多孔介质对麻醉蒸发器蒸发效果影响的计算分析

摘要

In order to improve the accuracy of anesthesia drug control and provide a theoretical basis for optimizing the structure of evaporator, the influence of physical characteristics of the porous medium evaporator core on the evaporation was investigated. Actual anesthetic evaporators were measured and a three - dimensional structure model was established with the Pro/E software. The effect of porous media on evaporation process in anesthesia vaporizer was simulated with CFD. Using FLUENT software, we analyzed the influence of physical properties of porous media on the performance of the evaporator and mixing process of the vaporized drugs with air. According to stochastic particle tracking in turbulent flow, the moving track of droplet of anesthesia drug in porous media space was traced. Then, the internal gas flow variation, the concentration distribution of drug volatilization process and mixing process with gas were obtained. Numerical simulation results showed that the porous media permeability, flow resistance during anesthesia drug volatilization and mixing process between anesthesia drug vapor and diluted gas all had influence on the accuracy and stability of the volatilization concentration for anesthesia drugs. The existence of porous medium reduced the flow rate of dilution gas. The increase of the porosity of porous media could promote drug evaporation and uniformity of the mixed gases. Due to the absorption of heat in the porous medium area, the maximum evaporation of drug was needed to determine the range of temperature compensation, ensuring the output stability and accuracy of the anesthetic drug concentration in the evaporator.%研究麻醉蒸发器的多孔介质蒸发芯物理特性对蒸发的影响,为优化改进蒸发器结构提供理论依据,提高药物控制精度.通过实际测量麻醉蒸发器,用Pro/E软件建立了三维结构模型,采用CFD方法,利用FLUENT软件分析多孔介质物性对蒸发器工作性能以及麻醉药物蒸发与空气混合情况的影响.在计算分析中采用湍流随机跟踪方法,对麻醉药物蒸发雾滴在多孔介质区域的运动进行轨迹追踪,得到了蒸发器多孔介质区域内气体速度场变化,麻醉药物挥发以及与稀释气体混合过程中浓度场变化等.结果表明,多孔介质孔隙率、流动阻力对药物蒸发以及药物蒸气与稀释气体混合过程有较大影响,最终影响蒸发药物浓度的稳定性与精确性.多孔介质的存在减缓了蒸发器内部稀释气体的流动速度,使流动阻力增加.多孔介质的孔隙率越大药物的蒸发量与稀释气体的混合均匀性越高.并且在多孔介质区域内存在挥发吸热过程,需要根据药物最大蒸发量来确定温度补偿范围,以确保麻醉蒸发器药物浓度输出的稳定性和精确性.