Question

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 Cv = 0.718 kJ/kg-K, find (a) final temperature - K, (b) mass leaving the cylinder - kg, (c) work - kJ, (d) total entropy change - kJ/K. Assume the enthalpy of the exiting air is that of air at the average of the initial and final temperatures.

Answer #1

In a cylinder/piston arrangement, air is compressed in a
reversible polytropic process to a final state of 800 kPa, 500 K.
Initially air is at 110 kPa and 25oC. During the
compression process heat transfer takes place with the ambient
maintained at 25oC. Assume air as an ideal gas (R =0.287
kJ/kg) and has constant specific heats of Cp = 1.004
kJ/kgK and Cv = 0.717 kJ/kgK. If the mass of air in the
cylinder is 0.1286 kg, determine
a)...

A 0.2 m3 piston/cylinder contains air at 400 K and
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A piston cylinder device contains a mixture of 0.2 kg of H2 and
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Consider a cold air-standard Diesel cycle. At the beginning of
compression, 102 kPa, and 300 K. The mass of air is 0.120 kg, the
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For a cold air-standard analysis use the following values: cp =
1.005 kJ/kgK, cv = 0.718 kJ/kgK, k=1.40, M=28.97 kg/kmol.
Determine the following :
(a) pressure at end of compression stroke, in kPa
(b) temperature at end of compression stroke, in K
(c) maximum temperature in...

A piston cylinder contains 2 lbm of air and operates at a
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A piston-cylinder device with a set of stops initially contains
0.35 kg of steam at 1.0 MPa and 900 degrees C. The location of the
stops corresponds to 44 percent of the initial volume. Now the
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the final state is (A) 1.0 MPa and 600 degrees C and W=. kJ (B) 500
kPa. W=. kJ (C) Also determine the temperature at the final state
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1-kg water in a frictionless piston-cylinder device is initially
at 250°C and 300 kPa (state
1). A total of 700 kJ of work is done ON the water
in order to isothermally reduce its volume to
1/20 of its initial volume (state 2). Determine the magnitude and
direction of the heat transfer
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Answer: -1147 kJ.

A quantity of air is contained in a cylinder provided
with a movable piston. Initially the
pressure of the air is 4 × 107 N/m2
, the volume is 1.5 m3
and the temperature is 400 K.
Assume air is an ideal gas. (a) What are the final volume and
temperature of the air if it is
allowed to expand isothermally from initial conditions until the
pressure is 3 × 107 N/m2
and
then is cooled at constant volume until...

A hot air balloon, initially an expandable sphere 10 meters in
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Centigrade. 1000 KJoules of heat are transferred to the gas.
(Helium cp=5.19 kJ/(kg-K), cv=3.12
kJ/(kg-K)(Volume of a sphere = 4/3*Pi*r3)
What is the final pressure in the balloon if the process takes
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What is the final volume in the balloon if the process takes
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1 kg of water in a piston cylinder arrangement is initially in a
saturated liquid state at 1 bar. It undergoes expansion at constant
pressure due to external heat supply to it, to a final state of
saturated vapor.
(i) What is the initial temperature of water in C? (a) 93.50 (b)
96.71 (c) 99.63 (d) 111.4 (e) 12.2
(ii) What is the change in enthalpy of water (kJ/kg-K)? (a)
417.46 (b) 2258.0 (c) 2675.5 (d) 2506.1
(iii) What is...

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