businessIndustry Information

Tube Heat Exchangers

Tube heat exchangers are one of the many types of heat exchangers, which are devices made to facilitate heating and cooling by transferring heat from one from gaseous or liquid substance to another. The purpose of tube heat exchangers in particular, which are also known as shell and tube heat exchangers, is to transfer heat energy from one liquid to another. Tube heat exchangers are made up of a series of tubes within a shell or a large pressure vessel. They are popular in such as industries as: aerospace, automotives, food processing, heating and cooling, pharmaceuticals and waste treatment.

Manufacturers have many type options from which to choose when they are designing the tube element of heat exchangers. The first choice available to manufacturers is the choice of material. The most important aspect of a tube material is its thermal conductivity. The material must have excellent thermal conductivity because, because the tubes will be transferring heat and because of the tendency of tubes towards thermal stresses. In addition, manufacturers must also consider that, for the sake of corrosion prevention, a tube material must be able to handle both tube side and shell fluids for long periods of time, no matter the operating conditions. Thermally conductive, strong and corrosion resistant materials like these include metals and polymers such as: stainless steel, carbon steel, non-ferrous copper alloy, copper alloy (such as the material sold by the suppliers listed here), nickel Inconel, Hastelloy, titanium, Perfluoroalkoxy alkane (PFA), Fluorinated ethylene propylene (FEP) and other fluoropolymers.

Some of the tube types that tube heat exchangers may implement include: U-tubes, which are bent in a “U” shape, and plain or longitudinally finned tubes, which may either be in either a bundle, or set, of straight or U-tubes. In brief, tube heat exchangers may be made using one of three main designs. These are: U-tube heat exchangers straight-tube heat exchangers and spiral heat exchangers. Other than tube shape, however, the design of one exchanger is not much different than another. Inside the shell of tube exchangers resides the aforementioned tube bundle. Of this bundle, one tube contains the fluid to be heated or cooled, called the incoming fluid, and another tube holds the liquid intended to transfer the heating or cooling energy. This latter liquid is known as the outgoing fluid. To successful transfer thermal energy from one liquid to the other, the second tubing runs over the first, with only the tube walls separating them. The tube walls act as metal partitions and conductors between the two fluids. Also, the surface area of said tube walls directly influence efficiency and speed; the larger the surface area of a tube wall, the more efficient and quicker the heat transfer. With tube heat exchangers, thermal energy flows only from the hotter liquid to the cooler liquid, in an effort to reach an equilibrium.

The section above outlines the basic design and function of tube heat exchangers. From here, tube exchangers differ based on their design: In the U-tube exchanger design, the tube bundle is used to house the fluid on the its outside area. In order to direct the fluid into the tube bundle, a U-tube exchanger has a head assembly bolted to its shell. Straight-tube heat exchangers, on the other hand, allow them to exchange heavy flowing fluids, as well as handle applications in which temperature cross conditions occur. Finally, as their name implies, spiral heat exchangers have spiral bodies. These bodies exist inside the exchanger shell. They are created out of two flat surfaces, usually metal strip surfaces with welded on spacer studs, that are either coiled or rolled around a central core, in order to form two spiral channels or a helically configured pattern. To ensure they work well, the alternate sides of each of the channels are welded with two conical or flat gasket covers bolted over the sides of the spiral body.

Because of the shapes of their design, tube exchangers are extremely durable. This durability is an important feature of these exchangers because they, one, they are designed to disallow any direct contact or mixing between liquids, and, two, they are typically used with high temperature and high pressure applications. Tube heat exchangers are so frequently used for high stakes liquid heat exchange applications that they are considered the most commonly used type of heat exchanger used in large chemical processes and oil refineries. As such, tube heat exchanger manufacturers offer many different modifications to the basic model, in order to accommodate a variety of applications. Such applications include: air conditioning, boiler sample coolers, hot tubs, oil coolers, process heat removal, transmission and engine coolers and waste water heat recovery. Spiral exchangers in particular are incredibly well-suited to applications dealing with alcohol, chemical processing, food processing, oil and gas, mining, pharmaceuticals, waste water treatment and other liquids that may contain solids.