Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-08-01T12:12:38Z No. of bitstreams: 1 GuilhermeKeitiAoyama_DISSERT.pdf: 15234104 bytes, checksum: 840b7a842bd5ddf42c7ae593a0b9117a (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-08-03T19:57:19Z (GMT) No. of bitstreams: 1 GuilhermeKeitiAoyama_DISSERT.pdf: 15234104 bytes, checksum: 840b7a842bd5ddf42c7ae593a0b9117a (MD5) / Made available in DSpace on 2017-08-03T19:57:19Z (GMT). No. of bitstreams: 1 GuilhermeKeitiAoyama_DISSERT.pdf: 15234104 bytes, checksum: 840b7a842bd5ddf42c7ae593a0b9117a (MD5) Previous issue date: 2017-03-27 / Canais compostos s?o caracterizados por possu?rem canais principais, regi?es mais largas onde o fluido escoa axialmente com maior facilidade, e canais secund?rios (fendas) que s?o regi?es mais estreitas onde o fluido ? desacelerado devido aos efeitos viscosos. Para determinar os coeficientes de transfer?ncia de calor e de atrito nos canais compostos ? necess?rio entender o comportamento dos escoamentos turbulentos que ocorrem neles, por?m isto continua sendo um desafio para a engenharia. Estes canais apresentam, al?m do fluxo axial paralelo ao canal, flutua??es na velocidade transversal que est?o associadas a estruturas de grande escala denominadas de estruturas coerentes. Assim, neste trabalho buscou-se analisar os efeitos do aparecimento dessas estruturas e as suas consequ?ncias para o escoamento, tanto na parte din?mica como na t?rmica. Para isto foi utilizado uma geometria empregada em trabalhos experimentais, que ? composta por um canal retangular com um tubo interno, de di?metro D, que est? a uma dist?ncia W/D da parede inferior do canal. O fluido escoa axialmente apenas na parte externa do tubo. No total foram analisados cinco casos, modificando apenas a rela??o W/D (espa?amento da fenda). Para examinar as caracter?sticas do escoamento turbulento no interior deste canal, empregou-se o pacote ANSYS CFX 13 com o modelo de turbul?ncia SAS-SST. Os resultados mostraram que quanto maior a rela??o W/D, mais elevados foram os valores do Fator de Desempenho T?rmico. Este fator ? uma rela??o entre o n?mero de Nusselt e o fator de atrito e, quanto maior seu valor, melhor ? o desempenho t?rmico do canal. Em rela??o as estruturas coerentes, nos canais em que surgiram, elas t?m uma grande influ?ncia sobre os escoamentos, j? que essas estruturas acabam elevando os valores locais dos coeficientes de transfer?ncia de calor e de atrito superficial, o que torna esse fen?meno indispens?vel nos projetos e an?lises de seguran?a de equipamentos que possuem fendas. / Compound channels are characterized by having main channels, wider regions where the fluid flows axially more easily, and narrower regions (gaps) where the fluid is decelerated due to the viscous effects. In order to determine the heat transfer coefficients in these channels it is necessary to understand the behavior of the turbulent flows in them, but this remains a challenge for engineering. These channels have, in addition to axial flow parallel to the channel, a cross flow velocity in the gap region that are associated with large scale structures called coherent structures. Thus, the goal of this work is to compare the effects on the appearance of coherent structures of large scale and its consequences for the flow in dynamic and thermal characteristics. To accomplish this, the same geometry used in the experimental works was applied, which is composed of a rectangular channel with an internal tube of diameter D and it is located at a distance W/D from the lower wall of the channel. The fluid flows axially only on the outside of the tube. In total, five different cases were analyzed, modifying only the W/D ratio (gap distance). To examine the characteristics of the turbulent flow inside this channel, ANSYS CFX13 with SASSST turbulence model was applied. The results showed that the W/D ratio increase also caused an increase in the values of the Thermal Performance Factor. This factor is a relationship between the Nusselt number and the friction factor, and the higher its value, better is the thermal performance of the channel. In relation to the coherent structures, in the channels in which they arise, they have a great influence on the flows, since these structures end up raising the local values of heat transfer and friction coefficients, making this phenomenon indispensable in projects and safety analyzes of equipment with gap.