2 research outputs found
Simulation model for solar energy harnessing by the solar tunnel dryer
Models were developed to predict global solar radiation and the energy harnessed by a solar tunnel dryer, and simulated in Visual Basic 6. In addition, the simulated data were compared with actual data. Using a 10% absolute residual error interval, the developed model achieved 78.4% and 83.3% performance for global solar radiation and energy harnessing, respectively. Further, the relationship between global solar radiation and the ten years mean satellite solar radiation, and that between the actual and simulated plenum chamber temperatures were linear, with coefficients of determination (R2) of 0.788 and 0.962. Thus, it shows that there is the existence of strong correlation between satellite and predicted global solar radiation, and between predicted and actual plenum chamber temperatures. Furthermore, Student’s t-test did not show any significant difference between simulated and actual data for solar radiation and energy harnessing. Finally, this study shows that the developed model can be used to predict solar radiation and the energy harnessed by the solar tunnel dryer.Keywords: modeling, tunnel-dryer, global, direct, solar-radiation, plenum-temperature Citation: Kituu G. M., D. Shitanda, C. L. Kanali, J. T. Mailutha, C. K. Njoroge, J. K.Wainaina, and J. S Bongyereire. Simulation model for solar energy harnessing by the solar tunnel dryer. Agric Eng Int: CIGR Journal, 2010, 12(1): 91-98
Thin Layer Drying Kinetics Of Amaranth ( Amaranthus Cruentus ) Grains In A Natural Convection Solar Tent Dryer
An experimental solar tent dryer under natural convection was used to
study thin layer drying kinetics of amaranth ( Amaranthus cruentus )
grains. Drying of grains in the dryer was carried out on a drying rack
having two layers; top and bottom. The ambient temperature and relative
humidity ranged from 22.6-30.4°C and 25-52%, respectively, while
the inside temperature and relative humidity in the solar dryer ranged
from 31.2-54.7°C and 22-34%, respectively. Freshly harvested
amaranth grains with an average moisture content of 64% were dried
under the solar tent dryer for seven hours to a final moisture content
of 7% (dry basis). A non-linear regression analysis was used to
evaluate six thin layer drying models (viz., Newton, Page, Modified
Page, Henderson & Pabis, Logarithmic and Wang & Singh) for
amaranth grains. The models were compared using coefficient of
determination (R2), root mean square error (RMSE), reduced chi-square
(χ2) and prediction performance (ηp) in order to determine
the one that best described thin layer drying of amaranth grains. The
results show that the Page model satisfactorily described the drying of
amaranth grains with R2 of 0.9980, χ2 of 0.00016 and RMSE of
0.01175 for bottom layer and R2 of 0.9996, χ2 of 0.00003 and RMSE
of 0.00550 for top layer of the drying rack. Based on a ± 5%
residual error interval, the Page model attained the highest prediction
performance (ηp = 80%) when drying the grains in both layers of
the dryer. This shows that there was a good agreement between the
predicted and experimental moisture changes during solar drying of
amaranth grains under natural convection. The transport of water during
dehydration was described by applying the Fick's diffusion model and
the effective moisture diffusivity for solar tent drying of amaranth
grains was found to be 5.88 x 10-12 m2s-1 at the bottom layer and 6.20
x 10-12 m2s-1 at the top layer. High temperatures developed at the top
layer of the dryer led to high effective moisture diffusivity and this
showed that temperature strongly influences the mechanism of moisture
removal from the grains