scholarly journals Features of heat and mass transfer at drying of ceramic products with overglaze paints

2021 ◽  
pp. 7-12
Author(s):  
O.M. Nedbailo ◽  
O.G. Chernyshyn
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Heat And Mass Transfer ◽  
Heat Flux Density ◽  
Heat Dissipation ◽  
Mass Transfer Process ◽  
Drying Process ◽  
Air Velocity ◽  
The Heat Transfer Coefficient

The basic results of researches of process of a heat exchange are instanced and parsed at drying glasour ceramic colors. Character of change of importance number of Rebinder is established at drying colors and dependence of intensity of a heat dissipation on velocity of air is spotted. The main results of researches of heat and mass transfer process at drying of overglaze ceramic paints in a stream of drying agent are resulted and analyzed. The nature of the change in the value of the Rebinder number for drying paints is established and the dependence of the heat transfer intensity on the air velocity is determined. Analysis of the temperature coefficient of drying and Rebinder's number determined the directions of heat consumption in the drying process of overglaze ceramic paints. It is established that the heat flux density depends on the temperature and velocity of the coolant and does not depend on the chemical composition of the paints. It is shown that the heat transfer coefficient depends on the velocity of the coolant. Compared with heat transfer during laminar flow around the plate during drying, the intensity of heat transfer increases by 75%.

Heat and Mass Transfer Processes and the Performance Evaluation in Single-Slope Solar Stills

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
David A. Aderibigbe
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Glass Cover ◽  
Transfer Processes ◽  
Mass Transfer Processes ◽  
Basin Water ◽  
The Heat Transfer Coefficient

The paper reviews the present understanding of the analysis of the heat and mass transfer processes in single-slope solar stills. By using the results of published experiments, it is proposed that the heat and mass transfer phenomena from the basin water to the glass cover are coupled. This coupling makes it possible to derive the dependence of the heat transfer coefficient for condensation on the inclination of the glass cover of the still. The derived relation, i.e., Nucon = 0.738 (Grcon*Prcon*sin β/Ja*)¼ A−1 where A is the aspect ratio, has been demonstrated to be an important expression for predicting the heat transfer coefficient for condensation hcon necessary for a more realistic evaluation of the overall efficiency of single-slope solar still of a given cover angle β.

Numerical Study on Heat and Mass Transfer of Plate Falling Film Absorber with Wire-Meshed Fins

2012 ◽  
Vol 204-208 ◽  
pp. 4305-4314
Author(s):  
Jing Jing Zhang ◽  
Dan Dan Zhao ◽  
Lu Chun Wan ◽  
Bao Huai Zhang ◽  
Ya Ping Chen
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Absorption Rate ◽  
Numerical Study ◽  
Mass Transfer Process ◽  
Falling Film ◽  
Better Than

A mathematical model of heat and mass transfer process in plate falling film absorber with wire-meshed fins was developed. The model could predict temperature and concentration distribution as well as the solution side heat transfer coefficient and the absorption rate. The results verify that heat and mass transfer performance of the plate falling film absorber with wire-meshed fins is better than the past absorber. Compared with the plate falling film absorber without fins, heat transfer coefficient of the absorber in this article increases 1.06 times and the absorption rate increases 2.32 times.

Heat and Mass Transfer Characteristics of a Finned-Tube Evaporator Under Frosting Conditions

2001 ◽  
Author(s):  
Y. H. Kim ◽  
Y. J. Park ◽  
Y. C. Kim ◽  
S. C. Shim ◽  
S. K. Oh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Air Temperature ◽  
Early Stage ◽  
Finned Tube ◽  
Airflow Rate ◽  
Air Velocity ◽  
Frost Formation ◽  
Transfer Characteristics

Abstract An experimental study was performed to investigate the heat and mass transfer characteristics of a finned-tube evaporator coil utilized in a domestic refrigerator under frosting conditions. Airside heat transfer coefficient was measured as a function of air temperature, humidity ratio, air velocity, and evaporating temperature. In addition, frost thickness was monitored and measured by visualization tests during frosting operation. Based on the experimental results, the degradation of heat transfer performance due to frost formation was explored as a function of operating parameters. The rate of frost formation on the evaporator increases at relatively high humidity, high airflow rate, low inlet air temperature and low refrigerant temperature. As the frost thickness increases, airflow rate gradually decreases, while the capacity increases at the early stage of frost formation and then significantly drops.

Heat Transfer and Air Diffusion Phenomena in a Bed of Polymer Powder Using Apparent Heat Capacity Method: Application to the Rotational Molding Process

2007 ◽  
Author(s):  
M. Boutaous ◽  
E. Pe´rot ◽  
A. Maazouz ◽  
P. Bourgin ◽  
P. Chantrenne
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Heat And Mass Transfer ◽  
Granular Media ◽  
Transfer Model ◽  
Melting Front ◽  
Polymer Powder ◽  
Air Diffusion

The process of rotational moulding consists in manufacturing plastic parts by heating a polymer powder in a biaxial rotating mould. In order to optimise the production cycle of this process, a complete simulation model has to be used. This model should describe the phenomena of heat and mass transfer in a moving granular media with phase change, coalescence, sintering, air evacuation and crystallization during the cooling stage. This paper focus on the study of heat and mass transfer in a quiescent polymer powder during the heating stage. An experimental device has been built. It consists in an open plane static mold on which an initial thickness, e, of a polymer powder is deposited. This powder is then heated until it melts. An inverse heat conduction method is used to determine the heat flux and temperature at the interface between the mold and the powder. This interfacial heat flux is taken as a boundary condition in a numerical heat transfer model witch takes into account the heat transfer in granular media with phase change, coalescence, sintering, air bubbles evacuation and rheological behaviour of the polymer. For the numerical simulation of the heat transfer, the apparent specific heat method is used. This approach allows to solve the same energy equation for all the material phases, so one do not have to calculate the melting front evolution. This fine modelling, close to the real physical phenomena makes it possible to estimate the temperature profile and the evolution of the polymer powder characteristics (phase change, air diffusion, viscosity, evolution of the thermophysical properties of the equivalent homogeneous medium, thickness reduction, air volume fraction...). Several results are then presented, and the influence of different parameters, like the thermal contact resistance, the process initial conditions and the polymer’s rheological characteristics are studied and commented. Indeed the predictions of the temperature rises in the polymer bed, agree well with the experimental measurements.

An Inverse Method for Drying at High Mass Transfer Biot Number

2003 ◽  
Author(s):  
Gligor H. Kanevce ◽  
Ljubica P. Kanevce ◽  
George S. Dulikravich ◽  
Marcelo J. Colac¸o
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Biot Number ◽  
Temperature Sensitivity ◽  
Sensitivity Coefficient ◽  
The Heat Transfer Coefficient

The inverse problem of using temperature measurements to estimate the moisture content and temperature-dependent moisture diffusivity together with the heat and mass transfer coefficients is analyzed in this paper. In the convective drying practice, usually the mass transfer Biot number is very high and the heat transfer Biot number is very small. This leads to a very small temperature sensitivity coefficient with respect to the mass transfer coefficient when compared to the temperature sensitivity coefficient with respect to the heat transfer coefficient. Under these conditions the relative error of the estimated mass transfer coefficient is high. To overcome this problem, in this paper the mass transfer coefficient is related to the heat transfer coefficient through the analogy between the heat and mass transfer processes in the boundary layer. The resulting parameter estimation problem is then solved by using a hybrid constrained optimization algorithm OPTRAN.

scholarly journals Characteristics of supercritical heat transfer during filmboiling of nanofluids on a vertical heated wall

2018 ◽  
pp. 29-35
Author(s):  
А. Avramenko ◽  
M. Kovetskaya ◽  
A. Tyrinov ◽  
Yu. Kovetska
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Heat Flux ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Heated Surface ◽  
Heated Wall ◽  
Film Boiling

Nanofluid using for intensification of heat transfer during boiling are analyzed. The using boiling nanofluids for cooling high-temperature surfaces allows significantly intensify heat transfer process by increasing the heat transfer coefficient of a nanofluid in comparison with a pure liquid. The properties of nanoparticles, their concentration in the liquid, the underheating of the liquid to the saturation temperature have significant effect on the rate of heat transfer during boiling of the nanofluid. Increasing critical heat flux during boiling of nanofluids is associated with the formation of deposition layer of nanoparticles on heated surface, which contributes changing in the microcharacteristics of heat exchange surface. An increase in the critical heat flux during boiling of nanofluids is associated with the formation of a layer of deposition of nanoparticles on the surface, which contributes to a change in the microcharacteristics of the heat transfer of the surface. Mathematical model and results of calculation of film boiling characteristics of nanofluid on vertical heated wall are presented. It is shown that the greatest influence on the processes of heat and mass transfer during film boiling of the nanofluid is exerted by wall overheating, the ratio of temperature and Brownian diffusion and the concentration of nanoparticles in the liquid. The mathematical model does not take into account the effect changing structure of the heated surface on heat transfer processes but it allows to evaluate the effect of various thermophysical parameters on intensity of deposition of nanoparticles on heated wall. The obtained results allow to evaluate the effect of nanofluid physical properties on heat and mass transfer at cooling of high-temperature surfaces. The using nanofluids as cooling liquids for heat transfer equipment in the regime of supercritical heat transfer promotes an increase in heat transfer and accelerates the cooling process of high-temperature surfaces. Because of low thermal conductivity of vapor in comparison with the thermal conductivity of the liquid, an increase in the concentration of nanoparticles in the vapor contributes to greater growth in heat transfer in the case of supercritical heat transfer.

scholarly journals Analysis of heat and mass transfer mechanism of vacuum freeze-drying in the primary drying

2007 ◽  
Vol 3 (2) ◽  
pp. 183-191
Author(s):  
Hua Li ◽  
Lihua Li ◽  
Xingli Jiao ◽  
Xueli Qin
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transfer Process ◽  
Present Status ◽  
Freeze Drying ◽  
Mass Transfer Process ◽  
Transfer Mechanism ◽  
Drying Process ◽  
Mass Transfer Mechanism ◽  
At Home

The freeze-drying process is a complex heat and mass transfer process virtually. The drying process of freeze-drying is not only the key stage which decides the success of freeze-drying, but also the most difficult stage to control. There are lots of papers about heat and mass transfer in vacuum freeze drying at home and abroad. The present status of research on heat and mass transfer during vacuum freeze drying in the primary drying is summed up and analyzed, the trend of research in this field is discussed in this paper.

scholarly journals Mathematical model of vacuum freeze-drying in the secondary drying

2007 ◽  
Vol 3 (2) ◽  
pp. 192-196
Author(s):  
Hua Li ◽  
Lihua Li ◽  
Xingli Jiao ◽  
Xueli Qin
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transfer Process ◽  
Present Status ◽  
Freeze Drying ◽  
Mass Transfer Process ◽  
Drying Process ◽  
Secondary Drying ◽  
At Home

The freeze-drying process is a complex heat and mass transfer process virtually. The drying process of freeze-drying is not only the key stage which decides the success of freeze-drying, but also the most difficult stage to control. There are lots of papers about heat and mass transfer in vacuum freeze drying at home and abroad. The present status of research on heat and mass transfer during vacuum freeze drying in the secondary drying is summed up and analyzed, and the trend of research in this field is discussed in this paper.

Using Direct Simulation Monte Carlo With Improved Boundary Conditions for Heat and Mass Transfer in Microchannels

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
J. Yang ◽  
J. J. Ye ◽  
J. Y. Zheng ◽  
I. Wong ◽  
C. K. Lam ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Heat And Mass Transfer ◽  
Wall Temperature ◽  
Gas Flow ◽  
Wall Heat Flux ◽  
Entrance Region ◽  
Mass Flowrate

Micro-electromechanical systems and nano-electromechanical systems have attracted a great deal of attention in recent years. The flow and heat transfer behaviors of micromachines for separation applications are usually different from that of macro counterparts. In this paper, heat and mass transfer characteristics of rarefied nitrogen gas flows in microchannels are investigated using direct simulation Monte Carlo with improved pressure boundary conditions. The influence of aspect ratio and wall temperature on mass flowrate and wall heat flux in microchannels are studied parametrically. In order to examine the aspect ratio effect on heat and mass transfer behaviors, the wall temperature is set constant at 350 K and the aspect ratio of the microchannel varies from 5 to 20. The results show that as the aspect ratio increases, the velocity of the flow decreases, so does the mass flowrate. In a small aspect ratio channel, the heat transfer occurs throughout the microchannel; as the aspect ratio of the microchannel increases, the region of thermal equilibrium extends. To investigate the effects of wall temperature (Tw) on the mass flowrate and wall heat flux in a microchannel, the temperature of the incoming gas flow (Tin) is set constant at 300 K and the wall temperature varies from 200 K to 800 K while the aspect ratio is remained unchanged. Results show that majority of the wall heat flux stays within the channel entrance region and drops to nearly zero at the halfway in the channel. When Tw<Tin, under the restriction of pressure-driven condition and continuity of pressure, the molecular number density of the flow decreases along the flow direction after a short increase at the entrance region. When Tw>Tin, the molecular number density of the flow drops rapidly near the inlet and the temperature of the gas flow increases along the channel. As Tw increases, the flow becomes more rarefied, the mass flowrate decreases, and the resistance at the entrance region increases. Furthermore, when Tw>Tin, a sudden jump of heat transfer flux and temperature are observed at the exit region of the channel.

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