This application highlight addresses the measurement of e-liquids for use in e-cigarettes using the Transient Hot Wire (THW).
In the design and performance of e-cigarettes (vapes), the thermal behaviour of the e-liquid plays a critical role in determining vaporization efficiency, aerosol composition, and overall user experience. In these devices, a battery-powered coil (heating element) raises the temperature of the surrounding e-liquid, turning it into an inhalable vapour. The efficiency of this process depends on heat transfer characteristics, as conduction through the e-liquid is the primary transfer mechanism. The coil’s heat must conduct into the liquid, often via a wick that holds the liquid, since there is minimal fluid motion (convection) in the confined space of a vape coil assembly. Thermal conductivity (k) is the property that quantifies how well a material conducts heat. For e-liquids, this determines how quickly and uniformly the coil’s heat distributes into the fluid. If an e-liquid cannot conduct heat away efficiently, even a modest-sized coil can develop a steep temperature gradient: extremely hot at the coil surface and much cooler just a short distance away.
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