Patent ID: 7128139

Claim:
A method to increase by at least 5% the convection heat transfer from an external fluid heat transfer medium to a vertical surface selected from the group consisting of metal or ceramic in a radiant fired heater box, and increasing the total heat flux into the surface by at least 2% used to heat an internal process fluid by increasing the turbulent flow of the fluid heat transfer medium at the external surface comprising forming on the external surface ribs which have: (i) a ratio of the rib height to the diameter of the tube (e/D) from 0.05 to 0.35; (ii) a ratio of the distance between the leading edge of consecutive ribs to rib height (P/e) less than 40; and (iii) a ratio of the thickness of the rib to the height of the rib (t/e) from 0.5 to 3.