Heat exchanger having superposed spacer inserts
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Solution Overview
Problem
The assembly of brazed plate and fin heat exchangers with intensified surfaces is challenging due to issues with brazing defects caused by porous coatings or reliefs at connection zones, leading to mechanical and thermal property issues, and the exchanger's mechanical strength is compromised during vacuum brazing, especially with low-density fin structures.
Innovation Solution
A heat exchanger design featuring superposed intermediate elements with angled channels and surface texturing, allowing for improved mechanical strength and accessible texturing for enhanced thermal performance while maintaining robust brazing joints, using a configuration where the acute angle between channel directions is less than 30° and surface texturing is strategically applied to maximize heat exchange without compromising the brazing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface texturing (porous coatings or reliefs) is applied to heat exchange structures, then thermal performance is improved, but brazing quality deteriorates due to filler metal filling porosities and creating defects
Solution Approach 1:
The patent applies surface texturing to intermediate elements before assembly, allowing the texturing process to be performed on accessible surfaces. The intermediate elements are then assembled into the heat exchanger, so the textured surfaces end up in the fluid channels away from brazing zones, preserving both thermal performance and brazing quality
Solution Approach 2:
The patent applies surface texturing selectively only to specific regions of the intermediate elements that will be exposed to fluid flow, while leaving the brazing surfaces smooth and untextured. This localized application ensures enhanced heat transfer where needed without interfering with the brazing process
2Area of stationary object
If low-density fin structures are used, then heat exchange surface area is improved, but mechanical strength deteriorates during vacuum brazing
Solution Approach 1:
The patent divides the heat exchange structure into separate components: smooth plates for structural strength and intermediate elements with fins for heat exchange surface area. The intermediate elements are assembled into the passages between plates, allowing the plates to provide mechanical strength during brazing while the finned intermediate elements provide the required heat exchange surface area
Solution Approach 2:
The intermediate elements act as mediators between the smooth structural plates and the heat exchange fluid. They provide the finned heat exchange surfaces needed for thermal performance while being contained within the structurally sound framework of the smooth plates, resolving the conflict between surface area and mechanical strength
3Reliability
If surface texturing is applied after brazing, then thermal performance is improved, but accessibility to channels deteriorates making texturing difficult or impossible
Solution Approach 1:
The patent performs surface texturing on intermediate elements before they are assembled into the heat exchanger. At this stage, the surfaces are fully accessible for texturing operations. Once textured, the intermediate elements are assembled into the passages between plates, where the textured surfaces are positioned to face the fluid channels, achieving both manufacturing ease and thermal performance
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 design enhances the mechanical strength of the exchanger during brazing, facilitates surface texturing for improved thermal performance, and maintains the integrity of brazing joints, addressing the challenges of assembly and mechanical strength in existing intensified surface heat exchangers.
Implementation Method 1
heat exchange with a calorigenic gas
Implementation Method 2
heat exchange with at least another fluid
Implementation Method 3
surface texturing is strategically applied to maximize heat exchange
Implementation Method 4
surface deposits of porous coatings or coatings forming reliefs on the surface of the structures
Implementation Method 5
the connection of the constituent elements of the exchanger is carried out by brazing with the use of a filler metal, called solder or brazing agent, the assembly being obtained by melting and diffusion of the brazing agent within parts to be brazed, without melting them
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a heat exchanger of the type with brazed plates and fins comprising a plurality of plates arranged parallel to one another so as to define a series of passages (33) for the flow of a first fluid to be brought into heat exchange relationship with at least one second fluid, at least one passage (33) being formed between a successive first plate (6) and second plate (7) and comprising at least one first spacer element (221) extending opposite the first plate (6) and defining, within the passage (33), a first set of channels (26) for the flow of the first fluid, at least one second spacer element (222) extending opposite the second plate (7) and defining, within the passage (33), a second set of channels (27) for the flow of the first fluid, said first and second spacer elements (221, 222) being superposed in the height (H) of the passage (33), measured perpendicularly to the plates (6, 7). According to the invention, the channels (26) of the first set extend generally parallel to a first direction (z1) parallel to the first and second plates (6, 7) and the channels (27) of the second set extend generally parallel to a second direction (z2) parallel to the first and second plates (6, 7), the first direction (z1) forming, in cross section in a plane parallel to the first and second plates (6, 7), an acute angle (A) with the second direction (z2).