Shell and tube heat exchangers are widely used in process industries due to their large heat transfer area to volume ratio and mechanical durability. They consist of tubes bundled together in a shell, with one fluid flowing inside the tubes and another on the shell side. Baffles are used to direct shell side flow across the tubes, improving heat transfer. Kern's method allows simple calculation of shell side heat transfer coefficients and pressure drop through use of fictitious flow parameters. Design of shell and tube heat exchangers involves determining fluid allocation, velocities, number of tubes, and performing thermal and hydraulic analyses of both tube and shell sides.