Number of tube passes of shell and tube heat exchanger

There are several tube passes from 1 to 8, and the commonly used ones are 1, 2 or 4 tube passes. As the number of tube passes increases, the flow velocity in the tube increases, and the convective heat transfer coefficient also increases. However, the flow rate in the tube is limited by the pressure drop of the tube side. The flow rate commonly used in industrial production is: the flow rate of water and similar fluids is generally 1 to 2.5 m/s. The cooling water flow rate for large condensers can be increased to 3m/s. The flow velocity of gas and steam can be selected in the range of 8-30m/s.