The physical form of particles in a packed layer significantly affects how heat is transferred through the material, influencing everything from industrial sintering processes to thermal energy storage systems. Unlike the uniform spheres typically employed in models, real-world powders exhibit a wide range of geometries—irregular, elongated, flaky, or angular—each contributing uniquely to the thermal behavior of the bed. These structural irregularities alter the contact points between particles, the porosity of the packed structure, and the pathways available for heat conduction, convection, and radiation.

When particle geometry approaches a perfect sphere, they tend to pack more densely and uniformly, resulting in a higher number of stable contact points. Particle-particle junctions act as dominant thermal pathways, meaning that spherical morphologies increase effective thermal diffusivity. Particles with complex geometries create uneven packing with fewer and less consistent contacts. This leads to increased void spaces and air gaps, which act as low-conductivity zones since air-filled pores severely limit conductive pathways. As a result, the overall thermal conductivity of the powder bed decreases significantly when composed of non-spherical particles.

The directional arrangement of anisotropic particles also play a critical role. Rod-like or flake-shaped particles may align in specific directions under pressure or during compaction, creating directionally dependent thermal transport. Heat flows readily parallel to orientation but faces resistance perpendicular to it. These geometric biases hinder accurate thermal forecasting and can lead to focused heat accumulation and differential expansion. During processes such as additive manufacturing or sintering, where even heat flow maintains product quality, this becomes particularly critical.

The shape of grains directly modulates internal gas flow by influencing gas flow dynamics within the interstitial spaces. Rough or 粒子形状測定 asymmetric particles disrupt smooth gas circulation, reducing heat transfer via gas movement. When inert or reactive gases circulate through packed beds, this can result in inefficient cooling and delayed reaction kinetics. Uniformly shaped grains enable controlled, laminar convective paths, improving thermal management and operational precision.

Radiative contributions, usually secondary below high-temperature thresholds, becomes more relevant at elevated temperatures. Here, particle shape influences surface area exposure and the geometry of radiation paths. Irregular, jagged, or porous grains offer greater radiative exposure, increasing their ability to exchange infrared energy. This can partially offset conductive losses through increased emissivity, partially compensating for reduced conductive pathways in irregularly shaped beds.

Accurately accounting for shape effects enables better system performance. In metal powder bed fusion processes, using powders with optimized sphericity can ensure consistent energy absorption and cooling. This lowers the risk of structural failure. For solid dosage form production, particle shape influences how heat is conducted during drying or compression, affecting final product performance and dissolution rates. When storing heat in packed granular media, the shape of grains governs thermal response time.

Innovative approaches are being engineered to map morphological impacts on heat transfer. Methods including micro-CT scanning and DEM simulations allow scientists to capture true morphology and evaluate multi-physics transport phenomena. They facilitate a transition from abstract to empirical understanding and toward computationally robust frameworks reflecting real-world heterogeneity.

Particle form is an essential parameter shaping heat transfer dynamics. Neglecting shape effects causes poor thermal control and design failures. By tailoring granular shape to thermal requirements, engineers can fine-tune conductivity and convective behavior for desired outcomes. Whether product uniformity or energy savings are prioritized, advancements will hinge on precise shape control, not solely on material formulation.