Turbulent Dispersion Simulation of Radioactive Aerosol Applied to the Infrastructure of the NPP-2006 Industrial Site

The goal of this work is to simulate the processes of transport and deposition of aerosol particles in a turbulent flow, taking into account the infrastructure of the industrial site of the NPP. The developed model for calculating the dynamics of the spread of the pollutant emissions in emergency situations is presented, the limits of applicability of turbulence models are determined and the main mechanical and thermal sources of turbulence in the NPP infrastructure are analyzed. The mechanisms of radioactive substances deposition for emergency situations have been assessed taking into account turbulent effects. According to the results of the numerical modeling, the zones of predominant deposition of radioactive aerosols on the characteristic surfaces of the NPP infrastructure have been determined, which is the basis for emergency actions planning and assessment of the personnel doses.

Demultiplexer of Multi-Order Correlation Interference in Nitrogen Vacancy Center Diamond

We reported the second- and third-order temporal interference of two non-degenerate pseudo-thermal sources in a nitrogen-vacancy center (NV−). The relationship between the indistinguishability of source and path alternatives is analyzed at low temperature. In this article, we demonstrate the switching between three-mode bunching and frequency beating effect controlled by the time offset and the frequency difference to realize optical demultiplexer. Our experimental results suggest the advanced technique achieves channel spacing and speed of the demultiplexer of about 96% and 17 ns, respectively. The proposed demultiplexer model will have potential applications in quantum computing and communication.

An optimisation approach for spatial allocation of energy sources to district heating networks

District heating networks (DHN) combined with low-carbon heat sources are a promising way to reduce greenhouse gas emissions from heating. However, few works have addressed the problem of allocating localised thermal energy supplies to DHN heating demands considering the spatial proximity constraint of transporting heat energy. The work improves an existing spatiotemporal analysis method by introducing an adapted form of Hitchcock transportation problem and linear programming to solve the optimal allocation problem in network of supplies and demands. The new method is compared with the original method and is found to improve the accuracy of estimating the allocable industrial excess heat supply in a Swiss case study. The method could be applied to diverse thermal sources, such as industrial excess heat, geothermal, lakes and rivers, etc.

Numerical Study on Optics and Heat Transfer of Solar Reactor for Methane Thermal Decomposition

This study aims to reduce greenhouse gas emissions to the atmosphere and effectively utilize wasted resources by converting methane, the main component of biogas, into hydrogen. Therefore, a reactor was developed to decompose methane into carbon and hydrogen using solar thermal sources instead of traditional energy sources, such as coal and petroleum. The optical distributions were analyzed using TracePro, a Monte Carlo ray-tracing-based program. In addition, Fluent, a computational fluid dynamics program, was used for the heat and mass transfer, and chemical reaction. The cylindrical indirect heating reactor rotates at a constant speed to prevent damage by the heat source concentrated at the solar furnace. The inside of the reactor was filled with a porous catalyst for methane decomposition, and the outside was surrounded by insulation to reduce heat loss. The performance of the reactor, according to the cavity model, was calculated when solar heat was concentrated on the reactor surface and methane was supplied into the reactor in an environment with a solar irradiance of 700 W/m2, wind speed of 1 m/s, and outdoor temperature of 25 °C. As a result, temperature, methane mass fraction distribution, and heat loss amounts for the two cavities were obtained, and it was found that the effect on the conversion rate was largely dependent on a temperature over 1000 °C in the reactor. Moreover, the heat loss of the full-cavity model decreased by 12.5% and the methane conversion rate increased by 33.5%, compared to the semi-cavity model. In conclusion, the high-temperature environment of the reactor has a significant effect on the increase in conversion rate, with an additional effect of reducing heat loss.

A Passive Solar Air-House Conditioning System Integrated in Tunisian households

In Tunisia, the buildings’ space heating sector represents a major part of the total energy consumption budget. These issues have been increasingly prominent concerns since the energy crisis. Hence, interests have been growing to adopt renewable energies as viable sources of energy that offer a wide range of exceptional benefits with an important degree of promise, especially in the buildings sector. However, the management of renewable energy sources for space air heating/cooling is usually not economically feasible compared with the traditional carriers. In this chapter, we present a passive energy system, called air-conditioning cupboard which exploits renewable energies (hot water supplied from solar collector [40-50°C] and cold groundwater (19°C)) as thermal sources, is conceived and tested in our laboratory (Laboratory of Thermal Procedure, LPT Tunisia). To evaluate the air-conditioning cupboard efficiency indoor experiments were carried out under varied Tunisian environmental conditions for several days. Results show that the air-heating system has good thermal effectiveness (80 %). It permits to the maintenance of the temperature inside the experimented room at the range of [24-27°C] during the cold months and [20-23°C] during hot months. A theoretical model is employed for the sizing of the air-conditioning cupboard to obtain the required temperature values. This model allows also the determination of the air-cupboard conditioning thermal performances.

MRI-accreting inner regions of protoplanetary discs

<p>Short-period super-Earths and mini-Neptunes have been shown to be common, yet it is still not understood how and where inside protoplanetary discs they could have formed. To form these planets at the short periods at which they are detected, the inner regions of protoplanetary discs must be enriched in dust. Dust could accumulate in the inner disc if the innermost regions accrete via the magneto-rotational instability (MRI). We developed a model of the inner disc which includes MRI-driven accretion, disc heating by both accretion and stellar irradiation, vertical energy transport, dust opacities, dust effects on disc ionization, thermal and non-thermal sources of ionization. The inner disc is assumed to be in steady state, and the dust is assumed to be well-mixed with the gas. Using this model, we explore how various disc and stellar parameters affect the structure of the inner disc and the possibility of dust accumulation. We show that properties of dust strongly affect the size of the MRI-accreting region and whether this region exists at all. Increasing the dust-to-gas ratio increases the size of this region, suggesting that dust may accumulate in the inner disc without suppressing the MRI. Overall, conditions in the inner disc may be more favourable to planet formation earlier in the disc lifetime, while the disc accretion rate is higher.</p>

Improvement and Nocturnal Extension of the Efficiency of a Solar Still

Various studies have been made to improve the efficiency of the solar still. These studies had devoted to the combination of solar collectors with solar still. This article proposes the use of all forms of solar thermal or photovoltaic energy. In addition, photovoltaic electric storage systems convert them to thermal energy that increases the temperature of a greenhouse solar still. We investigated the possibility of improving the productivity of a greenhouse still and prolong solar distillation overnight. The proposed system is the incorporation of thermal energy produced by a parabolic-cylindrical concentrator, a greenhouse still, and photovoltaic solar energy by panels. The production at 14 pm reaches 110 L/m2 thanks to the various thermal sources made up of the hybrid still. It has better productivity than other distillers. The distillation is extended in the evening thanks to a storage system using electric batteries. The production at 18 pm to 18 L/m2 is reduced at 24 pm to 5 L/m2 in the dark. The accumulated temperature decreases the negative influence of the physical parameters on the production which exceeds 100 L/m2 per day. In the evening, the production is reached 16 L/m2 at 22 pm, which is an advantage compared to other distillers.

HIGHLY RESPONSIVE AND ACCURATE TEMPERATURE MEASUREMENTS IN ORTHOGONAL CUTTING THROUGH INNOVATIVE SINGLE LEG THERMOCOUPLE

During machining, most of the thermal sources are resulting from the conversion of mechanical energy during the chip shearing mechanism and the intense frictions between the tool, the chip, and the machined surface. Thermal gradients are high and localized, especially for low thermal diffusivity material like titanium alloys. Moreover, heat rates come close to few million degrees per second in the shearing zones. Even though several authors performed thermography techniques to determine the temperature distribution into the machined material, their results remain underestimated due to experimental limitations. In this research, a new temperature measurement technique has been developed based on a single wire thermocouple to measure at one exact location both the temperature and the heating rate during orthogonal cutting test. The tests are performed with uncut chip thicknesses of 0.020 mm and 0.100 mm and with a cutting speed of 120 m/min with two different cutting angles. Results are discussed and compared to prior studies.