TEMA heat exchanger types provide a standard way to describe a shell-and-tube heat exchanger. Codes such as BEM, BEU and AES are not model numbers. Each letter identifies one major component, helping engineers, buyers and manufacturers discuss configuration and fabrication requirements clearly.
This guide explains how to read the code, compares common three-letter configurations and illustrates the E, F, G, H, J, K and X shell types.
How to Read a Three-Letter TEMA Designation
A TEMA designation normally contains three letters in a fixed order:
| Position | Identifies | BEM example |
|---|---|---|
| First | Front-end stationary head | B: bonnet with integral cover |
| Second | Shell type and shell-side flow path | E: one-pass shell |
| Third | Rear-end head | M: fixed-tubesheet rear head |
Therefore, BEM combines a B front head, an E shell and an M rear head. Changing one letter can affect inspection access, bundle removal, thermal expansion or the shell-side flow path.
The code does not define size or performance. Two BEM exchangers may have different dimensions, materials, pressure ratings and heat duties.
Common TEMA Heat Exchanger Types
The following examples show differences between fixed-tubesheet, U-tube and floating-head construction.
| TEMA type | Basic construction |
| BEM | Bonnet, E shell, fixed tubesheets |
| AEM | Removable channel cover, E shell, fixed tubesheets |
| BEU | Bonnet, E shell, U-tube bundle |
| AEU | Removable channel cover, E shell, U-tube bundle |
| AES | Removable channel cover, E shell, floating head with backing device |
| AET | Removable channel cover, E shell, pull-through floating head |
Fixed tubesheets are relatively simple, but shell-side cleaning and differential expansion need attention. U-tubes accommodate expansion, although their bends are harder to clean internally. Floating heads offer removable-bundle access and expansion flexibility with greater complexity.
These examples all use an E shell. A different middle letter indicates another shell-side flow arrangement.
E, F, G, H, J, K and X Shell Types Compared
These simplified flow diagrams are not fabrication drawings. Actual nozzle, baffle, support and bundle details depend on engineering calculations.
| Shell | Flow arrangement | Common reason for consideration |
| E | One-pass | General heating and cooling |
| F | Two-pass | A more countercurrent temperature pattern |
| G | Split flow | Low pressure drop in specialized duties |
| H | Double split flow | Longer, high-flow, low-pressure-drop duties |
| J | Divided flow | Reduced shell-side velocity and pressure drop |
| K | Kettle reboiler | Boiling with vapor disengagement space |
| X | Crossflow | Very low shell-side pressure drop |
E Shell – One-Pass Shell
The E shell is the basic one-pass arrangement. Fluid enters near one end and leaves near the other. Transverse baffles may guide flow across the tubes and support the bundle; their spacing affects heat transfer, pressure drop and vibration risk.
F Shell – Two-Pass Shell
An F shell uses a longitudinal baffle to create two shell-side passes. Fluid travels to the far end and returns on the other side. This can produce a more countercurrent temperature pattern, but leakage around the longitudinal baffle must be considered.
G Shell – Split-Flow Shell
A G shell has central inlet and outlet nozzles separated by a longitudinal baffle. The stream splits toward both ends, turns, recombines at the center and exits. Its shorter parallel paths reduce shell-side pressure drop.
H Shell – Double Split-Flow Shell
An H shell is essentially two G flow sections together. Two inlet and two outlet regions create additional parallel paths for longer, low-pressure-drop duties. Flow distribution and tube support still require review.
J Shell – Divided-Flow Shell
In a J 1–2 arrangement, fluid enters at the center, divides and exits near both ends. The reverse 2–1 arrangement uses two inlets and one central outlet. Both reduce shell-side velocity and pressure drop.
K Shell – Kettle-Type Reboiler
A K shell provides enlarged space above the bundle for vapor disengagement. It serves boiling or flooded evaporation rather than ordinary cooling. Liquid level, circulation, the weir and vapor outlet require project-specific design.
X Shell – Crossflow Shell
In an X shell, fluid crosses the tube bundle instead of following a repeated baffled path. It can provide very low pressure drop for gas, vapor or condensing duties, but distribution and tube vibration still require evaluation.
What Determines the Appropriate TEMA Configuration?
No TEMA type is best for every project. Selection should consider:
- cleaning method and bundle-removal space;
- differential expansion between shell and tubes;
- flow, temperature program and allowable pressure drop;
- single-phase, condensing or boiling duty;
- distribution, nozzle velocity and vibration risk;
- materials, corrosion and applicable requirements.
Thermal and mechanical design must evaluate these factors together. Lower pressure drop may also reduce velocity and affect heat transfer.
TEMA Type vs TEMA Class vs ASME Code
A TEMA type identifies the front head, shell and rear head. A TEMA class—R, B or C—relates to mechanical requirements for different service categories. The ASME Boiler and Pressure Vessel Code addresses pressure-vessel design, fabrication, inspection and certification when specified.
A BEM or AES designation alone does not demonstrate TEMA-class or ASME compliance. State the applicable standard, edition, inspection and documentation in the specification. Read more about ASME Code requirements for heat exchangers.
From a Confirmed Drawing to Custom Manufacturing
If your drawing or datasheet specifies a TEMA designation, JED can manufacture according to the confirmed drawing and technical specifications. Our engineering team checks materials, dimensions, connections, design conditions, inspection and testing requirements before production.
For replacement equipment, mounting points, nozzle orientation and critical dimensions must match. For a new unit, provide the fluids, flow rates, temperatures, design pressure, allowable pressure drop, materials and applicable codes.
Send JED your drawing, datasheet or operating data for a custom shell-and-tube heat exchanger engineering review.
Frequently Asked Questions
Does this TEMA nomenclature apply to plate heat exchangers?
No. The three-letter system discussed here describes shell-and-tube exchanger construction, not plate-and-frame exchanger types.
Can every shell letter be combined with every front and rear head?
Not automatically. Mechanical compatibility, bundle construction, maintenance access and project requirements limit which combinations are practical.
Can an existing exchanger be converted to another TEMA type?
Changing the head, shell or rear-end type may require major redesign rather than a simple modification. Thermal performance, dimensions, pressure design and applicable code requirements must all be reviewed.
