Heat and mass transfer of a porous permeable wall in a high temperature gas dynamical flow is considered. Numerical simulation is conducted on the ground of the conjugate mathematical model which includes filtration a...Heat and mass transfer of a porous permeable wall in a high temperature gas dynamical flow is considered. Numerical simulation is conducted on the ground of the conjugate mathematical model which includes filtration and heat transfer equations in a porous body and boundary layer equations on its surface. Such an approach enables one to take into account complex interaction between heat and mass transfer in the gasdynamical flow and in the structure subjected to this flow. The main attention is given to the impact of the intraporous heat transfer intensity on the transpiration cooling efficiency.展开更多
A self-similar solution of unsteady mixed convection flow on a rotating cone embedded in a porous medium saturated with a rotating fluid in the presence of the first and second orders resistances has been obtained. It...A self-similar solution of unsteady mixed convection flow on a rotating cone embedded in a porous medium saturated with a rotating fluid in the presence of the first and second orders resistances has been obtained. It has been shown that a self-similar solution is possible when the free stream angular velocity and the angular velocity of the cone vary inversely as a linear function of time. The system of ordinary differential equations governing the flow has been solved numerically using an implicit finite difference scheme in combination with the quasi-linearization technique. Both prescribe wall temperature and prescribed heat flux conditions are considered. Numerical results are reported for the skin friction coefficients, Nusselt number and Sherwood number. The effect of various parameters on the velocity, temperature and concentration profiles are also presented here.展开更多
Based on the transport mechanism of heat and mass transfer and by using the minimum gradient theory for unsaturated flow in capillary porous media, a mathematical model is developed for heat and mass transfer in unsat...Based on the transport mechanism of heat and mass transfer and by using the minimum gradient theory for unsaturated flow in capillary porous media, a mathematical model is developed for heat and mass transfer in unsaturated wet porous media considering the effect of capillary hysteresis. The heat and mass transport properties in the derived differential equations are analyzed in detail. which opens new way to further develop practical methods for determining heat and mass transport properties in wet porous media.展开更多
Drying of the banana in the hot water has a negative impact on the quality of the product and drying effect. The purposes of this study are increasing the drying rate, using the relatively low temperature to improve t...Drying of the banana in the hot water has a negative impact on the quality of the product and drying effect. The purposes of this study are increasing the drying rate, using the relatively low temperature to improve the quality (40℃, 50℃ and 60℃) and investigate the use of electromagnetic waves to increase the drying speed. Therefore, experiments are performed using 5 kHz,10 kHz and 15 kHz low frequency electromagnetic waves in the air velocity values of 0.5 m/s, 1 m/s, 1.5 m/s and 2 m/s and 40℃, 50℃, 60℃ centigrade degrees of air blast in a special compartment. Mathematical model of the drying process has been created as using the electrical circuits methods and experimental results. As a result, a simple equation describing the drying process has been obtained. Nonlinear expression of the diffusion coefficient for a different situation in this equation has been identified for the first time. The obtained theoretical results and experimental results have been provided a good agreement. This study is considered to be useful for all studies in the drying area.展开更多
Penetration of chemicals in the soil ground through irrigation water or rainfall induces important risks for the environment. These risks are badly known and may lead to direct contamination of the environment (atmosp...Penetration of chemicals in the soil ground through irrigation water or rainfall induces important risks for the environment. These risks are badly known and may lead to direct contamination of the environment (atmosphere or ground water) or harmful effects on organisms living at ground level, indirectly affecting men. It is thus necessary to estimate these potential chemical risks on the environment. For that reason, the gradual change of these products (fertilizers, solutions, pollutants, ...) in the ground has been the subject of a lot of recent research works, based in particular on the study of non-saturated porous media in a theoretical, numerical or experimental way. Most of these works are incomplete and, in order to simplify the problem, they don’t take into accounts some process, which may be of prime importance under particular natural conditions. Complexity of such studies results from their multidisciplinary nature. In this communication, we study simultaneous transport of pollutant, the water that provides transport and the heat transfer in a 200 cm long cylindrical column full of sand taken as a non-saturated porous medium. We consider two kinds of conditions on the temperature at the column surface: the case of constant temperature and the case of sinusoidal temperature. We evaluate the influence of this temperature on the transfers. This study is purely numerical. We use the control volume method to determine hydrous, thermal and pollutant concentration profiles.展开更多
Experiments with potatoes were carried out in order to analyze the variation of the temperature and the mean dry basis moisture content over time,the effect of the drying conditions on the drying rate,and the relation...Experiments with potatoes were carried out in order to analyze the variation of the temperature and the mean dry basis moisture content over time,the effect of the drying conditions on the drying rate,and the relationship between deformation and dry basis moisture content.A two-way sequentially coupled thermo-hydro-mechanical math model was developed on the basis of Fickian diffusion theory,Fourier’s law of heat conduction and thermoelasticity mechanics in order to analyze the spatio-temporal distributions of moisture,temperature and drying stresses in the potatoes.The transient mathematical model,composed of a system of partial differential equations,was solved by finite difference methods.The numerical results obtained by using the mathematical model were in good agreement with the experimental data.The variations in temperature and moisture distributions,drying curves and stresses within potatoes over time were simulated,and the ways in which these are affected by the drying conditions were discussed.This work could help in developing an understanding of the relationship between mass and heat transfer,shrinkage,stress,and physical degradation of biological materials.展开更多
This paper studies the thermal-diffusion and diffusion thermo-effects in the hydro-magnetic unsteady flow by a mixed convection boundary layer past an imperme- able vertical stretching sheet in a porous medium in the ...This paper studies the thermal-diffusion and diffusion thermo-effects in the hydro-magnetic unsteady flow by a mixed convection boundary layer past an imperme- able vertical stretching sheet in a porous medium in the presence of chemical reaction. The velocity of t^he stretching surface, the surface temperature, and the concentration are assumed to vary linearly with the distance along the surface. The governing partial differential equations are transformed into self-similar unsteady equations using similarity transformations .and solved numerically by the Runge-Kutta fourth order scheme in as- sociation with the shooting method for the whole transient domain from the initial state to the final steady state flow. Numerical results for the velocity, the temperature, the concentration, the skin friction, and the Nusselt and Sherwood numbers are shown graph- ically for various flow parameters. The results reveal that there is a smooth transition of flow from unsteady state to the final steady state. A special case of our results is in good agreement with an earlier published work.展开更多
A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure ...A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.展开更多
The coupling of temperature gradient and concentration gradient and it's effects on heat and mass transfer are considered for natural convection in a porous enclosure. By use of the penalty finite element method, ...The coupling of temperature gradient and concentration gradient and it's effects on heat and mass transfer are considered for natural convection in a porous enclosure. By use of the penalty finite element method, the distributions of flow, temperature and concentration fields are numerically simulated in four kinds of boundary condition. The profiles of heat and mass transfer coefficients along with the vertical wall are shown in the peper.展开更多
基金The project supported by the National Natural Science Foundation of China (19889209)Russian Foundation for Basic Research (97-02-16943)
文摘Heat and mass transfer of a porous permeable wall in a high temperature gas dynamical flow is considered. Numerical simulation is conducted on the ground of the conjugate mathematical model which includes filtration and heat transfer equations in a porous body and boundary layer equations on its surface. Such an approach enables one to take into account complex interaction between heat and mass transfer in the gasdynamical flow and in the structure subjected to this flow. The main attention is given to the impact of the intraporous heat transfer intensity on the transpiration cooling efficiency.
文摘A self-similar solution of unsteady mixed convection flow on a rotating cone embedded in a porous medium saturated with a rotating fluid in the presence of the first and second orders resistances has been obtained. It has been shown that a self-similar solution is possible when the free stream angular velocity and the angular velocity of the cone vary inversely as a linear function of time. The system of ordinary differential equations governing the flow has been solved numerically using an implicit finite difference scheme in combination with the quasi-linearization technique. Both prescribe wall temperature and prescribed heat flux conditions are considered. Numerical results are reported for the skin friction coefficients, Nusselt number and Sherwood number. The effect of various parameters on the velocity, temperature and concentration profiles are also presented here.
基金The project supported by the National Natural slence Foundatlonof吼na and ShangdongProvince.
文摘Based on the transport mechanism of heat and mass transfer and by using the minimum gradient theory for unsaturated flow in capillary porous media, a mathematical model is developed for heat and mass transfer in unsaturated wet porous media considering the effect of capillary hysteresis. The heat and mass transport properties in the derived differential equations are analyzed in detail. which opens new way to further develop practical methods for determining heat and mass transport properties in wet porous media.
文摘Drying of the banana in the hot water has a negative impact on the quality of the product and drying effect. The purposes of this study are increasing the drying rate, using the relatively low temperature to improve the quality (40℃, 50℃ and 60℃) and investigate the use of electromagnetic waves to increase the drying speed. Therefore, experiments are performed using 5 kHz,10 kHz and 15 kHz low frequency electromagnetic waves in the air velocity values of 0.5 m/s, 1 m/s, 1.5 m/s and 2 m/s and 40℃, 50℃, 60℃ centigrade degrees of air blast in a special compartment. Mathematical model of the drying process has been created as using the electrical circuits methods and experimental results. As a result, a simple equation describing the drying process has been obtained. Nonlinear expression of the diffusion coefficient for a different situation in this equation has been identified for the first time. The obtained theoretical results and experimental results have been provided a good agreement. This study is considered to be useful for all studies in the drying area.
文摘Penetration of chemicals in the soil ground through irrigation water or rainfall induces important risks for the environment. These risks are badly known and may lead to direct contamination of the environment (atmosphere or ground water) or harmful effects on organisms living at ground level, indirectly affecting men. It is thus necessary to estimate these potential chemical risks on the environment. For that reason, the gradual change of these products (fertilizers, solutions, pollutants, ...) in the ground has been the subject of a lot of recent research works, based in particular on the study of non-saturated porous media in a theoretical, numerical or experimental way. Most of these works are incomplete and, in order to simplify the problem, they don’t take into accounts some process, which may be of prime importance under particular natural conditions. Complexity of such studies results from their multidisciplinary nature. In this communication, we study simultaneous transport of pollutant, the water that provides transport and the heat transfer in a 200 cm long cylindrical column full of sand taken as a non-saturated porous medium. We consider two kinds of conditions on the temperature at the column surface: the case of constant temperature and the case of sinusoidal temperature. We evaluate the influence of this temperature on the transfers. This study is purely numerical. We use the control volume method to determine hydrous, thermal and pollutant concentration profiles.
基金the Program for New Century Excellent Talents in Universities(No.NCET-13-0651)。
文摘Experiments with potatoes were carried out in order to analyze the variation of the temperature and the mean dry basis moisture content over time,the effect of the drying conditions on the drying rate,and the relationship between deformation and dry basis moisture content.A two-way sequentially coupled thermo-hydro-mechanical math model was developed on the basis of Fickian diffusion theory,Fourier’s law of heat conduction and thermoelasticity mechanics in order to analyze the spatio-temporal distributions of moisture,temperature and drying stresses in the potatoes.The transient mathematical model,composed of a system of partial differential equations,was solved by finite difference methods.The numerical results obtained by using the mathematical model were in good agreement with the experimental data.The variations in temperature and moisture distributions,drying curves and stresses within potatoes over time were simulated,and the ways in which these are affected by the drying conditions were discussed.This work could help in developing an understanding of the relationship between mass and heat transfer,shrinkage,stress,and physical degradation of biological materials.
文摘This paper studies the thermal-diffusion and diffusion thermo-effects in the hydro-magnetic unsteady flow by a mixed convection boundary layer past an imperme- able vertical stretching sheet in a porous medium in the presence of chemical reaction. The velocity of t^he stretching surface, the surface temperature, and the concentration are assumed to vary linearly with the distance along the surface. The governing partial differential equations are transformed into self-similar unsteady equations using similarity transformations .and solved numerically by the Runge-Kutta fourth order scheme in as- sociation with the shooting method for the whole transient domain from the initial state to the final steady state flow. Numerical results for the velocity, the temperature, the concentration, the skin friction, and the Nusselt and Sherwood numbers are shown graph- ically for various flow parameters. The results reveal that there is a smooth transition of flow from unsteady state to the final steady state. A special case of our results is in good agreement with an earlier published work.
文摘A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.
文摘The coupling of temperature gradient and concentration gradient and it's effects on heat and mass transfer are considered for natural convection in a porous enclosure. By use of the penalty finite element method, the distributions of flow, temperature and concentration fields are numerically simulated in four kinds of boundary condition. The profiles of heat and mass transfer coefficients along with the vertical wall are shown in the peper.
