Numerical and experimental study of dryer in forced convection

The drying process of Stevia leaves was studied from 30 to 80C. Experimental drying curves showed that the drying process took place only in the falling rate period. Effective moisture diffusivity of Stevia leaves was in the range of 4.67-14.9 × 10 −10 m 2 /s. Several drying models available were evaluated based on statistical tests as a sum squared error (SSE), chi-square and determination coefficient. A value of 38.78 kJ/mol was determined as an activation energy. When comparing the experimental with predicted drying curves, the Midilli-Kucuk model was found to give the best fit quality (SSE < 0.001, χ 2 < 0.001, r 2 > 0.99). In addition, all drying curves were generalized and then modeled by Midilli-Kucuk model (r 2 = 0.99), showing this equation can very accurately predict the drying time of Stevia leaves under the drying conditions studied. At last, energy consumption and efficiency values for Stevia leaves drying process were found to be in the range of 316.59-716.19 kJ/kg and 21.46-54.34%, respectively. PRACTICAL APPLICATIONSA great demand for medicinal plants with extended shelf life has urged the dried food industry to look for raw materials of desirable nutritional and functional properties. Stevia rebaudiana leaves, with its high content of biologically active health-promoting components (natural non-caloric sweetener compounds, antibacterial capacity, antioxidant activity and other), is therefore an excellent raw material for the healthy food industry. Dehydration has the potential to deliver safe food products through decreasing moisture content and water activity. Therefore, knowledge about moisture transfer kinetics, as well as energy consumption and/or data normalization, is needed by the industry to manage and control efficiently drying process. Thus, this could serve to demonstrate the environmental consciousness of the food processing industry, greatly appreciated by consumers.

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“…) had been reported by Youcef‐Ali et al . ().

η = \frac{d λ Δ X}{F_{normala} C_{normala} Δ T t}

λ = 4186.8 (597 - 0.56 \cdot T)

…”

Section: Methodsmentioning

confidence: 97%

Dehydration of S tevia rebaudiana Bertoni Leaves: Kinetics, Modeling and Energy Features

Lemus‐Mondaca

Vega‐Gálvez

Moraga

et al. 2014

Journal of Food Processing and Preservation

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“…Step "j" of the drying chamber [50] Heat balance is established between the heated air, the product and the interior face o f the brick wall leading to:…”

Section: Application To the Dry Ing Chambermentioning

confidence: 99%

“…. Product temperature profile [50] Also some studies show that drying kinetics of the dried product and its temperature is affected [1]: by the surface of the solar collector, by the characteristic dimensions of the product, by the mass of the product putted on each tray and by the air flow rate [50].…”

Section: Application To the Dry Ing Chambermentioning

confidence: 99%

An Overview on Application of Exergy and Energy for Determination of Solar Drying Efficiency

Bennamoun¹

2012

IJEE

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The main objective of this work is to give an overview of the different used mathematical methods for modeling and calculating the energy and exergy efficiency of a solar dry ing system. For determination of the energy efficiency of thin or thick layers, heat and mass balances are established to the different co mponents. In the case of thick layers equations of porous med ia are used. These methods allow fo llo wing, in particular, the variat ions of the heated air and the product temperature and humidity. As a second part, the common way for the calculus of the exergetic efficiency passes through the establishment of exergy balance and after calculating the input, output and exergy loss. The influence and illustration of several parameters are as well presented in this paper.

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“…Among various configurations of solar thermal collectors, solar air heaters were found suitable for low and moderate temperature applications (Garg and Adhikari 1999), such as active building heating, air conditioning and drying process (Duffie and Beckman 1991;Youcef-Ali et al 2001;Prakash and Kumar 2013). A major disadvantage that solar air heaters suffer from is that air has low thermal properties compared with other working fluids, which often brings limitations to the overall efficiency of this type of solar collectors, especially the conventional flat plate configuration.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of new solar air heater design

Mahboub

Moummi

Brima

et al. 2015

International Journal of Green Energy

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The suitable design is the most important key to a cost-effective solar air heater. Although, there are many techniques that have been proposed to improve the solar air heaters' performance by means of different turbulence promoters, they cannot ensure a compromise between the cost and the effectiveness. The aim of this study is to find simple and tolerable solution to get rid of the inconvenience resulting from the widely adopted heat transfer enhancement techniques by providing an optimized solar air heater design. The proposed design consists of a slightly curved smooth flow channel with an absorber plate of convex shape. A prototype of a curved solar air heater of 1.28 m 2 collector area was built and tested under summer outdoor conditions in Biskra (Algeria). The performance was evaluated in terms of thermal and effective efficiency for mass flow rates of 0.0172, 0.029 and 0.0472 kg/sm 2 . It is observed that the overall efficiency of this solar air heater is considerably higher in comparison with the efficiency range of the conventional smooth flat plate heaters reported in the literature for similar operating conditions.

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Numerical and experimental study of dryer in forced convection

Cited by 29 publications

References 14 publications

Dehydration of S tevia rebaudiana Bertoni Leaves: Kinetics, Modeling and Energy Features

Dehydration of S tevia rebaudiana Bertoni Leaves: Kinetics, Modeling and Energy Features

An Overview on Application of Exergy and Energy for Determination of Solar Drying Efficiency

Experimental study of new solar air heater design

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