Finite element analysis of thermoelectric systems with applications in self assembly and haptics

 

Abstract:    Micro-scale self assembly is an attractive method for manufacturing sub-millimeter sized thermoelectric device parts. Challenges controlling assembly yield rates, however, have caused research to find novel ways to implement the process while still resulting in a working device. While a typical system uses single n-type and p-type material elements in series, one method used to increase the probability of a working device involves adding redundant parallel elements in clusters. The drawback to this technique is that thermal performance is affected in clusters which have missing elements. While one-dimensional modeling sufficiently describes overall performance in terms of average junction temperatures and net heat flux, it fails when a detailed thermal profile is needed for a non-homogeneous system. For this reason, a three-dimensional model was created to describe thermal performance using Ansys v12.1. From the results, local and net performance can be described to help in designing an acceptable self-assembled device.

        In addition, a haptic thermal display was designed using thermoelectric elements with the intention of testing the thermal grill illusion. The display consists of 5 electrically independent rows of thermoelectric elements which are controlled using pulse width modulating direct current motor controllers.




Comparison of results between the 1D analytical model and 3D Ansys numerical model. The model configuration is shown at their respective data points.

 

The three goals of my research:

  1. 1)Validate a thermoelectric FEA model against published one-dimensional methods by comparing average temperature and net heat flux solutions.


  1. 2)With the model validated, test a variety of cases and configurations and analyze how non-homogeneities affect local and net thermal performance.


  1. 3)Design and model a new haptic display and analyze how thermal information is presented to temperature receptors within human skin.

    The thermoelectric effect (TE) describes the conversion of energy between thermal and electronic states, where the conversion can occur in both directions. Semiconducting materials exhibit the best properties and can be designed to have low electrical resistivity, low thermal conductivity, and high Seebeck coefficients, which is optimal. The Seebeck coefficient is a special property which directly relates the energy conversion and has units of volts divided by absolute temperature.


    Popular applications of the effect include temperature measurement (thermocouples), microchip cooling, automotive seat heating/cooling, energy scavenging and long-term satellite power supply.

Verification results where the solid lines correspond to the 1D analytical model, and bulleted lines from the 3D numerical solution.

Temperature profiles for various cases where Path A is within an element in the center of the array and Path B is within an element along the edge.

Left: FEA model configuration where each set of four same-type elements are electrically in parallel.

Right: Mesh of full system including entry and exit conduction zones (shown as orange substrate).

Verification of the Model

Analysis of a Self-Assembled System

This section in currently being put together

The Thermal Grill Effect - Thermal Haptics