Electrically-induced transport phenomena in EHD drying – A review. (August 2016)

• Record Type: Journal Article
• Authors: Martynenko, Alex; Kudra, Tadeusz
• Is Part Of: Trends in food science & technology. Volume 54(2016)
• Page Start: 63
• Page End: 73
• Publication Date: 2016-08
• Subjects: EHD -- Mass transfer -- Energy transfer -- Momentum transfer -- Electric wind -- Biomaterials; Food industry and trade -- Periodicals; Food -- Biotechnology -- Periodicals; 664.005
• DOI: 10.1016/j.tifs.2016.05.019
• Languages: English
• ISSNs: 0924-2244

Abstract

Abstract: Background: Electrohydrodynamic (EHD) drying is non-thermal and energy efficient technology, which appears to be a viable alternative to thermal drying. However, transport phenomena in EHD are not well understood, which limits practical applications of EHD for drying of biomaterials. Scope and approach: This paper provides a comprehensive review of the fundamentals of electrically-induced physical processes relevant to the theory of EHD drying with particular emphasis on yet existing gaps in the knowledge. Key findings and conclusions: Essential phenomena pertinent to high-voltage electric field and electric wind were examined in terms of heat and mass transfer at the gas-solid interface. The gaps in the knowledge caused by simplifying assumptions in theoretical and experimental studies, as well as omitting some crucial electrically-induced transport phenomena were identified. These include: (i) quantifying energy balance in EHD drying, (ii) uncovering electrically-induced mechanisms of mass transfer in solid, gas and gas-solid boundary layer; (iii) identifying interactions and possibly synergetic effects between electric charge and heat/mass transfer processes; (iv) determining whether average electric wind velocity adequately represents spatial distribution of wind velocity in non-uniform electric field, (v) explaining of some experimental findings, such as temperature drop at the liquid-gas interface, distortion of the free water surface and tangential component of electric wind at the material plane. Highlights: EHD is highly promising technology for premium quality food drying. Gaps in the knowledge are caused by simplifying assumptions and omitting some crucial electrically-induced transport phenomena. The Coulomb force is recognized as a major driving force of charge transfer and electric wind. Mass and heat transfer is enhanced by the effect of electric wind on the solid-gas boundary layer.