Numerical Optimization and Energetic Advantages of an Innovative Solar Power System Based on Scheffler Receiver Coupled with Volumetric Expanders

In the current context of increasing public awareness of the externalities of fossil fuel-based energy consumption, improvement in new technologies for energy-saving systems has become a crucial target to reduce both global warming and air pollution. Being motivated by such a critical matter, this study presents an innovative solar thermal plant based on volumetric expanders as work-producing devices coupled with Scheffler solar receivers as a thermal source. Nowadays, Scheffler receivers are well performing owing to high efficiency of the focal receiver which reduce heat losses. Simultaneously, screw expanders are volumetric machines which are able to convert thermal to mechanical power with acceptable efficiency also by expanding vapor-liquid blends at low operating pressures. The numerical model presented in this study evaluates the energetic benefits of the proposed solar power system for various operating situations. Parametric optimization of this solar power plant is then performed in a broad range of operating conditions: the optimum evaporation temperatures, together with the corresponding maximum global efficiencies, were so defined under various solar radiation intensities. The numerical results attained in this research prove that solar electricity generation systems based on screw expanders coupled with the Scheffler receivers are a promising technology.

Analytical Solution of Heat Exchange in Typical Electrocaloric Devices

Most of electrocaloric devices reported so far can be simplified as a multilayer structure in which thermal source and sink are different materials at two ends. The thermal conduction in the multilayer structure is the key for the performance of the devices. In this paper, the analytical solutions for the thermal conduction in a multilayer structure with four layers are introduced. The middle two layers are electrocaloric materials. The analytical solutions are also simplified for a hot/cold plate with two sides being different media - a typical case for thermal treatment of materials. The analytical solutions include series with infinite terms. It is proved that these series are convergent so the sum of a series can be calculated using the first N terms. The equation for calculating the N is introduced. Based on the case study, it is found that the N is usually a small number, mostly less than 40 and rarely more than 100. The issues related to the application of the analytical solutions for the simulation of real electrocaloric devices are discussed, which includes the usage of multilayer ceramic capacitor, influence of electrodes, and characterization of thin film.

Heat Flow and Thermal Source of the Xi’an Depression, Weihe Basin, Central China

The Xi’an Depression of the Weihe Basin, located in the transition zone where the North China, Qinling and Yangtze plates collide with each other, is an important area of geothermal energy utilization in China. Studies of heat flow and thermal sources are of great significance to the exploration and development of geothermal resources in this area. In this paper, six temperature logs boreholes, and 14 thermal conductivity samples have been used to study the geothermal gradient and terrestrial heat flow in the area. The results show that the geothermal gradients of Xi’an Depression range from 20.8 C/km to 49.1 C/km, with an average of 31.7 ± 5.0 C/km. The calculated heat flow is 59.4–88.6 mW/m2, and the average value is 71.0 ± 6.3 mW/m2, which indicates a high thermal background in the area. The high anomalous zones are near the Lintong-Chang’an Fault zone in the southeast, the Weihe Fault in the north, and the Fenghe Fault in the central Xi’an Depression. These deep and large faults not only control the formation of the Xi’an Depression but also provide an important channel for the circulation of groundwater and affect the characteristics of the shallow geothermal distribution. The temperature of the Moho in the Xi’an Depression ranges from 600 to 700°C, and the thermal lithosphere thickness is about 90–100 km. The characteristics of lithospheric thermal structure in Xi’an Depression indicate that the higher thermal background in the study area is related to lithospheric extension and thinning and asthenosphere thermal material upwelling.

The Influence of Self-Heating Iron on the Thermal, Mechanical, and Swelling Properties of PDMS Composites for Organic Solvents Removal

Volatile organic compounds pollute the environment and pose a serious threat to human health due to their toxicity, mutagenicity, and carcinogenicity. In this context, it is highly desirable to fabricate high-performance poly (dimethylsiloxane) (PDMS) composites to remove organic solvents from the environment using a simple technique. Therefore, in the present study, Fe-PDMS composites were fabricated using a technique based on magnetic induction heating with iron particles serving as a self-heating agent. Under an alternating magnetic field, the iron particles served as a thermal source that assisted in the progression of PDMS crosslinking. The influence of self-heating iron on the properties of the fabricated Fe-PDMS composites was also investigated. The hydrosilation reaction occurring during the crosslinking process was controlled using FT-IR. The heating efficiency of PDMS 1, PDMS 2, and PDMS 3 was studied as the function of induction time (0–5 min) and the function of iron content (0%, 1%, and 30% wt.%). The results revealed that the mechanical properties of the PDMS 2 composite were enhanced compared to those of the PDMS 1 and PDMS 3 composites. The mechanical properties of PDMS 3 were the least efficient due to cluster formation. PDMS 3 exhibited the highest thermal stability among all composites. Furthermore, the swelling behavior of different materials in various organic solvents was studied. PDMS was observed to swell to the greatest extent in chloroform, while swelling to a large extent was observed in toluene, pentane, and petroleum ether. PDMS swelling was the least in n-butanol. The elastomeric behavior of crosslinked PDMS, together with its magnetic character, produces stimuli-responsive magneto-rheological composites, which are quite efficient and suitable for applications involving the removal of organic solvents.

Nd:YVO4 Laser Irradiation on Cr3C2-25(Ni20Cr) Coating Realized with High Velocity Oxy-Fuel Technology—Analysis of Surface Modification

The high-velocity oxy-fuel (HVOF) technique has been extensively used for the deposition of hard metal coatings. The main advantage of HVOF, compared to other thermal spray techniques, is its ability to accelerate the melted powder particles of the feedstock material to a relatively high velocity, leading to good adhesion and low porosity. To further improve the surface properties, a mechanical machining process is often needed; however, a key problem is that the high hardness of the coating makes the polishing process expensive (in terms of time and tool wear). Another approach to achieving surface modification is through interaction with a thermal source, such as a laser beam. In this research, the effects of laser scanning rate, scanning strategy, and number of loop cycles were investigated on an HVOF-coated surface. Cr3C2-25(Ni20Cr) was selected as the coating and Nd:YVO4 as the laser source. The results demonstrate the significance of the starting coating morphology and how the laser process parameters can be tuned to generate different types of modifications, ranging from polishing to texturing.

Origin of Lithium–Potassium-Rich Brines in the JianghanBasin, South China: Constraints by Water–Rock Reactions of Mesozoic–Cenozoic Igneous Rocks

A large number of lithium–potassium-rich brines have been found in Paleocene reservoirs in the Jianghan Basin, South China. First, the brines have exceptionally high lithium and potassium contents that are even higher than those in other closed basins on the Tibetan Plateau. Second, the enriched brines are widely distributed in the center of the basin. The Mesozoic and Cenozoic igneous rocks in the Jiangling depression are mainly basalt and granite, and their distribution area exceeds 50% of the basin. The large basalt body provided a thermal source for the water–rock reaction. The igneous rocks in the study area could have provided ore-forming elements, such as lithium and potassium, for the brine. A static immersion experiment at room temperature shows that fluids with certain salinities are more likely to activate K ions in basalt. However, weakly alkaline solutions more easily dissolve K. High-temperature water–rock experiments show that the dissolution rates of Ca, Mg, and Sr decrease with increasing temperature, while the dissolution rates of K and Li first increase and then decrease with increasing temperature. The dissolution of K and Li is easier when saline fluid reacts with volcanic rock. The dissolution rate of K is higher than that of Li in basalt, and the dissolution rate of Li is higher than that of K in granite. Compared with the results at normal temperatures, the ability of the fluid to leach elements at higher temperatures is significantly enhanced. Temperature is the main factor controlling the ability of fluid to leach elements. High-salinity fluid is the main carrier of ore-forming elements. According to the water–rock experiments, the mineral composition of the ancient brine in the Jiangling depression that formed during the Paleocene is consistent with that of the ore-rich brine found today, but different by a few orders of magnitude, indicating that the formation of lithium–potassium-rich brines requires a long time. The water–rock reaction is one of the important processes of brine formation, and surface evaporation and concentration are the main mechanisms of brine mineralization.

Identification of radiant source in an enclosure by reduced model

We propose an original method to recover from a few measurement points the integrity of the temperature field of a furnace heated by a radiant thermal source. The radiant thermal source is first identified via a low order reduced model based on based on AROMM (Amalgam Reduced Order Modal Model) method which preserves the integrity of the geometry. The minimization is performed via a trust-region reflective least squares algorithm implemented in MATLAB “lsqcurvefit” function. From that identified heat flux, the integrity of the thermal field is then recovered by direct simulation thanks to a reduced model of higher rank to have a better precision. The treated application is a complex titanium piece heated by two radiant panels placed in a furnace. With four measuring points, the temperature of the whole thermal scene is retrieved at all times with an average error around 1 K on the studied object.