Latent Heat Exchanger with Drawn Casing for Drain Corrosion Control

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Solution Overview

Problem

Conventional latent heat exchangers face issues with corrosion due to strong acidic drain retention in welded or brazed areas, leading to reduced anti-corrosion ability and increased complexity in assembly, especially when using anti-corrosive metals like stainless steel or titanium.

Innovation Solution

A latent heat exchanger design featuring a casing with integrally formed walls by drawing a single metal plate, eliminating the need for welding or brazing in the lower area, and incorporating a side baffle plate to enhance heat efficiency and prevent drain retention, allowing for smooth drain discharge and improved corrosion resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If multiple metal plates are connected by welding or brazing to form the casing, then the casing can be assembled with separate components, but the welded or brazed areas become prone to corrosion due to drain retention and the anti-corrosion ability deteriorates

Engineering Contradiction:
Improvecasing assemblyVSAvoidanti-corrosion ability
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent merges multiple separate metal plates into a single integrally formed casing body made from one stainless steel plate. This eliminates all welded or brazed connection areas where drain could be retained, thereby preventing corrosion at connection points while maintaining manufacturing feasibility through integral forming processes

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent extracts and eliminates the welded or brazed connection areas from the casing structure by adopting an integrally formed design. This removes the problematic areas where drain retention and subsequent corrosion occurred, while still achieving the necessary casing assembly through forming operations

Inventive Principle:
Principle #2Taking out (Extraction)

2Ease of manufacture

If multiple metal plates are connected by welding or brazing to form the casing, then the casing can be assembled with separate components, but the number of members increases and the assembling work becomes complicated

Engineering Contradiction:
Improvecasing assemblyVSAvoidnumber of members
Core Design Contradiction:
Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent combines multiple separate casing plates into a single integrally formed casing body, reducing the number of individual members from multiple plates to one unified structure. This simplifies the overall assembly process while maintaining the necessary casing functionality

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

While the casing body is integral, the patent segments the heat absorbing pipe into multiple sections that can be assembled within the casing. This allows modular assembly of internal components while maintaining an integral external casing structure, balancing manufacturing ease with component accessibility

Inventive Principle:
Principle #1Segmentation

3Ease of manufacture

If the casing is formed by welding or brazing multiple metal plates, then the casing can be constructed from standard metal plates, but the strong acid drain is retained in the connection areas causing corrosion

Engineering Contradiction:
Improvecasing constructionVSAvoidcorrosion from drain
Core Design Contradiction:
Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent merges multiple metal plates into a single integrally formed casing body, eliminating all connection areas where drain could be retained. This prevents the harmful corrosion effect while maintaining manufacturing ease through integral forming processes using stainless steel

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent uses the properties of stainless steel (corrosion resistance) to maximum advantage by eliminating the conditions (welded connections) that would allow drain retention. The material's inherent anti-corrosion properties are fully utilized when connection areas are eliminated, converting the material selection into a protective benefit

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

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 durability by preventing drain retention and corrosion, simplifies the manufacturing process with fewer components, and improves heat efficiency by ensuring efficient gas flow and contact with heat absorbing pipes.

Implementation Method 1

latent heat in the combustion gas is absorbed by the latent heat exchanger... by cooling water vapor in the combustion gas below the dew point temperature and condensing the water vapor

Methodology Applied
Scientific EffectCondensation: Condensation

Implementation Method 2

latent heat in the combustion gas is absorbed by the latent heat exchanger

Methodology Applied
Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 3

the back wall, the front wall, the bottom wall, the one side wall, and the other side wall are integrally formed by drawing one single metal plate

Methodology Applied
Scientific EffectPlastic deformation: Plasticity

Data Source

PatentEP2660530B1Latent heat exchanger and hot water supply device
Publication Date: 2017.08.30 RINNAI CORP
  • EP2660530B1 patent drawingFigure 1
  • EP2660530B1 patent drawingFigure 2
  • EP2660530B1 patent drawingFigure 3

AI summary

A latent heat exchanger (1) has a casing (2), a heat-absorbing tube (50) accommodated in the casing (2), an inlet header (60), and an outlet header (70). The casing (2) has a casing main body (10) and a top plate (40) closing an upper opening (16) of the casing main body (10). The back wall (11), the front wall (12), the bottom wall (13), one side wall (14), and the other side wall (15) of the casing main body (10) are formed integrally by draw-processing a single metal plate.