To address the growing problem of pollution and global warming, it is necessary to steer the development of innovative technologies towards systems with minimal carbon dioxide production. Thermal storage plays a crucial role in solar systems as it bridges the gap between resource availability and energy demand, thereby enhancing the economic viability of the system and ensuring energy continuity during periods of usage. Thermal energy storage methods consist of sensible heat storage, which involves storing energy using temperature differences; latent heat storage, which utilizes the latent heat of phase change materials; and thermochemical heat storage, which utilizes reversible chemical reactions through thermochemical materials. The objective of this review paper is to explore significant research contributions that focus on practical applications and scientific aspects of thermal energy storage materials and procedures. For each type of storage, different materials have been examined, taking into consideration the most recent studies, both for medium and long-term storage and, when possible, comparing methodologies for the same purpose. It has been observed that TCHS systems have the potential to reduce the volume of chemical storage tanks by 34 times using chemical reactions. Among the SHS materials, water, molten salts, and graphite exhibit the highest energy density, with graphite also possessing remarkable thermal conductivity. Nanoparticles can enhance the thermophysical properties of TES materials by increasing their thermal conductivity and wettability and improving intermolecular characteristics. The use of biobased PCMs for applications that do not require very high temperatures allows for maximizing the efficiency of such storage systems.

The analysis two-phase flow inside centrifugal pumps is a fundamental issue in several engineering applications. This often represents a bad working condition with respect to single phase one, causing head reduction, efficiency decrease, and higher operational costs in terms of energy and money. The paper reports a numerical analysis of bubbles behavior inside centrifugal pumps. Equations regulating the air bubble motion within the rotor of a centrifugal pump have been solved considering the effects of all forces acting. Coalescence phenomena have been investigated too, in order to identify how gas zone presence in the rotor can lead to anomalous working condition. Results are reported in graphs and diagrams varying bubble dimension and water flow rate. An experimental approach to visualize the two-phase flow field inside the impeller is presented too. Images have been acquired, elaborated, compared with numerical results, and discussed in order to understand the interaction between gas phase and liquid phase and to correlate this behavior with the energy dissipation phenomena for a centrifugal pump.

The performance of spool valves can deteriorate and noise can occur due to cavitation. The noise sound levels caused by cavitation are influenced by many parameters, among which the most important is not-optimal geometry of components. In this article, a two ways—two positions directional control valve was studied using experimental and numerical approaches. Tests were performed on a plexiglass body and steel spool analyzing the cavitating area that develops in U-notches. A dedicated test rig was equipped with a high-speed camera placed directly in front of the area of interest where cavitation occurs. Different working conditions were tested by varying the upstream pressure to encourage the development of cavitation. Images were acquired and postprocessed, focusing the contour extraction between the liquid and gaseous phases. The images were compared with results from three-dimensional computational fluid dynamic numerical simulations performed using commercial software. The numerical estimation of flow characteristics corroborated the results from investigations carried out using a fast camera, including periodic cavitation structures. This study demonstrates the importance and usefulness of using a three-dimensional computational fluid dynamic approach during the prototyping phase to create quieter component designs

Optimizing heat transfer in the evaporator tubes is essential for obtaining optimal coefficients. Deviation from ideal nucleated boiling configurations can lead to rapid transitions to film boiling conditions, compromising the exchange coefficients. Detecting critical bubble flow conditions is invaluable in preventing thermal overloads and safeguarding operational integrity. The aim is to detect the type of bubble motion established in the ducts using non-intrusive techniques. To achieve this aim, accelerometric devices detect the vibrations induced by the passage of bubbles. The bubble's movement is also recorded contextually by a fast video camera capable of detecting images through a vertical transparent quartz duct. The accelerometric data, processed using discriminant analysis theory and then associated with the recorded images, give a good relationship, more than 95%, between the motion of the bubbles and their behavior characteristics. The latter in this work is represented on the plane of the phases.

This paper introduces a numerical model dedicated to simulating SO₂ adsorption during the dynamic interplay between combustion gases and water droplets. The research delves into essential chemical–physical parameters governing mass transfer in these interphase interactions. The proposed simplified model provides preliminary results regarding the granulometric curve of sprays, particularly focusing on the minimal droplet size crucial for effective wet scrubber operation. Our findings underscore a critical diameter below which the spray loses its efficacy under varied boundary conditions. Notably, a single droplet with a maximum diameter of 2 mm absorbs more SO₂ than smaller counterparts, peaking at 4.36 × 10⁻⁵ g of SO₂ within the simulation timeframe. Furthermore, the study explores a specific water mass, revealing that smaller droplets, such as 1 mm, significantly optimize the absorption process. These droplets achieve a SO₂ absorption quantity over 5.77 times greater than that of a 2 mm droplet. This research serves as an initial tool for optimizing droplet distribution in sprays, thereby enhancing capture efficiency. The insights presented here offer valuable guidance for designing efficient wet scrubber systems, crucial for pollution control in industrial and environmental applications.

This article examines the prospects of Scheffler solar receivers integrated into renewable energy power plants for civil applications. This kind of solar receiver can offer satisfactory energetic performance with acceptable energy conversion efficiency when compared to other technologies to harness solar energy since the high-quality focal receiver can reduce heat losses also supposing great levels of evaporation temperature. In this research, energetic optimization and a broad assessment of Scheffler-type solar receivers are thoroughly conducted for variable sun radiation and considering a broad range of working conditions. To achieve this goal, thermodynamic optimization of the chief factors was attained via a numerical model which calculated the energy efficiency of the Scheffler solar receiver at part-load working conditions by computing all energy losses negatively affecting the heat exchange phase in the cavity receiver. The results obtained in this study show that the solar collector efficiencies of Scheffler receivers appear more promising than that of usual parabolic trough collectors; moreover, Scheffler receivers persisted with less sensitivity to reductions in solar radiation intensity. For these reasons, solar power systems based on Scheffler-type systems can be used from tens to hundreds of kW to ensure the energetic supply of small urban settlements with acceptable efficiency, optimistic investments, simple construction and reduced overall sizes.