HI,
I am looking for stainless steel which needs to have a dull fininsh, i need the best heat transfer, heat transfer to teh stainless is due to radiation on one side, and water flow (forced convection) the other.
What finish can I get?
Get a rolled-on matte surface. Producers such as J%L and Allegheny sell them under trade names. Check their websites. These surfaces are made non-reflective by being temper passed with rolls that have been roughened by an electro-discharge technique. This gives them a much more uniform texture and better corrosion resistance than blasted steel.
J%L's surface is called Architex,I think. It was used on the Reagan Airport roof very successfully. It has enhanced surface area for heat transfer, but no crevices or exposed inclusions.
BobUXL is right. Pickling will give you as rough a surface as a polish will. It won't have a uniform appearance, but that is probably a secondary concern. Despite the widespread use of stainless for heat exchanger tubes, no serious development has been attempted to optimize finishes in this regard.