This work examines the thermal-hydraulic performance of Al₂O₃-water nanofluids inside a backward-facing step (BFS) configuration characterized by insulated hot walls and semi-circular grooves, employing computational fluid dynamics (CFD) simulations in ANSYS Fluent. The main objective is to analyze the effects of nanoparticle concentration (2 %, 4 %, and 6 % by volume) and flow Reynolds number (10–250) on heat transfer and flow dynamics, with an emphasis on improving thermal management systems. The study primarily examines the lack of comprehension of nanofluid behavior in BFS geometries under laminar flow circumstances and investigates the correlation between flow recirculation, reattachment processes, and thermal boundary layer attributes. The findings indicate that elevated Reynolds numbers and nanoparticle concentrations markedly enhance heat transfer rates, with thermal convection coefficients rising by approximately 1.031, 1.063, and 1.096 times for 2 %, 4 %, and 6 % nanofluid concentrations, respectively, in comparison to the base fluid. The findings offer significant insights for enhancing thermal systems, including heat exchangers and cooling devices, with recommendations for further research in turbulent regimes and different geometries. This study enhances the existing research on nanofluid uses in sophisticated thermal management systems.

The present work offers a thorough analysis of the impact of water velocity on phase change material (PCM) melting in a vertical cylindrical container. A detailed quantitative analysis uses sophisticated numerical techniques, namely the ANSYS/FLUENT 16 program, to clarify the complex relationship between enthalpy and porosity during the melting process. The experimental focus is on phase transition materials based on paraffin wax, particularly Rubitherm RT42. This study’s primary goal is to evaluate the effects of different water velocities (that is, at velocities of 0.01 m/s, 0.1 m/s, and 1 m/s) on the PCM’s melting behavior at a constant temperature of 333 K. This work intends to make a substantial contribution to the development of thermal energy storage systems by investigating new perspectives on PCM behavior under various flow circumstances. The study’s key findings highlight the possible ramifications for improving PCM-based thermal energy storage devices by revealing significant differences in melting rates and behavior that correlate to changes in water velocities. Future research is recommended to explore the impact of temperature variations, container geometries, and experimental validation to improve the accuracy and practicality of the results and to advance the creation of sustainable and effective energy storage solutions.

Drinking water production has been thrust to the forefront of global issues as a direct result of the critical need for accessto clean water and the expanding environmental difculties. Solar stills are becoming an increasingly popular technologyfor the purifcation of water since they provide a greener and more cost-efective alternative to the production of distilledwater of a high standard. Recent research has focused on the incorporation of nanofuids, which are suspensions of metallicor non-metallic nanoparticles, into base fuids such as water and oil in the hopes of further increasing the efectiveness ofsolar distillation. This novel technique intends to improve thermophysical and evaporation parameters, which will eventuallylead to greater production in solar stills. In this paper, a complete overview of the most recent developments in the use ofnanofuids in solar still technology is presented. This research investigates the potential of nanofuid-flled solar still systemsby focusing on their one-of-a-kind qualities. These qualities include increased thermophysical properties, better thermalconductivity, and enhanced thermal absorptivity. The innovative nature of this method is highlighted by the fact that the use of nanofuids in active solar stills has proven a decrease in the amount of pumping power that is required. For instance, ithas been ascertained that the inclusion of carbon quantum dots nanofuids to a solar still can expressively improve the waterproduction, boosting the output by 57.9% to 823 mL compared to the 521 mL produced by a conventional still. Also, usinga concentration of 0.9%, Al₂O₃, TiO₂, CuO nanofuids and multiwall carbon nanotubes can boost the water production by11.57%, 7.16%, 6.32%, and 4.66%, respectively, if compared to a solar still without nanofuids. This study serves as a pioneering examination of the future possibilities of nanofuid-enabled solar still systems, shining light on a transformational routetoward environmentally friendly and efective water purifcation technologies. In light of these astonishing discoveries, thisresearch serves as a pioneering exploration of the future prospects of nanofuid-enabled solar desalination units. 

Concentration of solar energy may be obtained by reflection, refraction, or a combination of the two. The collectors of a reflection system are designed to concentrate the sun’s rays onto a photovoltaic cell or steam tube. Refractive lenses concentrate light by having it travel through the lens. The sun’s rays are partially reflected and then refracted via a hybrid technique. Hybrid focus techniques have the potential to maximize power output. Fresnel lenses are an efficient tool for concentrating solar energy, which may then be used in a variety of applications. Development of both imaging and non-imaging devices is occurring at this time. Larger acceptance angles, better concentration ratios with less volume and shorter focal length, greater optical efficiency, etc., are only some of the advantages of non-imaging systems over imaging ones. This study encompasses numerical, experimental, and numerical and experimental studies on the use of Fresnel lenses in various solar energy systems to present a comprehensive picture of current scientific achievements in this field. The framework, design criteria, progress, and difficulties are all dissected in detail. Accordingly, some recommendations for further studies are suggested.

Composites made from polymers and nanoparticles have promise to be effective solar collectors and thermal energy storage devices due to benefits including improved thermal characteristics and increased structural stability. This study intends to fabricate polyacrylic acid/silicon carbide (PAA−SiC) nanocomposites and examine the optical properties for use in solar collectors and thermal energy storage (TES) fields. The optical properties of PAA−SiC nanocomposites are investigated within the wavelength between 340 and 840 nm. The findings indicate that an increase in SiC concentration in the PAA aqueous solution to 50 g/L at a wavelength of λ = 400 nm causes an increase in the absorption by 50.2% besides a reduction in transmission by 6%. Furthermore, the energy band gaps were reduced from 3.25 eV to 2.95 eV to allow for the transition, and subsequently reduced from 3.15 eV to 2.9 eV to allow for forbidden transition as a result of the increasing SiC concentration from 12.5 g/L to 50 g/L. The optical factors of energy absorption and optical conductivity were also enhanced with a rising SiC concentration from 12.5 to 50 g/L. Specifically, an improvement of 61% in the melting time of PAA−SiC−H2O nanofluids is concluded. Accordingly, it can be said that the PAA−SiC−H2O nanofluids are suitable for renewable energy and TES systems.

In recent years, yearly climatic changes, continuous temperature increases, and the impact of global environmental change have seriously affected agricultural production. The solar greenhouse (SG) system is designed to maintain suitable temperatures and humidity levels for cultivating plants. For this purpose, an earth-to-air heat exchanger (EAHE) can be coupled with the SG to provide the necessary heating and cooling required to maintain suitable conditions for vegetation. This review presents a comprehensive literature survey on SG-EAHE systems. The thermal characteristics of heating and cooling modes are presented for SG-EAHE systems. Reports indicate that integrating EAHE with the SG can meet the heating and cooling needs of the SG while significantly reducing water consumption. The design parameters of EAHE, such as configuration, pipe diameter, pipe length, and buried depth, can affect the performance of SG-EAHE systems. Additionally, integrating photovoltaic (PV) and photovoltaic/thermal (PVT) systems with SG-EAHE systems was discussed. Moreover, the challenges and prospective aspects of SG-EAHE systems were identified.

An effective ventilation system is an important component of a building’s service infrastructure. It serves the dual purpose of creating a comfortable and healthy indoor environment for occupants, thereby enhancing their well-being and productivity. However, the ventilation system is also a part of the building that uses a high amount of energy.

The main objective of this study is to evaluate a novel implementation of the impinging jet ventilation system by placing the supply inlet at the corners of the space or room, rather than in the traditional mid-wall section. The focus of this study is to test and evaluate corner impinging jet ventilation in a medium-sized office environment within a building that requires moderate amount of heating and cooling.

In the first part of this study (summer condition), the system is evaluated in an experimental environment, where it is compared against other systems such as displacement ventilation and mixing ventilation. The evaluated parameters indicates that corner impinging ventilation system performs better than mixing ventilation but show similar results to displacement ventilation in terms of airchange effectiveness. This experimental setup was also tested in winter condition and the results showed that the system was most effective during summertime compared to wintertime. In wintertime the results for the air change effectiveness were similar to those of a mixing system.

In the second part, numerical simulations were utilized to delve deeper into the behaviour of the corner impinging jet ventilation system close to the floor surface. A numerical model was created and validated against experimental measurements. In this part, the spreading of the air jet across the room floor was examined, and its relation to various parameters such as inlet velocity, inlet shape and discharge height. Results indicated that diffuser geometries have almost no impact on velocity profile along the floor's centreline, jet spreading rate and maximum velocity decay. The results also showed a high degree of flexibility for the room size, between 25-100 m2 for which the results were applicable. The results also concluded that there was a noticeable confinement effect present and that the jet was able to travel far into the room.

In the third part numerical simulations was used for validating and to create a model for an office room containing two office workstations. The office room was evaluated in terms of local thermal comfort, close to the sitting area. In addition, the indoor air quality was also examined. The results showed that corner impinging ventilation system performed better than conventional mixing ventilation system, especially when evaluating the indoor air quality in terms of mean age of air. This evaluation also took into account both outdoor summer and winter conditions, as well as different inlet surface areas. Different locations for the workstations were also evaluated with good results, except for placing the work-stations close to the inlets. Due to the system’s effectiveness of providing fresh air to the occupants, further analysis was made to try and reduce the air flowrate but keep the same indoor air quality level as an equivalent fully mixing ventilation system. By using this method, the study was able to demonstrate reduction in the energy use by reducing the air flowrate of the supply inlet. The study showed a possible reduction of the energy use by 7-9 % for outdoor temperatures ranging between -15 °C to 25 °C.

Ett effektivt ventilationssystem är en viktig komponent i en byggnads serviceinfrastruktur. Den tjänar det dubbla syftet att skapa en bekväm och hälsosam inomhusmiljö för de boende, därigenom förbättrande deras välbefinnande och produktivitet. Dock är ventilationssystemet också en del av byggnaden som använder en hög andel energi.

Den huvudsakliga målsättningen med denna studie är att utvärdera en ny implementering av impinging jet ventilationssystem genom att placera inloppen i hörnen av rummet, i stället för den traditionella mellanväggsektionen. Fokus för denna studie är att testa och utvärdera corner impinging jet ventilation (CIJV) i en medelstor kontorsmiljö i en byggnad som kräver måttlig uppvärmning och kylning.

I den första delen av denna studie utvärderas systemet i en experimentell miljö, där det jämförs med andra system såsom deplacerade ventilation och omblandad ventilation för sommar fall. De utvärderade parametrarna indikerar att CIJV presterar bättre än omblandad ventilation men visar liknande resultat som deplacerad ventilationssystem när det gäller luftväxlingseffektivitet. Denna experimentella uppställning testades också under vinterförhållanden och resultaten visade att systemet var mest effektivt under sommartiden jämfört med vintertiden. Under vintertiden var resultaten för luftväxlingseffektiviteten liknande de för omblandande ventilationssystem.

I den andra delen användes numeriska simuleringar för att fördjupa förståelsen av CIJVs beteende nära golvytan. En numerisk modell skapades och validerades mot experimentella mätningar. I den här delen granskades spridningen av luftstrålen över golvet och dess relation till olika parametrar som tilluftshastighet, ventilationsdonet geometri och ventilationsdonets höjd över golvytan. Resultaten indikerade att ventilationsdonet geometri har en marginell inverkan på hastighetsutvecklingen längs golvvägens mittlinje, maximal hastighetsminskning och strålens spridningshastighet. Resultaten visade också en hög grad av flexibilitet när det gäller rumsstorlek, mellan 25–100m2 för vilka resultaten var tillämpliga. Resultaten konstaterade också att det fanns en märkbar restriktionseffekt närvarande och att strålen kunde färdas långt in i rummet.

I den tredje delen användes numeriska simuleringar i en kontorsmiljö med två arbetsstationer. Kontorsrummet utvärderades både när det gällde den lokaltermisk komforten och luftkvalitén inomhus. Resultaten visade att CIJV presterade bättre än ett konventionellt omblandande system, särskilt när man utvärderade luftkvalitén med avseende på luftens medelålder. Utvärderingen beaktade också både utomhusförhållanden på sommaren och vintern samt olika flödeshastigheter. Olika platser för arbetsstationerna utvärderades också med goda resultat, förutom att när arbetsstationerna placerades nära inloppen.

På grund av systemets effektivitet när det gäller att förse frisk luft till kontorsarbetarna gjordes en ytterligare analys för att försöka minska luftflödet men behålla samma nivå av luftkvalitén som ett motsvarande omblandande system. Genom att använda denna metod kunde studien visa på en minskning i energiförbrukningen genom att minska luftflödet för tilluften med 7-9 % för utomhustemperaturer som sträckte sig från -15 °C till 25 °C.

Air pollution significantly threatens human health and natural ecosystems and requires urgent attention from decision makers. The fight against air pollution begins with the rigorous monitoring of its levels, followed by intelligent statistical analysis and the application of advanced machine learning algorithms. To effectively reduce air pollution, decision makers must focus on reducing primary sources such as industrial plants and obsolete vehicles, as well as policies that encourage the adoption of clean energy sources. In this study, data analysis was performed for the first time to evaluate air pollution based on the SPSS program. Correlation coefficients between meteorological parameters and particulate matter concentrations (PM1, PM2.5, PM10) were calculated in two urban regions of Romania (Craiova and Drobeta-Turnu Severin) and Turkey (Adana). This study establishes strong relationships between PM concentrations and meteorological parameters with correlation coefficients ranging from −0.617 (between temperature and relative humidity) to 0.998 (between PMs). It shows negative correlations between temperature and particulate matter (−0.241 in Romania and −0.173 in Turkey) and the effects of humidity ranging from moderately positive correlations with PMs (up to 0.360 in Turkey), highlighting the valuable insights offered by independent PM sensor networks in assessing and improving air quality.

This study employs COMSOL software v 5.6 to investigate a novel approach to heat transfer via mixed convection in an open hollow structure with an unheated 90° baffle elbow. Two 20 W heat sources are strategically positioned on the cavity’s bottom and right-angled wall for this research. Notably, the orientation of the baffle perpendicular to the airflow is used to direct external, unrestricted flow into the square cavity. The research investigates a range of air velocities (0.1, 0.5, 1.0, and 1.5 m/s) and the intricate interaction between input air velocity, dual heated sources, and the presence of a right-angle baffle on critical thermodynamic variables, such as temperature distribution, isotherms, pressure variation, velocity profile, air density, and both local and mean Nusselt numbers. Validation of the applicable computational method is achieved by comparing it to two previous studies. Significant findings from numerical simulations indicate that the highest velocity profile is in the centre of the channel (2.3–2.68 m/s at an inflow velocity of 1.5 m/s), while the lowest profile is observed along the channel wall, with a notable disruption near the inlet caused by increased shear forces. The cavity neck temperature ranges from 380 to 640 K, with inflow air velocities varying from 0.1 to 1.5 m/s (Re is 812 to 12,182), respectively. In addition, the pressure fluctuates at the channel-cavity junction, decreasing steadily along the channel length and reaching a maximum at the intake, where the cavity neck pressure varies from 0.01 to 2.5 Pa with inflow air velocities changing from 0.1 to 1.5 m/s, respectively. The mean Nusselt number exhibits an upward trend as air velocity upon entry increases. The mean Nusselt number reaches up to 1500 when the entry air velocity reaches 1.5 m/s. Due to recirculation patterns, the presence of the 90° unheated baffle produces a remarkable cooling effect. The study establishes a direct correlation between input air velocity and internal temperature distribution, indicating that as air velocity increases, heat dissipation improves. This research advances our understanding of convective heat transfer phenomena in complex geometries and provides insights for optimising thermal management strategies for a variety of engineering applications.