JPS5758093A - Condensing heat transfer pipe - Google Patents

Abstract

PURPOSE:To improve the condensing heat transfer efficiency of the captioned heat transfer pipe by a method wherein a spiral fine groove and a spiral rising are provided on the inner wall surface of the heat transfer pipe and a plurality of streak- like wet-proof sections which do not get wet from a condensed liquid are provided over the groove and the rising so as to intersect the latters. CONSTITUTION:The spiral groove 2 having a number of closely spaced continuous turhns and the rising 3 separating the turns of the groove are formed on the inner wall surface of the condensing heat transfer pipe 1. Further, the streak-like and wet-proof sections 4 which do not get wet from the condensed liquid are provided over the groove and the rising in the longitudinal direction of the pipe 1. For the formation of the wet-proof sections 4, a coating of an ethylene tetrafluoride or a noble metal plating or the like is utilized. With the above structure, a film of the liquid formed on the surface of the rising 3 as a result of condensation of the liquid flows into the groove due to the surface tension of the liquid and is splashed by the liquid cutting action of a stream of liquid vapor at each of the wet-proof sections 4 so that the liquid becomes drops. Thus, the heat transfer surface of the pipe 1 which is effective for the condensation of the liquid is always subjected to the liquid vapor and therefore, the heat transfer efficiency of the pipe can be improved.