Bent-Fin Heat Exchanger Tube Assembly for Compact Water Heaters

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Solution Overview

Problem

Conventional water heaters with heat exchanger tubes face inefficiencies in thermal transfer due to the lack of optimized designs for compactness and material usage, particularly in non-condensing systems, which limits their thermal efficiency and size constraints.

Innovation Solution

The design incorporates two rows of heat exchanger tubes with bent fins and a corrugated baffle, where the second row fits into gaps between the first row, enhancing heat transfer by slowing combustion fluid flow and utilizing copper or copper-nickel alloys for efficient heating, achieving a thermal efficiency of 83% to 84% in a compact footprint.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional heat exchanger tubes with straight fins are used, then the structure is simple and easy to manufacture, but the thermal efficiency is limited and the device size must be larger

Engineering Contradiction:

Improvethermal efficiencyVSAvoidtube structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies curvature to the fin surfaces by introducing bend patterns (U-bends, zigzag, wave patterns) on the outer circumference of the fins. This curved geometry increases the surface area for heat transfer without proportionally increasing material usage, thereby improving thermal efficiency while maintaining manufacturing feasibility through standard tube bending processes

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention adds a circumferential dimension to the fin structure by creating bends around the tube perimeter. This transforms the traditional planar fin into a three-dimensional corrugated structure that captures heat from multiple angles and increases the effective heat transfer surface area without significantly increasing the axial length of the tube

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Loss of energy

If more heat exchanger tubes are added to increase thermal efficiency, then the heating performance improves, but the device volume increases

Engineering Contradiction:

Improvethermal efficiencyVSAvoidwater heater volume

Core Design Contradiction:

Loss of energyVSVolume of stationary object

Solution Approach 1:

The patent arranges heat exchanger tubes in nested rows where tubes in one row are positioned within the gaps between tubes in adjacent rows. This nesting configuration maximizes the density of heat transfer surfaces within the available volume, allowing more tubes to be packed into a compact space without significant volume increase

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The heat exchanger is divided into multiple rows of tubes with different bend patterns (first row with one pattern, second row with another pattern). This segmentation allows optimized heat transfer in different zones while maintaining a compact overall structure that fits within the reduced volume constraints

Inventive Principle:

Principle #1Segmentation

3Loss of energy

If high-grade materials are used for heat exchanger tubes, then the thermal conductivity and efficiency improve, but the manufacturing cost increases

Engineering Contradiction:

Improvethermal efficiencyVSAvoidmanufacturing cost

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The patent changes the geometric parameters of the fins (bend patterns, fin spacing, fin height) to optimize heat transfer performance. This allows the use of lower-grade materials with adequate thermal conductivity by compensating for material limitations through enhanced geometric design, thereby reducing manufacturing costs while maintaining or improving thermal efficiency

Inventive Principle:

Principle #35Parameter changes

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

This configuration increases thermal efficiency by 1.5% to 2% and allows for a more compact design, maintaining compliance with standards while using lower-grade materials effectively, reducing fuel consumption and waste.

Implementation Method 1

heat exchanger configured to receive heated air from the burner... heat exchanger tubes... transfer a fluid through a volume of space, thereby altering the thermal properties of the fluid

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a plurality of fins on the exterior of the tube positioned concentrically around the tube... enhancing heat transfer

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Data Source

PatentUS11499747B2Heat exchanger tubes and tube assembly configurations

Publication Date: 2022.11.15 RHEEM MFG CO

AI summary

A water heater can include a baffle and a slab heat exchanger with at least two rows of heat exchanger tubes, each row comprising a plurality of heat exchanger tubes. At least one of the heat exchanger tubes comprises a tube and a plurality of fins on the exterior of the tube circumscribing the tube, wherein the outer edge of each fin of the plurality of fins is bent at least at the same three areas of each fin such that the bends form at least three flat or concave areas running along the length of the heat exchanger tube.