Experimental investigations on thermal performance characteristics of a solar cavity receiver

Abstract

The experimentation is carried out to examine the influence of receiver aperture/opening ratio (receiver's aperture diameter to the maximum diameter ratio, d/D), glass cover thickness and inclination angle of cavity receiver on its collection efficiency for various flow rates of ordinary water as a working fluid. Experimental tests have been conducted at lower incident energy, i.e., at lower cavity wall temperatures (less than 200 °C). The aperture ratio examined encompasses values as 0.46, 0.6, 0.7, and 0.93 for water flowing at flows of 0.8, 0.65, 0.5, and 0.4 LPM that corresponds to Reynolds numbers (Re) of 1880, 1525, 1175, and 938, respectively. The glazing thicknesses of 6, 4, and 2 mm were provided at an aperture. A modified cavity-type receiver is made inclined at angles 90°, 60°, 45°, and 30° (with 90° as down-facing receiver opening and 30° as close to sideway-facing of receiver opening). The tests have been conducted for cavity surface temperatures ranging from 90° to 180 °C. It is observed that an aperture ratio of 0.6 demonstrates maximum receiver performance for the values of Reynolds number studied, while the receiver performance exhibited reducing trend with reduction in receiver tilting angle from 90° to 30°.Keywords Modified cavity receiver · Aperture/opening ratio · Collection efficiency · Inclination Non-dimensional numbers d/D Ratio of receiver's aperture diameter to the receiver maximum diameter ∕D Glazing thickness ratio Gr Grashof number Nu Nusselt number N RC Radiation-conduction number = T 4 w D 2 (Tw−Tamb)kf Re Reynolds number T R Temperature ratio = T amb T w o Angle ratio Symbols Surface absorptivity δ Thickness (m) Emissivity of the surface Receiver collection efficiency or receiver performance parameter

Experimental performance analysis of an improved receiver for Scheffler solar concentrator

“…Further, they concluded that heat losses could be suppressed with forced air circulation. Bopche and Kumar examined [14] the effect of the aperture opening, glass cover thickness, and inclination angle of cavity receiver on thermal performance. They have reported the contribution of convective and radiative heat losses in each case of the receiver.…”

Thermal Performance Analysis of Glazed and Unglazed Receiver of Scheffler Dish

“…Shukla [27] reported a 4.35% increase in receiver temperature and enhancement in heat transfer coefficient with dual glass cover helical coil receiver compared to horizontal tube receiver. According to S. Bopche and S. Kumar [28] glazing thickness, 4 mm gives better transmittance and reduces losses due to convective and radiative mode heat transfer. In the work of O. Lopez et al [29] losses from the receiver due to increases aperture area of the receiver are reduced by glazing the cavity aperture with a glass cover.…”

Thermal performance analysis of a Solar parabolic dish concentrator system with modified cavity receiver

“…The opening ratio of the receiver was chosen as 0.6, i.e. aperture diameter ( D ap, r ) equal to 18 cm for a cavity diameter of 30 cm ( D ), as reported by Bopche and Kumar (2019).…”

“…Receiver losses can be reduced by using insulation, varying receiver opening size and by providing fins inside the aperture disc. The influence of cavity opening size on the system thermal efficiency is presented by Bopche and Kumar (2019), wherein an optimum opening ratio reported is equal to 0.6.…”