Question 2 of 4 · Ideal Gases and Property Relations · Intermediate · About 17 min

Constant-pressure cooling of a piston charge

Air inside a frictionless piston-cylinder starts at $170\,\mathrm{kPa}$ absolute, $315\,\mathrm{K}$ and $0.320\,\mathrm{m^3}$ . During slow cooling the pressure stays constant while the volume falls to $0.270\,\mathrm{m^3}$ . Use $R=0.287$ , $c_p=1.005\,\mathrm{kJ/(kg\,K)}$ . Find the gas mass, final temperature, boundary work by the gas, and heat transfer.

An ideal gas cools beneath a moving piston while pressure remains constant. — Schematic, not to scale unless dimensions are given.

Given

P = 170 kPa
T1 = 315 K
V1 = 0.320 m³
V2 = 0.270 m³
R = 0.287 and cp = 1.005 kJ/(kg K)

Find

Gas mass
Final temperature
Boundary work by gas
Heat transfer into gas

Assumptions

Ideal gas; quasistatic constant-pressure cooling; no other work.

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Constant-pressure cooling of a piston charge

Given

Find

Assumptions

Worked solution