Heat Transport Through MBBA Due to Induced Electrohydrodynamic Motion

Abstract

Abstract Turbulent electrohydrodynamic (EHD) motion occurs in the liquid crystal MBBA [p-methoxybenzylidene p-(n-butyl)aniline when subjected to large AC (sine wave) voltages. The onset of EHD motion substantially increases the transport of heat across a cell encapsulating the liquid crystal. This observed increase in heat transfer, or “heat valve effect,” can be characterized by an “apparent” thermal conductivity ka of the liquid crystal. The magnitude of the increase in ka is a strong function of frequency, temperature, voltage, and the liquid-crystal phase. This ka is actually a measure of the EHD motion within the cell. Structure in the ka versus frequency curves indicates possible transitions in flow behavior. Internal heating also occurs within the liquid crystal and is shown to vary in strength with frequency, temperature, and applied voltage. Variations in the usual power factor normally associated with dielectric heating suggest that ionic double layers are formed below some critical frequency.