Hot water corrugated heat transfer tube

Abstract

The present invention relates to a hot water corrugated heat transfer tube that exchanges heat between its interior and exterior. A plurality of projections, each whose height (H 1 ) is in the range of 0.5 mm-1.5 mm, is provided in at least one part of the inner surface of a portion positioned in a section of a corrugated heat transfer tube, where the Reynolds number (Re) of the fluid flowing in the interior of the tube is less than 7,000. The height H 1 of the projections is in the range of 0.05-0.15 times the inner diameter D or the height H 1 of the projections is in the range of 1-3 times the depth (Hm) of the corrugated grooves. As a result, with a simple structure, the heat transfer performance in the low Reynolds number zone is improved, and the pressure loss inside the tube is small.

1 . A hot water corrugated heat transfer tube configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections each having a height of 0.5-1.5 mm, the plurality of projections being provided in at least one part of an inner surface of a portion positioned in a section where the Reynolds number of a fluid flowing in the interior is less than 7,000.   
   
   
       2 . A hot water corrugated heat transfer tube configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections each having a height 0.05-0.15 times an inner diameter of an inner tube surface, the plurality of projections being provided in at least one part of an inner surface of a portion positioned in a section where the Reynolds number of a fluid flowing in the interior is less than 7,000.   
   
   
       3 . A hot water corrugated heat transfer tube configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections each having a height 1-3 times a depth of the corrugated grooves, the plurality of projections being provided in at least one part of an inner surface of a portion positioned in a section where the Reynolds number of a fluid flowing in the interior is less than 7,000.   
   
   
       4 . A hot water corrugated heat transfer tube configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections being provided in at least one part of an inner surface of a portion positioned in a section where the Reynolds number of a fluid flowing in the interior is less than 7,000,   the value of a pitch of the plurality of projections being different from the value of a pitch of the corrugated grooves.   
   
   
       5 . A hot water corrugated heat transfer tube used in a heat exchanger of a hot water heater and configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections each having a height (H 1 ) of 0.5 mm-1.5 mm, the plurality of projections being provided on an inner surface of a portion positioned in the vicinity of an inlet into which water, which is the fluid flowing in the interior, flows.   
   
   
       6 . A hot water corrugated heat transfer tube used in a heat exchanger of a hot water heater and configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections each having a height 0.05-0.15 times an inner diameter, the plurality of projections being provided on an inner surface of a portion positioned in the vicinity of a fluid inlet into which water, which is the fluid flowing in the interior, flows.   
   
   
       7 . A hot water corrugated heat transfer tube used in a heat exchanger of a hot water heater and configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections each having a height 1-3 times a depth of the corrugated grooves, the plurality of projections being provided on an inner surface of a portion positioned in the vicinity of a fluid inlet into which water, which is the fluid flowing in the interior, flows.   
   
   
       8 . A hot water corrugated heat transfer tube used in a heat exchanger of a hot water heater and configured to exchange heat between its interior and exterior, comprising:
 helically corrugated grooves being provided inside the tube; and   a plurality of projections being provided on an inner surface of a portion positioned in the vicinity of a fluid inlet into which water, which is the fluid flowing in the interior, flows,   the value of a pitch of the plurality of projections being different from the value of a pitch of the corrugated grooves.   
   
   
       9 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the flow speed of the fluid flowing in the interior is 0.1-0.6 m/s.   
   
   
       10 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the cross sectional shape at any height of each of the projections is a smooth closed curve.   
   
   
       11 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 a smooth part not provided with the projections is formed in an inner surface of a portion positioned in the vicinity of a fluid outlet out of which the fluid flows.   
   
   
       12 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 a groove having a depth shallower than the height of each of the projections is formed on the inner surface.   
   
   
       13 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the plurality of projections is provided parallel to a tube axial direction.   
   
   
       14 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the plurality of projections is helically provided.   
   
   
       15 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the plurality of projections is provided such that the projections are paired at opposing positions in the radial direction.   
   
   
       16 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the ratio of the pitch of the plurality of projections to the inner diameter is 0.5-10.   
   
   
       17 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 small projections each whose height is less than 0.5 mm are provided between the plurality of projections.   
   
   
       18 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 a smooth part not provided with the projections exists on the inner surface.   
   
   
       19 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the projections are formed by the application of force from the exterior, the projections are formed in a linear part of the tube, and the projections are not formed in a bent part of the tube.   
   
   
       20 . The hot water corrugated heat transfer tube according to  claim 1 , wherein
 the projections are formed by the application of force from the exterior, and the projections are not formed in a portion that intersects a bent surface in a bent part of the tube.   
   
   
       21 . The hot water corrugated heat transfer tube according to  claim 1 , further comprising:
 a second heat transfer tube configured to flow a second fluid that exchanges heat with the fluid is disposed in the exterior of the hot water corrugated heat transfer tube; wherein   the second heat transfer tube contacts an outer surface of the hot water corrugated heat transfer tube, and   the projections are formed on the inner surface by depressing the outer surface, and are formed at a location outside of the portion that contacts the second heat transfer tube.