Estudo do escoamento e transferência de calor em um sistema pneumático de irradiação de amostras.

Abstract

Muito obrigado por todo aprendizado e convivência. Aos pesquisadores do IPEN que tive contato durante os trabalhos do RMB e que suas informações e conhecimentos foram aplicados no desenvolvimento desta dissertação Dra. Mitiko e Dr. Edson. Ao departamento de Engenharia Mecatrônica da Poli (PMR) e técnicos do Laboratório de Usinagem por prover acesso e ajuda na utilização das máquinas operatrizes para construção do estudo experimental desenvolvido neste trabalho. Aos meus pais Roberto, Evanide e minha noiva Renata pela paciência, suporte e motivação incondicional. ABSTRACTPneumatic irradiation system facilities are used in nuclear research reactors. Its main function is to provide a fast means of sending materials to irradiation positions located near the reactor core. Capsules containing the sample materials are sent through pipes using a gaseous fluid propellant. Upon reaching the desired position, the capsule undergoes exposure to radiation from the reactor enabling the transformation of the material allocated inside, but as a consequence of exposure, its thermal heating also occurs. This study investigated numerically, using computational fluid dynamics (CFD), and experimentally the flow and heat transfer during the irradiation process. The results showed a significant heating for irradiation times on the order of 1 minute, considering a constant heat generation rate, thus causing increase in the capsule temperature up to critical values, for the materials that are commonly used for their manufacture. In particular, this is the case of the high density polyethylene (HDPE). Furthermore, the velocity, pressure and temperature fields were obtained for the propellant fluid and cooling water inside the irradiation tube house during its irradiation and the response of different turbulence modeling in the numerical simulations were analyzed. Based on the results obtained, it was possible to conclude that the developed study exemplified the heating process of the capsules and provided information about the characteristics of the flow inside the irradiation tube that houses the capsules during the exposure process. The use of different turbulence models in the simulations generated similar results for the study, however small variations in regions of flow near to the wall and inside recirculation zones were found.