Combustion-thermoelectric tube

In direct combustion-thermoelectric energy conversion, direct fuel injectio n and reciprocation of the air flowing in a solid matrix are combined with the solid-gas interfacial heat transfer and the solid conduction to allow f or obtaining superadiabatic temperatures at the hot junctions. While the so lid conductivity is necessary, the relatively large thermal conductivity, o f the available high-temperature thermoelectric materials (e.g., Si-Ge allo ys) results in a large conduction loss from the hot junctions and deteriora tes the performance. Here, a combustion-thermoelectric tube is introduced a nd analyzed Radially averaged temperatures are used for the fluid and solid phases. A combination of external cooling of the cold junctions, and direc t injection of the fuel, has been used to increase the energy conversion ef ficiency for low thermal conductivity, high-melting temperature thermoelect ric materials. The parametric study (geometry, flow, stoichiometry, materia ls) shows that with the current high figure of merit, high temperature Si0. 7Ge0.3 properties, a conversion efficiency of about II percent is achievabl e. With lower thermal conductivities for these high-temperature materials, efficiencies about 25 percent appear possible. This places this energy conv ersion irt line with the other high efficiency, direct electric power gener ation methods.