The key-element in any heat recovery application is the heat exchanger. Many heat exchangers have been suggested for heat recovery applications among them Multi-Tube Tank (MTT). MTT is a heat exchanger that has been recently proposed especially for heat recovery processes that involve two fluids one at rest and the other one in motion. That said, MTT can be adopted for a broad spectrum of heat recovery applications and can be applied within a wide panel of geometrical configurations. Notwithstanding, operational conditions may impose thermal constraints on the outlet fluids. All things considered, to efficiently utilize MTT heat exchangers it is unavoidable to understand its thermal behavior. In the frame of this view, the present paper, examines the anatomy of MTT using a computational code. A heat recovery process is considered where exhaust gas is used to heat water. The thermal model is based on the heat equation along with different boundary conditions. Furthermore, an optimization procedure is developed in order to find the best scenario among three different configurations incorporating, respectively, one tube, three tubes, and six tubes. Three optimization criteria are considered, maximum water temperature, maximum recovered energy, and minimum gas temperature threshold. Results reflect the flexibility of the optimization assessment. To give an illustration, for a fixed interval of time, if the selection criterion is the maximum-recovered energy the configuration of six tubes is the optimal solution whereas if the criterion is a minimum gas temperature threshold then MTT with one tube is the best configuration.