TEMA Designations and Options for Shell and Tube Heat Exchangers
Shell and tube heat exchangers have several specification requirements that must be met to ensure optimal performance and efficiency. To ensure that the shell and tube heat exchanger meets these requirements, it should be designed per TEMA (Tubular Exchanger Manufacturers Association). This article will discuss the TEMA type and optional features for shell and tube heat exchangers.
Defining Shell and Tube Heat Exchangers
TEMA type is how most shell and tube heat exchangers are defined. By assigning a TEMA type, anyone can have a quick understanding of the heat exchanger’s general configuration, diameter, and length. The type is defined by using three letters in series (eg, BEU, NEN, or AES). The first letter will define the front head (channel) and is typically designated as A, B, C, D, or N type. The second letter is used to define the shell; most of the time, this is an E type. The third letter will define the rear head, with U, S, and T being the most common removable bundle types, and L, M, and N being the common fixed bundle (non-removable) types.
The Importance of TEMA Type
The TEMA type is important for several reasons. Primarily, it is used as a quick reference to understand the configuration and complexity of the heat exchanger, accessibility for repair, replacement, and maintenance, and a clue to the overall function of the exchanger.
Features of Shell and Tube Heat Exchangers
Features of shell and tube heat exchangers can include:
Finned tubes – Finned tubes are used to increase the surface area of the tubes, which results in higher heat transfer efficiency. Fins can be on the inside or outside of the tubes, or both. They are typically used for gas services to increase surface area and thus heat transfer.
Split-flow – Split-flow is used to reduce the overall size of the heat exchanger by dividing the shell-side flow into two parallel flows. This is found in TEMA J, G, and H shell configurations and helps reduce pressure drop when higher flows are present.
U-tubes – U-tubes are the most cost-effective way to have a removable bundle (vs S and T heads). Typically the tube-side fluid should not be high-fouling as it can be difficult to effectively clean the internal U-bend areas. U-tube bundles are typically a maximum of 20 feet long to account for bundle handling and to not exceed overall tube lengths of 48 feet for commonly available tubing.
Floating heads – Floating heads (S and T) are used when the tube-side fouling is too high for U-tubes, and the shell-side fouling such that bundles must be removable. This configuration has another advantage over fixed bundles, in that differential thermal expansion between the tubes and shell is accommodated.
Helical Baffles – Baffles in a helical pattern are available as a licensed technology, Helixchanger, via Lummus Technology. Helical baffles provide higher average shell-side velocities and provide performance and cost advantages for high-viscosity and high-fouling services. Altex is a Helixchanger licensee.
Impingement Rods or Impingement Baffles – These devices are used to protect the tubes from impinging flow that can cause damaging vibration and erosion caused by higher-velocity flow at the shell inlet nozzle. The requirements of these impingement devices are defined in TEMA and/or customer specifications and are a function of velocity and fluid density.
Order Your Shell and Tube Heat Exchanger From Altex
When you want the best shell and tube heat exchanger for your application, look no further than Altex. Our heat exchangers are designed to meet all of your specification requirements, and we offer a range of optional features to ensure optimal performance. Contact us today to discuss your needs and to get a quote on your shell and tube heat exchanger needs.