HEAT EXCHANGING BENT TUBE HAVING INNER FACE PROTRUSION

摘要

PROBLEM TO BE SOLVED: To provide a bent tube excellent in heat exchanging performance being used as a thermal decomposition reaction tube for producing ethylene. SOLUTION: A bent tube 1 has protrusions 4 on the inner surface thereof. It is produced through high frequency bending of straight tubes having protrusions of heat resistant alloy formed as a build up welding layer on the inner surface of a centrifugal casting tube made of heat resistant casting steel. The protrusions 4 are formed spirally, for example. The protrusions 4 enhance heat transfer to fluid in the tube from the outside through turbulence forming effect of the fluid. The bent tube 1 is combined with a straight tube having a inner protrusion to constitute piping in a thermal decomposition reaction furnace for producing ethylene.