Heat Exchanger World Magazine May 2023 | Page 30

Tema Standards
Limitations
• Shell fluids limited to non-volatile , non-toxic materials
• Packing limits the shell-side design temperature and pressure
• All tubes are attached to two tubesheets . Tubes cannot expand independently , so large thermal shock applications should be avoided
• Less surface per given shell and tube diameter than AEW or BEW
Applications
• Flammable or toxic liquids in the tube circuit
• Good for high fouling liquids in the tube circuit
Removable bundle , internal split ring floating head - Type AES , BES Ideal for applications requiring frequent tube bundle removal for inspection and cleaning . Uses straight-tube design suitable for large differential temperatures between the shell and tube fluids . More forgiving to thermal shock than AEW or BEW designs . Suitable for cooling volatile or toxic fluids .
Advantages
• Floating head design allows for differential thermal expansion between the shell and the tube bundle
• Shell circuit can be inspected and steam-cleaned . If it has a square tube layout , tubes can be mechanically cleaned
• Higher surface per given shell and tube diameter than ‘ pull-through ’ designs such as AET , BET
• Provides multi-pass tube circuit arrangement
Limitations
• Shell cover , split ring , and floating head cover must be removed to remove the tube bundle ; this results in higher maintenance cost than pull-through
• More costly per square foot of surface than fixed tube sheet or U-tube designs
Applications
• Chemical processing applications for toxic fluids
• Special intercoolers and aftercoolers
• General industrial applications
Removable bundle , pull-through floating head - Type AET , BET Ideal for applications requiring frequent tube bundle removal for inspection and cleaning as the floating head is bolted directly to the floating tubesheet . This prevents having to remove the floating head in order to pull the tube bundle .
Advantages
• Floating head design allows for differential thermal expansion between the shell and the tube bundle
• Shell circuit can be inspected and steam- or mechanically cleaned
• Provides large bundle entrance area for proper fluid distribution
• Provides multi-pass tube circuit arrangement
• Suitable for toxic or volatile fluid cooling
Limitations
• For a given set of conditions , this TEMA style is the most expensive design
• Less surface per given shell and tube diameter than other removable designs
Applications
• Chemical processing applications for toxic fluids
• Hydrocarbon fluid condensers
• General industrial applications requiring frequent cleaning
Removable bundle , U-tube - Type BEU , AEU Especially suitable for severe performance requirements with maximum thermal expansion capability . Because each tube can expand and contract independently , this design is suitable for larger thermal shock applications . While the AEM and AEW are the least expensive , U-tube bundles are still an economical TEMA design .
Advantages
• U-tube design allows for differential thermal expansion between the shell and the tube bundle as well as for individual tubes .
• The shell circuit can be inspected and steam- or mechanically cleaned
• Less costly than floating head or packed floating head designs
• Provides multi-pass tube circuit arrangement
• Capable of withstanding thermal shock applications
• Bundle can be removed from one end for cleaning or replacement
Limitations
• Because of U-bend , tubes can be cleaned only by chemical means ( although nowadays , new techniques of fluid pressurized scraper , similar to a pipeline pig , are available )
• Because of U-tube nesting , individual tubes are difficult to replace
• No single tube pass or true counter current flow is possible
• Tube wall thickness at the U-bend is thinner than at straight portion of tubes
• Draining of tube circuit is difficult when mounted with the vertical position with the head side up
Applications
• Oil , chemical , and water-heating applications
• Excellent in steam to liquid applications
Shell types TEMA E : The most common TEMA shell type is the " E " shell as it is most suitable for most industrial process cooling applications . However , for certain applications , other shells offer distinct advantages . TEMA F : A TEMA-F shell design provides for a longitudinal flow plate to be installed inside the tube bundle assembly . This plate causes the shell fluid to travel down one half of the tube bundle , then down the other half , in effect producing a counter-current flow pattern which is best for heat transfer . An F-type is suitable when pure counter flows are needed at two tube sides .
30 Heat Exchanger World May 2023 www . heat-exchanger-world . com