第三类边界条件下套管内天然气中CO_2凝华换热分析

Analysis of carbondioxide anti-sublimation heat transfer in natural gas flow in a tube heat exchanger under the third class boundary condition

针对带压液化天然气(PLNG)流程中对高二氧化碳含量天然气进行二氧化碳凝华分离的设想,分析了天然气中二氧化碳在套管内的凝华换热。将天然气简化为甲烷+二氧化碳的二元混合物,该混合物在圆管内流动,被管外冷氮气冷却直至其中二氧化碳凝华析出。建立了该传热过程的数学模型,采用四阶Runge-Kutta法求解微分方程,分析了天然气和氮气流速、二氧化碳进口体积分数、氮气进口温度、管长对第三类边界条件下凝华换热过程的影响。

Taking the idea that removing carbondioxide by anti-sublimation in a pressurized liquefied natural gas （PLNG） process as the background, carbondioxide anti-sublimation heat transfer in natural gas flow in a tube heat exchanger was analyzed. Natural gas was simplified as methane ＋ carbondioxide binary mixture. The mixture flows in the inner tube while being cooled by cold nitrogen in the outer tube, and car- bondioxide was formed by anti-sublimation. A mathematical model of this heat transfer process was built, and the fourth-order Runge-Kutta method was used to solve the differential equations. The affects of flow ve- locity for natural gas and nitrogen, the inlet carbondioxide concentration, the temperature of inlet nitrogen, and the length of the tube heat exchanger on the carbondioxide anti-sublimation heat transfer process were analyzed under the third class boundary condition.