Electrostatic Heating With an Electrostatic Nozzle Assembly
An urgent demand for new chemical agent spraying system in Indian agriculture is urgently needed. The paper attempts to design and build an air-charged electrostatic nozzle on induction-charging basis with some special focus on Indian geographical and agricultural situation. The main task was to study the effects of the nozzle on electrostatic charge and its effects on the spraying of aerial spraying. The results of the experiment were remarkably encouraging for this application.
The electrostatic nozzle proposed in this paper is different from the conventional model in many ways. It involves a low noise generating system and high energy output capability that make it a real time machine spraying system. The nozzle assembly is made of metallic, ductile iron for high strength and reliability or else the application could not be completed. It consists of a high frequency crystal collector, high power dielectric coupler, high frequency switching device and a high temperature switch.
When we refer to high frequency, it means that the system operates at high speed which results in superheterodyne effect. With the help of high frequency crystal collector, a charge separation occurs between the liquid particles and the metal rod. This separation produces electrostatic charge due to the attraction and repulsion of the charged particles. Thus the distance between the two regions is decreased by the attraction and repulsion effect of the charged particles.
The size of the nozzle needs to be selected such that the liquid particles are appropriately distributed. This distribution is important because if the same sized nozzles are used at different locations then there is likelihood of electrostatic discharge. In this case the nozzle size becomes critical for proper performance. At the same time it is necessary that the size of the electrode material charging conductor is suitable so that the electrostatic spray can be applied effectively. For electrostatic spraying a low resistance electrode material charging conductor is required which can be provided by the company through welding.
A common application of electrostatic spraying is for pest identification. In the field of agriculture, most of the spraying is done for the identification of the pest before treatment or removal. It is quite common for the use of air-assisted electrostatic nozzle for this purpose.
Electrostatic nozzle is of two types namely, closed-loop and open-loop. In the closed-loop type the inner surface extends outwardly and the outer surface is formed in a distinct pattern. The inner surface of the nozzle is formed by passing the compressed gas through a T-shaped electrode. The T-shaped electrode formed a ring, hence the name “T” shaped.
The open-loops consist of a continuous air passageway adapted to receive a continuous stream of compressed air. As the continuous air flow is obtained, the discharge of the sprayed particles into the atmosphere occurs. Electrostatic nozzle assembly serves as a connecting link between the continuous flow of air and the nozzle formed on the outer surface of the electrostatic nozzle body. In case of open-loops, the T-shape electrode assembly extends outwardly and extends the same width as the non-domed outer surface. This type of nozzle assembly is called a continuous flow nozzle assembly.
The other kind of nozzle assembly consists of two venturi ports, one on the inner surface and the other on the opposite side of the nozzle. These vents open to create a back-and-forth air stream motion inside the chamber. These jets of air stream are similar to the spray stream produced by a fan. An air flow having a smaller diameter than the diameter of the nozzle, will produce a back and forth stream motion within the chamber but will not be able to remove the charged particles emitted from the discharge orifice.