Study On Influences Of Thomson Effect And Geometry On Performance Of Thermoelectric Generators

Thermoelectric power generation technology is a green energy conversion technology based on the Seebeck effect of thermoelectric material that directly converts heat energy into electricity.However,relatively low thermoelectric conversion efficiency of thermoelectric generators has greatly limited widely application of this technology.The typical thermoelectric generator is made up of the p-type and n-type thermoelements,cold-and hot-ends,whose performance is influenced by multiple factors,such as temperature difference between the cold-and hot-ends,Thomson effect,contact resistance,geometry of thermoelectric legs,arrangement method of the thermoelements and so on.Among them,Thomson effect,geometry of thermoelements strongly affect the heat generation and transfer,thus affecting the output power and conversion efficiency.In this thesis,we set up the models of thermoelectric generators.The heat and electric coupling equation is applied to describe the thermoelectric generator,while the k–ε turbulence control equation and NK heat transfer control equation are adopted to describe the fluid.The influences of Thomson effect and geometry of thermoelectric legs on performance of thermoelectric generators are studied.We also compare the performances of the annular(ATEG)and flat-plate thermoelectric generators(FTEG)under various conditions.Our results are addressed as follows:(1)The Thomson effect weakens the performance of TEG when the temperature difference is relatively small and the Seebeck coefficient of the thermoelectric materials is relatively large.In contrast,in the range with larger temperature difference and smaller Seebeck coefficient,the performance of the TEG with Thomson effect considered is better than that without Thomson effect.Moreover,the Thomson effect decreases the enhancement of TEG performance by increasing ZT.(2)When the temperature difference between cold and hot ends is high,the output power of the TEG with rectangular thermoelement is higher than that of the thermoelectric generator with trapezoidal thermoelement,which indicates that using the t rectangular thermoelement is helpful to achieve higher output power.However,the geometry of thermoelement has relatively little influence on the conversion efficiency of TEG.(3)The output powers and the conversion efficiencies of ATEG and FTEG both increase with the increases of the inlet velocity,inlet temperature and the convective heat transfer coefficient.When the inlet temperature and/or convective heat transfer coefficient are large,the conversion efficiency of ATEG is greater than that of FTEG.In contrast,the output power of ATEG has no obvious difference with that of FTEG.This study addressed the condition when the ATEG has obvious advantage compared to the FTEG with cylindrical heat source applied.It could be a helpful guide for choosing suitable geometry of TEGs for energy harvesting in complex condition.