Impact of Yaw angle on the Effectiveness of an Air Curtain for Solar Cavity Receivers

An experimental study was performed to quantify the effectiveness of an air curtain through the direct measurement of the convective heat losses from a scaled-down heated cavity receiver (0.3 m ID, 0.45 m length and 0.1 m aperture) in a large wind tunnel. The tilt angle of the cavity was kept constant at 15° while the yaw angle changed from 0° to 45° and 90° for wind speeds of 0, 3, 6 and 9 m/s. A blowdown purpose-designed air curtain was used to establish an aerodynamic barrier across the aperture of the cavity. The velocity of the air curtain flow was changed from 4.5 to 9 and 18 m/s with two different discharge angles of 0° and 30°. The results show that a low velocity side-wind decreases the convective heat losses. It is also found that the application of the blowdown air curtain with a side wind (yaw angles of 45° and 90°) increases the convective heat losses by 2.7 times over the no air curtain case for these conditions.