Molecular dynamics (MD) studies on heat transfer from a heated nanoparticle into the surrounding fluid have indicated that the fluid next to a spherical nanoparticle can get heated well above its boiling point without observing a phase change, while a contradicting behavior was observed for a flat surface-fluid interface. Another interesting observation is that the critical heat flux was found to increase with increase in the wetting characteristics of solid. Thus, the interfacial tension or free energy of solid-liquid interface could play a pivotal role in the mechanism of heat transfer. A recent study by Gloor et al. [J. Chem. Phys. 123, 134703 (2005)] has proposed test area simulation method (TASM) for the determination of interfacial tension. The present study involves the determination and the comparison of solid-liquid interfacial tension for planar and spherical interfaces using MD based on TASM and analyze the results. A higher interfacial tension value is observed for spherical nanoparticle fluid interface compared to flat surface fluid interface. The results also indicate that the solid-liquid interfacial tension is a size and temperature dependent property. The results from this study are also expected to give better insights into the possible reasons for the observed differences in the thermal transport for spherical nanoparticle-liquid interface compared to planar-liquid interface.
Fused Deposition Modeling (FDM), a fast growing rapid prototyping technology, is a process for developing physical objects by adding fused layers of materials according to a three dimensional CAD geometry. FDM can be used to produce parts with complex geometries. Hence it gains distinct advantages in industries. One of the major drawbacks of FDM is the reduced part quality measured in terms of dimensional accuracy, surface finish and mechanical characteristics. The major share of research literature related to the field of FDM process parameter optimization focuses on flat and circular surfaces, while only a few studies are available on helical surfaces. This paper is based on a close study conducted to understand the effect of four parameters, namely, layer thickness, raster width, print speed and support material density on dimensional accuracy, tensile strength and surface finish of FDM processed helical surfaces. The experiments were designed by taking three levels of each process parameter selected. Optimum parameter level for improving dimensional accuracy, tensile strength and surface finish simultaneously were obtained by Grey Relational Analysis. The main effect plots were also analyzed.
A better understanding of submicron-scale heat transfer is rapidly gaining interest due to the complex phenomena involved in nanometer scales. We discuss the role of interfacial resistance, in particular that of curvature effects, and the possibility of achieving high temperatures inside the particles without creating a phase transition in the surrounding fluid. The heat transfer from a heated nanoparticle into surrounding fluid is studied using molecular dynamics (MD) simulations. The results show that the particle size and wetting strength between the nanoparticle–liquid influence the heat transfer characteristics. The interfacial conductance and Kapitza length for a model solid–liquid interface were calculated. Both quantities are found to be strongly dependent on particle size and temperature. Smaller nanoparticles are observed to have a stronger bonding with the interfacial fluid when the temperature of the particle is higher, while larger nanoparticles have better affinity with the liquid at lower temperatures.
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