Dryer evaluation to optimize small-scale litchi processing in Northern Thailand
- Publikations-Art
- Kongressbeitrag
- Autoren
- Precoppe M F; Nagle M; Janjai S; Mahayothee B; Müller J
- Erscheinungsjahr
- 2010
- Veröffentlicht in
- Proceedings of the XVIIth World Congress of the International Commission of Agricultural Engineering (CIGR)
- Seite (von - bis)
- 1-9
- Tagungsname
- XVIIth World Congress of the International Commission of Agricultural Engineering (CIGR) - Section VI: Postharvest Technology and Process Engineering
- Tagungsort
- Quebec City (Canada)
- Tagungsdatum
- 13-17 June 2010
In Thailand, litchis are produced primarily by smallholders in northern mountainous areas of the country. Currently, the profitability of this crop is jeopardized by unstable farmgate prices and insufficient access to markets. Local production of dried litchis by farmer cooperatives is a promising solution, yet existing drying technology for small-scale food processing yields products with heterogeneous quality and has low energy performance. With the aim to develop energy-saving technology for producing high-quality dried fruits at an affordable cost, a locally-available batch dryer used for litchi was evaluated at a farmer’s cooperative. Non-uniform temperature distribution in the drying chamber was identified, resulting in fruits with heterogeneous moisture content, water activity and color. Each batch yielded approximately 15 kg of dried litchi and required about 15 kg of fuel. Specific thermal energy consumption of the dryer was 10.3 MJ per kilogram of evaporated water. Analysis of instantaneous indices, calculated to evaluate energy performance, demonstrated that the main heat losses were via exhaust air and that increasing the dryer’s recirculation ratio or reducing the airflow rate could decrease these losses. Installing a frequency-converter to control the speed of the blower would allow for an adjustable airflow rate and thus, the gradual reduction of airflow over the drying process. Convective heat losses through the dryer’s walls were also high, which might be reduced by insulation. Overall, it is believed that the proposed modifications would produce significant improvements in dryer performance.