Grooved Fin Tubes for Heat Exchanger Flow Guidance

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Solution Overview

Problem

Conventional tube heat exchangers with external fins suffer from inefficient heat exchange due to laminar air flow and significant recirculation zones, leading to poor cooling performance and increased pressure drops, especially at the rear of the tubes where heat exchange is minimal.

Innovation Solution

The use of finned tubes with relief-structured grooves of varying dimensions that decrease radially away from the tube, guiding air flow towards the rear of the tubes to reduce recirculation zones and enhance heat exchange without significantly increasing pressure drops.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional flat fins are used in tube heat exchangers, then the structure is simple and manufacturing is easy, but heat exchange efficiency is poor due to laminar air flow and significant recirculation zones at the rear of tubes

Engineering Contradiction:

Improvefin structure simplicityVSAvoidheat exchange efficiency

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The fin surface is modified with grooves at specific locations (radially spaced apart) to create localized turbulence promoters. These grooves are positioned where they most effectively disrupt laminar flow and reduce recirculation zones, while the rest of the fin maintains its simple flat structure for ease of manufacture.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The grooves on the fin surface create curved flow paths that guide air flow around the tubes. The curved geometry of the grooves promotes turbulence and reduces recirculation zones, improving heat exchange efficiency while maintaining manufacturing simplicity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Productivity

If grooves are added to fins to increase heat exchange, then heat exchange efficiency improves, but pressure drops increase

Engineering Contradiction:

Improveheat exchange efficiencyVSAvoidpressure drop

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The grooves are positioned radially spaced apart rather than continuously, creating localized turbulence promoters that improve heat exchange only where needed. This selective placement reduces the overall increase in pressure drop compared to continuous groove patterns.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of covering the entire fin surface with grooves, only specific radial positions are grooved. This partial action approach provides sufficient turbulence promotion and recirculation zone reduction while minimizing the penalty in pressure drop.

Inventive Principle:

Principle #16Partial or excessive action

3Speed

If air flows through finned tubes at low face velocity (1.5-4 m/s), then the flow regime is laminar with some local turbulences, but heat exchange is poor and recirculation zones are significant

Engineering Contradiction:

Improveair flow velocityVSAvoidheat exchange efficiency

Core Design Contradiction:

SpeedVSProductivity

Solution Approach 1:

The grooves create curved flow paths that guide air flow around the tubes, converting some laminar flow into turbulent flow even at low face velocities. This curvature-induced turbulence improves heat exchange efficiency without requiring higher flow velocities.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The grooves act as flow disruptors that create localized turbulence and vibration in the air flow. This mechanical disturbance promotes better heat transfer coefficients even at low velocities by preventing smooth laminar flow and creating mixing zones.

Inventive Principle:

Principle #18Mechanical vibration

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 design significantly improves thermal performance by reducing recirculation zones and increasing heat exchange efficiency, while maintaining manageable pressure drops, resulting in a performance gain of 10-25% per unit length of the exchanger.

Implementation Method 1

the flow regime of the ambient air is overall laminar with some local turbulences

Methodology Applied

Scientific EffectTurbulence: Turbulence

Implementation Method 2

the grooves of a fin have different dimensions that decrease on moving away from the tube in said radial direction so as to form a guide for a fluid around the tube

Methodology Applied

Scientific EffectFlow guidance:

Implementation Method 3

the cooling of the fluid takes place in the external finned tubes through heat exchange with a second fluid circulating around the tubes and external fins, particularly ambient air

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 4

heat exchange between the air and the fin

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Data Source

PatentUS8376033B2Heat exchanger comprising tubes with grooved fins

Publication Date: 2013.02.19 GEA BATIGNOLLES TECH THERMIQUES

AI summary

Tube heat exchanger comprising finned tubes, wherein the tubes extend in a certain axial direction and are provided with heat exchange fins. Each fin has a heat exchange surface surrounding a tube that extends in a certain radial direction in relation to the tube and which is relief structured to form grooves spaced apart from one another in said radial direction. The grooves of a fin have different dimensions that decrease on moving away from the tube in said radial direction so as to form a guide for a fluid around the tube.