Log in

Login to your account

Username *
Password *
Remember Me

Hairpin Heat Exchangers

  • Closer temperature approach
  • Higher heat transfer rates
  • Efficiency in design
  • Convenient accessibility
  • Variety of solutions

The Process Advantage

Hairpin heat exchangers utilize true counter-current flow. Unlike multi-pass shell-and-tube designs where correction factors are used to account for inefficiencies resulting from co-current passes, this process maximizes temperature differences between shellside and tubeside fluids. When a process calls for a temperature cross (hot fluid outlet temperature is below cold fluid outlet temperature), a hairpin heat exchanger is the most efficient design, with fewer sections and less surface area. Double-pipe heat exchangers utilize a single pipe-within-a-pipe design and are commonly used for high fouling services such as slurries where abrasive materials are present, and for smaller duties. Standard shell diameters range from 2” (50,8 mm.) to 6” (152,4 mm.). Multi-tube heat exchangers are used for larger duties with standard designs for shell diameters up to 30” (762 mm.) and surface areas in excess of 10,000 ft2 (930 m2) per section. BROWN FINTUBE® range of products includes a variety of unique enhancement devices for different process conditions.

hairpin250x150   hairpin_counter_current

 

Shellside Enhancement Devices

  • Longitudinal fintubes - Provide extended heat transfer surface with relatively low resulting pressure drops. They can be cut-and-twisted or used in conjunction with peripheral baffles for further enhancement.
  finned_tube

 

  • TWISTED TUBE® bundle technology - Simultaneously enhances both shellside and tubeside heat transfer rates. They are self-supporting and allow straight-through cleaning of the shellside, despite being on a triangular tube pitch. The risk of flow-induced vibration is eliminated with this design and shellside fouling is minimized due to the elimination of “dead” spots commonly found when traditional segmental baffles are utilized.

 

twisted_tube_42s

 

  • Low Pressure Drop LOK-BAFFLE™ baffles - Act primarily as tube supports. These are used for high shellside flow rates, low allowable pressure drops, or when the shellside coefficient does not limit the overall heat transfer rate.
   

 

  • Segmental baffles - These are traditional baffles that can be used in conjunction with seal-strips.

 

   

 

Tubeside enhancement devices

  • TWISTED TUBE® bundles - Promote turbulence of the tubeside fluid. They are also used for vaporizing services and when tube inserts are not preferred.

 

twisted_tube_41stube_inserts_2_l

 

 

  • Tube inserts - BROWN FINTUBE® technology offers a variety of tube inserts, which maximize the heat transfer rates of viscous fluids. They are also used for vaporizing services.

 

tube_inserts_5_ltube_inserts_3_l

Large radius U-bends

The free-floating U-tube bundle compensates for the differential shell-tube expansion and eliminates the need for expansion joints or packed joints commonly used in shell & tube type heat exchangers. Large radius U-bends are easily cleaned with flexible shaft tube cleaners.

hairpin250x150

The mechanical advantage

  1. Separate tubesheets: Handle high temperature differences and cycling more effectively than shell-and-tube exchangers.
  2. Durable baffle cage construction: Welded to the tie rods without the need for “sleeves” or internal nuts.
  3. Moveable support brackets: Allow shell expansion and contraction and eliminate the need for sliding plates commonly used for fixed supports. Our brackets are slotted for anchor bolts on all four sides for flexibility in installation, and the ability to add sections in the future.
  4. Patented closure technology: Suits your specific design needs (click here for details).
  5. Tubeside and shellside connections are the on the same end: Easy installation and piping.
  6. No internal bolting!
  7. Double-pipe exchangers: Use pipe in lieu of thin wall tubing to enhance integrity.
  hairpin_2366_006_s

 

fpso_gas_cooler__fuel_superheater_s

Separated-head low pressure closure

Our separated-head closure uses independent tubeside and shellside flanges, bolting and gasketing. This closure is used for moderate pressures up to 1,300 psi (92 kg/cm2), cyclic service, high temperature differences, and/or for temperatures below -20°F (-28.8°C) or greater than 650°F (343°C).

TAPER-LOK® high pressure closure

Our TAPER-LOK® closure is typically used for high pressure up to 15,000 psi (1055 kg/cm2) applications. Like our separated-head, the TAPER-LOK® closure uses separate tubeside and shellside flanges, bolting, and gasketing. The unique feature this closure offers is a reusable TAPER-LOK® ring which acts as a self-energizing seal. TAPER-LOK® is the registered trademark of Taper-Lok Corporation. Koch Heat Transfer Company has an exclusive license for TAPER-LOK® closures for use in double-pipe and multi-tube hairpin heat exchangers.

LOK-FLANGE® closure

The LOK-FLANGE® closure uses common through-bolting with independent gaskets and is typically used for design pressures below 1,000 psi (70 kg/cm2). The center flange of this closure is threaded, which allows removal of the tube-end flange for inspection and cleaning of the tubes while maintaining pressure on the shellside. This closure allows the maximum number of tubes in a given shell diameter.

ZR CLOSURE™ closure

The ZR CLOSURE™ closure is the newest addition to the BROWN FINTUBE® family of closures. This closure bridges the gap between the separate-head and the LOK-FLANGE® closure by providing separate tubeside and shellside flanging and bolting, while retaining the maximum number of tubes in a given shell diameter.

Return end bonnet closure

This closure is a conservative through-bolted design. When the bonnet is removed, the U-bends of the tubes are completely exposed to permit full field inspection.

 

stacked_hairpin_bonnet_s

Superior closure design

Our closure designs provide an effective means of providing a removable tube bundle for a variety of design conditions and applications. All of our closures have the following features:

  • External split rings - Split rings are used to lock the bundle to the shell. On outdated models these rings were internal and came into contact with the shellside fluid. Internal split-rings are still used by others.
  • Through bolting - Earlier models used studded bolting that could seize or break off, and are still used by other manufacturers.
  • Better gasketing - Unlike other manufacturers, our gaskets do not seat on the tubesheet face where misalignment can easily occur and the potential for erosion exists. Our shellside gaskets are easier to remove than wedge gasketing used by competitors.
  • Separate tubeside and shellside gaskets - Prevent interstream leakage.
  • Round flanges - More effective gasket seating than square flanges.

 

hairpin_dscf2758_l

Exemplary hairpin applications

When to use BROWN FINTUBE® hairpin heat exchangers

A hairpin heat exchanger should be considered when one or more of the following conditions exist:

  • The process results in a temperature cross.
  • High-pressure tubeside application.
  • A low-allowable pressure drop is required on one side.
  • Cyclic service.
  • High flowrate ratios between shellside and tubeside fluids.
  • High terminal temperature differences (300°F/149°C or greater).
  • When an augmentation device will enhance the heat transfer coefficient.
  • When the exchanger is subject to thermal shock.
  • When flow-induced vibration may be a problem.
  • When heating or cooling vapors.
  • When complete vaporization is required.
  • When solids are present in the process stream.
  • When the mechanical advantages of a hairpin are preferred.
  hairpin_2232_3_s

Koch Heat Transfer maintenance support

Maintenance

Operation and maintenance manuals are available that address the disassembly and reassembly of specific designs. In general, the bundle of a hairpin exchanger is removed by first removing the tubeside bolting, flanges and split rings. The next step is to remove the shellside bolting, flanges and split rings. Finally, the return bonnet bolting is removed and the bonnet is placed to the side. The tube element can now be pulled from the back end of the shell by placing a sling around the U-bends. On larger multitubes, a plate is installed around the U-bend for proper sling placement. Assembly is performed by reversing the process and utilizing new gaskets.

Spare parts

Replacement parts for BROWN FINTUBE® or BAS-TEX exchangers are readily available. One complete set of gaskets is recommended for one year’s operation.

Surveys

For facilities with numerous hairpin exchangers, Koch Heat Transfer Company will perform a survey of the facility and establish design equivalents to current BROWN FINTUBE® models. We will also evaluate ways to establish common designs for multiple services to allow commonality of spare parts and elements, resulting in reduced spare parts inventories and maintenance. Please contact a Koch Heat Transfer Company sales representative for more details.