Experiments on mixed convection heat transfer for airflow in a horizontal and inclined channel

Onset of secondary flow and enhancement of heat transfer in horizontal convergent and divergent channels heated from below

“…Theoretical analysis [14][15][16] were also performed to predict the onset of the thermal instability. The predictions are close to the experimental [8,9], but were not reported in the experiments with air [2,6]. From the review of literature, it appears that the results obtained for the critical Rayleigh number for the initiation of the plume, the number of plume produced and the heat transfer characteristic between the experiments with water and the ones with air are different.…”

“…In a horizontal parallel-plate channel, however, the onset point was found to approach the leading edge of the heater when the Rayleigh number increases or the Reynolds number decreases. The dimensionless onset point, X*, has been correlated in terms of a critical Grashof number [6] or Rayleigh number [2]. If the deposition process can be performed before the onset point of the secondary flow, the complicated three-dimensional transport process can be avoided and a relatively uniform deposition of solid film can be obtained.…”

“…For the experiments with water,the complete transformation process of the secondary flow from the mushroom shaped plume to the vortices, the breakdown of vortices and the transition to the turbulent flow is visualized [8,9]. The critical Rayleigh numbers for the onset of secondary flow were also studied in the fully developed region [10][11][12] and the thermal entry region [1,2,6,13]. Correlations for the onset of thermal instability are obtained for both the experiments with water and air.…”

Magnetic effect on the formation of longitudinal vortices in natural convection flow over a rotating heated flat plate

“…The onset position can be determined by comparison of the heat transfer rate between the experimental data of secondary flow and the basic flow (6-30% of Nu p =Nu b by Incropera et al [17], 15% of Nu p =Nu b by Maughen and Incropera [18], 10% of Nu p =Nu b by Chou and Han [19], etc.). Also, comparing the onset criterion between Nu p =Nu b ¼ 0:2 and Nu p =Nu b ¼ 0:1 in the numerical experiment, the values of onset position x * increases less than 4%.…”

Combined heat and mass transfer for laminar flow of moist air in a 3D rectangular duct: CFD simulation and validation with experimental data

“…There are a lot of research works on the determination of heat and mass transfer coefficients considering the effect of buoyancy forces and a large share of it belongs to the internal flows . Whereas some of the works consider only heat transfer [9][10][11][12][13][14][15][24][25][26][27][28] to quantify Nusselt number, many of them treat simultaneous heat and mass transfer [16][17][18][19][20][21][22][23]29,30] to determine Nusselt and Sherwood numbers together. Most of the works in the literature present numerical data and correlations [9][10][11][12][13][16][17][18][19][20][21][22][24][25][26][27][28]30] with only a few presenting experimental data and correlations [14,15,23,29].…”