Influence of moist air in copper heat sinks: Analysis through the entropy generation minimization criterion

Abstract

Many factors affect heat transfer during the cooling of modern electronic devices. Today, knowledge accrues from modeling, simulation, and experimentation. This allows predicting and calculating features of heat transfer phenomena, to some extent. Examples include the amount of heat generated and removed, the required physical properties of the working fluid, and the required material properties of the heat sink, among other parameters. This article describes some simulation results of using air with a given relative humidity (10 %, 50 % and 90 %). Its influence on the heat transfer process was also analyzed. Results show a measurable effect of using humidified air instead of dry air and copper as a bulk material. The heat transfer rate increased about 20 % when using air with 90 % relative humidity passing through a rectangular microchannel heat sink made of copper.Keywords: Heat sinks, microelectronics, global optimization, entropy generation minimization, moist air. RESUMENSon muchos los factores que afectan la transferencia de calor durante el enfriamiento de los dispositivos electrónicos modernos. En la actualidad, el conocimiento acumulado proviene del modelado, la simulación, y la experimentación. Esto permite predecir y calcular características de fenómenos de transferencia de calor, hasta cierto punto. Ejemplos de ello incluyen la cantidad de calor generado y removido, las propiedades físicas necesarias para un fluido de trabajo, y las propiedades requeridas para el material de un disipador de calor, entre otros parámetros. Este artículo describe algunos resultados de simulación utilizando aire con un valor de humedad relativa dado (10, 50 y 90 %). Su influencia en el proceso de transferencia de calor también fue analizado. Los resultados muestran un efecto medible del uso de aire humedecido en lugar del aire seco y del cobre como material del disipador. La tasa de transferencia de calor incrementó alrededor de 20 %, utilizando aire con 90 % de humedad relativa que atraviesa un disipador de calor de microcanales rectangulares hecho de cobre.Palabras clave: Disipadores de calor, microelectrónica, optimización global, mínima generación de entropía, aire húmedo.

Generation of entropy in micro thermofluidic and thermochemical energy systems-A critical review

“…Entropy generation rate in single-phase multi-component flows such as airflow through microchannels was studied in different investigations [79][80][81][82]. In a theoretical investigation [79], studies were reported on entropy generation rate in hydrodynamically and thermally fully developed airflow through parallel plate microchannels with asymmetric heat fluxes on top and bottom walls.…”

“…Investigations on Entropy Generation Minimization of moist air flow through bundles of microchannels were reported in Ref. [82]. Moisture transfer irreversibilities were included in entropy generation rate by heat transfer.…”

“…Further, results showed that rising relative humidity of moist air increases convective heat transfer coefficient and decreases the entropy generation rate of airflow. For example, as relative humidity was intensified from 0 to 0.9, convective heat transfer coefficient was enhanced by 20 % and entropy generation rate decreased by 2.1 % [82].…”

“…The above studies [79][80][81][82] have provided useful information on the entropy generation rate of airflow through empty microchannels. However, effects of inserts in microchannels and enhanced heat and mass exchanges on the entropy generation rate have remained unstudied and form a gap in the literature.…”