Heat exchangers are essential in daily life and industries, but evolving demands, like miniaturization and electrification, challenge traditional designs. The Generalized Graetz Decomposition method offers a powerful solution, capable of efficiently modeling heat exchangers, even under these new conditions. Unlike conventional approaches, it generates analytical expressions that require minimal meshing, reducing computational costs. It accounts for all diffusion components, facilitating realistic modeling of low-velocity flows. This method provides a versatile tool for various boundary conditions. The software based on this method simplifies heat exchanger analysis, enables parametric studies, and has the potential to help heat exchanger design, impacting both research and industry.