Chapter 6, Problem 6.36P

Interpretation Introduction

Interpretation:

The heat involved and the work done by 4 kg of steam during a reversible isothermal expansion process from 400 kPa and $175\text{C}$ to a final pressure where the steam is just saturated.

Concept introduction:

According to the first law of thermodynamics, the change in internal energy of the system is given as:

$\begin{array}{l}\text{ΔU = Q - W}\\ \text{where, Q is the heat and W is the work done}\end{array}$

$\begin{array}{l}\text{Since this is an isothermal expansion process, }\Delta \text{U=0}\\ \text{Q = W = nRTln}\frac{{\text{V}}_{\text{2}}}{{\text{V}}_{\text{1}}}\\ {\text{here, V}}_{\text{1}}{\text{ and V}}_{\text{2}}\text{ are the initial and final volumes of steam}\\ \text{n = number of moles of steam}\end{array}$