Heat transfer pipe for heat exchanger, heat exchanger, refrigeration cycle apparatus, and air-conditioning apparatus

Abstract

A heat transfer pipe for a heat exchanger including high threads and low threads that are lower than the high threads. The high threads and the low threads are provided at respective prescribed heights in a helical manner in a pipe axial direction on an inner surface of a pipe, the high threads are formed with 11 to 19 threads, the low threads are formed with 3 to 6 threads between each pair of the high threads, the high threads before expansion of the pipe each have a trapezoidal shape in cross-section so that a crest before the expansion of the pipe is flat, and a ratio W 1 /D of a tip width W 1 of the crest portion after the expansion of the pipe to an outer diameter of the heat transfer pipe is 0.011 to 0.040. Further, the high threads before the expansion of the pipe are higher by 0.04 mm or more than the low threads.

1 . A heat transfer pipe for a heat exchanger, comprising:
 high threads; and   low threads that are lower than the high threads, wherein   the high threads and the low threads are provided at respective prescribed heights in a helical manner in a pipe axial direction on a pipe inner surface,   the high threads are formed with 11 to 19 threads, the low threads are formed of 3 to 6 threads between each pair of the high threads,   the high threads before expansion of the pipe each have a trapezoidal shape in a cross-section such that a crest thereof is flat, ratio of a tip width of the crest portion after the expansion of the pipe to an outer diameter of the heat transfer pipe is 0.011 to 0.040, and   a curvature radius of the flat surface of the crest portion and one side surface and a curvature radius of the flat surface of the crest portion and the other side surface in each of the high threads before the expansion of the pipe are 0.01 mm to 0.03 mm.   
     
     
         2 . The heat transfer pipe for a heat exchanger of  claim 1 , wherein the high threads before the expansion of the pipe are higher by 0.04 mm or more than the low threads. 
     
     
         3 . (canceled) 
     
     
         4 . The heat transfer pipe for a heat exchanger of  claim 1 , wherein an apex angle of the high threads before the expansion of the pipe is 15 to 30 degrees, and an apex angle of the low threads is 5 to 15 degrees. 
     
     
         5 . The heat transfer pipe for a heat exchanger of  claim 1 , wherein a curvature radius of crests of the low threads is 0.03 mm to 0.045 mm. 
     
     
         6 . The heat transfer pipe for a heat exchanger of  claim 1 , wherein a direction in which the threads extend relative to a pipe axial direction makes 10 to 50 degrees. 
     
     
         7 . A heat exchanger, comprising:
 a plurality of fins for exchanging heat; and   the heat transfer pipe of  claim 1  that penetrates the fins, wherein   the heat transfer pipe is pressurized from an inner surface to be expanded, and is fixed to the fins.   
     
     
         8 . The heat exchanger of  claim 7 , wherein a height of the high threads after the expansion of the pipe is 0.10 mm to 0.26 mm. 
     
     
         9 . A refrigeration cycle apparatus, comprising:
 a refrigerant circuit including a compressor that compresses a refrigerant, a condenser that condenses the refrigerant by heat exchange, an expansion means for decompressing the condensed refrigerant, and an evaporator that evaporates the decompressed refrigerant by heat exchange to circulate the refrigerant, the refrigerant circuit being connected by piping, the refrigeration cycle apparatus, wherein   the heat exchanger of  claim 7  is provided to both or either one of the condenser and the evaporator.   
     
     
         10 . The refrigeration cycle apparatus of  claim 9 , wherein as the refrigerant, either one of an HC single refrigerant, a mixed refrigerant including HC, R32, R410A, R407C, tetrafluoropropene, a non-azeotropic refrigerant mixture consisting of HFC refrigerant having a boiling point that is lower than the tetrafluoropropene, or carbon dioxide is used. 
     
     
         11 . An air-conditioning apparatus, comprising the refrigeration cycle apparatus of  claim 9  that carries out cooling or heating of a conditioned space.