Model of Heat Exchangers for Waste Heat Recovery from Diesel Engine Exhaust for Thermoelectric Power Generation
Model of Heat Exchangers for Waste Heat Recovery from Diesel Engine Exhaust for Thermoelectric Power Generation
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DOI：
10.1007/s11664-012-1915-y
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发表时间：
2012-02
影响因子：
2.1
通讯作者：
Chad Allan Baker;Prem Vuppuluri;Li Shi;M. Hall
中科院分区：
文献类型：
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作者：
Chad Allan Baker;Prem Vuppuluri;Li Shi;M. Hall
建立了一个假设的热电发电机系统的性能和工作特性的模型，该系统设计用于从中型涡轮增压柴油发动机的排气中提取废热。有限差分模型包括两个集成的子模型：热交换器模型和热电器件模型。热交换器模型指定了一个矩形横截面几何形状，冷却液在冷侧，并考虑了从排气到冷却液的传热速率之间的差异。考虑到热电特性的空间变化，热电装置模型计算热电元件给定的温度边界条件的热侧和冷侧热通量，迭代直到温度和热通量边界条件满足排气和冷却剂的对流条件，以及热电装置中的热传递。下坡单纯形法被用来优化影响电功率输出的参数，包括热电腿高度，热电型top-type腿面积比，热电腿面积与空隙面积比，负载电阻，排气管高度，冷却剂管高度，排气管中的翅片间距，在发动机排气系统中的位置，以及在受约束的封装体积内的流动路径的数量。计算结果表明，对于总高度为5.5 cm的单通道，在30 cm宽的通道上，采用32个直肋的结构是最佳的。此外，三个逆流平行管道或流动路径被认为是一个最佳的数量为5.5厘米的总高度的给定的尺寸限制，和逆流平行管道是一个更好的配置比蛇形流。基于MnSi 1.75和Mg 2Si 0.5Sn 0.5的热电性能，对于16.5 L的封装体积和122 kW的排气流焓通量，逆流布置中的三个平行流路实现的最大净电功率为1.06 kW。
The performance and operating characteristics of a hypothetical thermoelectric generator system designed to extract waste heat from the exhaust of a medium-duty turbocharged diesel engine were modeled. The finite-difference model consisted of two integrated submodels: a heat exchanger model and a thermoelectric device model. The heat exchanger model specified a rectangular cross-sectional geometry with liquid coolant on the cold side, and accounted for the difference between the heat transfer rate from the exhaust and that to the coolant. With the spatial variation of the thermoelectric properties accounted for, the thermoelectric device model calculated the hot-side and cold-side heat flux for the temperature boundary conditions given for the thermoelectric elements, iterating until temperature and heat flux boundary conditions satisfied the convection conditions for both exhaust and coolant, and heat transfer in the thermoelectric device. A downhill simplex method was used to optimize the parameters that affected the electrical power output, including the thermoelectric leg height, thermoelectricn-type top-type leg area ratio, thermoelectric leg area to void area ratio, load electrical resistance, exhaust duct height, coolant duct height, fin spacing in the exhaust duct, location in the engine exhaust system, and number of flow paths within the constrained package volume. The calculation results showed that the configuration with 32 straight fins was optimal across the 30-cm-wide duct for the case of a single duct with total height of 5.5 cm. In addition, three counterflow parallel ducts or flow paths were found to be an optimum number for the given size constraint of 5.5 cm total height, and parallel ducts with counterflow were a better configuration than serpentine flow. Based on the reported thermoelectric properties of MnSi1.75and Mg2Si0.5Sn0.5, the maximum net electrical power achieved for the three parallel flow paths in a counterflow arrangement was 1.06 kW for package volume of 16.5 L and exhaust flow enthalpy flux of 122 kW.