Take CV as the Ammonia, constant mass — small flexible bag contains 10oC and 300 kPa material such that pressure — Continuity

A small flexible bag contains 0.1 kg ammonia at –10oC and 300 kPa. The bag material is such that the pressure inside varies linear with volume. The bag is left in the sun with with an incident radiation of 75 W, loosing energy with an average 25 W to the ambient ground and air. After a while the bag is heated to 30oC at which time the pressure is 1000 kPa. Find the work and heat transfer in the process and the elapsed time.

SOLUTION

Take CV as the Ammonia, constant mass.

Continuity Eq.: m2 = m1 = m;

Energy Eq.5.11: m(u2 − u1) = 1Q2 – 1W2

Process: P = A + BV (linear in V)

State 1: Compressed liquid P > Psat, take saturated liquid at same temperature.