Hairpin heat exchangers utilize true counter-current flow, which maximizes the temperature differences between the shell side and the tube side fluids, unlike the multi-pass Shell and Tube designs where correction factors are used to account for the inefficiencies resulting from co-current passes.
When a process calls for a temperature cross (when the hot fluid outlet temperature is below the cold fluid outlet temperature), a hairpin heat exchanger is the most efficient design and will result in fewer sections and less surface area.
Double-pipe heat exchangers use 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” to 6”.
Multi-tube heat exchangers are used for larger duties with standard designs established for shell diameters up to 30”; with surface area in excess of 10,000 ft² per section.
Koch Heat Transfer (formerly Brown Fintube) has a variety of unique enhancement devices for different process conditions.
When to use 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 tube side application
- A low allowable pressure drop is required on one side
- Cyclic service
- High flow rate ratios between shell side and tube side fluids
- High terminal temperature differences (300°F 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 vapours
- When complete vaporization is required
- When solids are present in the process stream
- When the mechanical advantages of a hairpin are preferred