Paraffin waxes are organic phase change materials possessing a great potential to store and release thermal energy. The reversible solid–liquid phase change phenomenon is the under-lying mechanism enabling the paraffin waxes as robust thermal reservoirs based on inherently high latent heat (i.e., ~200–250 J/g). However, the main drawback of paraffin waxes is their inability to expedite the phase change process owing to low thermal conductivity (i.e., ~0.19–0.35 Wm−1 K−1). This drawback has long been documented as a technological challenge of paraffin waxes especially for temperature-control applications where faster thermal storage/release is necessitated, encompassing thermal management of batteries, thermoelectric modules and photovoltaic panels. Besides, sustaining the solid-like form of paraffin waxes (shape-stability) is also recommended to avoid the liquid drainage threats for crucial applications, like thermal management of buildings and fabrics. These objectives can be met by developing the paraffin wax-based thermal composites (PWTCs) with help of various thermal reinforcements. However, PWTCs also encounter severe challenges, probably due to lack of design standards. This chapter attempts presenting the recent advances and major bottlenecks of PWTCs, as well as proposing the design standards for optimal PWTCs. Also, the fundamental classification of phase change phenomenon, paraffin waxes and potential thermal reinforcements is thoroughly included.
Part of the book: Paraffin
Mimicking the topographic structures and designs of living surfaces (e.g., lotus leaf, pitcher plant and beetle) onto the non-living surfaces (e.g., metallic plates, glass wafers, wood and fabrics) is known as bioinspiration. Consequently, the pristine topography of the non-living surfaces is robustly modified, known as bioinspired smart surfaces, providing novel surface regimes, i.e., wetting regimes and droplet dynamic regimes. Herein, factors affecting the droplet dynamics and its applications in bioinspired smart surfaces are presented. The droplet dynamics is a complicated phenomenon being affected by the various factors, encompassing the surface roughness, axial structural interspacing (ASI), structural apex layer (SAL), surface positioning, structural alignment, liquid droplet-surface interaction (LD-SI), and various stimuli, etc. Further, the droplet dynamics can be seen many applications, such as droplet manipulation, self-cleaning effect, design of controllable chemical reactors and electric circuits, water harvesting and condensation heat transfer, and oil/water separation, amongst others. The chapter has been mainly divided in three sections enclosed between the introduction and conclusion, comprehensively elaborating the classification of surface regimes, factors affecting the droplet dynamics and the applications at lab and industrial scales. In all, the contents are expected to serve as the guideline to accelerate advancement in the surface science.
Part of the book: Droplet Dynamics