Segmented Thermoelectric Flat Tubes for Thermal Stress Relief

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Solution Overview

Problem

Thermoelectric heat exchangers in electric vehicles face mechanical integrity issues due to shear stresses caused by thermomechanical loads during operation, which can impair heat transfer efficiency.

Innovation Solution

The use of segmented flat tubes connected by soft elements to absorb thermal stresses, allowing for electrical and thermal connections between thermoelectric pellets and shunts while maintaining mechanical stability and preventing electrical short circuits, with the soft elements being made of materials like elastomers or thermoplastic elastomers to absorb shear stresses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermoelectric heat exchangers use continuous flat tubes with soldered shunt connections, then electrical and thermal connections are achieved, but shear stresses from thermomechanical loads cause mechanical integrity failures

Engineering Contradiction:

Improvemechanical integrityVSAvoidresistance to shear stress

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The flat tube is divided into multiple segments that can expand and contract independently, with expansion joints positioned at regular intervals to accommodate thermal expansion without generating excessive shear stresses that would compromise soldered shunt connections

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The flat tube structure incorporates expansion joints that change the physical parameters of the system by introducing controlled discontinuities, allowing the tube to adapt its dimensional parameters in response to thermal loading conditions

Inventive Principle:

Principle #35Parameter changes

2Reliability

If flat tubes are segmented to reduce thermal stresses, then mechanical integrity is improved, but fluid flow resistance may increase

Engineering Contradiction:

Improvemechanical integrityVSAvoidfluid flow resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The expansion joints are designed with local quality variations - the joint regions have different geometric properties than the straight tube sections, with gradual transitions that minimize flow disruption while maintaining stress relief functionality

Inventive Principle:

Principle #3Local quality

3Reliability

If shear stresses are reduced through design modifications, then mechanical integrity improves, but heat transfer efficiency may be compromised

Engineering Contradiction:

Improvemechanical integrityVSAvoidheat transfer efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The expansion joints act as intermediary elements between the thermoelectric modules and the fluid flow path, mediating the thermal stress relief function while being designed to minimize their impact on the primary heat transfer function

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces shear stresses, enhances mechanical integrity, and allows for scalable thermoelectric heat exchangers with improved heat transfer efficiency by compensating for thermal stresses without increasing fluid flow resistance.

Implementation Method 1

the flat tube consists of at least a first and a second sub-segment, which are fluidically connected at their interface by means of at least one soft element to compensate for thermal stresses that occur

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a plurality of thermoelectric pellets arranged between mutually facing surfaces of the first and second flat tubes

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 3

a large number of first shunts arranged on its upper and/or lower side, which thermally and electrically connect one with a large number of thermoelectric pellets with one another

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP2573831B1Segmented flat tube of a thermoelectric heat pump and thermoelectric heat transfer unit

Publication Date: 2015.12.16 VOLKSWAGEN AG

Figure 1
Figure 1a~1b
Figure 2~3

AI summary

In a flat tube of a thermoelectric heat exchanger, which has a plurality of first shunts (103) arranged on its top and/or bottom and thermally and electrically connect a plurality of thermoelectric pellets (101a, 101b), wherein the thermoelectric pellets (101a, 101b) are thermally and electrically connected on the opposite side to a plurality of second shunts (103a, 103b), it is provided that the flat tube consists of at least a first and a second sub-segment (201, 201a) which are connected to each other at their interface (203) by means of at least one soft element (202) to compensate for thermal stresses occurring.The invention further relates to a thermoelectric heat exchanger unit for transferring a heat flow between a first and second fluid flow, comprising a first flat tube (104) for guiding the first fluid flow and a second flat tube (104a) for guiding the second fluid flow, with a plurality of thermoelectric pellets (101a, 101b) arranged between the mutually facing surfaces of the first and second flat tube, wherein it is provided that the first and/or second flat tube (104, 104a) consists of at least a first and second sub-segment (201, 201a), which are connected to each other at their interface (203) by means of a soft element (202) to compensate for thermal stresses occurring.