Design of Novel Cooling Systems Based on Metal Plates with Channels of Shapes Inspired by Nature

The effect of the channel shape of aluminum plates on cooling capacity was evaluated by studying different configurations. Common shapes of the channel, such as square and fork shapes, were compared with novel configurations inspired by shapes found in nature, specifically the shape of the outline of flowers, inspired these new configurations, consisting of channels with crateriform, salverform, and cruciform shapes. The aim of the study is to evaluate the effect of the channel shape on the cooling capacity of the metal plate. To that end, all the configurations were analyzed from a geometrical point of view, determining the minimum distance of each point across the plate to the channel. A finite difference method was implemented to study both transient and steady state heat dissipation across the plates for each configuration. Even though the effect of the channel shape on the average temperature of the plate is slight, the maximum temperature, the size and location of hot spots, and the temperature homogeneity of the plate are strongly affected by the shape of the channel through which the cooling fluid is circulated. A reduction in the maximum temperature of the plate during transient cooling of around 2 C for the crateriform and salverform channels and approximately 4.5 C for the cruciform channel can be attained, compared to the standard configurations. The steady state heat dissipation analysis concluded that the crateriform and salverform configurations reduced the maximum variation in temperature of the common configurations by roughly 15%, whereas a reduction of approximately 28% could be reached by the cruciform configuration. Regarding the homogeneity of temperature across the plate, a reduction up to 34.5% of the index of uniform temperature can be attained using the novel configurations during the steady state refrigeration of the plate. The cruciform channel is the optimal configuration for both transient and steady state cooling processes, reducing the size and temperature of hot spots and improving the temperature homogeneity of the plate, a result already anticipated by the geometrical analysis. In fact, the main conclusions attained from the cooling study are in good agreement with the results of the geometrical analysis. Therefore, the geometrical analysis was found to be a simple and reliable method to design the shape of channels of a cooling system.The authors gratefully acknowledge the financial support provided by Fundación Iberdrola under the program “Programa de Ayudas a la Investigación en Energía y Medioambiente”. This work has been supported by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M (“Fostering Young Doctors Research”, NANOCOOLEVBCM- UC3M) and in the context of the V PRICIT (Research and Technological Innovation Regional Programme). Eduardo Cano-Pleite acknowledges support from the CONEX-Plus programme funded by Universidad Carlos III de Madrid and the European Union’s Horizon 2020 programme under the Marie Sklodowska-Curie grant agreement No. 801538

The influence of an outer bath on the dewetting of an ultrathin liquid film

We report a theoretical and numerical investigation of the linear and nonlinear dynamics of a thin liquid film of viscosity µ sandwiched between a solid substrate and an unbounded liquid bath of viscosity λ µ. In the limit of negligible inertia, the flow depends on two nondimensional parameters, namely λ and a dimensionless measure of the relative strengths of the stabilizing surface tension force and the destabilizing van der Waals force between the substrate and the film. We first analyze the linear stability of the film, providing an analytical dispersion relation. When the viscosity of the outer bath is much larger than that of the film, λ ≫ 1, the most amplified wavenumber decreases as km ∼ λ −1/3 , indicating that very slender dewetting structures are expected when λ becomes large. We then perform fully nonlinear simulations of the complete Stokes equations to investigate the spatial structure of the flow close to rupture revealing that the flow becomes self-similar with the minimum film thickness scaling as hmin = K(λ)τ 1/3 when τ → 0, where τ is the time remaining before the singularity. It is demonstrated that the presence of an outer liquid bath affects the self-similar structure obtained by16 through the prefactor of the film thinning law, K(λ), and the opening angle of the self-similar film shape, which is shown to decrease with λ.This research was funded by the Spanish MCIU-Agencia Estatal de Investigación through project PID2020-115655GB-C22, partly financed through FEDER European funds

Experimental determination of the forced convection heat transfer coefficient of an aluminum cooling plate with a channel shape inspired by nature

Proceedings of: 16th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics (HEFAT2022), 8-10 August 2022, Virtual ConferenceCooling is a crucial aspect in numerous applications where the optimal operation of electric, electronic, or electrochemical devices requires a controlled operating temperature. In this sense, metallic cooling plates are a suitable solution to dissipate heat from the surface of these equipment. The refrigeration capacity of cooling plates can be improved by circulating cold fluid along channels drilled in the metallic plate. The shape of these channels plays a critical role on the performance of the cooling plate since they affect both the distribution of temperature across the plate and the pressure drop required to pump the cooling fluid along the channel. The channel shape of a cooling plate can be optimized considering the Constructal law, which proposes the use of configurations found in nature to improve the performance in industrial applications. Following the Constructal law, a cooling plate made of aluminum, inside of which there is a channel with a shape resembling the outline of a flower, was built by a 3D printer. The performance of the plate was experimentally evaluated refrigerating the plate with various flow rates of cold water. To that end, an experimental facility was specifically designed and built to test the cooling capacity of the plate. The experimental setup consists of an enclosure inside of which the temperature of the atmosphere is controlled by a PID system connected to a thermoresistance and a heater, and a thermostatic bath to control the temperature of the cooling water at the inlet of the plate. The temperature of the plate was measured by an IR camera and the heat transfer coefficient by forced convection to the fluid were derived from the tests for both laminar and turbulent flow regimes of the fluid, obtaining values of 1703 and 3639 W/m2K, respectively, with maximum variations of 1 % for three replicates of each test, proving the high repetitiveness of the experimental procedure proposed. The average characteristic cooling time of the plate was measured to be 34.9 and 16.5 s for Reynolds numbers of the cooling flow of 1249 and 4918, respectively. Thus, an increase on the flow rate by 4 times results in a reduction of the characteristic cooling time by approximately 50 %.The authors gratefully acknowledge the financial support provided by Fundación Iberdrola under the program "Programa de Ayudas a la Investigación en Energía y Medioambiente". This work has been supported by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with UC3M ("Fostering Young Doctors Research", NANOCOOLEVB-CM-UC3M), and in the context of the V PRICIT (Research and Technological Innovation Regional Programme)