In the steel production industry, two of the main technologies for direct iron reduction and the production of sponge iron are PERED and MIDREX processes. One of the key components in such plants is the heat recovery unit, also called the recuperator. The recuperator plays a crucial role in exchanging heat between the combustion products of the reformer burners and three distinct streams: fresh combustion air, natural gas, and feed gas. Optimizing the performance of this recuperator is essential for various reasons, and so it is required to develop a computational tool for simulation of recuperators for both design objectives and thermal-hydraulic behavior prediction. Thermal and hydraulic design of such a complicated multi-bundle recuperator necessitates arrangement of basic heat transfer correlations in a way that the whole bundle heat exchange can be formulated. This study details the development process of a computational tool for thermal-hydraulic simulation of Direct Reduced Iron (DRI) process recuperators; that includes the generation of correlations for thermophysical properties as polynomial functions of temperature for the streams involved, formulation of algorithms, and implementation of both Design and Off-Design approaches. It also involves selecting and utilizing suitable heat transfer and hydraulic, i.e. pressure drop, relations and analysis of their sensitivity. The developed tool is versatile and can be applied to different plants with varied design objectives.