S. V. Patankar 和 D. B. Spalding 提出了分布阻力的概念，来表征壳程固体表面对流体流动的影响，即把壳程内的换热管束、支撑板以及折流挡板等固体结构看成是多孔介质的骨架，用体积多孔度来表示流体流动所占有的空间占到整个换热器名义空间的百分比，形成了简化的换热器流体流动和传热的数学模型。这种方法既保留了用微分方程来描述壳程流体流动与传热的特点，又简化了换热器的复杂的几何结构，从而实现了管壳式换热器壳程流场的数值模拟。尽管 S. V. Patankar 和 D. B. Spalding 所研究的换热器较简单，网格划分较粗，计算精度也较低，未准确地得到换热管束间的流体流动情况。但是其模拟过程阐述了流动的数值模拟技术，为常用换热器的三维流场数值模拟提供了一定基础。 用另一种语言表示

S. V. Patankar and D. B. Spalding proposed the concept of distributed resistance to characterize the effect of solid surfaces on fluid flow in shell-and-tube heat exchangers. They treated the solid structures such as heat transfer tube bundles, support plates, and baffle plates as a porous medium skeleton and used the volume porosity to represent the percentage of space occupied by fluid flow in the nominal space of the heat exchanger. This formed a simplified mathematical model for fluid flow and heat transfer in heat exchangers. This approach retained the characteristics of using differential equations to describe fluid flow and heat transfer in shell-side flow, while simplifying the complex geometry of the heat exchanger, thus achieving numerical simulation of the shell-side flow field. Although the heat exchanger studied by S. V. Patankar and D. B. Spalding was relatively simple, the grid division was coarse, and the computational accuracy was low, it did not accurately obtain the fluid flow between the heat transfer tube bundles. However, their simulation process elucidated the numerical simulation technology of fluid flow and provided a certain foundation for the three-dimensional flow field numerical simulation of commonly used heat exchangers.