Active drying of unripened bananas (Musa Nendra) in a multi-tray mixed-mode solar cabinet dryer with backup energy storage

• Published in: Solar energy 2019-08, Vol.188, p.1002-1012
• Main Authors: Arun, K.R., Srinivas, M., Saleel, C.A., Jayaraj, S.
• Format: Article
• Language: English
• Subjects: Air temperature; Bananas; Drying; Energy consumption; Energy storage; Flat plates; Flow rates; Flow velocity; Food preservation; Mixed-mode; Moisture content; Moisture removal; Pretreatment; Slicing; Solar energy; Storage units; Temperature distribution; Thickness; Tray sequencing; Trays; Unripe bananas; Water content
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2019.07.001

•A novel tray sequencing pattern for multi-tray mixed-mode solar cabinet dryer (MMSCD).•Drying uniformity ensured irrespective of non-uniform temperature distribution in MMSCD.•Flexibility to the user to choose between preliminary considerations for drying.•Average pickup, drying efficiency and cost of drying was 21.4%, 37.8%, and $0.35/kg.•Dried banana flakes had good color (no blackening), texture, and natural aroma. Uniform moisture removal inside a multi-tray mixed-mode solar cabinet dryer (MMSCD) within a limited time is a significant concern primarily due to the non-uniform temperature distribution. Primary factors such as heated air and flow rate along with preliminary considerations such as slicing, loading intensity, spacing, and choice of with or without pre-treatment influence the drying behaviour. Hence, the primary objective of the present work is to identify whether only tray sequencing can be sufficient to ensure drying uniformity inside the MMSCD. A double-pass flat plate collector containing discrete cylindrical macro-encapsulated energy storage units deliver the heated air. Untreated unripe bananas with an average initial moisture content of 180% (db) are tested. In this work, the effect of tray sequencing (peculiar pattern) under a single layer loading intensity per tray with different flake thickness, multi-tray spacing, and flow rate are studied. Drying characteristic curves revealed that with tray sequencing the final moisture content was reduced below 16% (db) in all the trays. The specific energy consumption, efficiencies (collector, pickup, drying), drying cost, and open sun drying are discussed. Thus, based on the requirement, the MMSCD along with energy storage offers greater flexibility in drying for the user and ensures drying uniformity.