heat exchanger

Heat exchangers transfer thermal energy between two fluids for temperature control without mixing the fluids. **Principle**: Hot and cold fluids flow through adjacent channels separated by thermally conductive material. Heat transfers from hot to cold side. **Types in fabs**: **Shell and tube**: One fluid through tubes, other in surrounding shell. Robust, common. **Plate**: Thin corrugated plates create fluid channels. Compact, efficient heat transfer. **Types by application**: **Liquid-liquid**: PCW to tool coolant, chemical temperature control. **Air-liquid**: Cooling towers, dry coolers. **Process applications**: Temper chemicals before delivery, recover heat from exhaust, cool process loops, HVAC systems. **Materials**: Stainless steel, titanium, or specialty materials for corrosive fluids. Material compatibility critical. **Fouling**: Scale and buildup reduce efficiency. Regular cleaning and water treatment. **Sizing**: Based on heat load, flow rates, temperature differential, and allowable pressure drop. **Maintenance**: Inspect for leaks, clean surfaces, monitor performance degradation.