FORCED CONVECTION BOILING AND POST-DRYOUT HEAT TRANSFER IN HELICAL COILED TUBE
Forced convection toiling and post-dryout heat transfer has been investigated in straight and coiled tubes. The experiments were done at high pressure water loop. Forced convection boiling heat transfer coefficients in helical coils are higher than that in horizontal straight tubes. In post-dryout region the ratio of tube diameter to coil diameter(d/D) affects strongly on the circumferential distribution of wall surface temperature. The circumferential distribution of surface temperature is related to the thickness of liquid film and the deposition rate of droplets. The location of the highest surface temperature at the perimeter of the tube depends on d/D, mass velocity, steam quality and pressure, which varied downward from dryout position. Some peculiar behaviors at post-dryout region in coils are presented. The post-dryout heat transfer coefficient in coiled tube is higher than that in straight horizontal tubes.