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This paper is to study the effect of CaCO 3 precipitated crystal scale mixed with different particles on the scaling characteristics under the action of electromagnetic field. The simulation of industrial field experiments, based on the electromagnetic water treatment dynamic experimental bench, change the type of particles, concentration, magnetic field strength, according to the experimental results of the thermal resistance and scale inhibition rate curve under different working conditions, through the scanning electron microscope microscopy analysis of the fouling samples, to study the effect of CaCO 3 fouling mixed with different particles in the role of the magnetic field on the effect of the law on the deposition characteristics. The results show that: electromagnetic field on MgO particles dirt and CaCO 3 dirt deposition have inhibition effect; CaCO 3 and different concentrations of CaCO 3 crystalline particles mixed, CaCO 3 particles, the more the electromagnetic field on the formation of CaCO 3 precipitation scale inhibition effect is not obvious; CaCO 3 precipitation scale and MgO particles mixed in the magnetic field can significantly enhance the effect of the field of the inhibition of the scale, magnetic field Under the action of the magnetic field, as the content of MgO particles increases, the scale inhibition effect on the dirt is first enhanced and then weakened until it tends to be about 0. Scanning electron microscopy analyses showed that the morphology and degree of aggregation of calcium carbonate fouling crystals were influenced by MgO particles under the action of electromagnetic fields, and CaCO 3 fouling was transformed from regular ortho-hexahedra to acicular aragonite and amorphous CaCO 3 , which made the stripping phenomenon more significant. Comprehensive experimental results and scanning electron microscopy analyses of fouling samples show that the mixture of CaCO 3 solution with a small amount of MgO particles can be an effective means to inhibit the precipitation of crystalline fouling under the environment of alternating electromagnetic field. This study provides theoretical guidance for the application of alternating magnetic field in the future, and provides new ideas and methods for solving the problem of crystalline fouling in industry. • This paper is to study the effect of CaCO 3 precipitated crystalline scale mixed with different particles on the scaling characteristics under the action of electromagnetic field. • Electromagnetic fields have an inhibitory effect on the deposition of both MgO particulate fouling and CaCO 3 fouling. • Under the mixing of CaCO 3 with different concentrations of CaCO 3 crystalline particles, the more CaCO 3 particles the less obvious the inhibition effect of electromagnetic field on CaCO 3 precipitation scale formation. • With the increase of the content of MgO particles, the scale inhibition effect on the dirt is first enhanced and then weakened until it tends to be about 0. • Under the alternating electromagnetic field environment, CaCO 3 solution mixed with a small amount of MgO particles can be an effective means to inhibit the precipitation crystal fouling. [ABSTRACT FROM AUTHOR]

Due to the serious overheating problem of end parts in the large turbogenerator end region, accurate calculation of end-part temperature has become a key design factor. In this paper, 3-D fluid and thermal coupling model in the end region of 1250 MW turbogenerator are given. The loss values gained from 3-D transient electromagnetic field calculation are applied to the solving end region as heat sources. Pressure value of fan outlet and fluid velocities of end region inlets from flow network calculation are applied to the solving end region as boundary conditions in the 3-D fluid and thermal coupling analysis model. The fluid flow and temperature distribution of end parts in the end region of large turbogenerator with magnetic shield structure are studied under the different operation conditions. The distribution of fluid velocity in the ventilation duct of stator end core is obtained. The temperature distribution laws of stator-end copper coils, screen plate, finger plate, press plate, and magnetic shield are researched under the different operation conditions. The location of the highest temperature point in the turbogenerator end region with magnetic shield structure is determined. The accuracy of numerical calculation is validated by experimental measured values. [ABSTRACT FROM AUTHOR]

The paper presents an advanced numerical study of industrial switchgear with the joint electric resistance included. The fundamental thermal problems (radiation, convection and conduction) in copper busbars, supporting parts and cooling air were coupled with the electromagnetic field to accurately define the power losses. The mathematical model was based on the validated model of the simplified laboratory switchgear. However, more sophisticated busbar system was employed in this study. The model results were compared with the measurements data for two switchgear configurations of different type of a top cover, i.e. ventilated and solid ones. Then, the “what-if” studies for basic configuration were considered. In the considered problem, the influence of the busbar surface emissivity modification, the changes in enclosure inlet/outlet grids and application of the radiator without fan on the local and global temperature reduction within the switchgear was analysed. The results obtained show the importance of radiative heat transfer and emphasize the influence of the surface emissivity in the switchgear cooling process. [ABSTRACT FROM AUTHOR]

Domestic multimode microwave (MW) systems have been extensively used to process biomass materials for proof of concept. However, one of the major drawbacks for these systems is the non-uniform heating. Therefore, the aim of this article was to predict the heating behavior of empty fruit bunch (EFB) biomass in both bed and pellet form using finite element based COMSOL Multiphysics software. The temperature data from a modified domestic multimode MW system at 2.45 GHz frequency was used. Quantitative validation of 10 s heating profile was performed by comparing the simulated temperature profile with the experimental temperature. The agreement of simulated temperature profiles depended on various factors such as biomass loading bed height, defining specific heat capacity value and form of biomass shape (bed or pellet). Interestingly, the location of local hot spots during MW heating of EFB bed and pellets were almost close enough in both simulation and experimental study. An optimal biomass loading height was found whereby maximum MW energy is absorbed by the sample. The effect of biomass loading height on the distribution of electromagnetic fields is discussed in the paper. This study provides a framework and required model parameters to predict temperature and optimum biomass loading for a specific geometry of MW cavity. Further, the model can be effectively used to identify hot and cold spots in the biomass material during MW heating and thereby help to design and optimize the MW applicators in terms of heating uniformity. The proposed model can also be useful to identify the electromagnetic field distribution inside the cavity. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a numerical investigation of the effect of microwave heating on a continuous flow of water in a duct. A high frequency electromagnetic field and thermal fluid model were developed in ANSYS Multiphysics to calculate the temperature change in water flow using a 915 MHz microwave unit. It was assumed that no phase change in water occurs during the heating process and in addition the water maintains the hydrodynamically fully developed flow condition. Various factors were examined in the course of this numerical investigation; namely, the effects of inlet velocity, applicator height and applicator diameter on the temperature field. The results of the assumptions in this work have been compared with the constant dielectric properties case. Average outlet temperature decreases with inlet velocity increasing. Moreover, heat absorption drops significantly with raising the applicator diameter more than a critical value. [Copyright &y& Elsevier]

Abstract: In the present paper, a numerical model of spot pulsed current GTA welding for partially and fully penetrated weld pools is presented. Heat transfer and fluid flow in the weld pool driven by the combination of electromagnetic force, buoyancy force, surface tension gradient and latent heat are included in our model. A new formulation of the electromagnetic problem is introduced to take into account eddy current in the weld pool. The shape of the free deformable surface under the action of pulsed arc force is also handled after the magneto-hydrodynamic calculation. The numerical model was applied to 304 stainless steel welding. We compare the influence of various pulsed welding parameters such as pulse frequency and current ratio on the weld quality. Experimental study is conducted to compare our numerical prediction with welding macrographies. It shows a good agreement of the model. [Copyright &y& Elsevier]