EHD Pumps Research Articles

Pocketable and Smart Electrohydrodynamic Pump for Clothes.

Seamlessly fusing fashion and functionality can redefine wearable technology and enhance the quality of life. We propose a pocketable and smart electrohydrodynamic pump (PSEP) with self-sensing capability for wearable thermal controls. Overcoming the constraints of traditional liquid-cooled wearables, PSEP with dimensions of 10 × 2 × 1.05 cm and a weight of 10 g is sufficiently compact to fit into a shirt pocket, providing stylish and unobtrusive thermal control. Silent operation coupled with the unique self-sensing ability to monitor the flow rate ensures system reliability without cumbersome additional components. The significant contribution of our study is the formulation and validation of a theoretical model for self-sensing in EHD pumps, thereby introducing an innovative functionality to EHD pump technology. PSEP can deliver temperature changes of up to 3 °C, considerably improving personal comfort. Additionally, the PSEP system features an intuitive, smartphone-compatible interface for seamless wireless control and monitoring, enhancing user interaction and convenience. Furthermore, the ability to detect and notify users of flow blockages, achieved by self-sensing, ensures an efficient and long-term operation. Through its blend of compact design, intelligent functionality, and stylish integration into daily wear, PSEP reshapes the landscape of wearable thermal control technology and offers a promising avenue for enhancing personal comfort in daily life.

EHD gas pump in a square channel with electrodes mounted on one wall

Gas pumping using corona wind generator in a square channel has been experimentally examined for three electrode configurations and two operating stages. For the proposed EHD pump, the emitting electrodes are flush mounted on one side of the channel walls so that the air flow produced is similar to that of a wall jet. Three electrode configurations (separately with 1, 3, and 7 emitting electrodes) are investigated for their effectiveness in sustaining and enhancing the volume flow rate as well as reducing the power requirement. Also investigated is the performance of the pump, a measure of the effectiveness in gas pumping, when it is operated in series. The results obtained are compared with those reported in the literature for EHD pumps with electrodes mounted all around the channel walls. It has been found that the performance of the proposed EHD pump is comparable to, if not better than, that of the previous ones while using fewer electrodes. Through the assessment of their performance, present results can provide important implications for practical applications of this technology.

DC negative corona discharge characteristics in air flowing transversely and longitudinally through a needle-plate electrode gap

The electrical characteristics of a steady-state DC negative corona discharge in air flowing transversely or longitudinally in relation to the needle-to-plate (or mesh) electrode axis were experimentally investigated. The velocity of air flowing into the corona discharge chamber was limited to a range from 0 to 6 m/s, typical of electrostatic precipitators, gas ionisation sensors and EHD pumps. The investigations showed that in this airflow velocity range three discharge current modes of the DC negative corona could exist: the Trichel-pulse corona mode, the ‘Trichel pulses superimposed on the steady current (or DC) component’ mode and the steady glow (the steady current or DC) corona mode, regardless of the airflow direction. The average corona discharge current, which is a macroscopic corona discharge parameter, was almost not affected by the airflow. However, both microscopic corona discharge parameters: the electric charge and the repetition frequency of Trichel pulses were influenced by the airflow. The transverse airflow caused an increase in the electric charge and a decrease in the repetition rate of Trichel pulses, the both by about 25% at a velocity of 6 m/s. In the case of longitudinal airflow the average corona current slightly increased when the airflow was directed towards the mesh and decreased when the airflow was directed towards the needle tip. Similarly as in the case of transverse airflow, the electric charge and the repetition frequency of Trichel pulses were affected by the longitudinal airflow. The electric charge and the repetition frequency of Trichel pulses increased and decreased, respectively, with growing airflow in the direction towards the needle electrode. The airflow growing in the direction towards the mesh electrode produced the opposite effect - the electric charge and the repetition frequency of Trichel pulses decreased and increased, respectively. The opposite behaviours of the electric charge and the repetition frequency of Trichel pulses with growing airflow velocity could explain the weak dependence of the negative corona average current on transverse or longitudinal airflow. Therefore, the independence of the negative corona average current of the airflow cannot be considered as sufficient proof that the airflow (up to 6 m/s) does not affect the negative corona parameters.

Simulating Electrohydrodynamic Ion-Drag Pumping on Distributed Parallel Computing Systems

Objectives: This paper aims to simulate EHD ion-drag pumping model using Finite Difference Method (FDM) and to apply the idea of parallelism to reduce the computational time. Methods: The numerical simulation of EHD ion-drag pumping plays an important part not only to understand the different working principles but also enables to model the designs with better performance. Since the performance of EHD pumps depends on the shapes and geometries of the actuator electrodes, therefore the variation in the geometric dimensions of the electrodes require dense and fine meshes for numerical solution. Consequently, the numerical simulations take unacceptably more execution time on sequential computers. For that reason, a Data Parallel Algorithm for EHD model (DPA-EHD) is designed. To implement the parallel algorithm a distributed parallel computing system using MATLAB Distributed Computing Server (MDCS) is configured. The computational time and speedup with respect to the different number of processors is evaluated. Findings: This results show that the parallel algorithm for EHD simulations may provide 4.14 times more speedup over sequential algorithm for large grid sizes. Improvements: This study shows the feasibility of using the parallelism to reduce the computational time in the EHD model enabling to simulate the micropumps with very small dimensions of electrodes.

Design of a Prototype EHD Air Pump for Electronic Chip Cooling Applications

This paper presents the design, optimization and fabrication of an EHD air pump intended for high-power electronic chip cooling applications. Suitable high-voltage electrode configurations were selected and studied, in terms of the characteristics of the generated electric field, which play an important role in ionic wind flow. For this purpose, dedicated software is used to implement finite element analysis. Critical design parameters, such as the electric field intensity, wind velocity, current flow and power consumption are investigated. Two different laboratory prototypes are fabricated and their performances experimentally assessed. This procedure leads to the fabrication of a final prototype, which is then tested as a replacement of a typical fan for cooling a high power density electronic chip. To assist towards that end, an experimental thermal testing setup is designed and constructed to simulate the size of a personal computer's CPU core of variable power. The parametric study leads to the fabrication of experimental single-stage EHD pumps, the optimal design of which is capable of delivering an air flow of 51 CFM with an operating voltage of 10.5 kV. Finally, the theoretical and experimental results are evaluated and potential applications are proposed.

A System for Cooling Electronic Elements with an EHD Coolant Flow

A system for cooling electronic components where the liquid coolant flow is forced with ion-drag type EHD micropumps was tested. For tests we used isopropyl alcohol as the coolant and CSD02060 diodes in TO-220 packages as cooled electronic elements. We have studied thermal characteristics of diodes cooled with EHD flow in the function of a coolant flow rate. The transient thermal impedance of the CSD02060 diode cooled with 1.5 ml/min EHD flow was 7.8°C/W. Similar transient thermal impedance can be achieved by applying to the diode a large RAD-A6405A/150 heat sink. We found out that EHD pumps can be successfully applied for cooling electronic elements.

Dielectrophoresis flow control in microchannels

Abstract The control of flow in microscale is one of the most important problems in microfluidic devices, which in particular, are used as micro heat exchangers. The use of electric field is one of the efficient methods of control of dielectric liquid flow in microscale. The electric field influences liquid flow by the EHD force which affects liquid behaviour in terms of the flow rate and pressure. The EHD force consists of three components: the first is the electrostatic force due to free charges present in the liquid, the next one is the force due to the gradient of permittivity of material, and the third one is caused by the change in the electric field intensity. The EHD force is used also in many commercial devices, for example EHD pumps or dielectrophoretic separators. An own approach to apply the EHD force to control the liquid flow rate is presented in this paper. Authors paid a close attention to the dielectrophoresis effect. Dielectric liquid in a non-uniform electric field tends to drift/migrate towards the region of high electric field intensity. With decreasing the electrode dimensions, the dielectrophoresis force becomes relatively stronger. For the dimensions under 400 μm the dielectrophoresis phenomenon can be used for control and actuation of the liquid flow in microchannels. The originally developed design of such flow controller is presented in this paper. The experimental investigations covered flow rate measurement of 2-propanol in microchannel flow controller with application of AC field. It was showed that the dielectrophoresis phenomenon could effectively control the flow. The results for distilled water are also comparatively discussed in the paper.

Improvement for Pressure Performance of Micro-EHD Pump with an Arrangement of Thin Cylindrical Electrodes

A micro-electrohydrodynamic (EHD) pump is experimentally tested. In order to improve the static pressure performance, the EHD pump examined in this paper was fabricated with a series of thin stainless steel wires (the outer diameter is 0.3mm). The overall dimensions of the EHD pump were 30× 30×4.9mm and of the pumping channel were 24× 24× 0.9mm. An electrode pair consisted of one emitter electrode and two collector ones. The five sets of pumps were prepared for experiment. Those pumps were consisting of the number of electrode pairs from 1 to 5. The static pressure is measured with dibutyl-sebacate as a working fluid which has a dielectric constant, e / e 0=4.8 and a low electric conductivity, σ=4.7× 10-10S/m. The experimental results are compared with the theoretical results. In the theoretical model, the pressure is generated by Coulomb force which forces to move the unipolar ions in the high electric field. The experimental results indicate that the pressure increase as the number of electrode pairs increases and is generated up to 350Pa at an applied voltage of 1kV with 5 electrode pairs. Also, the experimental results show a good agreement with the theoretical ones. It is found that the theoretical model is useful for design of the high performance EHD pumps.

Influence of electrode geometry on ion-drag pump static pressure

A research program aimed at developing an EHD pump for insulating liquids is in progress at the Electrical Engineering Department of the University of Genova. The initial part of this program considered a single stage ion drag pump and was aimed at the optimization of the relevant electrodes (materials and geometry) and interelectrode gap to obtain a high hydrostatic pressure. The experimental data on three different technical grade liquid dielectrics (oils) are reported. They allow a comparison with two different theoretical pressure vs. voltage relations, due to Stuetzer and to Pickard, for each tested liquid. The general validity of such relations is discussed and questioned. The latter point and the experimental data here reported illustrate that, at present, it is necessary to introduce, early in the design process of this kind of EHD pumps, an experimental stage, specific to each liquid to be used.

Investigation of electroconvection and electroconvective heat transfer in liquid dielectrics with unipolar injection conductivity

The characteristics of electroconvection and electroconvective heat transfer in liquid dielectrics possessing unipolar injection conductivity [1, 2] are investigated and certain types of EHD pumps are calculated. These investigations are necessary because so far there is no theoretical explanation for the slowing of heat transfer with increase in voltage in strong fields [3, 4]. Moreover, there is no satisfactory theory of EHD pumps that would make it possible not only to establish the basic operating principles of existing (grid [5], knife-edge [6] and other [7, 8]) equipment but also to predict the performance of high-pressure EHD pumps.

EHD Induction Pumping in Annuli

EHD pumps will normally be enclosed in circular pipes, but previous analysis of such pumps was most often undertaken in two-dimensional geometries which cannot represent the curvature and finite size associated with a pipe. One practical version of an EHD induction pump includes an active travelling wave electrode running along the center of a grounded cylindrical pipe. Laminar flow which takes place in the annulus between pipe and electrode is modeled theoretially in terms of an induced charge layer situated at an arbitrary distance from the center electrode. If a hetero-charge layer is present, attraction pumping, in which the fluid follows the electric field wave, results. For a homo-charge layer, repulsion pumping occurs. Calculation of flow rates for various choices of electrical excitation and geometry are given as functions of voltage, frequency, and location of the charge layer. The attraction pump and the heavily loaded repulsion pump both give maximum flow rates at a single non-zero frequency, but the lightly loaded repulsion pump operates best at dc. The implications of these results are discussed in the context of several applications.