Heat Mass Transfer Model Research Articles

Dynamic Interactions: Non-Integer-Order Heat-Mass Transfer in Magnetohydrodynamic Flow of Non-Newtonian Fluid over Inclined Plates

The heat and mass transfer phenomenon in the presence of a moving magnetic field has a wide range of applications, spanning from industrial processes to environmental engineering and energy conversion technologies. Understanding these interactions enables the optimization of various processes and the development of innovative technologies. This manuscript is about a non-integer-order heat-mass transfer model for Maxwell fluid over an inclined plate in a porous medium. The MHD flow of non-Newtonian fluid over the plate due to the natural convection of the symmetric temperature field and general motion of the inclined plate is investigated. A magnetic field is applied with a certain angle to the plate, and it can either be fixed in place or move along with the plate as it moves. Our model equations are linear in time, and Laplace transforms form a powerful tool for analyzing and solving linear DEs and systems, while the Stehfest algorithm enables the recovery of original time domain functions from their Laplace transform. Moreover, it offers a powerful framework for handling fractional differential equations and capturing the intricate dynamics of non-Newtonian fluids under the influence of magnetic fields over inclined plates in porous media. So, the Laplace transform method and Stehfest’s numerical inversion algorithm are employed as the analytical approaches in our study for the solution to the model. Several cases for the general motion of the plate and generalized boundary conditions are discussed. A thorough parametric analysis is performed using graphical analysis, and useful conclusions are recorded that help to optimize various processes and the developments of innovative technologies.

Influence of particle parameters on the melting/migration of silicon particles and turbulent heat transfer during CCZ monocrystalline silicon growth

The Continuous Czochralski (CCZ) is a promising approach for preparing low-cost high-quality monocrystalline silicon in the photovoltaic field. To investigate the coupled mechanism of silicon particles melting/migration and melt turbulent heat transfer during the CCZ monocrystalline silicon growth, based on the Euler–Lagrange framework, a three-dimensional transient heat-mass transfer model is developed using the LES method considering the heat exchange between the silicon particles and the silicon melt as well as the particles size change. In addition, we investigated the effects of key silicon particle parameters such as feeding temperature, particle size and feeding speed, on the silicon particles melting/migration and melt turbulent heat transfer. The results show that appropriately increasing the feeding temperature and speed contributes to achieve more concentrated particles distribution and weaken the movement of silicon particles towards the crystalline interface simultaneously, which conduce to eliminate the adverse impact of continuous feeding on monocrystalline silicon growth. And the feeding temperature has a great effect on the temperature fluctuation near the crystalline interface. In addition, when the feeding speed exceeds 1.5m/s, increasing feeding speed has no significant effect on the particles distribution and melting process. Besides, the feeding particle size has a significant effect on the maximum penetration depth of particles. The small silicon particles prefer moving to the crystalline interface driven by thermophoretic force, which is detrimental to the high-quality CCZ monocrystalline silicon growth.

A ventilated wall integrated with heating/catalytic blinds: Catalyst, system design and performance study

A Trombe wall with thermal catalytic blinds (TC-Blind/TW) for indoor heating/cooling, air purification and shading was proposed. In this paper, we has fully explored the advancement and feasibility of the system from thermal catalytic material preparation and performance testing, system construction and system steady state experiment testing, system heat-mass transfer model establishment and verification, and finally to the analysis of system operation strategy. The main conclusions are as follows: Firstly, thermal catalytic material MnOx-CeO2 behaved excellent heating and purification performance, the formaldehyde degradation followed L-H model. Secondly, the thermal efficiency and formaldehyde single-through conversion of system during the daytime were between 35%-55% and 32%–42%, respectively. Thirdly, the established heat-mass transfer model had the high accuracy, with the maximum RSMD of 0.8%. Finally, the blinds turning angle has a great influence on the system performance, then the optimal annual operation angles in four cities were suggested. Take Beijing as an example, the annual generated clean air was 11355.6 m3/m2, the reduced heating and cooling loads were 341.2 and 318.3 MJ/m2, respectively.

Optimal reinforcement for improving the thermal performance of a permafrost tunnel based on coupled heat-mass transfer

Over 80% of cold-region tunnels (CRTs) suffer from heavy periodic freeze–thaw actions, and therefore, their normal safe operations cannot be guaranteed. To mitigate freeze–thaw damage to CRTs, thermal insulation layers (TILs) were used to prevent external heat from penetrating the surrounding rock of CRTs. TILs were often laid between two linings of CRTs with a uniform thickness along the whole tunnel based on a single thermal conduction calculation or engineering analogy method, which was not only uneconomical but also unsafe. Thus, freeze–thaw damage still occurred at the entrance of the CRTs. To solve this engineering problem, we took the Fenghuoshan Tunnel in permafrost regions as an example and proposed a coupled heat-mass transfer model based on mass, energy and momentum conservation principles. The numerical model was indicated to be accurate by comparing the computed and monitored temperatures. The subsequent numerical results show that the heat and mass exchanges between the air inside the tunnel and tunnel wall make the air velocities vary with seasonal alternation, and therefore, temperatures of the surrounding permafrost exhibit evident differences on the temporal and spatial scales, according to which the most unfavorable position and time point are selected to design an optimal reinforcement for improving the thermal performance. Based on a series of heat-mass transfer simulations with different thicknesses of aerogel felt, an optimal changeable thickness of aerogel felt along the whole tunnel is obtained to improve the thermal performance of the Fenghuoshan Tunnel. If the permafrost tunnel is reinforced by this approach, the highest temperatures of the surrounding permafrost near the tunnel are less than approximately −0.44 °C, implying that the optimal reinforcement is effective and can control the freeze–thaw damage of the Fenghuoshan Tunnel. This study provides theoretical support for designing a safe and economical reinforcement on permafrost tunnels and understanding the coupled heat-mass transfer processes in tunnels.

A thermal modification technique combining bulk densification and heat treatment for poplar wood with low moisture content

This study aimed to obtain the most suitable process parameters of the bulk densification and heat treatment for the modification of poplar wood with a moisture content of approximately 3–5%. Based on the heat-mass transfer model, the best preheating temperature and time for the bulk densification process were 180 °C and 361 s, respectively. The optimal heat treatment temperature and time were 190 ℃ and 3 h, respectively. The resultant wood samples exhibited the highest storage modulus and the lowest loss factor, indicating that this kind of wood product has a long service life, suitable for solid wood flooring applications.

Modelling the cooling energy saving potential of facade greening in summer for a set of building typologies in mid-latitudes

Densely populated city quarters lacking green increase the urban heat island effect and thermal discomfort outdoors and indoors. Facade greenings (FG) cool buildings and their surroundings through shading, insulation and transpiration, as demonstrated experimentally. FG also reduces energy consumption for building cooling. Because of complex interrelationships, to assess the performance of FG towards different buildings is not trivial.Therefore, a validated numerical heat-mass transfer model is proposed and applied to describe the energy saving potential of a one-layered FG for nine wall compositions representing relevant building types, climatic conditions in Berlin, Germany and Ljubljana, Slovenia and the south- and westward exposition. The buildings represent several functions and a range of wall insulation levels. For each scenario, temperatures and energy in- and outflows are calculated from June to September (20-year average).FG can reduce exterior and interior wall temperatures by up to 17 K and 2.9 K, respectively. For the whole period, energy savings range from 2 to 16 kWh m–2 depending on building and climate. Results show that both, level of insulation, thermal inertia, exposition and climatic conditions must be considered when predicting FG’s energy saving potential for buildings. The introduced model (http://dx.doi.org/10.14279/depositonce-10512) can be used to predict cooling performances and to identify priority buildings for FG implementation in cities.

Modeling and simulation of heat-mass transfer and its application in wood thermal modification

Abstract Wood is a type of renewable and natural material, with most of its end application related to building materials. However, hygroexpansion and anisotropy in wood markedly shorten its service life and value. In this study, wood thermal modification was used to improve wood quality, and a heat-mass transfer model was established based on practical production process. The software COMSOL Multiphysics was used to solve this coupling transfer model. Relationships between temperature and moisture content, temperatures of the medium under thermal treatment, and treatment time, were established. Results indicated that this coupling model and method can be used to simulate and solve heat-mass transfer during wood thermal treatment, and the simulation results were found to be consistent with the measured results. The temperatures at the wood surface could achieve the target temperature within a considerably short time, whereas that at the wood central point was difficult to obtain. The cross-section of the heat convection boundary obtained the highest temperature and the lowest moisture content, whereas the cross-section of the symmetry boundary obtained the lowest temperature and the highest moisture content. These results can be used to devise a wood thermal treatment schedule, determine the heat and moisture distribution, and control the wood heat treatment process. Consequently, guidance for wood thermal treatment is provided to reduce energy and time consumption.

Modeling of Heat Mass Transfer in High-Temperature Reacting Flows with Combustion

A multiprocessor computer system suitable for physical, mathematical, and chemical models, as well as an exact method for the solution of a system of differential equations that describe the actual combustion of a pulverized coal flare, are necessary to study the numerically complex, physicochemical processes occurring in the combustion chambers of power plants. The results of numerical simulation can provide quite a high accuracy. However, the task of setting up a physical and mathematical model with the correct initial and boundary conditions has yet to be completed. In this paper, we studied heat and mass transfer in high-temperature reacting flows during the burning of Karaganda coal in the combustion chamber of an actual power boiler of a thermal power plant in Kazakhstan. The optimal conditions for computational experiments that correspond to real combustion processes are determined.

Understanding the influence of microwave on the relative volatility used in the pyrolysis of Indonesia oil sands

Abstract In this paper, pyrolysis of Indonesian oil sands (IOS) was investigated by two different heating methods to develop a better understanding of the microwave-assisted pyrolysis. Thermogravimetric analysis was conducted to study the thermal decomposition behaviors of IOS, showing that 550 °C might be the pyrolysis final temperature. A explanation of the heat–mass transfer process was presented to demonstrate the influence of microwave-assisted pyrolysis on the liquid product distribution. The heat–mass transfer model was also useful to explain the increase of liquid product yield and heavy component content at the same heating rate by two different heating methods. Experiments were carried out using a fixed bed reactor with and without the microwave irradiation. The results showed that liquid product yield was increased during microwave induced pyrolysis, while the formation of gas and solid residue was reduced in comparison with the conventional pyrolysis. Moreover, the liquid product characterization by elemental analysis and GC–MS indicated the significant effect on the liquid chemical composition by microwave irradiation. High polarity substances (e > 10 at 25 °C), such as oxy-organics were increased, while relatively low polarity substances (e

Potassium-cobalt sulphate crystal growth assisted by low frequency vibrations

Single crystals of K2Co(SO4)2·6H2O were grown from solution using the temperature reduction method enhanced by the axial low frequency vibration control technique (AVC-technique). Physical modeling of heat-mass transfer in solution under the AVC action was performed. The growth rate of the AVC grown crystal was found to be twice that of the crystal grown under natural convection conditions. Analysis of spectral characteristics (absorption and Raman spectra) as well as structural properties (dislocation density and microhardness) of the grown crystals showed the significant superiority of the AVC technique for the growth of K2Co(SO4)2·6H2O crystals.

A hydrothermal model to assess the impact of green walls on urban microclimate and building energy consumption

Covering a building envelope with vegetation provides a solution capable of mitigating the urban heat island phenomenon and its impact on the energy consumption of buildings. Simulation tools to assess the efficiency of such a solution are lacking, especially for green walls. The present research aims to offer a hydrothermal model of green walls and green roofs for implementation in the urban microclimate simulation software SOLENE-Microclimate. To this end, a fast, efficient coupled heat–mass transfer model has been developed. Simulation results are compared with experimental data obtained from the LEEA Laboratory in Geneva for three green wall samples. Aside from the level of uncertainty found for the evapotranspiration calculation, these results confirm that the model accurately characterizes the temperature evolution of all three prototypes. Results also show good correlation between measured and simulated temperatures. The model is indeed able to reproduce water stress and characterize various types of living walls.

Modeling of heat-mass transfer in porous cooling systems during phase transformations

The interaction of a porous cooling system and a high-enthalpy gas flow is considered. The effect of the phase transformation on the heat-mass exchange characteristics in a heat-resisting material is investigated.

Experimental and numerical modeling of Czochralski crystal growth under axial vibrational control of the melt

A novel scheme of application of axial vibration control (AVC) technique for Czochralski crystal growth has been realized by means of oscillating baffle submerged under the growing crystal. Modeling of heat-mass transfer in the growth system has been produced by both physical experiments with water–glycerol mixture and computer simulations using FLUENT software. The laminar vibrational flows, which suppressed thermoconvectional flows, have been arranged in the proposed AVC configuration. The vibrational flows were stable and well controlled in the viscosity range 1–400 cPz, whenever the crystal–melt interface was under or over the melt surface. The direction of the vibrational flows was favorable for crystal growth. Simulations demonstrated that the shape of the crystal–melt interface is strongly dependent on vibrational parameters.

Performance Deteriorations from Flow Maldistribution in Air-to-Air Heat Exchangers: A Parallel-Plates Membrane Core Case

Parallel-plates membrane cores have been widely used in air-to-air heat exchangers for fresh air heat and moisture recovery, which are also called total heat exchangers. Flow maldistribution and the consequent performance deteriorations are of great interest. The flow maldistribution is predicted with a CFD code, by treating the parallel-plates core as a two-dimensional porous media. Then, a coupled heat and moisture transfer model between the two air flows in the parallel-plates channels is set up. Using the CFD predicted flow distribution data on core face, the sensible heat and moisture exchange effectiveness and the performance deterioration factors are calculated with finite-difference scheme. Experiments are performed to validate the heat mass transfer model. The results indicate that for the current structure, when the channel pitch is below 2.0 mm, the flow distribution is quite homogeneous and the sensible and latent performance deteriorations due to flow maldistribution are below 9% and can be neglected. However, when the channel pitch is larger than 2 mm, the maldistribution is quite large and the consequent thermal and latent performance can be deteriorated by 28%. The flow maldistribution the consequent thermal and latent effectiveness deteriorations for parallel-plates cores are more serious than those for plate-fin cores previously reported.

Heat mass transfer model of fouling process of calcium carbonate on heat transfer surface

A new heat mass transfer model was developed to predict the fouling process of calcium carbonate on heat transfer surface. The model took into account not only the crystallization fouling but also the particle fouling which was formed on the heat transfer surface by the suspension particles of calcium carbonate in the supersaturated solution. Based on experimental results of the fouling process, the deposition and removal rates of the mixing fouling were expressed. Furthermore, the coupling effect of temperature with the fouling process was considered in the physics model. As a result the fouling resistance varying with time was obtained to describe the fouling process and the prediction was compared with experimental data under same conditions. The results showed that the present model could give a good prediction of fouling process, and the deviation was less than 15% of the experimental data in most cases. The new model is credible to predict the fouling process.

Investigations on transient directional solidification under microgravity on sounding rocket missions

Transient growth conditions are common to a variety of technical solidification processes and lead to modified materials properties. In directional solidification the microstructure at the solid-liquid interface of an alloy is a result of the interaction of diffusive and convective heat and mass transport in the bulk and of interface and thermophysical properties. We have carried out experiments under diffusive conditions without convection in microgravity during the sounding rocket missions TEXUS-36 and 40. The used transparent alloy succinonitrile-acetone freezes like metals and the solidification process was observed in-situ. Within a gradient furnace the solid-liquid interface is forced to move accelerated and to transform from planar into cellular and dendritic structures. The dynamics of the planar interface and of the spacing and the amplitude of diffusive grown cells and dendrites were observed directly with cameras and analyzed. A comparison of the TEXUS-40 results to predictions taken from a macroscopic thermal model, a coupled heat-mass transfer model and a phase-field model was carried out. A good agreement is found for the planar interface dynamics for the coupled heat-mass transfer model and the phase-field model, when using additional information from the thermal modelling. In the cellular and dendritic growth regime typical microstructure features can be reproduced by the phase-field model. The experimental results thus serve as important bench-marks for the validation of numerical models describing time-dependent solidification processes.

Comparison between heat transfer and heat mass transfer models for transportation process in an adsorbent bed

The heat and mass transfer (HMT) model for transportation process in adsorbent bed is studied in relation to heat transfer (HT) model, which is dependent on assumptions such as the conduction dominance and negligible mass transfer resistance. Two general criteria are generated by performing an order of magnitude analysis to determine when the HT model can be applied in practical situation as a good approximation in the evaluation of the temperature field as well as dimensionless uptake and the criteria are validated with the numerical results. It is seen that the criterion for conduction dominance (CR1) is usually satisfied for all practical situations, but the criterion towards negligible mass transfer resistance (CR2) turns out to be more important for the selection of an appropriate model.

Magma dynamics at the base of an evolving mafic magma chamber: Incompatible element evidence from the Partridge River intrusion, Duluth Complex, Minnesota, USA

A characteristic feature of the Partridge River intrusion of the Keweenawan Duluth Complex is the approximately fivefold to ninefold increase in the concentrations of incompatible elements in the lower zone compared with cumulates stratigraphically higher. The concentrations of incompatible elements decrease from the lower zone upward to steady state values, which is ascribed to variations in the proportions of trapped liquid rather than variable degrees of fractional crystallization of a single parental magma. The calculated average composition of trapped liquid using our algorithm is similar to typical Keweenawan low-alumina, high TiP basalts associated with the Duluth Complex but is different from the leading edge ferrodioritic liquid quenched in the chilled margin of the intrusion. This difference suggests that the chilled margin does not represent the original (parental) magma composition from which the whole intrusion solidified, and that the enrichment of incompatible elements may be related to the local flotation of magmatic suspensions. To test the latter hypothesis numerically, we have used heat-mass transfer models, assuming a sheet-like magma chamber, to calculate the parameters of the model that best reproduce the observed distribution of incompatible elements in a mush zone at the base of the Partridge River intrusion. The results indicate that a mush zone enriched in the incompatible elements is produced if the velocity of movement of the lower solidification front into the magma body was less than the floating velocity of the bulk crystal mush. The dynamic parameters that best reproduce the observed distribution of incompatible elements include a magma emplacement pressure of 2 kbar, critical crystallinities of 50–68% in the mush zone from which the liquid is being expelled, and an emplacement temperature of ∼ 1160°C for the initial magma.