Design and Manufacturing of Solar Injera Dryer
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Date
2020-10
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
About two-third of Ethiopian diet consists of injera, which has a strong cultural
significance and high nutritional value, as it is rich in fibre, amino acids, calcium, iron and most
importantly it is gluten-free. Injera is dried and prepared in times of food scarcity or for commercial
and household usage. The objective of this thesis was to design and evaluate a mixed-mode natural
convection solar injera dryer with unique vertical air distribution unite with 20 injera drying
capacity.
Three dimensional simulation of unloaded solar dryer was developed to simulate the
performance of the modified mixed mode solar dryer using the computational fluid dynamics
(CFD) software ANSYS FLUENT for month of July and April by solving the governing equations
describing the unsteady fluid flow. Dual-band discrete ordinates (DO) radiation model, Species
transport model and shear stress transport (SST) k-omega (k-ꙍ) turbulence models were
employed. The dimensions of the dryer were: 2 m, 2 m
, 1.4 m, 2.2 m, 1.5 m and 1 m for collector
length, collector area, height of the vertical air distributer channel, the height of the drying
chamber, length and width of the drying chamber respectively.
2
C above the
ambient throughout the drying period. The overall temperature distribution through the drying
trays shows a uniform temperature distribution. The average velocity and mass flow rate through
the drying trays were found to be 0.1 m/s and 0.061 kg/s respectively and both were uniformly
distributed through the drying trays. There was a pressure gradient through the drying tray, which
helps to maintain the airflow through the dryer.
The simulation result indicated the collector outlet temperature was 10
o
From the experimental result, it was clear that the modified mixed mode drier performance
was higher by 19% when compared with other similar mixed mode drier. In addition, the
temperatures of the drying air inside the drier was found to be more than 5
C from the ambient
temperatures. A uniform temperatures distribution was noticed through the drier, this is the result
of the vertical air distributer channel, which was newly developed and integrated through the
drying chamber, and the collector and drying efficiency of the drier were found to be 30% and
15.25% respectively. The drying rate of the drier was 2.634*10
o
kg/s and the Verma thin layerdrying
model
fits
best
for
injera
drying
based
on
the
X
-5
. The experimental result
was compared with the simulation result and the simulated temperature result showed an average
overestimation on drying chamber by -1.5% and underestimation on collector outlet by 1.6 %.
Description
Keywords
Solar drier, Mixed mode drier, Injera, Simulation, Vertical air distributer channel