| 摘要 |
PURPOSE:To increase heat transfer rate remarkably upon condensing and evaporating refrigerant in the heat transfer tube for a heat exchanger by as method wherein dovetail type cavities are formed in the main grooves formed on the internal wall of the tube. CONSTITUTION:The main grooves, formed spirally in the direction D of the heat transfer tube, are provided with crests 11 and troughs 12. When shallow sub grooves are formed in the direction E on the main grooves by a comb-type dice, the sub grooves, having the crests 21 and troughs 22, are formed, the crests 21 coincide with the crests 11 and both side surfaces of the troughs 12 of main grooves are extruded by the dice whereby dovetail type cavities 13 are formed. The depth (h2) of the sub groove is determined about half of the depth (h1) of the main groove. When the heat transfer tube, having 260-600 pieces of intersecting sections between the main grooves and sub grooves per cm<2> of heat transfer area, is compared with conventional heat transfer tube, the heat transfer rate is 2-2.5:1 in evaporation and 1.5-2:1 in condensation but a pressure loss when the refrigerant passes through the heat transfer tube is the same degree in both tubes. |
