Heat transfer coefficient measurement of LN2 and GN2 in a microchannel at low Reynolds flow. (December 2018)

• Record Type: Journal Article
• Authors: Baek, Seungwhan; Bradley, Peter E.; Radebaugh, Ray
• Is Part Of: International journal of heat and mass transfer. Volume 127(2018)Part C
• Page Start: 222
• Page End: 233
• Publication Date: 2018-12
• Subjects: Heat transfer coefficient -- Microchannel -- Axial conduction -- Single-phase -- Laminar flow -- Micro-scale; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2018.07.145
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Laminar flow heat transfer coefficient of LN2 and GN2 measured in a microchannel. Nusselt number decreased as the Reynolds number decreased in laminar flow. The 1-D model has been developed to investigate heat transfer in a microchannel. Analysis confirms that axial conduction affected Nusselt number estimation. Experiment and model investigation showed that Nusselt number is constant in laminar flow. Abstract: The heat transfer coefficients of single-phase fluids in the laminar flow regime have been studied for decades. However, inconsistent results are found in the literature. The common finding is that the Nusselt number is dependent on the Reynolds number in the laminar flow regime, which is contrary to laminar flow heat transfer theory. Recently, researchers indicated that axial conduction in the wall of the microchannel can affect the measurement. However, there have not been thorough studies that demonstrate consistency or lack thereof between experiment and theory. This study provides an experimental investigation on heat transfer performance of gaseous and liquid nitrogen flow through microchannels with hydraulic diameters of 110 μm and 180 μm. A model has been developed to investigate heat transfer in a microchannel from which analysis shows that the temperature profile of the fluid and wall change non-linearly along the length of the microchannel when the flow rate is low (e.g., Re < 1000). The non-linear temperature profile conflicts with the assumption of a linear temperature profile commensurate with the traditional Nusselt number estimation method, which leads to dependency on the Reynolds number. Comparison between the experiment and numerical model of the present work validates the conclusion that the heat transfer coefficient is uniform within the laminar flow regime ( Re < 2000) for microchannels.