Thermal-fluid-structure topology optimization of lightweight sandwich cold plates with thin-walled hollow channels

A thermal-fluid-structure topology optimization method is proposed to design lightweight sandwich-type cold plates with thin-walled hollow channels, targeting an integrated trade-off among heat dissipation, hydraulic loss, and load-bearing capacities. The integrated topology is described using a single density field to represent the interior fluid domain, thin-walled layer and exterior lightweight porous structure. Manufacturable thin walls with interior hollow fluid channel are generated through a two-step PDE filtering and Heaviside projection, in which the first filter-projection is used to separate the hollow-fluid and non-fluid domain, while a second one is used to generate the thin wall with controllable thickness between the fluid and porous-structure domain. A Brinkman-type porous penalization with RAMP interpolation is adopted for flow suppression in solids, while three-phase material interpolation is used for thermal and mechanical properties. A weighted sum of flow dissipation energy, domain-averaged temperature and structural strain energy is formulated as the topology optimization objective, and a global volume allowance and minimum length-scale are applied as the constraints to control the channel and thin wall domain. A single inlet-outlet parallel channel example is investigated, and the corresponding parametric effects of Reynolds numbers on optimized design are studied in terms of domain-averaged temperature, pressure drop, and structural strain energy. Finally, the proposed method is applied to a topology optimized cold plate (TCP), and benchmarked against a serpentine channel cold plate (SCP) and a rectangular channel cold plate (RCP) under the same bending load case with different inlet flow rates. The results show that the proposed TCP outperforms the SCP and RCP by reducing the average temperature by 1.78 K and 3.67 K, the pressure drop by 115.11 Pa and 94.57 Pa, and the mass-specific strain energy by 41.7% and 35.4% at 6 L/min, respectively.