1. A piston–cylinder device contains 5 kg of water at 800kPa and 70°C. The water is now cool at constant pressure until it exists as a liquid at 15°C. Determine the amount of heat loss and show the process on a T-v diagram with respect to saturation lines.

How do I determine the heat loss?

A piston–cylinder assembly contains air modeled
as an ideal gas with a constant specific heat ratio, k =
1.4. The air undergoes a power cycle consisting of
four processes in series: Process 1–2: Constanttemperature expansion at 600 K from p1 = 0.5 MPa to
p2 = 0.4 MPa. Process 2–3: Polytropic expansion with
n = 1.35 to p3 = 0.3 MPa. Process 3–4: Constantpressure compression to V4 = V1. Process 4–1:
Constant-volume heating. Determine (a) the work and
heat transfer for each process, in kJ/kg, and (b) the
thermal efficiency. 

3. Explain why, for a gas, the specific heat at constant volume has a different value 
from the specific heat at constant pressure.
An ideal gas is contained in a cylinder fitted with a piston. Initially the temperature of the 
gas is 15℃. If the mass of the gas is 0.035 kg, calculate the quantity of heat energy 
required to raise the temperature of the gas to 150 ℃ when:
(a) The piston is fixed;
(b) The piston moves and the pressure is constant.
For the gas, 𝑐𝑣 = 676 J/kg-K and 𝑐𝑝 = 925 J/kg-K.