scholarly journals Numerical Study of the Drying of Cassava Roots Chips Using an Indirect Solar Dryer in Natural Convection

2021 ◽  
Vol 3 (1) ◽  
pp. 138-157
Author(s):  
Merlin Simo-Tagne ◽  
Ablain Tagne Tagne ◽  
Macmanus Chinenye Ndukwu ◽  
Lyes Bennamoun ◽  
Marcel Brice Obounou Akong ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Transfer Coefficients ◽  
Drying Time ◽  
The Core ◽  
Cassava Root ◽  
Solar Dryer ◽  
Theoretical Results

In this work, an indirect solar dryer for drying cassava root chips was modelled and experimentally validated using the environmental conditions of Yaoundé in Cameroon and Yamoussoukro in Ivory Coast. The dryers were operational in natural convection mode. Resolution of the equations was achieved by finite differences and the 4th order of Runge–Kutta methods. A model was proposed for performing heat and mass transfer using thermophysical properties of cassava roots, and the obtained results were satisfactory for all conditions, with moisture content difference of less than 0.2 kg/kg between the experimental and theoretical results. The model showed that the core of the product takes more time to dry, which always prolongs the drying duration. The heat and mass transfer coefficients vary during the entire process of solar drying. The drying kinetics vary during the drying with values lower than 1.2 × 10−4 kg/(kg.s). The great gradients of humidity were observed in the thickness of the sample with a regular distribution of the temperature each drying time in the thickness of the sample.

The Experimental Investigation of Steam Condensation With Non-Condensable Gas Under Natural Convection

2018 ◽  
Author(s):  
Xizhen Ma ◽  
Wen Fu ◽  
Haijun Jia ◽  
Peiyue Li ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
High Pressure ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Vertical Wall ◽  
Experimental System ◽  
Steam Condensation ◽  
Transfer Coefficients ◽  
Calculation Results

The non-condensable gas is used to keep the pressure stable in the steam-gas pressurizer. The processes of heat and mass transfer during steam condensation in the presence of non-condensable gas play an important role and the thermal hydraulic characteristics in the pressurizer is particularly complicated due to the non-condensable gas. The effects of non-condensable gas on the process of heat and mass transfer during steam condensation were experimental investigated. A steam condensation experimental system under high pressure and natural convection was built and nitrogen was chosen in the experiments. The steam and nitrogen were considered in thermal equilibrium and shared the same temperature in the vessel under natural convection. In the experiments, the factors, for instance, pressure, mass fraction of nitrogen, subcooling of wall and the distribution of nitrogen in the steam, had been taken into account. The rate of heat transfer of steam condensation on the vertical wall with nitrogen was obtained and the heat transfer coefficients were also calculated. The characteristics curve of heat and mass transfer during steam condensation with non-condensable gas under high pressure were obtained and an empirical correlation was introduced to calculated to heat transfer coefficient of steam condensation with nitrogen which the calculation results showed great agreement with the experimental data.

A Study of Enhanced Heat and Mass Transfer From Variable Height Fin Array Undergoing Natural Convection

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Debayan Dasgupta ◽  
Kankan Kishore Pathak ◽  
Asis Giri
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Latent Heat ◽  
Numerical Study ◽  
Boussinesq Approximation ◽  
Heat Transfer Analysis ◽  
Simpler Algorithm ◽  
Fin Spacing

Abstract A numerical study is performed on simultaneous heat and mass transfer from a shrouded vertical nonisothermal variable height fin array, representing dehumidification process under natural convection. Fluid properties are treated as uniform, and the fluid is assigned to comply with Boussinesq approximation to include the effect of density variation with temperature and concentration. Semi-implicit method for the pressure linked equations revised (SIMPLER) algorithm is adopted to resolve pressure and velocity coupling. A detailed parametric investigation of fin spacing, variable fin height, and fin tip to shroud clearance for a range of thermal and mass Grashof number is undertaken. Results indicate that in case of smaller fin spacing, involving fin length of 0.3 m, coefficients of sensible and latent heat transfer increase with the decreasing variable height (H1*) of fin and become maximum at H1*=0.5, for all thermal and mass Grashof numbers considered presently. Further, total heat transfer analysis on a particular base length due to sensible heat shows a maximum of 24.4% enhancement, whereas same due to the latent heat shows a maximum of 25.8% enhancement, depending on the values of clearance. Induced velocities also increase with the decreasing variable height of fin (H1*), which influences the heat and mass transport. The output parameters of this analysis, like induced velocities and overall Nusselt numbers due to the sensible and latent heat, are correlated with the governing parameters. The correlation coefficients are found to be in a range from 0.97 to 0.99.

Evaluation of Convective Heat and Mass Transfer in Open Sun and Green House Drying

2008 ◽  
Author(s):  
S. K. Shukla
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Ambient Air ◽  
Natural Mode ◽  
Transfer Coefficients ◽  
Drying Time ◽  
Sun Drying ◽  
Green House ◽  
Hourly Data

In this communication, a study on open sun and green house drying has been performed to evaluate the convective heat and mass transfer coefficients as a function of climatic parameters. The hourly data for the rate of moisture removal, crop temperature, relative humidity inside greenhouse and outside greenhouse and ambient air temperature for complete drying have been recorded. The experiments were done in the premises of Allahabad Agricultural Institute-Deemed University, after the crop-harvesting season from February 2006 to April 2006. Using these data, the value of convective heat and mass transfer in open sun drying (OSD) and green house sun drying (GHD) under natural and forced convection mode, have been calculated. Also the empirical relations of convective heat and mass transfer with drying time under natural and forced modes have been developed. On the basis of the present study, it is inferred that the value of convective heat and mass transfer is more in open sun drying than in the green house drying under natural convection mode. However its value increases in forced mode of greenhouse drying as compared to natural mode in the initial stage of drying.

Heat and mass transfer in rectification of binary mixtures at turbulent vapour flow

1983 ◽  
Vol 48 (7) ◽  
pp. 1820-1828 ◽  
Author(s):  
Václav Kolář ◽  
Jan Červenka
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Binary Mixtures ◽  
Reflux Ratio ◽  
Hydrodynamic Conditions ◽  
Transfer Coefficients ◽  
Mass Transfer Mechanism ◽  
Simultaneous Heat ◽  
Theoretical Results

Theoretical analysis of the heat and mass transfer mechanism in rectification of binary mixtures was made at the use of earlier obtained relations for the heat and mass transfer coefficients. Theoretical results were applied to the mixture methanol-water and have revealed that the effect of simultaneous heat transfer on mass transfer is insignificant and is little affected by both the reflux ratio and hydrodynamic conditions.

scholarly journals Modelling Droplet Heat and Mass Transfer in Aero-Engine Bearing Chambers

2019 ◽  
Author(s):  
Dafne Gaviria Arcila ◽  
Hervé Morvan ◽  
Kathy Simmons ◽  
Stephen Ambrose ◽  
Michael Walsh ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Evaporation Rate ◽  
Numerical Study ◽  
Droplet Diameter ◽  
Air Flow ◽  
Core Region ◽  
Evaporation Process ◽  
Data Set ◽  
The Core

Abstract The oil inside aeroengine bearing chambers can be found in many forms, including droplets which interact with the core airflow. The ability to model such bearing chambers computationally is desirable and thus a better understanding of the evaporation process of oil droplets is of great interest. Previous studies have analyzed the flow of isothermal droplets in bearing chambers. However, further investigation is needed into the heating of droplets in the highly rotating core region. This will enable designers to evaluate the behavior of droplets in a chamber and the likelihood that they will evaporate. The aim of this research is to analyze the oil droplet evaporation process under aeroengine bearing chamber representative conditions. An ultimate goal is the ability to predict the oil-air heat and mass transfer in the core flow region, as well as to develop an understanding of the flow inside a droplet, and how this affects evaporation. This latter is important as it has not been studied before. This paper presents the results of a numerical study of the evaporation process of a single droplet under bearing chamber temperature and air flow conditions. The two-phase flow is simulated using ANSYS Fluent with the volume of fluid approach and the evaporation process with the “D−square law”. First, the modelling approach is validated against previous experimental and numerical analysis of fuel droplets in an air flow with heat transfer. The simulation results were in excellent agreement with a benchmarking data set. The validated approach is then applied for investigation to smaller, bearing chamber representative droplets of an oil base stock used in jet engines. The oil evaporation rate was quantified as well as the evolution of droplet diameter, which revealed the effect of different air velocities and temperatures on the droplet. The extent to which evaporation rate increased with air velocity and temperature is quantified. It is concluded that droplets of initial diameters less than 200μm that remain in the chamber core region for more than 0.3s are likely to evaporate completely. This study allows us to estimate droplet heat and mass transfer and the associated phase change in a bearing chamber. It also provides best practice to predict the performance of small droplets under the effects of high temperature and velocity convective air flows. In future work this methodology will be applied in simulations in a representative bearing chamber to predict how the cooling process is affected by oil evaporation.

Modeling of coupled heat and mass transfer during drying of ebony wood using indirect natural convection solar dryer

2019 ◽  
Vol 37 (14) ◽  
pp. 1863-1878 ◽  
Author(s):  
Merlin Simo-Tagne ◽  
Beguidé Bonoma ◽  
Lyes Bennamoun ◽  
Louis Monkam ◽  
Angélique Léonard ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Natural Convection ◽  
Heat And Mass Transfer ◽  
Solar Dryer
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