A review on the susceptor assisted microwave processing of materials

Single-phase fluid flow distribution and heat transfer in microstructured reactors

To date, numerous phase change materials (PCM) have been developed for application in latent heat storage systems. There are many issues in the process from the development of PCM to using them in storage systems, which should be resolved. The problem of heat transfer in PCMs during the phase change process is the most important one. Latent heat storage containers usually have simple geometrical forms such as a sphere, cylinder, cylindrical annulus, rectangular enclosure, etc. A large number of papers were published on melting and solidification processes in PCMs. Therefore, there is a pressing necessity for generalizing the art of the state in this field and establish how accumulated knowledge meets practical requirements. The present review considers the current state in investigations of heat transfer in a spherical shell. Heat transfer in PCMs during constrained melting (solid PCM fixed inside the vessel), unconstrained (unfixed) melting and solidification, and phase change in finned shells are analyzed. It is shown that currently, there is no satisfactory description of the constrained melting process. For unconstrained melting and solidification, some correlations are suggested, describing these processes. The applicability range of the proposed correlations, as well as their accuracy were investigated and established. To intensify the process of phase change inside the spherical container, the use of orthogonal fins is appropriate option compared to the employ of circumferential fins.

Melting and solidification of PCMs inside a spherical capsule: A critical review

Industrial waste derived biosorbent for toxic metal remediation: Mechanism studies and spent biosorbent management

Material processing adopting microwave heating has emerged as an alternative tool owing to faster processing, a cleaner environment, and several other advantages. This review provides a summary of recent reports of microwave synthesis of materials. This study reviews the use of microwave energy for application in several material processing technologies apart from food processing. A special emphasis has been made in the processing of glass adopting microwave energy. Melting of glass comprising SiO2, P2O5, B2O3 as the main building block has been discussed. It has been revealed that silica, a microwave transparent material as reported earlier, can be heated under microwave heating directly. Microwave absorption of raw materials and different glass system has been discussed. Dielectric properties, particularly loss tangent or loss factor, are presented for some glass composition. Less evaporation of ingredient and low contamination from the crucible wall are noticed during glass melting using microw...

An overview on microwave processing of material: A special emphasis on glass melting

A base glass suitable for immobilization of nuclear waste was prepared by melt quenching technique using microwave radiation as a heating source. Microwave absorption behavior of major raw materials was studied and presented. The glass was also prepared in a conventional resistance heating furnace using the same batch composition. X-ray diffraction analysis of the sample prepared in microwave furnace has confirmed glass formation, which is in a similar agreement with that of glass prepared in the conventional resistance heating furnace. Comparative property analysis indicated identical glass prepared in both the routes. In microwave furnace, total power consumption was found to be ˜5 kWh with the maximum power demand of 1.5 kW. Electrical power consumption in resistance heating furnace was studied in three different capacities of furnaces and compared with that of microwave furnace. Energy saving in the range ˜60% was recorded in microwave heating compared to resistance heating furnace. Further, the time ...

Energy Efficient Melting of Glass for Nuclear Waste Immobilization Using Microwave Radiation

This work reports the preparation of iron-doped alumino-phosphate glass using microwave (MW) radiation at 1723 K in comparision with a conventional resistance heating furnace at the same temperature. X-ray diffraction analysis of the sample prepared in an MW furnace has confirmed glass formation which is similar to that of glass prepared in an electric furnace. Glass transition temperatures (Tg) for MW and conventional melted glass samples were observed to be 866 and 873 K, respectively. Higher Fe2+/(Fe3+ + Fe2+) ratio was reported in glass prepared in the MW furnace compared with the conventional furnace. The Fourier transform infrared spectra for both the samples indicate identical nature. It was observed that the maximum power required for melting glass in MW heating was 0.85 kW, which is around 25–30% of the power consumed by the conventional resistance heating furnace. In addition, the time needed to melt the glass in the MW furnace was found to be 3–4-fold lesser than the time required in the resistance heating furnace.

Preparation of alumino-phosphate glass by microwave radiation

The paper demonstrates a standardized process of vapor phase doping to fabricate large core Yb–doped preforms with longer useful length in reproducible manner. The optimization of the process led to successful achievement of Yb-doped core thickness of 4.5 mm (in 14.8 mm of preform diameter) by depositing up to 30 number of core layers with controlled amount of generated precursor vapors. The influence of the process parameters was studied rigorously to enhance the useful preform length up to 380 mm. A combination of Yb and Al in different proportions was doped into the core with uniform dopant concentration along the length by adjusting few process parameters efficiently. The Al2O3 concentration up to the level of 17.8 mol% has been achieved successfully which resulted in NA of 0.31. This is the highest ever doping of Al in passive fibers by any modified chemical vapor deposition process. The Yb2O3 content in the active fibers is as high as 0.47 mol%.

An Optimized Vapor Phase Doping Process to Fabricate Large Core Yb-Doped Fibers

A review on the application of lattice Boltzmann method for melting and solidification problems

Various process parameters influence the melting and solidification phase change process. Studies on the influence of shape of cavity, thermo-physical properties of the phase change material and the boundary conditions, on the phase change process, has been carried out by various researchers worldwide. The effect of the thermal properties of the cavity material on the process is yet to be investigated thoroughly. In this work, melting process of paraffin wax is simulated in a spherical cavity for various cavity materials having different thermal properties and for different boundary conditions. The simulations results are obtained using enthalpy-porosity model for free surface melting process, solved using Ansys-fluent 16.2. Experimental studies were carried out for one type of cavity material. The experimental investigation included visualization of shape of solid fraction which is used to validate the numerical approach of this computational study. The results showed that the materials having higher thermal diffusivity has enhanced melting rate because of increased bouncy effect and convection. It has been found that the higher Stefan number shows the effect of higher natural convection and maximum velocity profile, resulting in enhanced melting process. These simulations are significant for selection of cavity material for different processes like energy storage, melting-solidification of metal in casting and others.

Chandan Guha

Papers

Energy Efficient Melting of Glass for Nuclear Waste Immobilization Using Microwave Radiation

Preparation of alumino-phosphate glass by microwave radiation

An Optimized Vapor Phase Doping Process to Fabricate Large Core Yb-Doped Fibers

A review on the application of lattice Boltzmann method for melting and solidification problems

Numerical and experimental investigation of paraffin wax melting in spherical cavity