Transferência de calor durante ebulição convectiva em dissipador de calor microaletado
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Data
19-01-23
Autores
Andrade, Bruno
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Universidade Estadual Paulista (Unesp)
Resumo
Dedico este trabalho, primeiramente às minhas irmãs, Cristina, Ana, Silvana e Juliana,
que sempre foram a base da minha vida, nunca me deixando faltar nada material ou afetivo,
me ensinando o real significado da palavra “família”. Obrigado por acreditarem em mim, por
me apoiarem e por serem pessoas incríveis. Amo vocês.
Ao meu cunhado Prof. Dr. Igor Vassilieff, uma das pessoas mais inteligentes que já
conheci, por toda sabedoria, apoio e inspiração, mostrando sempre que a generosidade e a
empatia são os pilares que sustentam o mundo. Sem o senhor, eu jamais teria conseguido.
Ao meu cunhado José Davi Tardivo, por ter desde o princípio me desafiado e me
incentivado a buscar conhecimento. Saiba que sempre terá minha admiração e amizade.
Ao meu pai Antônio e minha mãe Luzinete, por terem me dado a vida.
À minha namorada, Marília. Obrigado por me apoiar nessa jornada e me incentivar nos
momentos difíceis. Obrigado pela compreensão nos momentos de aflição, pelo carinho e pelo
cuidado. Com certeza não teria conseguido sem sua presença.
The development and improvement of technologies involving high processing capacity remain dependent on advances and innovations in thermal management and cooling; thus, research and work in these areas are fundamental. In this context, convective boiling is an attractive alternative due to its ability to dissipate high heat rates and its versatility, allowing it to be applied in devices of reduced size. Thus, this work analyzed heat transfer behavior during the convective boiling of HFE-7100 inside a heat sink based on square microfins manufactured by the micro-milling process. An aligned arrangement of microfins (160 µm high) was studied for two different mass velocities (1000 and 1200 kg/m²s) and two subcooling levels of the fluid at the inlet of the heat sink (10 and 20 °C). Thus, an analysis of the thermal performance (through boiling curves and Heat Transfer Coefficient, HTC) and fluid dynamics (through pressure loss) of the heat sink during convective boiling was carried out. Lower subcooling positively affects the HTC due to the effects of the heat transfer mechanisms of the nucleated boiling, mainly for samples with a smaller height of the microfins due to the confinement effect of the vapor bubbles; however, the dryout phenomenon is observed at much lower heat fluxes. Finally, regarding the fluid dynamic aspects, vapor on the surface causes an exponential increase in the pressure drop for the twophase region.
The development and improvement of technologies involving high processing capacity remain dependent on advances and innovations in thermal management and cooling; thus, research and work in these areas are fundamental. In this context, convective boiling is an attractive alternative due to its ability to dissipate high heat rates and its versatility, allowing it to be applied in devices of reduced size. Thus, this work analyzed heat transfer behavior during the convective boiling of HFE-7100 inside a heat sink based on square microfins manufactured by the micro-milling process. An aligned arrangement of microfins (160 µm high) was studied for two different mass velocities (1000 and 1200 kg/m²s) and two subcooling levels of the fluid at the inlet of the heat sink (10 and 20 °C). Thus, an analysis of the thermal performance (through boiling curves and Heat Transfer Coefficient, HTC) and fluid dynamics (through pressure loss) of the heat sink during convective boiling was carried out. Lower subcooling positively affects the HTC due to the effects of the heat transfer mechanisms of the nucleated boiling, mainly for samples with a smaller height of the microfins due to the confinement effect of the vapor bubbles; however, the dryout phenomenon is observed at much lower heat fluxes. Finally, regarding the fluid dynamic aspects, vapor on the surface causes an exponential increase in the pressure drop for the twophase region.
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Palavras-chave
Ebulição convectiva, Transferência de calor, Queda de pressão, Flow boiling, Heat transfer, Pressure drop