Supercooling of Peltier cooler using a current pulse

Abstract

Analytical and experimental studies on an innovative composite approach for enhanced thermoelectric performance AIP Conf.The operation of a Peltier cooler can be temporarily enhanced by utilizing the transient response of a current pulse. The performance of such a device, using (Bi,Sb) 2 Te 3 -based thermoelectric elements, was examined from Ϫ70 to 55°C. We establish both theoretically and experimentally the essential parameters that describe the pulse cooling effect, such as the minimum temperature achieved, maximum temperature overshoot, time to reach minimum temperature, time while cooled, and time between pulses. Using simple theoretical and semiempirical relationships the dependence of these parameters on the current pulse amplitude, temperature, thermoelectric element length, thermoelectric figure of merit and thermal diffusivity is established. At large pulse amplitudes the amount of pulse supercooling is proportional to the maximum steady-state difference in temperature. This proportionality factor is about half that expected theoretically. This suggests that the thermoelectric figure of merit is the key materials parameter for pulse cooling. For this cooler, the practical optimum pulse amplitude was found to be about three times the optimum steady-state current. A pulse cooler was integrated into a small commercial thermoelectric three-stage cooler and it provided several degrees of additional cooling for a period long enough to operate a laser sensor. The improvement due to pulse cooling is about the equivalent of two additional stages in a multistage thermoelectric cooler.

Elasto-thermoelectric non-linear, fully coupled, and dynamic finite element analysis of pulsed thermoelectrics

“…In the case of ∆T p (left ordinate), the agreement is very good for P ≤ 3 (maximum 11% error) and starts diverging for greater values, with a 17% difference for P = 4. The FECP result (dashed line) is remarkably very similar to the linear model described in [4] (not shown in the figure).…”

“…The pulse lasts ∆t p = 4.8 s, the hot face is atT h = -6.4 • C and the corresponding intensity isĪ = 0.675 A. For the calculations,T h has been slightly reduced to produce the same T css = -56 • C for the: i) analytical 1D model, ii) the 3D FE with CP (FECP) and iii) experimental from [4] (see next subsection). The fundamental properties α, γ, κ are indirectly calculated from the reference using simple closed-form expressions and values of ZT css , a and I, maintaining ρc p from Table 1.…”

“…In particular, the overcooling measurements are repeated for several conditions, fitting the empirical relationships: 2 (12) To check the validity of these general expressions, the material properties are taken not from [4] but from Table 1, and boundary conditions from Section 4. Due to symmetry, the mesh simulates a single TE with the same dimensions as before, and only two (top and bottom) cooper foils of thickness l Cu = 35 × 10 −6 m as depicted in the reference.…”

“…At present there are many experimental, analytical and numerical works in the literature, in particular experimental investigations were presented in [3] and [4]. Analytically, the pulse shape influences on the cooling power were studied in [5] considering constant (with respect to temperature, CP) material properties.…”

“…In Section 5 the FE algorithm is validated with experimental and semi-analytical methods. The first is towards empirical relations taken from experiments by [4], and the second towards a simplified analytical solution with CP based in the Laplace transform. Finally, in Section 6 a thorough study of thermal stresses present in the TC is discussed.…”