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.

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

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...

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...

1) The cp and the cv of air are, respectively, 0.24
and 0.17 Btu/Ibm.oR respectively. If 1000 Btu is added as heat to
20 Ibm of air in a nonflow, constant-pressure process, what is the
final temperature? How much work is done by the gas if the initial
temperature is 100 oF.

A rigid copper tank, initially containing 1 m3 of air at 295 K,
4 bar, is connected by a valve to a large supply line carrying air
at 295 K, 15 bar. The valve is opened only as long as required to
fill the tank with air to a pressure of 15 bar. Finally, the air in
the tank is at 310 K. The copper tank, which has a mass of 20 kg,
is at the same temperature as the...

A 0.2 m3 piston-cylinder initially contains 400 K air. A heavy
frictionless piston maintains a pressure of 500 kPa abs. Then, a
weakness in the cylinder wall blows out and creates a hole. Air
escapes through the hole until the piston drops far enough to cover
the hole. At that point, the volume is half the initial volume.
During this process, 75 kJ of heat is transferred to the 100 kPa,
300 K surroundings. Using Cp = 1.005 kJ/kg-K and...

Atmosphric air at 40 F and 50% relative humidity enters the heating
section of an airconditioning device at a volumetric flow rate of
100ft^3/min. Water vapor is added to the heated air to increase the
relative humidity to 55%. The temperature after the heating section
is 72F and the temperature at the exit is 74F. Using the
appropriate fomulas:
a) determine the rate of the heat transfer in Btu/min.
b) determine the mass flow of water vapor in lbm/min.

Consider one mole of air with initial temperature of 0 degrees
Celicus and pressure of 1000 mb. The air undergoes a polytropic
process, with its volume expanded 3 times at 250 mb. Calculate:
(a) The power n of the polytropic process;
(b) The final temperature;
(c) The change of internal energy, the work done on, and the
heat absorbed by the system.

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