Effect of artificial roughness on heat transfer and friction factor in a solar air heater

The Air Solar Collectors: Introduction of Chicanes to Favour the Heat Transfer and Temperature in the Air Stream Dynamics

“…For mass flow rate of 0.035 kg/s, it is observed that the air temperature increasing along the air stream dynamics length with a mean of (316.3 K) in the smooth case and with an average of (324.3 K, 329.5 K, 330.7 K and 332.1 K) in the case (without inclined part, 0°, 45° and 60°) with a rise of (2.52%, 4.17%, 4.55% and 4.99%)respectively. This is due to the secondary flow when it is trapped between two chicanes and the main flow where powered with a brewing phenomenon which provokes a heat transfer from the hot flow to the cold one, therefore the chicanes provide a delaying aspect for more and more time to the heat transfer process which is confirmed by Moummi et al [4][5][6][7][8][9][10][11][12][13]. …”

“…The presence of laminar sub-layer between the absorber plate and flowing air is generally considered to be the main cause of thermal resistance for heat transfer. Artificially roughened absorber plate is considered to be a good methodology to break laminar sub-layer in order to reduce thermal resistance and to increase heat transfer, Prasad and Saini [5].…”

Numerical study on overall thermal performance in SAH duct with compound roughness of V-shaped ribs and dimples

“…The boundary conditions for the V-shaped ribs combined with dimple ribs are applied as experimental conditions. [7][8][9][10][11][12][13][14][15][16][17][18] Fi g. It is therefore, RNG k-ε model has been employed for the present CFD study. Fig.4 shows the velocity profiles for the V-down shaped ribs combined with dimple ribs with different values of α = 35°-70°, and kept other rib parameters used to roughened an air duct with a fixed value of Re=8000.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23] Taslim et al 20) presented the effect of V-shaped rib roughness with variation of relative rib height, relative rib pitch and flow attack angle on heat transfer and friction factor in a flow through SAH duct. They reported that the V-shaped rib showed higher performance compared to the angled rib.…”

“…Saini and Verma 23) reported the experimental results of the turbulent fluid flow and heat transfer characteristics in a rectangular air channel with a dimpled roughness shape attached to the underside of a heated plate. They changed the range of Reynolds number from 2000 to 12000 with the relative roughness heights of 0.018-0.037 and the relative roughness pitches of [8][9][10][11][12]. For the range of parameters investigated, Nusselt number was found to be the maximum corresponding to relative roughness height of 0.0379 and relative roughness pitch of 10.…”