What are the main types of heat exchangers used in process plants?

Shell and tube: most common, versatile, handles high pressures and temperatures, TEMA standards. Plate heat exchangers: compact, high efficiency, good for clean fluids, easily expandable. Air coolers (fin-fan): uses air for cooling, no cooling water needed, higher capital but lower operating cost. Double pipe: simple, small duties, easy maintenance. Spiral: handles slurries and fouling fluids. Plate-fin: compact, cryogenic applications. Selection factors: temperature and pressure, fouling tendency, material compatibility, space constraints, and cost. Shell and tube dominates in refineries and chemical plants; plates common in food and pharmaceutical industries.