中文摘要：

为了研究分子蒸馏器内气体的微观特性,基于变径硬球分子模型,采用了直接模拟蒙特卡洛方法,考虑了分子转动能和平动能,建立了描述分子蒸馏气相传递过程的一维和二维模型,计算了不同蒸发温度下的蒸发效率,并将模拟计算值与实验数据对比,验证了模型的合理性.通过模拟分子的运动和碰撞过程,分析了蒸发温度、冷凝温度和蒸发面与冷凝面的间距等参数对气相空间的碰撞频率和分子平均自由程分布的影响.结果表明：碰撞频率和平均自由程分布的变化始终呈相反趋势;在蒸发面附近,碰撞频率和分子平均自由程分别处于各自最大值和最小值;从蒸发面到冷凝面的气相空间,碰撞频率逐渐减小,分子平均自由程逐渐增大;靠近冷凝面时,碰撞频率和分子平均自由程分别达到各自最小值和最大值;随着蒸发温度或冷凝温度的升高,气相空间同一位置处的碰撞频率增大而平均自由程减小;随着蒸发面与冷凝面的间距增加,碰撞频率在同一位置处有所增大,但在冷凝面附近更小;间距增加,同一位置处的分子平均自由程减小,但是冷凝面附近,间距越大时平均自由程也越大.

英文摘要：

To investigate the microscopic characteristics of vapors in molecular distillation,based on the variable hard sphere（VHS）molecular model,the direct simulation Monte Carlo（DSMC）method was adopted and molecular rotational energy was included as well as molecular translational energy when developing one- and two-dimensional model. The evaporation efficiency at different evaporator temperatures was compared with the published experimental data. The simulated results show a satisfactory agreement with the literature,indicating the simulation model is accurate. The influence of evaporator temperature,condenser temperature and distillation gap on the distribution of collision frequency and the mean free path in vapor space was discussed and analyzed by simulating the movement or collisions between molecules. It is found that the distribution of collision frequency and that of mean free path always show a reverse variation tendency. Near the evaporator surface,collision frequency reaches the maximum value while mean free path reaches the minimum value conversely. Near the condenser surface,the situation is opposite. In the vapor spaces that from the evaporator surface to the condenser surface,collision frequency decreases and the mean free path increases. With the increase of evaporator or condenser temperature,collision frequency in the vapor spaces increases whereas the mean free path decreases at the same location;The collision frequency also increases while the mean free path decreases at the same location with the increase of distillation gap between evaporator and condenser surfaces;Furthermore,the rising distillation gap leads to a smaller mean free path at the same location and a larger mean free path near the condenser surface.