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In the present study, natural convection in a porous cavity in the presence of a non-isothermal biochemical heat source is investigated numerically. The porous cavity is assumed to be homogenous and the Darcy model is used for the momentum equation. The porous cavity includes two species namely biomass and substrate. The heat source generated in the cavity is equal to the rate of consumption of the substrate by the biomass. The bio-chemical source in the energy equation is proportional to the generation rate of solute concentration governed by a Monod model. Heat generation in the porous media, the rate of consumption of a substrate by a biomass, temperature distribution in the cavity, and the local Nusselt number are analyzed completely. The effect of porosity on the biochemical process is completely analyzed in this paper. Results showed that increasing the porosity leads to an increase in the bio-chemical heat generation in the cavity.

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ABSTRACT A numerical investigation of mixed convection heat transfer with nanofluid and pure water from a heat source in a horizontal channel is performed. The walls of the channel are adiabatic and the heat source is placed at the bottom wall of the channel. Free flow at cold temperature enters channel and takes heat from heat source. Discretization of the continuity, momentums and energy equations are achieved through a finite volume method and solved with SIMPLE method. The Brownian motion of nanoparticles is simulated to determine the thermal conductivity of the nanofluid.The results show that using the nanofluid caused to heat diffusion and average temperature of source to increase. Also, increase in solid volume fraction causes increase in heat transfer especially at high Reynolds number. It is understand that with increase in ratio of length to height of source in its constant area, heat transfer decreases first and then increases.

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Application of feed pellets in animal and aquatic farming industries has grown because of both the physical and the nutritional benefits it provides. Development of feed pellets manufacturing industry is also considerable. Steam conditioning process, which plays an important role in pelleting production, includes heating feed particles, adding moisture, and mixing the mash. Pellets cooling and drying processes are also involved in heat transfer phenomena. In this study, thermal conductivity of feed pellets was determined at different temperatures ranging from 25 to 85°C and moisture contents of 11.8 to 18.2% wb. It was measured by the transient technique using the line heat source method assembled in a thermal conductivity probe. It turned out that decreasing moisture contents from 18.2 to 11.8% (wb) produced non-linear reduction in thermal conductivity. The average values of thermal conductivity changed from 0.1509 to 0.2143 W m^-1 °C^-1 at different moisture contents. Tests conducted on two pellet size categories (based on nominal diameter) revealed a significant difference in thermal conductivity between these categories. The thermal conductivities of the first category (minor than nominal dia.) appeared to be 8.5% higher than those of the second category (superior to nominal dia.). Average values of thermal conductivity changed from 0.1538 to 0.2333 W m^-1 °C^-1 for the first category and from 0.1235 to 0.2456 W m^-1 °C^-1 for the second category (in 25°C). In addition, some empirical models were developed to express thermal properties as a function of moisture content and temperature.

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In this paper, experimental data have been used to develop a semi empirical relationship for double-ellipsoidal heat source to model the welding process of a T-shape fillet weld of carbon steel AISI 1020 and stainless steel 304. This model is used in a finite element based computer code to simulate the three dimensional welding process and obtain the temperature profile around the weldment. Experimental data in the form of temperature for certain points have been recorded during the welding process using a computerized data processing system which has been designed for this purpose. Also, the thickness of the weldment layers has been compared by observing their hardness and crystallography. By comparing experimental data with numerical result, the coefficient of the model has been determined using “model updating” process. The effects of material properties and welding parameters have been studied to insure the generality of the model. This model can be used to evaluate the quality of the welding and thickness of the heat affected zone as well as the risks during the welding process such as burn-through and hot cracking. The main advantage of this model is that the number of coefficients is reduced to only one parameter and the rest have been related to the physical and geometrical characteristics of the weld. Results of the numerical simulation obtained using this model show that the major factors which affect the temperature distribution around the weldment are material conductivity, plate thickness, input heating and welding speed.

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Some solutions are presented to show the ability of the spectral line-based weighted sum of gray gases approach to solve the radiative transfer equation in absorbing-emitting non-gray media. The medium contains heat sources and is atradiative equilibrium state which occurs in high temperature systems. The non-gray gaseous medium is divided into a number of gray gases, and the radiative transfer equation is solved for each gray gas by the discrete ordinate method. The intensities are found by a summation over all gray gases, and the temperature field is updated by an iterative procedure. The updated coefficients obtained from high-temperature molecular spectroscopic database (2010thedition) are employed in the spectral line-based weighted sum of gray gases model. The method is verified through comparison with a benchmark problem for the case of a specified temperature distribution, and also for thecase of a variable temperature distribution (radiative equilibrium). Several examples are taken into account to show the ability and performance of proposed procedure for the radiative equilibrium calculations in media with heat sources and different boundary conditions (constant temperature and insulated walls).

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In this study, numerically investigated effect of magnetic heat sources (residual and hysteresis) that can be useful in hyperthermia and their effects on cancerous tissue. The governing equations of continuty, momentum, concentration, energy and Arrhenius tissue destruction equation in the form of couplings are defined, solved and investigated in the finite-element COMSOL software. For blood flow inside the cancerous capillary, non-newtonian and temperature dependent model is used. The geometric model is simulated in three dimensions, including the capillary and cancerous tissue. Thermophysical properties of blood and tissue are also temperature dependent. Results indicated that the residual heat source plays a major role in increasing the temperature of the blood and tissue and can be ignored the effect of hysteresis heat source. The residual heat source has an inverse relation to the particle size and is ineffective in the particle size above 100 nm but hysteresis heat source is directly related to the size of the nanoparticles, and for particles with a size of 150 nm, it will result in a 1 degree increase in temperature for the tissue. The increase in blood temperature for 25 nm magnetic nanoparticles with the residual heat source can lead to the most destruction in cancerous tissue. Also, the viscosity of blood has an inverse relation with the concentration of magnetic nanoparticles in the capillary wall and blood temperature.