Thermal Performance of Angled, V-Shaped, and W-Shaped Rib Turbulators in Rotating Rectangular Cooling Channels (AR=4:1)

Abstract

An experimental study was performed to measure the heat transfer distributions and frictional losses in rotating ribbed channels with an aspect ratio of 4:1. Angled, discrete angled, V-shaped, and discrete V-shaped ribs were investigated, as well as the newly proposed W-shaped and discrete W-shaped ribs. In all cases, the ribs are placed on both the leading and trailing surfaces of the channel, and they are oriented 45 deg to the mainstream flow. The rib height-to-hydraulic diameter ratio e/D is 0.078, and the rib pitch-to-height ratio P/e is 10. The channel orientation with respect to the direction of rotation is 135 deg. The range of flow parameters includes Reynolds number (Re=10,000–40,000), rotation number Ro=0.0-0.15, and inlet coolant-to-wall density ratio (Δρ/ρ=0.12). Both heat transfer and pressure measurements were taken, so the overall performance of each rib configuration could be evaluated. It was determined that the W-shaped and discrete W-shaped ribs had the superior heat transfer performance in both nonrotating and rotating channels. However, these two configurations also incurred the greatest frictional losses while the discrete V-shaped and discrete angled ribs resulted in the lowest pressure drop. Based on the heat transfer enhancement and the pressure drop penalty, the discrete V-shaped ribs and the discrete W-shaped ribs exhibit the best overall thermal performance in both rotating and nonrotating channels. These configurations are followed closely by the W-shaped ribs. The angled rib configuration resulted in the worst performance of the six configurations of the present study.

Effect of rib spacing on heat transfer and friction in a rotating two-pass square channel with asymmetrical 90-deg rib turbulators

“…Furthermore, heat transfer in high aspect ratios channels (2:1, 4:1) with ribs are investigated by Fu et al (2004) [23], Griffith et al (2002) [24] and Wright et al (2004) [25]. They reported M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 5 / 33 significant spanwise variation in the heat transfer coefficients on both leading and trailing surfaces.…”

Heat transfer in a rotating smooth wedge-shaped channel with lateral fluid extraction

“…They found that the rotational effects are diverse in the spanwise direction. Wright et al [21] investigated a narrow rotating cooling channel (AR ¼ 4, b ¼ 135 )…”

Effect of roughness width ratio in discrete Multi v-shaped rib roughness on thermo-hydraulic performance of solar air heater

“…The values of thermohydraulic parameter (g) determined for this geometry of discrete Multi v-rib have been compared with the corresponding values for inclined rib with gap [13], discrete v-rib [8], discreet v-rib [15], V-down discrete rib [16] and Multi v-ribs [12] as shown in Table2. It can be seen that the discrete Multi v-rib geometry results is best thermohydraulic performance.…”

“…Selected other parameters such as, relative roughness pitch (P/e) values is selected as 8, relative roughness height (e/D) values is selected as 0.043 and angle of attack (a) value is selected as 60°, based on the optimum values of theses parameters reported in the literature [6][7][8][9][10][11][12][13][14][15][16][17][18]25].…”

“…Prasad and Mullick [7], Wright et al [8] were the first who applied the conception of artificial roughness to improve the thermal performance of solar air heater for drying purposes. Roughness in the form of small diameter wires were attached to the underside of absorber surface by Prasad and Saini [9] and investigated the effect of transverse rib roughness height and pitch on heat transfer and friction factor in a flow through solar air heater duct.…”