Question

Air expands in a polytropic process (n = 1.35) from 2 MPa and 1200 K to 150 kPa in a piston/cylinder. Determine per unit mass of air the work produced and the heat transferred during the expansion process in kJ/kg.

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 piston cylinder device contains 0.15 kg of air initially at 2
MPa and 350 C. First, the air expands isothermally to a pressure of
500 kPa. Then, it is compressed polytropically back to the initial
pressure (2 MPa) with a polytropic exponent of 1.2. Find the work
performed or introduced by or to the air for each process. Express
it both times in kJ.

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...

Two kilograms of air undergo a polytropic process (n = 1.3) from
600 K and 200 kPa to 900 K. Considering the system and surroundings
as an isolated system, find the entropy change of the air and the
entropy production.
Answers: -0.1938 kJ/K, 0.284 (Engineering Thermodynamics)

0.5 kilograms of air are compressed from 100 kPa and 300 K in a
polytropic process, n = 1.3, to a state where V2 = 0.5
V1. The air is further compressed at constant pressure
until the final volume is 0.2 V1 . Draw a sketch of the
processes on a p-V diagram. Determine the work for each
process.

The state of 1.5 kg of air is polytropically changed from 0.088
MPa and 18?C to 0.981 MPa and 125?C. Determine (a) value of the n
constant in the expression PVn = C that describes the polytropic
process, (b) boundary work done in the process, in kJ, and (c)
whether the work is done “to” or “by” the system

A 0.2 m3 piston/cylinder contains air at 400 K and
400 kPa and receives heat from a constant temperature heat source
at 1300 K. The piston expands at constant pressure to a
volume of 0.6 m3. Determine the change of availability
of the system.

Consider an ideal Ericsson cycle with air as the working fluid
executed in a steady-flow system. Air is at 27°C and 110 kPa at the
beginning of the isothermal compression process, during which 150
kJ/kg of heat is rejected. Heat transfer to air occurs at 950 K.
The gas constant of air is R = 0.287 kJ/kg·K.
a.)The maximum pressure in the cycle is? kPa
b.)The net work output per unit mass of air is? kJ/kg
c.)The thermal efficiency of...

1) An air-standard Otto cycle has a compression ratio of 9. At
the beginning of the compression process, the temperature is 20°C,
and the pressure is 100 kPa. The heat added is 500 kJ/kg. Determine
the cycle efficiency, work output, and the heat rejected
2) An air-standard Otto cycle operates with a minimum
temperature of 300 K and a maximum temperature of 1700 K. The
compression ratio of the cycle is 7. At the beginning of the
compression process, the...

10) An air-standard Otto cycle has a compression ratio of 9. At
the beginning of the compression process, the temperature is 20°C,
and the pressure is 100 kPa. The heat added is 500 kJ/kg. Determine
the cycle efficiency, work output, and the heat rejected.
11)An air-standard Otto cycle operates with a minimum
temperature of 300 K and a maximum temperature of 1700 K. The
compression ratio of the cycle is 7. At the beginning of the
compression process, the pressure...

ADVERTISEMENT

Get Answers For Free

Most questions answered within 1 hours.

ADVERTISEMENT

asked 2 minutes ago

asked 2 minutes ago

asked 4 minutes ago

asked 8 minutes ago

asked 8 minutes ago

asked 12 minutes ago

asked 12 minutes ago

asked 12 minutes ago

asked 13 minutes ago

asked 15 minutes ago

asked 17 minutes ago

asked 17 minutes ago