WIRE WRAPPED CORD
Small OD tubes or solid rods with attached wire wrapped helically around the exterior surface at a set pitch; are designed to be placed inside another tube to promote turbulence.
The core tube or rod can be made from a range of materials including but not limited to: Carbon Steel, Stainless steel, and allow Alloy steel.
The external wire, likewise, can be from similar materials. Made to order based on the ID of your host tube and required length and material choices.
Long lead time or short, Tex-Fin is ready to help.