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We numerically evaluated the thermal performance of microchannel heat sinks, considering rectangular, hexagonal, and circular cross-sections. Moreover, as a passive heat transfer augmentation technique, dimples were added to improve the rectangular microchannel heat sinks. These simulations use nanofluids based on TiO2 nanoparticles or nanotubes dispersed in bidistilled water as working fluids. The mathematical model considered variable thermophysical properties of the nanofluids; for this purpose, polynomial fittings correlate the dependence of the thermophysical properties on the temperature. We considered a heat flux of q″ = 50 W/cm2 at the microchannel’s lower surface as a boundary condition along with laminar flow conditions. The numerical simulations allowed the Nusselt numbers and entropy generation calculation, which were the basis for the thermal performance calculation. Regarding the effect of TiO2 nanoparticles shape, spherical TiO2 nanoparticles based nanofluids using rectangular microchannels improve the Nusselt number. Moreover, the frictional entropy decreases with nanofluids based on TiO2 nanotubes, but the thermal entropy decreases with nanofluids based on TiO2 nanotubes. Incorporating dimples in the rectangular microchannel enhances the Nusselt numbers and lowers the entropy generation. Considering the Reynolds number range and from the perspective of Nusselt number and entropy generation, we concluded that the microchannels must be operated at a high Reynolds number to improve the microchannel heat sinks thermal performance.

Este trabajo formuló una propuesta metodológica dirigida a los profesores, para la implementación del enfoque de Educación para el Desarrollo Sostenible (EDS) en la primera infancia, en el Aula Pedagógica Infantil (API) del Instituto Tecnológico Metropolitano (ITM) de la ciudad de Medellín. El punto de partida fue la alta tasa bruta y neta de matrícula en educación inicial, así como el reconocimiento de los conceptos, los principios y las prácticas actuales de las profesoras del API en donde el modelo constructivista se aplica. Posteriormente se identificaron y definieron los elementos conceptuales que sustentaron la propuesta. Finalmente se realiza una comparación entre la metodología aplicada en el API y un posible modelo de aplicación de la EDS para de esta forma proponer otra metodología. El problema fundamental que se buscó subsanar fue la limitada implementación del enfoque de EDS en la educación para la primera infancia. Durante la investigación se evidenció que el aumento significativo en las tasas brutas de cobertura en educación inicial en Medellín son una oportunidad para fortalecer conceptos y prácticas que desde el enfoque de EDS, los cuales pueden ser considerados para el API y transferibles a otros contextos. This work stated a methodological proposal for teachers to helping them in the implementation of the Education for Sustainable Development (ESD) approach in early childhood education, within the Aula Pedagogica Infantil (API) of Instituto Tecnologico Metropolitano (ITM), located in the city of Medellin. The starting point was the high gross and net enrolment rate in early childhood education, as well as the recognition of concepts, principles and current practices performed by API´s teachers, which are based on the constructivist learning model. Subsequently, identification and definition of underpinning conceptual elements was made. Finally, a comparison between the conventional methodology used at API and a possible model based on ESD was made, in order to generate a new methodology. The central problem to be solved is the limited implementation of ESD during early childhood education. During the research, it became evident that the gross rates shown in early childhood education in Medellin, become a great opportunity to strengthen concepts and practices based on the ESD approach, which can be considered to be applied in the API, and to later be transferred to other contexts. Magíster en Desarrollo Sostenible maestría