the pressure inside the cylinder in kPa.
2. The cylinder contains 0.1 kg of water vapor, and the
temperature of the water vapor is 150oC. Find the volume and
internal energy of water vapor...

A piston cylinder device contains air with a volume of 0.05 m3
at 25oC and 100 kPa pressure. The gas is now compressed to a final
temperature of 95oC at 250 kPa. This compression is polytropic and
follows PVn=constant.
a. Determine how much boundary work was added to the gas [in
kJ]
b. How much heat was added or removed from this system during
this process? [in kJ]

Air enters the evaporator section of a window air conditioner at
14.7 psia and 90°F with a volume flow rate of 200 ft3 /min.
Refrigerant-134a at 20 psia with a quality of 30 percent enters the
evaporator at a rate of 4 lbm/min and leaves as saturated vapor at
the same pressure. Determine (a) the exit temperature of the air
and (b) the rate of heat transfer from the air.

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