**4. Thermoelectric self-cooling of devices (TSC)**

Recently, a new thermoelectric application has come out (Martinez et al., 2011), which allows the self-cooling of any device that generates a certain amount of heat, such as electrical power converters, transformers, control systems, etc. As can be seen in Figure 12, the Peltier module in this application works as an electric power generator, since it harnesses the thermal gradient between the heat source (device that generates a certain amount of heat and must be cooled) and the ambient to produce electric power, which in turn is used to operate a fan and attain forced convection over a dissipator, thus improving the cooling of the device without electricity consumption. At the same time, the hot side of the module absorbs heat by Peltier effect, which reinforces the cooling process of the device. This work describes the design and experimental study of a prototype of TSC composed of:

Figure 10 shows the sketch of a prototype thermoelectric refrigerator including the two types of thermosyphon explained along this section, for either end of the Peltier module.

Likewise, Figure 11 provides two photographs of this prototype, indicating the cited heat exchangers. This prototype served to conclude that including the developed thermosyphons (TSV and TMP) in a thermoelectric refrigerator, the COP increased by 66% with respect to that obtained with a similar thermoelectric refrigerator endowed with finned dissipators

Assembly

system TSV

TPM

Fig. 11. Photographs of the prototype with heat exchangers TMP and TSV.

Recently, a new thermoelectric application has come out (Martinez et al., 2011), which allows the self-cooling of any device that generates a certain amount of heat, such as electrical power converters, transformers, control systems, etc. As can be seen in Figure 12, the Peltier module in this application works as an electric power generator, since it harnesses the thermal gradient between the heat source (device that generates a certain amount of heat and must be cooled) and the ambient to produce electric power, which in turn is used to operate a fan and attain forced convection over a dissipator, thus improving the cooling of the device without electricity consumption. At the same time, the hot side of the module absorbs heat by Peltier effect, which reinforces the cooling process of the device. This work describes the design and experimental study of a prototype of TSC composed of:

**4. Thermoelectric self-cooling of devices (TSC)** 

(Vian & Astrain 2009b).


A DC fan type SUNON KDE1208PTS1-6, and a wind tunnel over the dissipator.

Fig. 12. Sketch of a thermoelectric self-cooling system.

This prototype served to conduct several experimental tests in order to study the thermal resistance between the heat source and the ambient, and compare it to that obtained when only the dissipator was mounted over the heat source (no modules, no fan), and finally compare it to the thermal resistance between the heat source and the ambient when no cooling system was mounted. Figure 13 shows the comparison between these three thermal resistances as functions of the heat flux generated by the heating resistors. As expected, the highest thermal resistance is achieved when no cooling system is attached to the device. More interesting is the fact that the TSC system always outperforms the dissipator alone, especially when the heat flux generated by the device exceeds 130 W. For lower values of heat flux, the electric power generated by the Peltier modules does not suffice to operate the fan. However for heat fluxes higher than 130 W, the electric power generated by the

Heat Exchangers for Thermoelectric Devices 305

thermoelectric devices. However, finned dissipators do not represent the most efficient heat exchangers, since constriction thermal resistances restrict, to a great extent, the global

Two different heat exchangers are presented, one for the hot side and the other for the cold side of the Peltier modules. On one hand, the TSF (phase-change thermosyphon) reduces the thermal resistance between the hot side of the module and the ambient by 51 %, which means an increase in the COP of thermoelectric refrigerators by 36.5 %. Subsequently, this TSF was improved and a thermosyphon with natural convection (TSV) came out, thus eliminating all moving parts. On the other hand, for the cold side of the Peltier modules, the described TMP joins thermosyphon and capillarity lift technologies and improves by 37 % the thermal resistance of a similar-in-size finned dissipator. Finally, a prototype that included the developed thermosyphons TSV and TMP showed an improvement on the COP by 66 % with respect to that attained with a similar prototype but including finned

In the last part of the chapter, the novel concept of thermoelectric self cooling has been introduced, which can be applied to any device that generates a certain amount of heat, such as electrical power converters, transformers and control systems. When the thermoelectric self cooling system is installed, the thermal resistance between the heat source and the

Astrain, D.; Vian, J. G. & Domínguez, M. (2003). Increase of COP in the Thermoelectric

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Astrain, D.; Lamuela, J. M.; García, S. & Vian, J. G. (2006a). Kältegerät und Peltier-

Astrain, D.; Vian, J. G.; Martínez, A. & Rodríguez, A. (2010). Study of the Influence of Heat

Bell, L. E. (2008). Cooling, Heating, Generating Power, and Recovering Waste Heat with

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Kühlvorrichtung dafür, 2006, WO2006010539, BOSCH-SIEMENS, Germany. *INTERNATIONAL PATENT*: F25B21/02; F25B21/02. EUROPEAN: F25B21/02 Astrain, D.; Lamuela, J. M.; García, S. & Vian, J.G. (2006b). Thermosiphon, 2006,

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environment decreases by up to 30 % without electricity consumption.

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thermal resistance of the dissipator.

dissipators.

**6. References** 

modules makes the fan rotate and, therefore, provides forced convection over the dissipator, which improves the heat transfer efficiency and decreases the thermal resistance between the heat source and the ambient by 30 % without electricity consumption.

Fig. 13. Thermal resistances between heat source and ambient versus heat flux generated.
