Drying of grape pomace with a double pass solar collector

ABSTRACT

This study aims to analyze the performance of a novel design of the double pass solar air collector (DPSAC)-assisted drying system and investigate the drying kinetics of grape pomace which is an agricultural by-product. The samples were dried to a moisture content of 0.01 g water/g dry matter between 100 and 250 min depending on the weather conditions. The average thermal efficiencies of DPSAC were calculated as 79.77, 79.85, and 69.46%. Average values of the coefficient of performance of DPSAC were determined as 5.32, 5.13, and 4.32. The highest specific moisture extraction rate value was achieved as 617.18 g water/kWh. Whereas the mass transfer coefficient (h_m) values ranged from 9.15E−11 to 1.04E−7 m/s, the effective moisture diffusivity (D_e) values were obtained between 3.04E−13 and 1.02E−10 m²/s. The qualitative analysis showed that the drying using DPSAC may be an alternative for drying applications in terms of short drying time and energy usage. Nevertheless, these results clearly suggest a complex and effective interplay between thermal performance and drying kinetics.

KEYWORDS:

• Double-pass solar air collector
• drying efficiency
• energy
• grape pomace
• solar drying

Abbreviations::

• COP: coefficient of performance
• DPSAC: double-pass solar air collector
• DR: drying rate, g water/g dry matter per min
• MR: moisture ratio
• SAC: solar air collector
• SMER: specific moisture extraction rate