Effects of mixed electric field on characterization of electrohydrodynamics drying system
الموضوعات : Journal of Theoretical and Applied Physics
Hamid Ghomi
1
(Laser and Plasma Research Institute, Shahid Beheshti University)
Pourya Seyfi
2
(Laser and Plasma Research Institute, Shahid Beheshti University)
Ahmad Khademi
3
(Laser and Plasma research institute, Shahid Beheshti University)
Amir Heidari
4
(Laser and Plasma Research Institute, Shahid Beheshti University)
الکلمات المفتاحية: Ionic wind, Modulated voltage, Electrohydrodynamic (EHD), Surface dielectric barrier discharge (SDBD), Corona discharge,
ملخص المقالة :
In this paper, we present a new structure of applying two electrical power supplies to generate ionic wind.In this configuration, two power supplies were applied simultaneously with a modulated voltage to anelectrohydrodynamic (EHD) system then corona discharge parameters and EHD thrust characterizationwas investigated by a corona dryer mechanism. The EHD thrust experiments were performed with a pinto plate and SDBD arrangements. The results show that with the simultaneous application of two powersupplies the drying rate in a drop of water as a standard sample was greatly enhanced and the drying time was reduced. Thus, the total evaporation was occurred in 1 minute in the SDBD structure with a power of 7 watts and in 1.5 minutes in pin to plate structure with a power of 2.5 watts. Eventually, it was observed that the use of mixed electric fields enhances the ionic wind, hence increases the non-thermal evaporation process significantly. Furthermore, the drying rate has grown notably In SDBD configuration.
Effects of mixed electric field on characterization of Electrohydrodynamics drying system
Amir Abbas Heidari1, Pourya Seyfi1, Ahmad Khademi1 and Hamid Ghomi1
Abstract
In this paper, we present a new structure of applying two electrical power supplies to generate ionic wind. In this configuration, two power supplies were applied simultaneously with a modulated voltage to an electrohydrodynamic (EHD) system then corona discharge parameters and EHD thrust characterization was investigated by a corona dryer mechanism. The EHD thrust experiments were performed with a pin to plate and SDBD arrangements. The results show that with the simultaneous application of two power supplies the drying rate in a drop of water as a standard sample was greatly enhanced and the drying time was reduced. Thus, the total evaporation was occurred in 1 minute in the SDBD structure with a power of 7 watts and in 1.5 minutes in pin to plate structure with a power of 2.5 watts. Eventually, it was observed that the use of mixed electric fields enhances the ionic wind, hence increases the non-thermal evaporation process significantly. Furthermore, the drying rate has grown notably In SDBD configuration.
Keywords Ionic wind, Modulated voltage, Electrohydrodynamic (EHD), Corona discharge, Surface dielectric barrier discharge (SDBD)
INTRODUCTION
Over the last decade, electro-hydrodynamic (EHD) technology has gained great interest to solve some problems in different industries [1-4]. Cooling and desalination systems based on electrohydrodynamic technology are among the industries that researchers have focused more on in recent years [5-7]. With the increasing advancement in microelectronics, cooling of the micro-sized components has become an important issue in which conventional cooling methods such as water-cooling and air-cooling systems may not be adequate [8-10]. So, due to some limitations in the use of these techniques, as well as high energy consumption and low efficiency, these methods are being replaced with electrohydrodynamic systems over time [11, 12]. Also, considering the importance of freshwater in the world, desalination systems equipped with an electro-hydrodynamic system are of special importance due to increasing the efficiency of these systems [13]. The electrohydrodynamic effect occurs when high voltage is applied to two asymmetric electrodes, mainly in the form of the pin to plate configuration which the sharp and the plate electrodes act as emitter and collector electrodes respectively [14-16].
1 Laser and Plasma Research Institute, Shahid Beheshti University, Evin 1983963113, Tehran, Iran
The structure of the electrodes and characteristics of the power supplies play a vital role in the discharge, thus any changes in the structure of the electrodes and arrangements of the power supplies will have a significant influence on the desired performance and output efficiency of electrohydrodynamic systems [17-19].The high intensity of the electric field around the sharp electrode leads to the ionization of the air in the vicinity of the electrode [20]. The ionized air leads to corona discharge and accumulation of space electric charge [21]. Eventually, this process leads to the propulsion of ionized molecules to the plate electrode, which is known as corona wind or electric wind [22]. The propagation of the corona wind can also be controlled by some special structures, which increases the application and popularity of EHD systems [23, 24]. These structures are based on the surface dielectric barrier discharge (SDBD) called plasma actuators [25-27]. The SDBD structure consists of two electrodes mounted on a dielectric surface with a specific pattern. Corona wind occurs when the strength of the electric field is high enough to ionize the gas followed by plasma discharge. The parameters of corona wind in this structure depend on factors such as electrode pattern, type and thickness of barriers, and applied power supplies [28, 29]. It has been proven that positive high voltage has a higher efficiency in electrohydrodynamic effects compared to negative high voltage [30]. In this paper, we want to investigate the effects of mixed electric fields on the efficiency modifications in the EHD effect by studying the non-thermal evaporation of water droplets in both pin-to-plate and SDBD structures.
MATERIALS AND METHODS
A scheme of the experimental setup is shown in Figure 1. This schematic is a pin to plate structure. A 5 cm steel needle was used as the pin. The plate used in this structure is made of metal (stainless steel (SUS;SUS304) (30×30 mm2)). The pin distance to the plate is fixed at two centimeters. In the first step, this structure is biased by a direct current power supply. The output voltage of this source varies from 0 to 30 KV. In the second step, as shown in the schematic in Figure 2, the bias of the structure changes. The two power supplies are used simultaneously as shown in Figure 2. The power source used in the experiments, capable of generating a variable high voltage with sinusoid amplitude at fixed frequency equal to 50 Hz, The corresponding waveform and voltage-current diagram versus time are shown in Figure 4. The other power source , capable of generating a variable amplitude of pulsed high voltage at 6 kHz frequency, the corresponding waveform and voltage-current diagram versus time are shown in Figure 5. In the last step, the surface dielectric barrier discharge (S-DBD) structure is used as shown in the schematic in Figure 3. The two electrodes are mounted exactly tangentially on the surface. The electrodes are selected from a 1 mm thick copper foil (electrode1 (10×10 mm2) and electrode2 (10×20 mm2)). The dielectric of the glass is also selected with a thickness of 2 mm (30×30 mm2). The temperature distribution on the substrate surface was measured by Fluke VT04A Visual IR Thermometer. The voltage and the current are measured by a high voltage probe (TEKTRONIX P6015 1:1000) and a current probe (TCP202 TEKTRONIX), respectively. The electrical signals are visualized using a TEKTRONIX TDS 2024B oscilloscope (200 MHz). The following equations are used to calculate the average electrical power applied to the plasma jet. Where Pave and P(t) are the average and time-dependent electrical power, respectively, Epulse is the energy per pulse, V(t) and I(t) are the time-dependent voltage and current, respectively.
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