PURPOSE:To greatly increase in overall air side heat transfer coefficient at the same fan power reference by setting the airstream row direction pitch of a heat transfer tube and a tube step pitch in a direction perpendicular to the airstream to specific dimensions and providing circular projections encircling the heat transfer tube on a plate-shaped fin and allowing respective heat transfer tubes to have partial lap with a plane of projection to the downstream side of any of heat transfer tubes located on the upstream side of the air stream. CONSTITUTION:With respect to the outer diameter D0 of a heat transfer tube 12, a tube row pitch L1 in the direction of an airstream 13 is set to satisfy 1.2D0=L1=1.8D0, and a tube step pitch L2 perpendicular to the airstream direction is set to satisfy 2.6D0=L2=3.3D0, and circular projections 14 encirculing the heat transfer tube 12 are provided on a plate-like fin 11. Thus, the heat exchanger is constituted such that a heat transfer tube 12b is partially overlapped on a plane 15 of projection of the heat transfer tube 12a on the upstream side. By this arrangement, the air side heat transfer perfomance can be exceedingly enhanced at the same fan power reference. Upon this occasion, a horse's hoof vortex is generated by the circular profections and an effect of promoting the heat transfer is displayed fully. Further, a high heat transfer zone is generated on the surface of the heat transfer tube 12b by the existence of the heat transfer tube 12a on the upstream side and the fin, a dead water zone is reduced and an effective heat transfer area is increased.
展开▼
