scholarly journals Mathematical Simulation of Temperature Profiles within Microwave Heated Wood Made for Wood-Based Nanocomposites

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Xianjun Li ◽  
Yongfeng Luo ◽  
Hongbin Chen ◽  
Xia He ◽  
Jianxiong Lv ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Microwave Heating ◽  
Wood Surface ◽  
Temperature Profiles ◽  
Thickness Direction ◽  
Heating Method ◽  
Microwave Pretreatment ◽  
Microwave Transmission ◽  
Modify Wood

High intensive microwave pretreatment is a new method to modify wood for the fabrication of wood-based nanocomposites. Based on the physical law on heat transfer, a mathematical model to describe the temperature profiles within wood heated by high intensive microwave was established and simulated in this research. The results showed that the temperature profiles within wood were related to microwave heating methods; The temperature inside wood firstly increased and then gradually decreased along the direction of microwave transmission when the unilateral microwave heating was applied, and the temperature difference along the thickness direction of wood was very significant; The temperature with wood firstly increased and then gradually decreased from the wood surface to interior when the bilateral microwave heating was applied. Compared with the unilateral microwave heating, bilateral microwave heating is a better microwave heating method for the more uniform wood microwave pretreatment.

A mathematical model for chemical vapor infiltration with microwave heating and external cooling

1991 ◽  
Vol 6 (4) ◽  
pp. 810-818 ◽  
Author(s):  
Deepak Gupta ◽  
James W. Evans
Keyword(s):  
Mathematical Model ◽  
Microwave Heating ◽  
Microwave Power ◽  
Heterogeneous Reaction ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Temperature Profiles ◽  
External Cooling ◽  
Structure Equations ◽  
Vapor Infiltration

A mathematical model has been used to compute temperature profiles in ceramic preforms that are heated by microwaves. The temperature profiles were then input to a second part of the model describing chemical vapor infiltration of the preform, that is the diffusion of gaseous reactants, heterogeneous reaction, and evolution of the pore structure. Equations were solved numerically for parameters corresponding to the infiltration of SiC preforms by pyrolysis of trichloromethylsilane. While based on some simplifications, the model leads to the conclusion that infiltration proceeds more rapidly, and to a greater extent, with microwave heating/external cooling than in isothermal infiltration. The model suggests that infiltration might be optimized by manipulation of microwave power and external cooling. The computed extent of infiltration is seen to be very sensitive to the initial pore size.

Numerical and Experimental Study on Heat Transfer Process Under Microwave Irradiation Using Reflector to Enhance Energy Absorption Rate

2008 ◽  
Author(s):  
M. Kumja ◽  
Ng Kim Choon ◽  
Wai Soong Loh ◽  
Christopher Yap
Keyword(s):  
Heat Transfer ◽  
Dielectric Constant ◽  
Microwave Irradiation ◽  
Energy Saving ◽  
Microwave Heating ◽  
Energy Absorption ◽  
Absorption Rate ◽  
Low Dielectric Constant ◽  
Heating Method ◽  
Low Dielectric

With the energy saving concerns, microwave heating method becomes much attention in heating process of various applications. Depending on applicator geometry design, type of work load, and position in a microwave heating system, it can save energy 20% to 40% more than the energy consumed by a conventional heating method. However, it is difficult to achieve this energy saving for low dielectric constant workload that cannot perform as a self-dielectric resonator (DR) load. This paper aspires to propose a new method of inserting reflector into the low dielectric constant load to enhance energy absorption rate under the microwave irradiation process. The spatial electromagnetic fields (E-field and H-field) patterns of this workload and applicator were simulated with the commercial HFSS software. By using the Poynting vector theorem, the dissipation power intensity can be calculated from the electromagnetic field and it is integrated to the second order heat transfer equation. The numerical temperature distribution result was resemblance with the experimental result. From both numerical and experimental results, the energy absorption rate of workload can be improved obviously by using a reflector as compared to the rate without using the reflector for low dielectric constant.

Tire Bead Overheating in Urban Buses and Trucks Using Drum Brake Systems

1998 ◽  
Vol 26 (1) ◽  
pp. 51-62
Author(s):  
A. L. A. Costa ◽  
M. Natalini ◽  
M. F. Inglese ◽  
O. A. M. Xavier
Keyword(s):  
Heat Transfer ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Energy ◽  
Structural Integrity ◽  
Experimental Temperature ◽  
Temperature Profiles ◽  
Element Analysis ◽  
Drum Brake ◽  
Fea Model

Abstract Because the structural integrity of brake systems and tires can be related to the temperature, this work proposes a transient heat transfer finite element analysis (FEA) model to study the overheating in drum brake systems used in trucks and urban buses. To understand the mechanics of overheating, some constructive variants have been modeled regarding the assemblage: brake, rims, and tires. The model simultaneously studies the thermal energy generated by brakes and tires and how the heat is transferred and dissipated by conduction, convection, and radiation. The simulated FEA data and the experimental temperature profiles measured with thermocouples have been compared giving good correlation.

Design of the Blast Furnace Wall Structure Made of Efficient Materials. Part 4. Calculation Examples

2020 ◽  
Vol 786 (11) ◽  
pp. 30-34
Author(s):  
A.M. IBRAGIMOV ◽  
◽  
L.Yu. GNEDINA ◽  
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Blast Furnace ◽  
Boundary Value Problems ◽  
Transfer Process ◽  
Rational Design ◽  
Boundary Value ◽  
Heat Transfer Process ◽  
Furnace Wall ◽  
Time Interval

This work is part of a series of articles under the general title The structural design of the blast furnace wall from efficient materials [1–3]. In part 1, Problem statement and calculation prerequisites, typical multilayer enclosing structures of a blast furnace are considered. The layers that make up these structures are described. The main attention is paid to the lining layer. The process of iron smelting and temperature conditions in the characteristic layers of the internal environment of the furnace is briefly described. Based on the theory of A.V. Lykov, the initial equations describing the interrelated transfer of heat and mass in a solid are analyzed in relation to the task – an adequate description of the processes for the purpose of further rational design of the multilayer enclosing structure of the blast furnace. A priori the enclosing structure is considered from a mathematical point of view as the unlimited plate. In part 2, Solving boundary value problems of heat transfer, boundary value problems of heat transfer in individual layers of a structure with different boundary conditions are considered, their solutions, which are basic when developing a mathematical model of a non-stationary heat transfer process in a multi-layer enclosing structure, are given. Part 3 presents a mathematical model of the heat transfer process in the enclosing structure and an algorithm for its implementation. The proposed mathematical model makes it possible to solve a large number of problems. Part 4 presents a number of examples of calculating the heat transfer process in a multilayer blast furnace enclosing structure. The results obtained correlate with the results obtained by other authors, this makes it possible to conclude that the new mathematical model is suitable for solving the problem of rational design of the enclosing structure, as well as to simulate situations that occur at any time interval of operation of the blast furnace enclosure.

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

Comparative study of conventional and microwave heating of polyacrylonitrile-based fibres

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guozhen Zhao ◽  
Jianhua Liu ◽  
Lei Xu ◽  
Shenghui Guo
Keyword(s):  
Microwave Heating ◽  
Surface Defects ◽  
Energy Dispersive Spectrometer ◽  
Xrd Analysis ◽  
Economic Benefits ◽  
Heating Time ◽  
Oxidation Temperature ◽  
Conventional Heating ◽  
Heating Method ◽  
Molecular Arrangement

Abstract The effects of the conventional heating method and the microwave heating method on polyacrylonitrile-based fibres in the temperature range of 180–280 °C were investigated. Fourier transform infrared spectroscopy, X-ray wide-angle scattering, Raman spectroscopy, energy-dispersive spectrometer, scanning electron microscopy and bulk density were used to characterise the properties of the samples. Results show that the microwave heating method can shorten the pre-oxidation time, reduce pre-oxidation temperature and reduce the number of surface defects. The pre-oxidised fibres obtained by the microwave heating method exhibit not only good crystallite size but also a smooth surface. Atomic morphology and molecular arrangement are orderly inside the fibre. The FT-IR spectrum shows that the oxidation reaction occurs at 220 °C, and the CI value of PAN fibers stabilised by microwave heating is the larger than the fibers stabilised by conventional heating. XRD analysis shows that fibers stabilised by microwave heating have low stack domains. The SEM and Raman spectra indicate that hydrogen peroxide can improve the surface finish of the fibers and reduce defects. Microwave heating can reduce the pre-oxidation temperature by about 20 °C and shorten the heating time. The economic benefits of using this method are significantly improved.

Natural Convection From Protruding Heat Sources in a Channel

2003 ◽  
Author(s):  
Tunc Icoz ◽  
Qinghua Wang ◽  
Yogesh Jaluria
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Rayleigh Scattering ◽  
Convection Heat Transfer ◽  
Separation Distance ◽  
Natural Convection Heat Transfer ◽  
Temperature Profiles ◽  
Heat Sources ◽  
Convection Heat

Natural convection has important implications in many applications like cooling of electronic equipment due to its low cost and easy maintenance. In the present study, two-dimensional natural convection heat transfer to air from multiple identical protruding heat sources, which simulate electronic components, located in a horizontal channel has been studied numerically. The fluid flow and temperature profiles, above the heating elements placed between an adiabatic lower plate and an isothermal upper plate, are obtained using numerical simulation. The effects of source temperatures, channel dimensions, openings, boundary conditions, and source locations on the heat transfer from and flow above the protruding sources are investigated. Different configurations of channel dimensions and separation distances of heat sources are considered and their effects on natural convection heat transfer characteristics are studied. The results show that the channel dimensions have a significant effect on fluid flow. However, their effects on heat transfer are found to be small. The separation distance is found to be an important parameter affecting the heat transfer rate. The numerical results of temperature profiles are compared with the experimental measurements performed using Filtered Rayleigh Scattering (FRS) technique in an earlier study, indicating good agreement. It is observed that adiabatic upper plate assumption leads to better temperature predictions than isothermal plate assumption.

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