Numerical investigation and comparative analysis of nanofluid cooling enhancement for TEG and TEC systems

Abstract

To enhance the energy conversion of thermoelectric devices, graphene nanoplatelets (GNPs) nanofluids are generally utilized into heat exchangers to boost the cooling capability for thermoelectric generators (TEGs) and thermoelectric coolers (TECs). In this study, a fluid-thermal-electric multiphysics coupled model is developed to uncover the performance enhancements of both TEG and TEC systems using nanofluids, by which the thermodynamic and thermoelectric performances associated with the nanofluid flow behaviors can be taken into account simultaneously. The enhancement effects of nanofluid weight concentration on heat transfer, TEG's electricity generation, and TEC's cooling capability are comprehensively investigated for varying Reynolds numbers (Re). The numerical analysis demonstrates the validity of performance improvements by using nanofluids in TEG/TEC systems, which also shows that the enhancement effect increases with the nanoparticle concentration but reduces with Re. Specifically, with a 0.1 wt% nanofluid used instead of water cooling for Re = 100, the output power and the conversion efficiency are enhanced by 11.38% and 5.7% for the TEG system, while the cooling power and the coefficient of performance (COP) of the TEC system are improved by 12.13% and 9.1%, respectively. The enhancement ratios, however, decrease rapidly to be less than 5% with the increasing Re, and gradually reach a steady level when Re exceeds 1200. Of particular interest is that the performance enhancement of the TEC system proves much stronger than that of the TEG system with nanofluids used as coolants in various Re cases, suggesting that the application of nanofluids seems more promising for a TEC system. This work provides a multiphysics coupling modeling approach to reveal the enhancement effect of nanofluids on thermoelectric performances, which may bring new implications for the optimization design of thermoelectric systems.