Double-wall-tube heat exchanger

Abstract

A double-wall-tube heat exchanger has an outer tube, and an inner tube disposed concentrically in and spaced apart from the outer tube. A clearance between the outer tube and the inner tube and the interior of the inner tube serve as respective refrigerant flow paths. The inner tube has a plurality of interior fins formed on its inner circumferential surface. The interior fins project radially inward; extend in a longitudinal direction of the inner tube; and are arranged at circumferential intervals. The inner tube has a plurality of elongated projections formed on its outer circumferential surface. The elongated projections project radially outward; extend in the longitudinal direction; and are arranged at circumferential intervals. The interior fins are greater in height than the elongated projections. The double-wall-tube heat exchanger exhibits excellent heat exchange performance.

1 . A double-wall-tube heat exchanger comprising an outer tube, and an inner tube disposed in and spaced apart from the outer tube,
 a clearance between the outer tube and the inner tube and the interior of the inner tube serving as respective refrigerant flow paths,   the inner tube having a plurality of interior fins formed on an inner circumferential surface thereof, the interior fins projecting radially inward, extending in a longitudinal direction of the inner tube, and being arranged at circumferential intervals,   the inner tube having a plurality of elongated projections formed on an outer circumferential surface thereof, the elongated projections projecting radially outward, extending in the longitudinal direction, and being arranged at circumferential intervals, and   a fin height of the interior fins being greater than a projecting height of the elongated projections.   
   
   
       2 . A double-wall-tube heat exchanger according to  claim 1 , wherein a radial clearance between an inner circumferential surface of the outer tube and a portion of the outer circumferential surface of the inner tube where the elongated projections are not formed is 0.4 mm to 1.2 mm inclusive. 
   
   
       3 . A double-wall-tube heat exchanger according to  claim 1 , wherein a clearance between projecting ends of the elongated projections of the inner tube and the inner circumferential surface of the outer tube is 0 mm to 0.5 mm inclusive. 
   
   
       4 . A double-wall-tube heat exchanger comprising an outer tube, and an inner tube disposed in and spaced apart from the outer tube,
 a clearance between the outer tube and the inner tube and the interior of the inner tube serving as respective refrigerant flow paths,   the inner tube having a plurality of interior fins formed on an inner circumferential surface thereof, the interior fins projecting radially inward, extending in a longitudinal direction of the inner tube, and being arranged at circumferential intervals, and   the outer tube having a plurality of elongated projections formed on an inner circumferential surface thereof, the elongated projections projecting radially inward, extending in a longitudinal direction of the outer tube, and being arranged at circumferential intervals.   
   
   
       5 . A double-wall-tube heat exchanger according to  claim 4 , wherein a radial clearance between a portion of the inner circumferential surface of the outer tube where the elongated projections are not formed and an outer circumferential surface of the inner tube is 0.4 mm to 1.2 mm inclusive. 
   
   
       6 . A double-wall-tube heat exchanger according to  claim 4 , wherein a clearance between projecting ends of the elongated projections of the outer tube and the outer circumferential surface of the inner tube is 0 mm to 0.5 mm inclusive. 
   
   
       7 . A double-wall-tube heat exchanger according to  claim 1 , wherein the interior fins of the inner tube have a fin thickness of 0.2 mm to 2.0 mm inclusive. 
   
   
       8 . A double-wall-tube heat exchanger according to  claim 1 , wherein the interior fins have a fin height of 1.0 mm to 3.0 mm inclusive. 
   
   
       9 . A double-wall-tube heat exchanger according to  claim 1 , wherein the inner tube has an inside diameter of 12 mm or greater. 
   
   
       10 . A double-wall-tube heat exchanger according to  claim 4 , wherein the interior fins of the inner tube have a fin thickness of 0.2 mm to 2.0 mm inclusive. 
   
   
       11 . A double-wall-tube heat exchanger according to  claim 4 , wherein the interior fins have a fin height of 1.0 mm to 3.0 mm inclusive. 
   
   
       12 . A double-wall-tube heat exchanger according to  claim 4 , wherein the inner tube has an inside diameter of 12 mm or greater.