Approximately 70-80% of the heat exchanger market is held by the shell-and-tube type heat exchanger. It is largely favored due to its long performance history, relative simplicity, and its wide temperature and pressure design ranges. In essence, a shell-and-tube exchanger is a pressure vessel with many tubes inside. One process fluid flow through the tubes of the exchanger while the other flows outside of the tubes within the shell. The tube side and shell side fluids are separated by a tube sheet. Specific heat exchangers differ in the number of shell passes and the number of tube passes. The simplest form, which involves single tube and shell passes, Baffles are usually installed to increase the convective heat transfer coefficient of the shell-side fluid by inducing turbulence and a cross-flow velocity component. As such, shell-and-tube heat exchangers have neither pure counter-flow nor pure cross-flow, and the thermal analysis can be quite complex
