###### Abstract
Nanofluids are a relatively new class of nanoscale materials which are synthesized by doping conventional fluids (water, oils, polymers and gels) with nanoparticles. The nanoparticles generally comprise either metals, oxides, carbides, nitrides, or non-metal in which the particles have diameter size between 1 and 100 nm. [PERSON] et al. [15] among others have confirmed that nanofluids achieve demonstrably greater thermal performance via augmented heat transfer properties than the base fluids (water, kerosene, ethylene glycol, methanol, polymeric solutions etc.). Numerous studies of nanofluid transport phenomena have been communicated. [PERSON] and [PERSON] [16] have conducted an extensive review of applications in medicine, fuel cells, biopolymers and other emerging fields including peristaltic nano-pumps and nano-bioreactor systems. However, in most computational investigations the nanofluids have been assumed to be in one state, i.e., they do not undergo a phase change. Melting of nano-materials and nanofluids, however, constitutes a major branch of nanoscience. Experimental studies in this regard have shown there is a substantial reduction in the melting point of a material when the particle size of the material approaches to the nanoscale ranges. Nanoscale materials change phase at temperatures hundreds of degrees lower than bulk materials. This phenomenon has been observed in many manifestations of nanomaterials, including base materials doped with nanowires, nanotubes and nanoparticles. The engineered nanomaterials consistently melt at lower temperatures than the bulk form of the same material; this has been attributed to the radically greater surface to volume ratio achieved compared to purely bulk materials. This serves to modify the thermodynamic and thermal properties [17]. Other important studies in this regard include one by [PERSON] et al. [18], who reported on the fabrication of an advanced class of nanofluid phase change materials which were synthesized by dispersing carbon nanotubes in water. [PERSON] et al. [19] investigated viscosity and thermal conductivity modifications in nano-encapsulated phase change materials. They observed that the viscosity of the nanofluids is lowered with greater temperature whereas it is enhanced with increasing solid nanoparticle concentration. Thermal conductivity of nanofluids is however elevated with increasing temperature. [PERSON] et al. [20] developed hybrid nanofluids by deploying nanoparticles made of phase-change materials. [PERSON] and [PERSON] [21] have presented a detailed thermodynamic analysis of the melting enthalpy of nanofluids. Boundary layer melting convection flows of nanofluids have recently stimulated some interest. [PERSON] and [PERSON] [22] presented numerical quadrature solutions for two-dimensional stagnation-point thermal convection of a nanofluid towards a melting stretching sheet of copper and silver nanoparticles in a water-based fluid. [PERSON] and [PERSON] [23] studied laminar nano-liquid flow to a melting vertical plate surface in a moving nano-liquid, noting an elevation in both wall heat transfer and mass transfer rate with melting effect, and furthermore an enhancement in heat transfer rate (Nusselt number) at the solid/fluid interface. [PERSON] et al. [24] quantified thermal properties of hybrid nanofluids by mixing a molten salt base fluid (NaNO\({}_{3}\)-KNO\({}_{3}\) (60:40 ratio) binary salt selected as phase change material) with nanoparticles using the direct-synthesis method as a possible working medium for concentrating solar plants. [PERSON] and [PERSON] [25] simulated the nanofluid flow over a stretching plate in the presence of a magnetic field, strong radiative heat transfer and melting, computing elevation in both nanofluid velocity and concentration with melting parameter. [PERSON] et al. [26] analyzed the melting of paraffin-based copper nanoparticle-doped nanofluids in an annulus using an unstructured finite volume method to track the solid and liquid interface.