EHD-enhanced drying with multiple needle electrode

Lai, F. C.; Sharma, Rajat

doi:10.1016/j.elstat.2004.10.004

Cited by 86 publications

(51 citation statements)

References 16 publications

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“…For a laminar tangential flow over a surface, the combined effect of inertia and electrical force could lead to a fourfold increase of the Nusselt and Sherwood numbers (Sadek et al 1972). Nevertheless, in the specific case of evaporation by a flow over a surface, the enhancement was not observed (Lai and Sharma 2005;Lai et al 2004). Experiments showed that the inertial effects were more predominant than the electrical effects.…”

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confidence: 86%

Assessment of the Electrohydrodynamic Drying Process

Ahmedou

Rouaud

Havet

2008

Food Bioprocess Technol

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Industries using energy-intensive processes are being forced to explore ways for reducing their energy consumption. In the food industry, air drying is one of the more energy-consuming processes. To reduce the energy consumption during this operation, alternative processes should be investigated. One promising alternative consists in the electrohydrodynamic (EHD) enhancement of heat and mass transfer. This paper analyses the literature and describes the great potential of this innovative process based on the generation of an electric wind by a corona discharge. The main aspects of this technique are discussed and special emphasis is given on its benefit for food processes. The main part of this paper concerns experimental investigations carried out to assess the EHD enhancement on the drying process. An experimental setup was designed to measure the weight losses on a food product submitted to an electrostatic field and to a cross air flow. Present results confirm that, for a low cross air velocity, the ionic wind leads to an enhancement of the drying rate. The best results are obtained for the smaller distance between the food surface and the corona electrode. Nevertheless, the process is less efficient for a high air velocity. The last part deals with a numerical model that was developed to evaluate the electric parameters and the flow field in turbulent regime. This model provides useful information on the coupled phenomena and permits to explain the experimental observations and to help in designing EHD drying processes. Nomenclature a surface (m 2 ) b ionic mobility (m 2 V −1 s −1 ) d food surface-electrode gap (m) e edge of the wind tunnel (m) E electric field (V m −1 ) F e electric body force (C m −2 s −1 ) g gravity (m s −2 ) I electric current (A) J current density (A m −2 ) k turbulent kinetic energy (m 2 s −2 ) L length of the wind tunnel (m) p pressure (Pa) U velocity vector (m s −1 ) v i ionic wind velocity (m s −1 ) V voltage (V) x distance along surface (m) y height above surface (m) φ diameter (m) ɛ turbulent dissipation rate (m 2 s −3 ) ɛ 0 permittivity of free space (C m −1 V −1 ) Ρ density of air (kg m −3 ) ρ c space charge density (C m −3 ) μ dynamic viscosity of air (Pa s −1 ) μ t turbulent viscosity (Pa s −1 )

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confidence: 86%

Assessment of the Electrohydrodynamic Drying Process

Ahmedou

Rouaud

Havet

2008

Food Bioprocess Technol

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“…The effect of PEF treatment on solid gain was minimal. Lai and Sharma (2005) reported that PEF pre-treatment (number of pulses 100, pulse width 840 μs, fi eld strength 2.67 kV/cm, 1 Hz; specifi c energy input 3.58 kJ/ kg) resulted in higher moisture loss and solid gain in mangoes during subsequent OD. Ade-Omowaye et al (2003) compared the quality characteristics of PEF-pre treated and osmotically-treated red paprika with osmotic treatment at higher temperature.…”

Section: Pulsed Electric Fi Eld (Pef)mentioning

confidence: 99%

Recent advances in drying and dehydration of fruits and vegetables: a review

2010

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Fruits and vegetables are dried to enhance storage stability, minimize packaging requirement and reduce transport weight. Preservation of fruits and vegetables through drying based on sun and solar drying techniques which cause poor quality and product contamination. Energy consumption and quality of dried products are critical parameters in the selection of drying process. An optimum drying system for the preparation of quality dehydrated products is cost effective as it shortens the drying time and cause minimum damage to the product. To reduce the energy utilization and operational cost new dimensions came up in drying techniques. Among the technologies osmotic dehydration, vacuum drying, freeze drying, superheated steam drying, heat pump drying and spray drying have great scope for the production of quality dried products and powders.

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“…Goodenough et al [30] commented, in a study on the efficiency of corona wind on paper towels and biscuits, that "the arrangements of the electrodes is crucial for effective operation." A recent study by Hamdi et al [31], which was similar in principle to Lai [29], investigated the direct heat transfer enhancement associated with EHD flow due to varying wire-electrode arrangements. In that particular study, a horizontal airflow channel was used to study three different wire-electrode arrangements (i.e.…”

Section: Introductionmentioning

confidence: 98%

“…Lai [29] investigated the effect of a multiple-needle electrode on the EHD drying of wetted glass beads and found, in terms of energy per mass, that a single electrode was more effective than multiple electrodes. Goodenough et al [30] commented, in a study on the efficiency of corona wind on paper towels and biscuits, that "the arrangements of the electrodes is crucial for effective operation."…”

Section: Introductionmentioning

confidence: 99%