Engineering reference for Indian students

Thermal & fluids

Thermodynamics

5 self-contained study topics — notes, diagrams, formulas, and worked examples for exams and GATE.

Topics

First Law of Thermodynamics
$\delta Q = dU + \delta W$ (differential form, P.K. Nag sign convention)
Second Law of Thermodynamics
$dS \ge \frac{\delta Q}{T}$ (Clausius inequality)
Entropy and Availability
$dS \ge \frac{\delta Q}{T}$ (Clausius inequality)
$Irreversibility I = T_{0} \Delta S_{gen}$
Properties of Pure Substances
For a pure substance the state in the wet region is fixed by pressure and dryness fraction x = m_vapour/m_total, giving h = h_f + x·h_fg and s = s_f + x·s_fg. Enthalpy h = u + Pv links to steam-table data, per P.K. Nag.
$Clapeyron: \frac{dh_{fg}}{T} = v_{fg} = \frac{h_{fg}}{T}(v_{g} - v_{f})$
Thermodynamic Cycles
A power cycle's thermal efficiency is η = W_net/Q_in = 1 − Q_out/Q_in; the net work equals the enclosed area on both the P–v and T–s diagrams. Clockwise cycles are engines, anticlockwise are refrigerators, per P.K. Nag.
$Back work ratio = \frac{W_{comp}}{W_{turbine}}$