How does thermodynamics underpin pinch analysis for heat integration?

Pinch analysis uses thermodynamic principles to set targets for energy recovery. First law: energy balance determines total heating and cooling duties. Second law: heat flows from hot to cold, imposing temperature driving force constraint (delta_T_min). Composite curves: plot cumulative enthalpy vs. temperature for hot and cold streams; closest approach is the pinch. Above pinch: heat sink (needs external heating only); below pinch: heat source (needs external cooling only). Thermodynamic targets: minimum hot utility = gap at top of composite curves; minimum cold utility = gap at bottom. Grand composite curve shows cascade of heat between temperature intervals. Correct heat exchanger network design achieves thermodynamic targets.