The Major Components of Heat Exchangers
June 13, 2016
Heat exchangers are not only one of the most common pieces of equipment found on industrial sites, they are also one of the most important. Despite the name, heat exchangers are used for both heating and cooling and are actually used more often for cooling, especially on industrial sites such as refineries or processing plants. These pieces of equipment are not “one size fits all.” In fact, there are many different types of exchangers and each has its own distinct advantages and disadvantages. Some are created for specific industries or purposes. Despite the differences, they all have the same basic setup.
Tubes are perhaps the most important component of a heat exchanger. Used to transfer liquids, tubing may be welded or seamless, but welded tubing is known to be more economical. Most heat exchangers have tube diameters of 5/8 inch, 3/4 inch or 1 inch. Some have smaller tubes, but these should be avoided if possible because they are harder to clean. Plants that wish to achieve a lower pressure drop might use tubes with larger diameters. Some tubes have inserts known as twisted tapes. These are installed to improve heat transfer when handling fluids in laminar flow conditions. All tubes are bundled together and held in a shell or casing.
Front and Rear Headers
The front and rear headers of heat exchangers are where the liquid enters and leaves the tubes. Fluid enters the front header, sometimes known as the stationary header, and then leaves the exchanger through the rear header before reentering the front header for multiple passes through the tubes.
Transfer Line Exchangers
Transfer Line Exchangers (TLX) are used to cool very hot gas very rapidly and are most prominent in very harsh conditions. The design of the TLX will depend on the arrangement of the tubes in the heat exchanger, but all require special designs in order to efficiently meet process needs. They connect to the radiant coil outlets via flange or welded joints and require internal insulation for areas that are exposed to hot gas but not cooled by water.
The Air Cooling System
The air cooling system in a heat exchanger consists of fin fans, condensers and chillers. The fin fans are designed to blow onto the hot tubes to effectively keep them cool. Condensers cool substances until they change to a liquid from a gas. Chillers use water as their cooling medium and keep the water temperature low enough to cool the equipment without freezing the water.
Why Heat Exchange Is Necessary
Overheated fluids can cause serious safety concerns, so properly working heat exchangers are vital for industrial worksites. Sometimes they are used to transfer steam exhaust so it can be used elsewhere. Transferring steam or heat exhaust can increase efficiency and save money.