AIR HEATER AND MANUFACTURING PROCESS FOR ITS HEAT-TRANSFER TUBES Russian patent published in 1999 - IPC

FIELD: thermal engineering; mine air heaters. SUBSTANCE: air heater has inlet and outlet headers and groups of plane-oval heat-transfer tubes carrying hot water; tubes are provided with ridges on their plane inner surfaces which function as water swirling vanes. In addition, tubes are mounted so that their oval axes are inclined through 45 deg. to horizon. Tubes are manufactured by compressing round source tube in rolls; the latter bear pins on their surfaces to form inner ridges of tube. This procedure may be followed by twisting the tube about its axis through certain angle. EFFECT: reduced size and improved heat-transfer coefficient of air heater, facilitated manufacture of tubes. 7 cl, 4 dwg