Implementation of a multi-layer radiation propagation model for simulation of microwave heating in hydrate reservoirs

Purpose This paper aims to present the implementation of a multi-layer radiation propagation model in simulations of multi-phase flow and heat transfer, for a dissociating methane hydrate reservoir subjected to microwave heating. Design/methodology/approach To model the induced heterogeneity due to dissociation of hydrates in the reservoir, a multiple homogeneous layer approach, used in food processes modelling, is suggested. The multi-layer model is incorporated in an in-house, multi-phase, multi-component hydrate dissociation simulator based on the finite volume method. The modified simulator is validated with standard experimental results in the literature and subsequently applied to a hydrate reservoir to study the effect of water content and sand dielectric nature on radiation propagation and hydrate dissociation. Findings The comparison of the multi-layer model with experimental results show a maximum difference in temperature estimation to be less than 2.5 K. For reservoir scale simulations, three homogeneous layers are observed to be sufficient to model the induced heterogeneity. There is a significant contribution of dielectric properties of sediments and water content of the reservoir in microwave radiation attenuation and overall hydrate dissociation. A high saturation reservoir may not always provide high gas recovery by dissociation of hydrates in the case of microwave heating. Originality/value The multi-layer approach to model microwave radiation propagation is introduced and tested for the first time in dissociating hydrate reservoirs. The multi-layer model provides better control over reservoir heterogeneity and interface conditions compared to existing homogeneous models.

Анализ пороговых условий и эффективности генерации замкнутых мод в больших прямоугольных резонаторах на основе лазерных гетероструктур AlGaAs/GaAs/InGaAs

Threshold conditions and efficiency analsis of a semiconductor laser emitter with a large (1x1mm) rectangular resonator based on AlGaAs/GaAs/ InGaAs heterostructures for high-power strip lasers operating on high-Q internally circulating structures is presented. Two designs of emitters with different laser radiation propagation region characteristics are proposed, and the possibility of differential efficiency characteristic as high as high-power broad lasers (70% and more) is demonstrated.

Physical processes in the channel of propagation of CO2 laser pulses during the generation of electric and magnetic fields

The mechanisms of generation of electric and magnetic fields during the propagation of microsecond pulses of a CO2 laser in the atmosphere over long paths are considered. The range of radiated waves selected for research is substantiated. The power of the source required for the realization of the pre-breakdown and breakdown modes of interaction of radiation with the medium is estimated. The dependence of the observed signals on the conditions of radiation propagation is investigated. Comparison of theoretical estimates and results of outdoorexperiments is carried out.

Special Issue “Numerical and Analytical Methods in Electromagnetics”

Like all branches of physics and engineering, electromagnetics relies on mathematical methods for modeling, simulation, and design procedures in all of its aspects (radiation, propagation, scattering, imaging, etc [...]

Analysis of Radiation Propagation inside a Hierarchical Solar Volumetric Absorber

The solar receiver is a critical component of concentrated solar power technology; it works as a heat exchanger, transforming the concentrated solar radiation into high-temperature heat. Volumetric receiver technologies, using air as a heat transfer fluid, are designed to reach higher temperatures than the current receiver technology, which is limited by material resistance and fluid instability. The higher temperature, up to 1200 K, could be used in high-temperature industrial processes or a high-temperature thermodynamic cycle. A correct radiation propagation is essential to develop their performances, reducing reflection and emission losses and promote the heat transfer to the fluid. In this study, the optical behaviour of a hierarchical volumetric receiver (HVR) developed in Bruno Kessler Foundation (FBK) has been studied using Monte Carlo ray tracing (MCRT) simulations. The simulations have been validated in an experimental setup that evaluates the light transmissivity of the HVR porous structure. Two different HVR structures are evaluated with MCRT simulations that use a real solar dish geometry to configure a complete concentrated solar power (CSP) plant. Results show that frontal and rear losses are, respectively, 12% and 3% of the incoming concentrated radiation. Inside the HVR, 15% of the incoming power is propagated trough the lateral void spaces. Therefore, the power spreading avoids the overconcentration of the centre of the focalized area. The HVR optical behaviour has been investigated, showing an optical efficiency of 85%.