The shell and tubes are typically made of metal alloys such as stainless steel, carbon steel, or titanium, depending on the specific application and requirements. The tubes are usually arranged in a bundle within the shell, with tube sheets at both ends to support and seal the tubes. The shell may have multiple passes for the fluid flowing around the tubes, increasing the heat transfer area and efficiency.

Shell and tube heat exchangers can have various flow configurations, including parallel flow, counterflow, and crossflow. In parallel flow, both fluids flow in the same direction, while in counterflow, they flow in opposite directions. Crossflow involves one fluid flowing perpendicular to the other.

Heat transfer in shell and tube heat exchangers occurs primarily through conduction across the tube walls. The temperature difference between the two fluids creates a thermal gradient across the tube walls, allowing heat to transfer from the hotter fluid to the cooler fluid. The efficiency of heat transfer depends on factors such as the design of the exchanger, flow rates, fluid properties, and fouling.