The coupling between the internal and external flows through a hybridized solar cavity receiver under isothermal conditions

An experimental investigation of the interaction between the internal and external flows through a simplified laboratory-scale hybrid solar cavity receiver is presented. The experiments were conducted under isothermal conditions using the Particle Image Velocimetry (PIV) technique. The device comprises a cylindrical chamber (70 mm inner diameter and 225 mm long) fitted with four jets (3.35 mm inner diameter) simulating fuel and air supply and an aperture. Four different configurations have been tested, with two different jet inclination angles (25 degrees and 50 degrees) and with two different jet azimuthal angles (0 degrees and 5 degrees). Water was used as the working fluid and the models were placed in a water channel with variable speed to allow the influence of an external flow to be simulated. The results show that the flow behaviour within the cavity is strongly dependent on the jets' configuration, the aperture ratio and tilt angle. A significant flow of external fluid was entrained through the aperture for all of configurations, with an additional 22% and 42% to the internal flow for the (alpha(j) = 25 degrees, gamma(j) = 0 degrees) case with zero and 0.24 m/s exteral velocity, respectively. The effect of opening the apreture on jet decay, turbulence intensity and recirculation pattern was also recorded. It is found that while opening the aperture and introducing an external flow have little qualitative influence on the flow pattern and jet decay, the turbulence intensity in the proximity of the aperture changes considerably. The need to manage the complex interactions between the external and internal flows through the cavity receiver is defined.