U Tube bundle Heat Exchangers
A heat-exchanger system consisting of a bundle of U tubes (hairpin tubes) bounded by a shell (outer vessel); one fluid flows through the tubes, and the other fluid flows through the shell, in the order of the tubes is U Tube bundle Heat Exchangers. Multitherm can duplicate any obtainable bundle to include dimensions, materials and performance. We can build “U” tube bundles, straight tube “floating” tube bundles, or we can retube fixed tube sheet heat exchangers when the bundles is not removable. multitherm is not locked into any one material. Most bundles tend to be build with copper tubes and steel tube sheets.
There can be a lot of variations on the shell and tube design. Typically, the ends of each tube are associated to plenums (sometimes called water boxes) through holes in tube sheets. The tubes may be straight or bent in the shape of a U, called U-tubes. In nuclear power plants called pressurized water reactors, large heat exchangers called steam generators are two-phase, shell-and-tube heat exchangers, which typically have U-tubes. They are used to boil water recycled from a surface condenser into steam to drive a turbine to produce power. Most shell-and-tube heat exchangers are 1, 2, or 4 pass designs on the tube side. This refers to the number of times the fluid in the tubes passes through the fluid in the shell. In a single pass heat exchanger, the fluid goes in one end of each tube and out the other. Surface condensers in power plants are often 1-pass straight-tube heat exchangers (see Surface condenser for diagram). Two and four pass designs are common because the fluid can enter and exit on the same side. This makes construction much simpler.
There are often baffles directing flow through the shell side so the fluid does not take a short cut through the shell side leaving ineffective low flow volumes. These are generally attached to the tube bundle rather than the shell in order that the bundle is still removable for maintenance. Counter current heat exchangers are most efficient because they allow the highest log mean temperature difference between the hot and cold streams. Many companies however do not use single pass heat exchangers because they can break easily in addition to being more expensive to build. Often multiple heat exchangers can be used to simulate the counter current flow of a single large exchanger.
Applications and Uses :
The simple design of a shell and tube heat exchanger makes it an ideal cooling solution for a wide variety of applications. One of the most common applications is the cooling of Hydraulic Fluid and oil in engines, transmissions and hydraulic power packs. With the right choice of materials they can also be used to cool or heat other mediums, such as swimming pool water or charge air. One of the big advantages of using a shell and tube heat exchanger is that they are often easy to service, particularly with models where a floating tube bundle (where the tube plates are not welded to the outer shell) is available. Can also be used on fixed tube sheet heat exchangers.