Compact nonimaging infrared systems for decondensing 2000 m 2 of spectator glazing at Singapore Kranji racetrack

Abstract

The Singapore Kranji racetrack complex includes a multi-tiered air-conditioned spectator facility with around 2000 m 2 of glazing that were plagued by excessive exterior condensation during nighttime events. The problem stemmed from a combination of high ambient humidity, warm outdoor temperatures and the required comfort cooling of the interior space. A number of mechanical and forced-convective heating solutions all failed to satisfy the severe constraints imposed on the placement of retrofit devices, e.g., not obscuring spectators' views, permitting a large view angle, ambient cross winds, and limited electrical capacity. We developed a compact efficient radiative solution based on nonimaging optics: highly asymmetric infrared reflectors, with the heating source being off-the-shelf rectangular ceramic elements. The challenges included: (1) achieving a high degree of flux uniformity on glazings 5 to 5.5 m in height and hundreds of meters wide; (2) luminaries having to be compact (about 20-40 cm in depth); and (3) luminaire siting being restricted to a small space close to, and just above, the glazing, out of the field of view of the spectators, which imposes a large and highly asymmetric field of irradiation. Good flux uniformity is essential for minimal electrical power requirements and the avoidance of hot spots that could prove annoying to spectators. Prototypes of our designs were fabricated, tested under worst-case conditions, and found to perform satisfactorily.