In this study a heat-pump-assisted dryer with an opener mechanism was constructed and tested at the Energy Laboratory, Mechanical Engineering Department, Balikesir University, Turkey. The test material used was wet wool, which is a fibrous material. The variables in the experiments were the air rate, the recirculation air ratio (RAR) and the bypass air ratio. In the experiments, the air mass velocities ranged from 0.78 to 1.50 kg/m(2)s. The bypass air and recirculation air ratios varied from 20% to 80%. For this system both coefficient of performance of the whole system (COPws) and the specific moisture extraction rate of the whole system (SMERws) increased as evaporator air ratios increased. COPws was found to range from 2 to 3.5 while SMERws varied between 1.5 and 2.8 kg/kW h depending on RAR. (C) 2002 Elsevier Science Ltd. All rights reserved.