板式气冷器中超临界CO_(2)侧表面换热系数研究

Study on heat transfer coefficient of supercritical CO_(2)side surface of plate gas cooler

为了探究板式气冷器中主导超临界CO_(2)侧表面换热系数h最值出现的因素及最值点的中移对平均换热系数大小的影响,采用基于MATLAB的换热器分布参数分析方法,研究了超临界CO_(2)侧表面换热系数h沿气冷器板片上的分布规律,并针对h最值出现的主导因素、改变板片尺寸和流量使最值点移动对平均换热系数的影响进行研究。结果表明,伪临界温度对板式气冷器中h最值的出现更具有决定性;一定压力下的C_(p)最大值会随着压力的增加不断增大,但伪临界温度逐渐降低;减小板片尺寸或者增大质量流量,可以使得平均换热系数增加,对应的换热量也会增大,而且由质量流量增加所带来的换热量增加幅度在3种工况下分别为12.72%,12.79%,11.75%,同时压降也会增加;当h最大值保持在6170 W/(m^(2)·K)或5120 W/(m^(2)·K)附近时,最值点中移不会使平均换热系数增加明显,而且对应的换热量也会减小。

In order to study the effect of the factors leading to the occurrence of the maximum surface heat transfer coefficient h on the supercritical CO_(2)side in plate gas coolers and the effect of shifting this maximum point on the average heat transfer coefficient,a MATLAB-based distributed parameter analysis method for heat exchangers was employed to investigate the distribution pattern of the surface heat transfer coefficient h along the plates of the gas cooler,and examine the dominant factors contributing to the appearance of h's maximum values,as well as the effects of changing plate dimensions and flow rates on moving the maximum point and its effect on the average heat transfer coefficient.The simulation results indicate that the pseudocritical temperature plays a decisive role in the occurrence of h's maximum values in the plate gas coolers;the maximum C_(p) at a given pressure increases with pressure,but the pseudocritical temperature gradually decreases;Reducing the size of the plates or increasing the mass flow rate can increase the average heat transfer coefficient,and correspondingly,the heat transfer rate will also increase.Moreover,the increases in heat transfer rate brought by the increased mass flow rate are respectively 12.72%,12.79%,11.75%across three different conditions,although the pressure drop will also increase.However,when the maximum value of h is maintained around 6170 W/(m^(2)·K)or 5120 W/(m^(2)·K),shifting the maximum value point does not significantly increase the average heat transfer coefficient,and the corresponding heat transfer rate will also decrease.