超临界CO_2换热特性实验研究

Experimental investigation on heat transfer characteristics of supercritical CO_2

超临界CO_2布雷顿循环发电系统具有动力设备体积小、效率高的优点,发展潜力巨大。超临界CO_2的换热特性是相关部件设计的关键,本文实验研究了超临界CO_2在水平直圆管中的换热特性,其中CO_2的最高压力达到15 MPa、最高温度达到500℃。结果表明:CO_2的压力越高,传热系数在准临界温度处的峰值越低,传热系数随CO_2温度的变化越平缓;而在高温状态下,传热系数主要取决于CO_2流量的大小。同时,本文提出了超临界CO_2在30～500℃范围内的传热关联式,该式既能较好地预测超临界CO_2准临界温度范围的传热特性,又能准确地预测高温状态的传热特性。

Due to the advantages of small power equipment and high efficiency,the supercritical CO2Brayton cycle power generation system has great potential for application.The heat transfer characteristics of supercritical CO2is one of the critical parameters for design of relative devices of the power generation system,and it is experimentally studied in a horizontal straight circular tube where the maximum pressure of supercritical CO2reaches15MPa and the maximum temperature reaches500℃.The results show that:the higher the pressure of the supercritical CO2,the lower the peak value of the heat transfer coefficient at the pseudo-critical temperature and the flatter the change of the heat transfer coefficient with the temperature;while at high temperatures,the heat transfer coefficient mainly depended on the mass flux.A heat transfer correlation of supercritical CO2at temperatures ranging from30℃to500℃was proposed,it can not only predict the heat transfer characteristics of supercritical CO2well in the vicinity of the pseudo-critical temperature,but also accurately predict the heat transfer characteristics at high temperatures.