Numerical and experimental study of heat transfer in a tall vertical closed cavity
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ORIGINAL
Numerical and experimental study of heat transfer in a tall vertical closed cavity Armando Pin˜a-Ortiz • Jesu´s F. Hinojosa-Palafox Jesu´s B. Pe´rez-Valenzuela
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Received: 30 August 2012 / Accepted: 8 March 2013 / Published online: 19 March 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract In this work the numerical and experimental results of heat transfer in a vertical tall closed cavity are presented. The cavity has an aspect ratio of 20, one of the vertical walls receive a constant and uniform heat flux, while the opposite wall is kept at a constant temperature. The remaining walls are assumed adiabatic. The cavity is full of air. The computational fluid dynamics software Fluent 6.3 was used for the simulation and an experimental prototype was built to obtain the heat transfer coefficients. The air temperature and the fluid velocity values are higher when emissivity (e) is 0.03 (almost pure natural convection). The experimental total heat transfer coefficient increases between 119.9 and 159.9 % when the emissivity of the walls changes from 0.03 to 0.95. List of symbols A Electric current (A) Ar Aspect ratio (H/W) Cp Specific heat at constant pressure (J/kg K) g Gravitational acceleration (m/s2) Gkt Generation of turbulent kinetic energy due to the buoyancy force (J/kg) Gr Grash of number nondimensional H Cavity wall height (m) Ig Intensity of radiation (W/m2) Ibg Blackbody intensity (W/m2) k Thermal conductivity (W/m K) A. Pin˜a-Ortiz J. F. Hinojosa-Palafox (&) Department of Chemical Engineering and Metallurgy, University of Sonora, Hermosillo 83000, Sonora, Mexico e-mail: [email protected] J. B. Pe´rez-Valenzuela Department of Civil Engineering and Mines, University of Sonora, Hermosillo 83000, Sonora, Mexico
kt kg L Nuc Nur Nut Nut Pkt q Ra* s ^s Tc Tc Th Th u v V W X, Y, Z i, j, k
Turbulent kinetic energy (J/kg) Absorptivity nondimensional Cavity wall length (m) Local convective Nusselt number, nondimensional Radiative Nusselt number nondimensional Total Nusselt number nondimensional Total average Nusselt number, nondimensional Generation of turbulent kinetic energy (J/kg) Heat flux (W) Modified Rayleigh number = gbqH4/amk, nondimensional Geometric path length (m) Propagation direction nondimensional Temperature of the cold wall (K) Average temperature of the cold wall (K) Temperature of the hot wall (K) Average temperature of the hot wall (K) Velocity horizontal component (m/s) Velocity vertical component (m/s) Voltage (V) Cavity wall width (m) Coordinate system (m) Unity vector components
Greek symbols a Thermal diffusivity (m2/s) b Thermal expansion coefficient (1/K) bg Coefficient of extinction nondimensional e Emissivity nondimensional et Turbulent kinetic energy dissipation (J/kg) hr Uncertainty associated to the random errors, nondimensional q Density (kg/m3) lt Turbulent viscosity (g/cm s)
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m rt rsg
Heat Mass Transfer (2013) 49:933–945
Kinematic viscosity (m2/s) Turbulent Prandtl number nondimensional Scattering coefficient nondimensional
1 Introduction At presen
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