Evaporator Burner Surface Structuring for Stable Boiling

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Solution Overview

Problem

Evaporator burners for mobile heating devices face challenges in controlling the evaporation process due to uncontrolled alternation between desired nucleate boiling and undesired film boiling, leading to instability and inefficiency.

Innovation Solution

The evaporator burner features a carrier body with a fuel preparation surface structured with depressions and elevations, enhancing heat transfer and vapor bubble formation, and optionally includes a porous evaporator element for improved mechanical and thermal connection, promoting a stable evaporation process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a smooth fuel preparation surface is used, then the device structure is simple, but the heat transfer intensity is insufficient and evaporation process is unstable

Engineering Contradiction:

Improveheat transfer intensityVSAvoidsurface structure complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The fuel preparation surface is equipped with a surface structuring comprising a multiplicity of depressions and elevations, creating locally differentiated zones that enhance heat transfer intensity and control vapor bubble formation, while the overall device structure remains relatively simple

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The surface structuring with depressions and elevations introduces curved surfaces that enhance heat transfer through increased surface area and improved fluid dynamics, leading to intensified heat transfer and more stable evaporation process

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If no surface structuring is provided, then the manufacturing is simple, but the evaporation process alternates uncontrolled between nucleate boiling and film boiling

Engineering Contradiction:

Improveevaporation process stabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The surface structuring creates specific local zones (depressions and elevations) that control vapor bubble formation and heat transfer, ensuring stable evaporation process and preventing uncontrolled alternation between nucleate boiling and film boiling

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The surface structuring is pre-formed on the fuel preparation surface to establish controlled vapor bubble formation characteristics before the evaporation process begins, preventing instability and ensuring reliable operation from the start

Inventive Principle:

Principle #10Preliminary action

3Productivity

If heat transfer to the carrier body is insufficient, then the structure is simple, but the evaporation process is inefficient and fuel consumption increases

Engineering Contradiction:

Improveevaporation efficiencyVSAvoidfuel consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The surface structuring with depressions and elevations creates local zones of enhanced heat transfer, improving evaporation efficiency and reducing fuel consumption through better heat utilization

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The curved surfaces of the depressions and elevations enhance heat transfer efficiency by increasing the effective heat transfer area and improving thermal contact between the carrier body and the fuel, leading to more efficient evaporation and reduced fuel consumption

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 surface structuring intensifies heat transfer and vapor bubble management, resulting in a more stable and controlled evaporation process, reducing the likelihood of film boiling and extending the service life of the burner.

Implementation Method 1

the surface structuring gives rise to an intensification of the heat transfer from the carrier body to the liquid fuel

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

the surface structuring positively influences the formation, the growth and the transporting-away of vapor bubbles

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

an uncontrolled alternation between desired nucleate boiling and undesired film boiling commonly occurs

Methodology Applied

Scientific EffectNucleate boiling: Boiling

Implementation Method 4

the fuel preparation surface, which surface is covered by an evaporator element composed of a porous, absorbent material

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 5

an evaporator element composed of a porous, absorbent material

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS10113742B2Evaporator burner

Publication Date: 2018.10.30 WEBASTO AG

AI summary

The invention relates to an evaporator burner (1; 101) for a mobile heating device, comprising: a combustion chamber (3), a fuel feed line (4) for feeding liquid fuel, and an evaporator for evaporating fed fuel. The evaporator has a support body (6; 106) made of a nonporous material, comprising a fuel preparation surface (6a; 106a) which faces the combustion chamber (3) and which comes into contact with the liquid fuel. A surface structuring (11) with a plurality of depressions (11a) and elevations (11b) is introduced into the fuel preparation surface (6a; 106a) and/or into a support body (6; 106) rear face (6b; 106b) facing away from the fuel preparation surface.