Dual-mesh algorithm for transient coupled heat transfer in multi-body enclosed systems

Currently, numerical algorithms for simulating transient coupled heat transfer in multi-body closed systems, involving solid heat generation and conduction, gas-phase natural convection, and surface radiation, still suffer from limitations in stability, convergence, and computational efficiency. To address these issues, a dual-mesh spatio-temporal region-decomposition and multi-time-step boundary coupling algorithm, named analytical tool for unsteady thermal environment (ATUTE), is proposed. The proposed method divides the computational domain according to different heat transfer mechanisms, in which the fluid region is further decomposed into a dense fluid mesh and a sparse fluid network. Based on the disparity between the flow evolution timescale and the thermal response rate of solid components, the continuous unsteady natural convection process is decomposed into a series of quasi-steady stages. When the wall temperature rise of a solid exceeds a prescribed threshold ΔT, the algorithm triggers a steady-state solution of the dense fluid mesh sub-process to update the convective heat transfer characteristics for the current stage. The steady natural convection field obtained from the dense fluid mesh provides the flow-driving characteristics, while the sparse fluid network is used to construct a thermal equilibrium model coupled with the solid domain. By dynamically adjusting the time step according to the spatio-temporal response of each region, the global solution frequency is effectively reduced. This establishes a high-efficiency modeling framework that combines regional decoupling, boundary coupling, and multi-time-step advancement, achieving a balance between local accuracy and overall computational efficiency. Numerical validations show that the proposed ATUTE method exhibits excellent accuracy and efficiency in typical natural convection and multi-body coupled heat transfer cases. Compared with the commercial software Fluent, the maximum relative error in the average device temperature is only 0.17%, while the total computation time is only about 1/63 of that of Fluent. These results demonstrate that ATUTE can significantly enhance the computational efficiency, scalability, and applicability of transient thermal simulations in complex closed systems without sacrificing accuracy.