内燃机排气余热回收温差电单偶的模拟分析

选取Bi2Te3和CoSb3两种温差电材料对温差电单偶建立了数学模型,导出温差电单偶的功率和效率计算公式,分析冷热端陶瓷片表面温度、温差电单偶长度以及表面对流传热系数对温差电单偶性能的影响,并对比两种材料在相同条件下的性能.分析结果表明:提高热面温度、降低冷面温度、缩短温差电单偶的长度和提高热表面对流传热系数均可以提高温差电单偶的最大输出功率,但最大转换效率却不能随之持续增大,缩短温差电单偶的长度甚至会使最大转换效率降低.两种材料的温差电单偶相比较,Bi2Te3材料制成的温差电单偶更适用于对600,K以下的低温热量进行回收,而CoSb3材料制成的温差电单偶则更适用于对内燃机排气等700,K以上的中高温热量进行回收.

Simulation and Analysis of Thermoelectric Unicouple Used for Waste Heat Recovery from the Exhaust of Internal Combustion Engine

In this paper, a mathematical model of thermoelectric unicouple was established using two kinds of ther- moelectric materials--Bi2Te3 and CoSb3. Calculation formule of the output power and thermoelectric conversion effi- ciency were derived. The impacts of some factors on thermoelectric unieouple performance were analyzed, including the surface temperature of ceramic on both hot and cold sides, the thickness of thermoelectric unicouple, and the con- vection heat transfer coefficient of hot surface on output power and thermoelectric conversion efficiency, and the per- formance of the two materials was also compared. The results show that the maximum output power of the thermoe- lectric unicouple can be improved by increasing the hot surface temperature, reducing the cold surface temperature, cutting down the thickness of the thermoelectric unicouple and increasing the convection heat transfer coefficient of hot surface. But the maximum conversion efficiency cannot be increased continuously under the above conditions. Reducing the thickness of the thermoelectric unicouple can even decrease the maximum conversion efficiency. As shown by the comparison of two thermoelectric unicouples made by Bi2Te3 and CoSb3 separately, BizTe3 thermoelec- tric unicouple is more suited for recovering low temperature （below 600 K） waste heat, while CoSb3 thermoelectric unicouple is more suited for recovering medium-high temperature （above 700 K） waste heat, such as the exhaust of internal combustion engine.