FIN-AND-TUBE TYPE HEAT EXCHANGER, AND ITS RETURN BEND PIPE

摘要

Provided is a fin-and-tube type heat exchanger using a return bend pipe capable of improving the evaporation performance of the heat exchanger still better. This heat exchanger comprises a hair pin unit having a multiplicity of hair pin pipes arranged in parallel, a return bend unit having a multiplicity of such return bend pipes arranged in parallel as are jointed to the individual hair pin pipe end portions of the hair pin portions, and a fin portion having a multiplicity of fins arranged in parallel at a constant spacing on the outer surfaces of the hair pin pipes. The pipe insides are fed with a coolant. The heat exchanger has first grooves formed in the inner faces of the return bend pipes. The groove pitch ratio (P1/P2) between a first groove pitch (P1), as taken in the section normal to the pipe axis, of the first grooves, and a second groove pitch (P2), as taken in the section normal to the pipe axis, of second grooves of a helical shape formed in the pipe inner faces of the hair pin pipes satisfies 0.65 to 2.2. At the same time, the groove sectional area ratio (S1/S2) between a first groove sectional area (S1) per groove, as taken in the section normal to the pipe axis, of the first grooves and a second groove sectional area (S2) per groove, as taken in the section normal to the pipe axis, of the second grooves satisfies 0.3 to 3.6.