Question

Three kilograms of steam undergoes an isothermal process from 27.5 bars and 320°C to 7 bars. Determine (a) the amount of heat transferred, in kJ, and (b) the non-flow work done, in kJ, during the process.

Answer 1

(a) The amount of heat transferred шs zero for all isothermal processes as the temperature does not change.

(b) The non-flow work done for such a process is

$$Q=\Delta E+W=0+W,\\ W=Q.\\\space\\ Q=RT\text{ ln}\frac{p_1}{p_2}=\\\space\\ =8.314·(273.15+320)\text{ ln}\frac{27.5}{7}=\\\space\\ =6750\text{ J, or 6.75 kJ}.$$