Solar thermal systems like solar water and solar air collectors (SCs) are generally used because of their simple structure and high thermal efficiency. Solar air collectors could be utilized in drying applications because they are easy applicable and economical. In this study, a novel parallel-pass SC with double baffles (PPSCDB), parallel-pass SC with baffles (PPSCB) and parallel-pass SC (PPSC) without baffle have been designed and tested for drying application. Baffles have been manufactured in plus-shaped and perforated to achieve high thermal performance. The performance of solar collectors has been analyzed numerically and experimentally. In addition, a drying chamber has been coupled with solar air collectors. Celery (Apium Graveolens L.) root has been dried as a product and dried samples' quality has been analyzed experimentally. The experiments have been conducted at 0.009 kg/s and 0.011 kg/s air mass flow rates. According to the experimental findings, average thermal efficiencies of PPSC, PPSCB and PPSCDB are in the range of 62.10-66.32%, 65.72-69.62% and 71.12-75.11%, respectively. The highest instantaneous efficiency was obtained as 84.30% in higher mass flow rate in PPSCDB. Also, maximum deviation between experimental and numerical results was 9.5%. (c) 2019 Elsevier Ltd. All rights reserved.