Purpose: The purpose of this paper is to improve the lattice Boltzmann method’s ability to simulate a microflow under constant heat flux. Design/methodology/approach: Develop the thermal lattice Boltzmann method based on double population of hydrodynamic and thermal distribution functions. Findings: The buoyancy forces, caused by gravity, can change the hydrodynamic properties of the flow. As a result, the gravity term was included in the Boltzmann equation as an external force, and the equations were rewritten under new conditions. Originality/value: To the best of the authors’ knowledge, the current study is the first attempt to investigate mixed-convection heat transfer in an inclined microchannel in a slip flow regime.

Latent Heat Transfer Thermal Energy Storage (LHTES) units are crucial in managing the variability of solar energy in solar thermal storage systems. This study explores the effectiveness of strategically placing layers of anisotropic and uniform metal foam (MF) within an LHTES to optimize the melting times of phase-change materials (PCMs) in three different setups. Using the enthalpy–porosity approach and finite element method simulations for fluid dynamics in MF, this research evaluates the impact of the metal foam’s anisotropy parameter (Kn) and orientation angle (ω) on thermal performance. The results indicate that the configuration placing the anisotropic MF layer to channel heat towards the lower right corner shortens the phase transition time by 2.72% compared to other setups. Conversely, the middle setup experiences extended melting periods, particularly when ω is at 90°—an increase in Kn from 0.1 to 0.2 cuts the melting time by 4.14%, although it remains the least efficient option. The findings highlight the critical influence of MF anisotropy and the pivotal role of ω = 45°. Angles greater than this significantly increase the liquefaction time, especially at higher Kn values, due to altered thermal conductivity directions. Furthermore, the tactical placement of the anisotropic MF layer significantly boosts thermal efficiency, as evidenced by a 13.12% reduction in the PCM liquefaction time, most notably in configurations with a lower angle orientation.

Thermal Energy Storage (TES) is a key feature in the sizing of thermal systems and energy management. The Phase Change Material (PCM) can store a huge amount of heat in the form of latent heat. However, a good design of the TES unit is required to absorb thermal energy and charge quickly. In the present study, a combination of optimum fin design and nanoadditives are used to design a shell and tube shape TES unit. The Taguchi optimization method is employed to maximize the melting rate by optimizing the arrangement shape of fins and the type and the volume fractions of nanoparticles. The results showed that long fins should be mounted at the bottom and short fins at the top, so that the PCM melts down at the bottom quickly, and consequently, a natural convection circulation occurs at the bottom and advances in the solid PCM. The short fins at the top allow a good natural convection circulation at the top. An increase in the volume fraction of nanoparticles increases the melting rate. An optimum design shows a 20% more melting rate compared to a poor design.