Double-Walled Heat Exchanger Tube With Pure Iron Interphase
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Solution Overview
Problem
Existing methods for manufacturing double-walled heat exchanger tubes are expensive and complicated, and they compromise thermal conductivity and fail to effectively prevent the propagation of fatigue defects.
Innovation Solution
A method involving the use of a pure iron interphase formed between the outer and inner tubes through coaxial assembly, brazing, co-deformation, and hot isostatic pressing to create a dense metallic junction, ensuring uniform mechanical and thermal conductivity without mechanical play.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical clearance is left between the inner and outer tubes, then it is possible to detect fluid piercing before integrity is altered, but thermal conductivity is penalized and simultaneous piercing cannot be prevented
Solution Approach 1:
A metallic interlayer is introduced as an intermediary substance between the inner and outer tubes. This interlayer fills the mechanical clearance completely, providing both thermal conduction pathways and detection capabilities. The interlayer acts as a mediator that transfers thermal energy efficiently while maintaining the detection function for fluid piercing.
Solution Approach 2:
The metallic interlayer is designed with controlled porosity or voids that allow it to maintain structural integrity while enabling thermal conduction. The porous structure allows the interlayer to detect fluid infiltration while the metallic matrix provides thermal pathways, resolving the contradiction between detection capability and thermal conductivity.
2Temperature
If the gap between tubes is filled with metal powder to improve thermal conductivity, then thermal properties improve, but manufacturing cost and complexity increase
Solution Approach 1:
The invention changes the physical state and form of the filling material from loose metal powder to a consolidated metallic interlayer with controlled density and porosity. This parameter change simplifies the manufacturing process by eliminating the need for complex powder filling and compaction operations, while maintaining improved thermal conductivity compared to mechanical clearance configurations.
3Temperature
If an intermediate layer is added between tubes to improve thermal conductivity, then thermal properties improve, but manufacturing process becomes more expensive and complicated
Solution Approach 1:
The metallic interlayer is manufactured and installed as an integrated component between the inner and outer tubes during the same manufacturing process sequence. This merging of the interlayer installation with the tube assembly process eliminates separate deposition or filling operations, reducing manufacturing steps and costs while achieving the thermal conductivity improvement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances thermal conductivity, prevents fatigue crack propagation, and ensures reliable sealing, thereby improving the efficiency and service life of the heat exchanger tubes while reducing industrial costs and complexity.
Implementation Method 1
hot isostatic pressing to create a dense metallic junction
Implementation Method 2
this method making it possible to achieve advantageous productivity and industrial implementation costs compared to the methods described in documents [1] and [2]
Implementation Method 3
ensuring a uniform mechanical and thermal conductivity without mechanical play
Data Source
AI summary
The invention relates to a method for manufacturing a double-walled heat exchanger tube comprising an outer tube and an inner tube, these tubes being metallic, cylindrical, and coaxial. This method comprises the following steps: (i) supplying: . a first tube having an inner diameter d1int and an outer diameter d1ext, this first tube being intended to form the outer tube, . a second tube having an inner diameter d2int and an outer diameter d2ext, this second tube being intended to form the inner tube, and .of a cylindrical and coaxial tubular strip of Fe0 having an internal diameter dint and an external diameter dext, such that 0.15mm≤d1int−dext≤0.25mm, 0.15mm≤dint−d2ext≤0.25mm, and 10μm≤dext−dint≤200μm; (ii) the coaxial assembly of the second tube and the tubular strip inside the first tube, the tubular strip being positioned between the first and second tubes; (iii) the brazing or bonding of one end of the assembly; (iv) the co-deformation of the assembly; (v) the cutting of the ends of the assembly; (vi) the welding of the cut ends of the assembly; and (vii) the heat treatment of the assembly by hot isostatic compression, thereby obtaining the double-walled heat exchanger tube.