The influence of wind speed, aperture ratio and tilt angle on the heat losses from a finely controlled heated cavity for a solar receiver

• Published in: Renewable energy 2019-12, Vol.143, p.1544-1553
• Main Authors: Lee, Ka Lok, Chinnici, Alfonso, Jafarian, Mehdi, Arjomandi, Maziar, Dally, Bassam, Nathan, Graham
• Format: Article
• Language: English
• Subjects: Concentrated solar thermal radiation; Heat loss; Solar receiver; Solar thermal power; Temperature distribution; Wind
• ISSN: 0960-1481; 1879-0682
• DOI: 10.1016/j.renene.2019.05.015

The first systematic experimental study of the combined influences of wind speed (0–9 m/s), aperture ratio (0.33–1) and tilt angle (15°–45°) on the mixed (free and forced) convective heat losses from a heated cavity, is presented. The cylindrical cavity is heated by 16 individually temperature-controlled heating elements in the open section of a wind tunnel. Heat flux distribution and total heat losses from the cavity were measured. A complex inter-dependence was found between aperture ratio, wind speed and convective heat losses. In particular, the total heat losses can vary by up to ∼75% by varying the aperture ratio from 0.33 to 0.75, for no wind condition, but the effect of aperture ratio is decreased as wind speed is increased. The tilt angle was found to have a small effect on the heat losses relative to the aperture ratio and wind speed. Nevertheless, the average minimum mixed heat loss for various wind speeds occurs for a tilt angle of between 15° and 30° for a downward tilting solar tower system. •Heat losses varied by up to 75% by increasing the aperture ratio of a cavity.•For high head-on wind, the influence of aperture ratio on total heat loss is low.•Heat losses from a cavity are not always decreased by increasing tilt angle.•About 60% of the total heat is lost from the lower section of the heated cavity.