Twisted tapes are an additional type of turbulator that CALGAVIN manufactures. Similar to hiTRAN Wire Matrix Elements, twisted tapes can also be installed as retrofits or for new designs of heat exchangers.
Twisted tape is a historically well-known heat transfer enhancement product, and as such a variety of heat transfer and pressure drop correlations are available in the public domain. For that reason CALGAVIN does not offer a thermal performance guarantee for this enhancement device.
Common awareness of twisted tapes is that the enhancement is achieved by inducing swirl flow of the tubeside fluid, resulting in higher near wall velocities and mixing of fluids thereby enhancing the heat transfer coefficient.
A reasonable flow velocity is required in order to induce effective swirl flow, for that reason twisted tapes are most effective in turbulent flows with limited pressure drop. Under laminar flow conditions the improvements achieved are limited. hiTRAN thermal systems are more efficient under these flow conditions.
The heat transfer and pressure drop characteristics can be varied by changing the twist pitch of the device. Typical twist pitch ratios possible to manufacture (360o twist pitch / tape width) are between 6 and 18. The width of the tape is specified to allow a small gap between the tape and the tube wall. Big clearances between tube wall and twisted tapes can cause bypass flow and thermal underperformance.
To secure the tapes a key wire connecting the twisted tapes can be passed through the holes provided at both ends of the tape (see picture). If required CALGAVIN can provide supervision service for installation.
CALGAVIN can produce twisted tapes to bespoke design specifications. For enquiries please specify the required twisted tape twist ratio, tape thickness and tape width and also the material requirements.
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