Shell and Tube heat Exchanger
Our shell & tube heat exchangers are utilized in many comfort & industry usages for cooling & heating fluids. They consist of a shell with traditional plain tubes or enhanced surface tubes for high thermal performance. The fluids can be liquids or gases, one of which flows inside the tubes while the other flows outside the tubes within the shell. There are single-phase or two-phase heat exchangers, and the latter is used to either boil or condense fluids.
Shell-and-Tube Heat Exchangers Construction Details
The shell-and-tube heat exchanger is named for its two major components - round tubes mounted inside a cylindrical shell.
The shell cylinder can be fabricated from rolled plate or from piping (up to 24 inch diameters). The tubes are thin-walled tubing produced specifically for use in heat exchangers.
Other components include: the channels (heads), tubesheets, baffles, tie rods & spacers, pass partition plates and expansion joint (when required). Shell & tube heat exchanger designs and constructions are governed by the TEMA and ASME codes.
Tubing may be seamless or welded. Seamless tubing is produced in an extrusion process; welded tubing is produced by rolling a strip into a cylinder and welding the seam. Welded tubing is usually more economical.
Normal tube diameters are 5/8 inch, 3/4 inch and 1 inch. Tubes of smaller diameter can be used but they are more difficult to clean mechanically. Tubes of larger diameter are sometimes used either to facilitate mechanical cleaning or to achieve lower pressure drop.
The normal tube wall thickness ranges from 12 to 16 BWG (from 0.109 inches to 0.065 inches thick). Tubes with thinner walls (18 to 20 BWG) are used when the tubing material is relatively expensive such as titanium.
Tubing may be finned to provide more heat transfer surface; fining is more common on the outside of the tubes, but is also available on the inside of the tubes. High flux tubes are tubing with special surface to enhance heat transfer on either or both sides of the tube wall. Inserts such as twisted tapes can be installed inside tubes to improve heat transfer especially when handling viscous fluids in laminar flow conditions. Twisted tubes are also available. These tubes can provide enhanced heat transfer in certain applications.
The shell-and-tube heat exchanger is by far the most common type of heat exchanger used in industry. It can be fabricated from a wide range of materials both metallic and non-metallic. Design pressures range from full vacuum to 6,000 psi. Design temperatures range from -250oC to 800oC. Shell-and-tube heat exchangers can be used in almost all process heat transfer applications.
The shell-and-tube design is more rugged than other types of heat exchangers. It can stand more (physical and process) abuse. However, it may not be the most economical or most efficient selection especially for heat recovery applications or for highly viscous fluids. The shell-and-tube heat exchanger will perform poorly with any temperature crosses unless multiple units in series are employed.
Typical applications include condensers, reboilers and process heaters and coolers.