Análise experimental do processo de ebulição em um termossifão de vidro

Abstract

Thermosyphons are devices with great potential for application in sustainable systems such as solar collectors for heating water for use in homes or industry. The high efficiency in various heating systems is due to the fact that the thermosyphons work with phase change inside, using the latent heat of vaporization of a working fluid to intensify the transfer of energy in the form of heat. In the design of a thermosyphon, several variables are involved in the design of the system, among them, the biphasic convective coefficient inside the evaporator. This coefficient depends on the characteristics of the flow inside the tube and, consequently, on the boiling modes found. Thus, this work encompasses a literature review on such boiling modes in a generalized way, as well as existing correlations in the literature in a way directed to thermosiphones. In addition, in order to verify the reliability of such correlations for different operational parameters, experiments were carried out on a bench with a glass thermosyphon. Water was used as working fluid and an electric resistor in order to simulate a heat source. The experimental data fed a proposed methodology, based on the energy balance applied to the thermosyphon evaporator, in order to estimate the experimental biphasic heat transfer coefficient of the boiling process. Finally, the experimental and theoretical coefficients were compared graphically.