Experimental and Numerical Studies of Natural Convection With Flow Separation in Upward-Facing Inclined Open Cavities

Abstract

Steady two-dimensional laminar natural convection heat transfer from isothermal horizontal and inclined open cavities of rectangular cross section has been investigated experimentally using a Mach-Zehnder interferometer and numerically by a finite difference technique. Experimental results are presented for Prandtl number, Pr = 0.7, Rayleigh numbers from 104 to 5 × 105, cavity aspect ratios, A (or h/w) = 0.25, 0.5, and 1.0, and inclination angles (or angles of rotation about the longitudinal axis), θ = 0, 30, 45, and 60 deg to the horizontal. The numerical model uses a relaxation technique to solve the governing elliptic, partial differential equations. Numerical results are presented for the range of Rayleigh number, 103 ≤ Raw ≤ 5 × 105, θ = 0 and 45 deg, and A = 1. Flow and temperature patterns, velocity and temperature profiles, and local and average heat transfer rates are presented. Flow recirculation with two counterrotating convective rolls developed in the cavity at Ra ≥ 105. The inclination of the cavity induced flow entrainment, causing flow separation at the lower corner and flow reattachment at the upper corner of the aperture opening except in shallow cavities, A < 0.5, where the flow reattachment occurred on the base of the inclined cavity. For all Ra numbers, the first inclination of the cavity from the horizontal caused a significant increase in the average heat transfer rate, but a further increase in the inclination angle caused very small increase in heat transfer rate. However, for every angle of inclination considered, the average heat transfer rate increased significantly as Ra was increased. The equation of the form Nu = mRan, where 0.018 ≤ m ≤ 0.088 and 0.325 ≤ n ≤ 0.484, correlates the experimental and numerical results satisfactorily for the range of Ra, 104 ≤ Ra ≤ 5 × 105 and of θ, 0 ≤ θ ≤ 60 deg. The present experimental and numerical results are in good agreement with the results reported in the literature.

Experimental and numerical study of turbulent natural convection in an open cubic cavity

“…The experiment also provided an assessment of the accuracy of the predicted average Nusselt number. Showole and Tarasuk [43] reported the experimental and numerical steady of laminar natural convection, from isothermal horizontal and inclined open cavities of rectangular cross section. The results show a flow recirculation with two counterrotating convective rolls developed in the cavity at Ra ≥10 5 .…”

“…In literature are reported several studies of heat transfer in open cavities, which can be classified as: (a) numerical , (b) experimental [38][39][40][41] and (c) numerical-experimental [42][43][44]. Most of numerical studies has been conducted with a two-dimensional approach, however the three dimensional description of the phenomena is more realistic.…”

Nusselt number for the natural convection and surface thermal radiation in a square tilted open cavity

“…During the past two decades, several experimental results and numerical calculations have been presented for describing the phenomenon of natural convection in open cavities [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. These studies have been focused to study the effect on flow and heat transfer of different Rayleigh numbers, aspect ratios and tilted angles.…”

The effect of a baffle on the heat transfer in underground auxiliary ventilation systems

“…A review of the literature indicates numerous studies on the flow field and heat transfer analysis of channels with open cavities Channels with open top upright cavities have been used by some researchers to simulate the heat transfer mechanism for either pure natural convection [1][2][3][4][5] or mixed convection [6][7][8]. Recently, Manca et al [9] presented a numerical study on mixed convection in an open cavity with a heated wall bounded by horizontally insulated plate.…”