Solar tunnel coffee dryer: numerical and experimental studies

Askal, Gerima

dc.contributor.author	Askal, Gerima
dc.date.accessioned	2022-02-21T08:21:12Z
dc.date.available	2022-02-21T08:21:12Z
dc.date.issued	2021-09
dc.identifier.uri	http://ir.bdu.edu.et/handle/123456789/13013
dc.description.abstract	This study presents experimental and simulated results of drying of coffee bean in indirect solar tunnel dryer with two AC fan. This dryer consists of two flat-plate solar air heater and two drying stages. A system of partial differential equations describing heat and mass transfer during drying of coffee bean in this solar tunnel dryer was developed and this system of nonlinear partial differential equations was solved numerically by the finite difference method. The numerical solution was programmed in MATLAB version 2014a. Furthermore, to investigate the experimental performance, a full-scale experimental run was conducted and 19 kg of coffee bean was dried. The drying air temperature varied from 33.3 to 53.8C for the first drying stages and 32.8 to 54.0 for the second one. The drying time in the solar tunnel dryer was 24 h to dry coffee bean from an initial moisture content of 71.5% (w.b) to a final moisture content of 10% (w.b), whereas it required 32h for open sun drying under similar conditions to reach a moisture content of 9% (w.b). To determine the drying characteristics of coffee four thin-layer drying model was investigated and finally the best model was two-term model with goodness of fitting 2 R = 0.9958, SSE= 0.0059 and RMSE= 0.0167 for drying stage one and also the goodness of fitting for drying stage two data was 2 R = 0.9954, SSE= 0.0063 RMSE= 0.0173. the comparison between simulated and experimental result was accomplished using root mean square difference (RMSD), and scatter index (SI). SI of the prediction of the collector’s outlet temperatures were 4.3% and 3.66% for collector unit one and two respectively, and also SI of the prediction of the drying stage’s outlet temperatures were 3.2% and 2.9% for drying stage one and two respectively, And also SI for the moisture content in wet basis 4.84% and 5.9% for drying stage one and two respectively. Since, predictions are within the acceptable limit (<10%) the model can predict the temperatures and moisture contents with a reasonable accuracy. Therefore, this numerical model can be used to provide the design data. Finally, thermal performance of the dryer was evaluated and the collector efficiency was found to be 40% for collector, and drying system efficiency 20.2%. The pick-up efficiency 15.98% and 16.9% for drying stage one and two.	en_US
dc.language.iso	en_US	en_US
dc.subject	ENERGY CENTER	en_US
dc.title	Solar tunnel coffee dryer: numerical and experimental studies	en_US
dc.type	Thesis	en_US