The effect of collector aspect ratio on the collector efficiency of ba
ffled solar air heaters has been investigated theoretically. With cons
tant collector area, the collector efficiency increases when the colle
ctor aspect ratio increases. This is the same results as those obtaine
d in the previous work for flat-plate solar air heaters without fins a
nd baffles. Although the collector efficiency of baffled solar air hea
ters is larger than that of flat-plate heaters without fins and baffle
s, the improvement of collector efficiency by increasing the collector
aspect ratio is reverse. (C) 1997 Elsevier Science Ltd.