Air return ratio measurements at the solar tower Jülich using a tracer gas method

Under low-wind conditions and without irradiation of the main receiver the air return ratio was measured to be (67.7±0.5)% for an air mass flow of (9.96±0.04)kg/s. A slightly higher air return ratio of (68.6±0.7)% was measured under irradiation with an air mass flow of (9.94±0.04)kg/s. The air return ratio was sensitive to the air mass flow, showing significantly lower rates when moving further away from the 10kg/s design air mass flow to 5kg/s.