Optimal Inclination for Maximum Convection Heat Transfer in Differentially-Heated Enclosures Filled with Water Near 4°C

ABSTRACT

Natural convection in water-filled square cavities inclined with respect to gravity, having one wall cooled at 0°C and the opposite wall heated at a temperature ranging between 4°C and 30°C, is studied numerically for cavity widths spanning from 0.02 m to 0.1 m in the hypothesis of temperature-dependent physical properties, with the main aim to determine the optimal tilting angle for maximum heat transfer. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. Once the vertical configuration, in which the cavity is differentially heated at sides, is identified by the zero tilting angle, and positive angles denote configurations with the heated wall facing upwards, it is found that the optimal tilting angle is positive if the heating temperature is equal or higher than 8°C, whereas it is negative whenever the heating temperature is lower than 8°C. Moreover, the optimal tilting angle is found to increase as the cavity width is decreased and the temperature of the heated wall is either decreased or increased, according as it is higher or lower than 8°C. Sets of dimensionless correlating equations are developed for the prediction of both the optimal tilting angle and the heat transfer rate across the enclosure.

Additional information

Notes on contributors

Alessandro Quintino

Alessandro Quintino is a post-doctoral student at “Sapienza” University of Rome, Italy. He received his M.S. degree in Aeronautical Engineering in 2000 and his Ph.D. in Thermal Sciences in 2011 from “Sapienza” University of Rome, Italy. His main research interests include convection of pure fluids and mixtures, heat transfer in nanofluids, and optimal design of HVAC systems. He has authored or co-authored more than 30 papers in archival journals and conference proceedings.

Elisa Ricci

Elisa Ricci is a Ph.D. student at “Sapienza” University of Rome, Italy. She received her M.S. degree in Biomedical Engineering in 2015, discussing a thesis on the effects of Brownian and thermophoretic diffusion in natural convection of enclosed nanofluids. Her research field is convection heat transfer of pure fluids, mixtures and nanofluids.

Stefano Grignaffini

Stefano Grignaffini is an Associate Professor of Thermal Sciences and HVAC Systems at “Sapienza” University of Rome, Italy. He received his M.S. degree in Civil Engineering in 1990 and his Ph.D. in Thermophysical Properties of Materials in 1994 from “Sapienza” University of Rome, Italy. His main research interests include heat transfer, thermodynamics and applied acoustics. He has authored or co-authored more than 100 refereed journal and conference publications.

Massimo Corcione

Massimo Corcione is a Full Professor of Thermal Sciences and HVAC Systems at “Sapienza” University of Rome, Italy. He received his M.S. degree in Mechanical Engineering in 1990 and his Ph.D. in Thermophysical Properties of Materials in 1995 from “Sapienza” University of Rome, Italy. His current research interests include convection of pure fluids and mixtures, heat transfer in nanofluids, and optimal design of HVAC systems. He is a member of ANS (American Nano Society), ASME (American Society of Mechanical Engineers) and UIT (Unione Italiana di Termofluidodinamica). He has authored or co-authored more than 120 refereed journal and conference publications, besides contributing to a number of books. He serves on the editorial boards of The Open Mechanical Engineering Journal, Energy Science and Technology, Open Journal of Energy Efficiency and The Open Conference Proceedings Journal.