Hemispherical PCM Evaporator for Homogeneous Solidification

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Solution Overview

Problem

Existing evaporators for motor vehicle air conditioning systems face issues with heterogeneous solidification of phase change materials (PCMs), inefficient heat transfer, and increased weight due to pressure differences and the need for additional fins, leading to suboptimal cooling performance when the engine is off.

Innovation Solution

The evaporator features refrigerant tubes with hemispherical-shaped housings for thermal storage materials, connected in a regular lattice pattern, which facilitates homogeneous and quick solidification, eliminates the need for fins, and enhances heat transfer efficiency by sharing a wall with the refrigerant tubes, reducing weight and pressure drops.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If tubes are made thicker to withstand pressure differences in checkerboard arrangement, then strength is improved, but weight increases

Engineering Contradiction:

Improvetube strengthVSAvoidevaporator weight

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent employs spherical PCM reservoirs instead of cubic or rectangular geometries. The spherical shape provides uniform stress distribution under pressure, eliminating the need for overly thick tube walls while maintaining structural integrity. This curvature-based design reduces material usage and evaporator weight without compromising strength.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Power

If fins are added to PCM reservoirs to improve heat transfer, then heat transfer efficiency is improved, but weight increases

Engineering Contradiction:

Improveheat transfer efficiencyVSAvoidevaporator weight

Core Design Contradiction:

PowerVSWeight of moving object

Solution Approach 1:

The spherical geometry of the PCM reservoirs inherently provides optimal heat transfer characteristics through uniform radial heat flow paths. This eliminates the need for additional fins or extended surface structures, achieving high heat transfer efficiency without the weight penalty of finned designs.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Quantity of substance

If PCM reservoirs are arranged in evaporator, then thermal storage capacity is improved, but pressure drop increases

Engineering Contradiction:

Improvethermal storage capacityVSAvoidpressure drop

Core Design Contradiction:

Quantity of substanceVSStress or pressure

Solution Approach 1:

The spherical shape of PCM reservoirs optimizes fluid flow characteristics by minimizing flow separation and turbulence compared to angular geometries. This reduces pressure drops in the ventilation fluid path while maintaining adequate thermal storage capacity through the phase change material.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Stability of the object's composition

If checkerboard arrangement is used for tubes and PCM reservoirs, then structural organization is improved, but homogeneous solidification deteriorates

Engineering Contradiction:

Improvestructural organizationVSAvoidhomogeneous solidification

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The spherical PCM reservoirs enable more uniform heat distribution and solidification patterns compared to cubic arrangements. The curved geometry promotes homogeneous cooling rates throughout the PCM volume, ensuring complete and uniform solidification during refrigeration cycles without compromising structural organization.

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

This design achieves efficient and rapid solidification of PCMs, improved heat transfer, and reduced weight, ensuring effective air cooling even when the engine is off, with a pressure drop limited to 30% compared to evaporators without thermal storage reservoirs.

Implementation Method 1

the refrigerant fluid circulating in the evaporator simultaneously cools the air passing through the evaporator and the reservoir of thermal storage material

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 2

When the PCM is in contact with the refrigerant fluid, it solidifies

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

the thermal storage material releases the frigories previously accumulated

Methodology Applied

Scientific EffectLatent heat: Latent Heat

Implementation Method 4

the thermal storage material releases the frigories previously accumulated in order to cool the air passing through the evaporator

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentUS10131198B2Storage evaporator with corrugated plate design facilitating the freezing of the PCM

Publication Date: 2018.11.20 VALEO SYST THERMIQUES SAS

AI summary

The evaporator (12) for a motor vehicle air conditioning device comprises at least one refrigerant tube (22, 22A) intended to allow the circulation of a refrigerant fluid and at least one storage member (10) comprising at least one housing (16, 20) comprising a material referred to as a thermal storage material (21) intended to store frigories and release them to a ventilation fluid intended to circulate towards an interior of the vehicle. The housing (16) has a substantially hemispherical shape.