Development of Self-Insulated Gas-to-Gas Heat Exchanger Using Functional Porous Media

1997学年，考虑到对主要参数换热特性的综合认识，同时考虑到数值计算的简化，设计制作了一维平板式气-气换热器。在高温段进气温度T_<gho>=400-600 C，多孔介质光学厚度tau_o=2.6, 6.5，高温段平均气速IOTA_<mh>=0.33m/s，热回收段和低温段平均气速IOTA_<mh>=IOTA_<mI>=0.11, 0.22, 0.33m/s的条件下进行了基础实验和相应的一维数值计算。结果表明，通过增加热回收段，换热器得到了有效隔热，系统的有效热回收率H_<eff>几乎提高了一倍。此外，该换热器的总体换热系数K=20-60W/m^2 / C。在1998学年度，设计并制造了圆柱形换热器。在T_<gho>=400-600 C, tau 0=6.5, (IOTA_<mh, > IOTA_<mr, >, IOTA_<mI,>)=(0.10, 0.07, 0.16), (0.07, 0.05, 0.11), (0.05, 0.04, 0.08) m/s的条件下进行了实验和简化计算。实验和理论研究表明，与平板系统一样，在系统中加入热回收段，可以使换热器外壁温度保持在较低水平，并获得较好的H_<eff>。此外，采用基于平板型模型的简化计算方法预测圆柱系统的H_<eff>误差在30%以内。此外，在IOTA_<mh> =0.07或0.05m/s的较低速度情况下，实验表明平板系统的H_<eff>比圆柱系统的H_<eff>高10%左右。对于非稳态特性，也得到了良好的实验和理论结果，即目前的换热器在加热后约5 ~ 10分钟内达到稳态。少

In the academic year 1997, considering synthetic understanding of heat transfer characteristics for principal parameters and at the same time simplification of numerical calculations, one-dimensional flat plate type of gas-to-gas heat exchanger was designed and fabricated. Fundamental experiments and corresponding one- dimensional numerical calculations were conducted under the conditions of the inlet gas temperature of the high temperature section T_<gho>=400-600ﾟC, the optical thickness of the porous media tau_o=2.6, 6.5, the mean gas velocity of the high temperature section IOTA_<mh>=0.33m/s, and the mean gas velocities of the heat recovery and the low temperature sections IOTA_<mh>=IOTA_<mI>=0.11, 0.22, 0.33m/s, for both the approaching and receding flows. As a result, it is shown that, by adding the heat recovery section, the heat exchanger is effectively insulated, and the effective heat recovery rate H_<eff> of the system is almost doubled. Further, the present heat exchanger is … More shown to have the overall heat transfer coefficient K=20-60W/m^2ﾟC.In the next academic year 1998, cylindrical type of heat exchanger was designed and fabricated. Experiments and simplified calculations based on the results obtained from the flat plate type model were performed for T_<gho>=400-600ﾟC, tau 0=6.5, (IOTA_<mh, > IOTA_<mr, >, IOTA_<mI,>)=(0.10, 0.07, 0.16), (0.07, 0.05, 0.11), (0.05, 0.04, 0.08) m/s. From the experimental and theoretical studies, it is shown that, in the same manner as the case of the flat plate system, the outer wall temperature of the heat exchanger is kept at a low level and favorable H_<eff> is obtained by adding the heat recovery section to the system. In addition, H_<eff> of the cylindrical system is shown to be predicted within 30% error by using proposed simplified calculation method based on the flat plate type model. Furthermore, in the case of lower velocity case of IOTA_<mh> =0.07 or 0.05m/s, it is shown experimentally that H_<eff> of the flat plate system is some 10% higher that that of the cylindrical system. As for the unsteady state characteristics, favorable experimental and theoretical results are also obtained, that is, the present heat exchanger reaches steady state within about 5 to 10 minutes after heating. Less