血液对流换热的数值计算

在血管壁施加第三类边界条件是计算血液与组织间对流换热的一种近似计算方法.为分析其可行性,用有限元数值模拟方法计算血管分支结构中血液与组织的对流换热,得到不同流速和半径下分支血管内血液的截面平均Nu数沿管长的变化曲线.结果表明,血管树中分支血管的Nu数变化幅度不大,且趋于稳定值的速度很快.以相同边界条件下包含简单血管系统的舌体为例,分别用近似方法和完全耦合计算方法,进行血液流场和舌体温度场模拟.通过比较计算结果,得出两种方法得到的温度场分布趋势基本相同;用完全耦合计算方法得到的舌体温度略高于用近似方法得到的舌体温度,两者差值小于0.2℃.

Convective Heat Transfer in Blood Vessels

Convective-type boundary conditions at interface of vessel walls are used in simulating convective heat transfer in blood vessels. To study feasibility of the method, convective heat transfer between blood and tissue in a simple furcated vessel system is computed with finite element analysis. Mean Nusselt number on cross-section along the vessel is obtained at various flow velocities or vessel radii. It shows that the mean Nueselt number in the branching vessel varies within a narrow range, and shows fast convergence rate. A tongue with a simple vascular tree is simulated as an example. Conjugated numerical method, and a approximate method are used to calculate 3-D velocity and temperature of the tongue. Distributions of temperature calculated are similar and quantitative difference between temperatures obtained by two methods is less than 0.2 ℃.