Browsing by Author "Samaranayake, W. J. M."

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Design of heat sink and simulation of electronic cooling of power transistor circuit
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Gunasinghe, L. M.; Samaranayake, W. J. M.; Hansameenu, W. P. T.
Heat sinks are utilized in industrial equipment to disperse surplus heat from heat-generating components to the surrounding environment. In recent years, efforts have been made to develop mechanical or electronic devices that are lighter, smaller, and more affordable. Heat dissipation from the heat sink is a major issue that many researchers are attempting to address. In this work, a traditional heat sink design technique of computer power supplies, which is extending fin topology, is used with four power transistors. This study attempts to improve the cooling of power transistor circuits by designing a new heat sink attached to four power transistors and seeing how the joule heating profile of the power transistor circuit and heat sink are changed. COMSOL Multiphysics version 5.6 software is used to graphically design the heat sink, four-transistor circuit and simulate the heat profile of the design. An electric currents interface and a heat transfer in solids interface are included in the Multiphysics interface. The multiphysics couplings add electromagnetic power dissipation as a heat source and investigate the joule heating and the temperature distribution on power transistors without the heat sink and with the heat sink. Transistors without the new heat sink get heated more than the transistors with the new heat sink with the same applied current density to the circuit board. It shows that joule heating is minimized with the new heat sink design. Here, the results of several studies of a new geometrical 3D model that focus on four power transistors attached to an aluminium heat sink are discussed. The results show the impact of the heat sink area and surface-to-ambient radiation to the power transistors and the circuit board. Based on the simulation results, four transistors become very cooled with the new heat sink design. How the heat-sink thermal performance is affected by shapes and space between fins is also reviewed. It could be observed that in the proposed design, the joule heating was reduced remarkably.
Study of the improvement of Ozone production: A simulation
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Amarakoon, A. M. M. N. B.; Hansameenu, W. P. T.; Samaranayake, W. J. M.
Ozone is an unstable, colourless gas that has a pungent odour which occurs naturally in small amounts in the stratosphere. Ozone is one of the strongest oxidants. Major applications of ozone are disinfection, deodorization, decolourization, bleaching processes, semiconductor industry, treatment of industrial wastes, treatment of flue gases, chemical synthesis, potable and wastewater treatments etc. In many industrial applications, ozone is being used as an alternative oxidant for chlorination processes. It has a minimal negative impact on the environment and the extra benefit of requiring less energy for its production than other alternatives. This work was focused on a numerical simulation using MATLAB software and this study was aimed at understanding the discharge phenomenon in the ozoniser in detail, which could not be observed by experiments. It considered the rate coefficients of different plasma chemical reactions as a function of time using a single pulse and multiple pulses. The simulation study was carried out using differential equations of the plasma chemical reactions with the peak pulsed voltage (42.5 kV), pulse repetition rate (100 pulses per second, pps), input energy per pulse (∼0.22 J), pulse width (FWHM 100 ns), flow rate (3.0 l/min), the gaseous gap spacing (36 mm), the reactor length (1 m) and 1 cm pitch length of the spiral wire forming the central electrode at a pressure of 1.01×105 Pa and a temperature of 293 K. A central copper wire (1 mm in diameter) made to a cylindrical configuration (22 mm in diameter) in a concentric coaxial electrode system without a dielectric barrier was considered. The concentration of ozone was found for a single pulse as well as for multiple pulses, and the production yield of ozone was found at different concentrations. The dependence of the densities of atomic oxygen, excited and ground state of molecular oxygen has been investigated. The concentration of ozone reached a saturated value of 137.2 ppm after about 18 μs when a single pulse was applied. When a large number of pulses (105 pulses) were used, ∼33% of ozone could be produced from oxygen. The production yield of ozone was found to be strongly dependent on the concentration of ozone and it showed an optimal behaviour for each and every repetitive pulse. The dependence of the concentration and production yield of ozone in oxygen on the parameters studied generally agreed with the published literature, thus confirming the validity of the simulation model. This study covered a wide range of ozoniser conditions, including low and high concentrations and low and high yields of ozone that can be applied to various industrial applications.