Download Prescription of Voltage versus Intensity in Thermoelectric Cells for

Prescription of Voltage versus Intensity in Thermoelectric Cells for
different Pulse Shapes and Thermoelement Geometries.
José L. Pérez Aparicio ∗ , Pablo Moreno-Navarro†
∗ Mecánica Medios Continuos Universitat Politècnica de València
Camino de Vera s/n, 46011 Valencia, Spain
e-mail: [email protected]
† Lab. de Mécanique Roberval Université de Technologie de Compiègne
Centre de Recherches Royallieu, 60200 Compiègne, France
e-mail: [email protected]
ABSTRACT
In this study, the prescription of pulses for Peltier cells using voltage or using intensity is studied,
showing that they produce different electrical and thermal results in the dynamic simulations. One of
the objectives is to find the optimal electric value that maximizes overcooling during the steady-state
period; the other to simulate the transient evolutions of the dual electric magnitude and of the
temperature.
For the targeted application of a Peltier heat pump, the optimal voltage only depends on the Seebeck
coefficient and the temperature of the hot face that it is independent of the TE geometry. However,
the optimal intensity requires expressions much more complicated, especially when the
thermoelement geometry is not of constant cross-section.
In the context of the numerical method Finite Element, voltage is of direct prescription since this
potential is the electric degree-of-freedom (essential boundary condition in the FE terminology). But
often electric intensity is used in the analytical analyses or even with FE, even if this prescription
requires especial techniques in the latter.
For power supplies of practical devices, the connection is almost always to a voltage drop. If constant
material properties are considered, the differences between both prescriptions can be significant
during the transient produced by the pulse although not during steady-state. If the more physical and
realistic variation of properties with temperature is included in the model, the differences are much
smaller even in transient, [1].
Extensive comparisons of the mentioned evolutions obtained with a special FE element developed in
previous publications and based in the research code FEAP [2] are presented, for three different pulse
shapes (rectangular, ramp and sinusoidal) and three different thermoelement geometries (rectangular,
increasing and decreasing pyramids). The results are explained identifying terms of fast and slow
dynamics from semi-analytical and simplified formulae. Finally and taking advantage of the full
coupling of the numerical model, the level of induced thermal stresses are given, signifying the
differences obtained with the two prescriptions.
REFERENCES
[1] J.L. Pérez-Aparicio and R. Palma and P. Moreno-Navarro, “Elasto-thermoelectric non- linear,
fully coupled, and dynamic finite element analysis of pulsed thermoelectrics”, Applied Thermal
Engineering, Vol. 107, pp. 398–409, (2016).
[2] R.L. Taylor, “FEAP A Finite Element Analysis Program: User Manual”, University of California,
Berkeley, (2010).