Droplet impact on heated solid surfaces governs heat transfer in spray cooling and thermal management, yet the coupled interfacial dynamics and transient heat transfer remain challenging to probe experimentally. This work introduces a novel experimental platform, featuring a transparent ITO-coated sapphire substrate that enables simultaneous high-speed infrared thermography (2000 Hz, and 25 & micro;m/pixel) of the liquid-solid interface, synchronized with side- and bottom-view visualization. This unique tri-modal approach (side-view, bottom-view, and IR thermography) captures causal links between wall superheat, bubble genesis, wetting behavior, and transient cooling during ethanol droplet impact over a wide temperature range (120 -240 degrees C) and Weber numbers (103-194). We identify three distinct regimes: i)At low wall temperatures (<= 150 degrees C), sustained bubbly boiling with vigorous nucleation yields the highest heat transfer, where the thermal contact area exceeds geometric spreading by up to 50%. ii) At intermediate temperature (similar to 180 degrees C), a remarkable fingering boiling pattern emerges in the transition boiling, characterized by spatially non-uniform heat flux and reduced liquid -solid contact; increasing Weber number compresses the vapor layer, suppressing fingering. iii)At higher wall temperatures (>= 210 degrees C), Leidenfrost-like bouncing occurs, with bottom-view confirmation of a continuous vapor layer at 240 degrees C. The regime transitions are quantified through cooling effectiveness, which peaks at 0.56 at 150 degrees C, and drops to 0.06 in film boiling. Comparison with prior studies suggest that Jakob number can be used as a universal predictor for boiling transitions upon droplet impact, independent of fluid properties. These findings provide a comprehensive experimental framework for distinguishing boiling regimes during droplet impact, which can inform the design of droplet and spray-based thermal management systems by identifying the optimal superheat for nucleate boiling and the conditions that trigger inefficient transition and film boiling.

Abstract This work examines bioinspired 3D printed architectures for enhanced fog harvesting and atmospheric water recovery. It analyzes the mechanisms governing droplet nucleation, growth, transport, and drainage on bioinspired 3D printed micro geometries through various additive manufacturing routes. A normalized performance comparison is presented for various engineered architectures to evaluate water collection enhancement. Numerical modeling approaches, current challenges, and future directions for robust, high-performance water-harvesting systems are also highlighted.

The demand for advanced heat transfer fluids (HTFs) has increased significantly in the past two decades due to the limited thermal performance of conventional fluids in handling the high heat fluxes from next-generation high-tech systems. Nanofluids (NFs) consisting of metal oxide nanoparticles (NPs) exhibit better thermophysical properties and dispersion stability than conventional HTFs. In this research, the thermal conductivity and viscosity of Zinc Oxide (ZnO)-based NFs in deionized water (DIW) were tested at mass concentrations ranging from 0.012 to 0.048 mass

Efficient and scalable solar evaporation systems are critical for sustainable seawater desalination and brine resource recovery. However, conventional strategies face material integration constraints: materials must simultaneously perform solar absorption, fluid transport, and evaporation functions. This coupling struggles to balance high evaporation rates with continuous salt harvesting, limiting long-term stability, and overlooks the potential of sidewall evaporation in 3D architectures. Here, we introduce a bottom-heated 3D solar convective evaporator (SCE) that spatially decouples the heating and evaporation processes. This design leverages bottom photothermal heating to induce natural convection, thereby enhancing sidewall heating and promoting efficient vapor removal. Through this synergy, the SCE achieves an 82.8% higher evaporation rate than 2D designs under the same solar-heated area at a pillar height of only 3 & times; the radius and outperforms conventional 3D systems in lab conditions once the heating radius exceeds 2 & times; the pillar radius. Importantly, this decoupled architecture also confines salt precipitation to the base rather than the evaporation surface, enabling continuous operation in seawater and hypersaline brines up to 17.5 wt.%. This work demonstrates a simple and scalable approach to high-efficiency solar desalination and hypersaline brine management.

ABSTRACT The concurrent generation of clear water and degradation of pollutants using sunlight represents a sustainable solution to global water scarcity. However, integrating photothermal evaporation and photocatalysis within a single device remains challenging due to competing requirements for light and mass management Inspired by natural transpiration, we engineer a bilayer porous hydrogel interfacial reactor that synergistically couples these processes through designed heat, mass, and charge transport. The reactor features an upper hydrogel layer embedding polydopamine modified TiO 2 and carbon black nanoparticles for broadband light harvesting and charge transfer, and a lower 3D‐printed insulating supporter for continuous capillary water supply and heat localization. Evaporation‐driven convection enriches pollutants at the catalytic interface, while photothermal heating enhances reaction kinetics, establishing a self‐reinforcing photothermal‐photocatalytic loop. Under 1 sun irradiation, the reactor achieves an evaporation rate of 2.14 kg·m −2 ·h −1 with an efficiency of 95.43%, while enabling continuous in situ photocatalytic degradation of organic contaminants. This work provides a versatile design principle for advanced multifunctional reactors, unifying solar energy conversion with efficient water remediation.

Superhydrophobic surfaces have a widespread range of applications, starting from microfluidics to energy, due to their self-cleaning and drag-reducing properties. This study aims to 3D print structures reaching static contact angles (CA) in the superhydrophobic range using readily available materials and simple experimental methods, and to offer quantitative insights for future scalable fabrication of water-repellent surfaces by investigating the impact of geometry, spacing, and surface coating on the wettability of 3D-printed microstructures. Five geometry types, i.e., cone, cylinder, pyramid, mushroom, and square micropillars, with a variable center-to-center spacing ranging from 40 to 100 & micro;m, were designed, fabricated via projection-micro stereolithography (P & micro;SLA), coated with a fluorosilane solution, and finally characterized by scanning electron microscopy (SEM) imaging and contact angle (CA) measurements. Surface geometry alone proved incapable of granting superhydrophobicity. The conical and pyramidal micropillars exhibited CAs exceeding 164 degrees at a 40 & micro;m spacing after fluorosilane coating, thereby significantly enhancing water repellency. Larger spacings clearly reduced the CAs and thus the superhydrophobicity, highlighting the importance of optimal geometry-spacing pairings to maintain extreme aquaphobicity.

Though numerous studies on droplet impact have been conducted, the maximum ambient pressure reported is limited to 100 bar, and our understanding of droplet behavior under higher pressures remains unexplored. This study presents the first experimental investigation of droplet impact under high ambient pressure (up to 200 bar) onto different superhydrophobic substrates under low Weber number conditions. Four different regimes are identified, i.e., no bouncing, droplet bouncing with both satellite droplet retention and gas entrapment, droplet bouncing with gas entrapment, and complete droplet bouncing. The transition among different regimes is highly dependent on the ambient pressure and substrate topology. The droplet bouncing capability increases with the increase of ambient pressure, and complete bouncing is achieved for all substrates at P ≥ 175 bar. A phenomenological mode is developed taking into the consideration of both enhanced cushioning effect and hydrodynamic impact dynamics at high pressure. With a modified water hammer coefficient, the hydrodynamic impact model can be used to explain the disappearance of satellite droplet. Such work advances droplet study into 200 bar domain, which is of high relevance to a few high‐pressure applications such as deep sea oil/water separation.

Superhydrophobic surfaces exhibit remarkably low wettability, enabling various liquids to form droplets and roll off the surface. Beyond their extreme aquaphobic behavior, self-cleaning, anti-corrosive, drag-reductive, oil-repellent, anti-icing, anti-reflection, and anti-biofouling attributes make these structures and surfaces highly valuable for numerous liquid-related applications. Despite these attractive features, developing these intricate three-dimensional microstructures using traditional manufacturing methods presents significant challenges. Recent advancements in 3D microprinting technology, with its unmatched design freedom and precise control over microfeatures, have revolutionized the fabrication of these superhydrophobic microstructures. This work presents a detailed analysis of the benefits and limitations of different 3D-printing technologies in fabricating superhydrophobic microstructures. Applications of these 3D-printed superhydrophobic microstructures in various engineering and scientific domains are analyzed. This work also discusses the need for future improvements in 3D-printing techniques to cope with the scalability issue, optimizing material properties for stability and durability of superhydrophobic microstructures, and developing innovative design strategies for higher levels of superhydrophobicity with desired functionalities.

The distinctive capability of Phase Change Materials (PCMs) to store and release thermal energy during the phase change process makes them important materials for tackling the energy efficiency-related challenges faced by modern compact energy systems. In this context, the present study explores the thermal and hydraulic performance of microencapsulated phase change materials (mPCMs) with a specific melting point of 37 degrees C within a microchannel heat sink (MCHS) operating under convective heat transfer conditions. Various performance parameters, including the thermal boundary layer (TBL), bulk fluid mean temperature, wall temperature, the local and average Nusselt numbers (Nu), the pressure drop (Delta P) across the MCHS, and the performance evaluation factor (PEF), were investigated under varying mass concentrations (5-15 %) and inlet velocities (0.55-1.20 m/s) of the mPCMs. The increase in the Nu and Delta P was found to be 21 % and 16.7 %, respectively, at an inlet velocity of 1.2 m/s and a mass concentration of 15 %. The PEF was found to reach a maximum value of 1.29 for a mass concentration of 10 % and an inlet velocity of 1.2 m/s. The PEF is a quantity that balances the gains achieved in heat transfer with the associated penalties due to the increase in pressure drop. These pressure drop penalties typically occur due to an increase in the viscosity of the slurry due to the rise of the mass concentration of the mPCMs. Parametric sensitivity analysis for key thermophysical properties, confirmed the robustness of the CFD model under +/- 10 % variations. The significant improvement in the thermal performance of the mPCM slurry underscores its potential for heat transfer and thermal energy storage in modern energy systems. Integrating mPCMs with microchannel heat exchange systems will enhance the energy efficiency of modern thermal energy storage and heat transfer systems and reduce operational and maintenance costs.

This experimental study deals with the heat transfer and thermohydraulic performance of nanofluids in horizontal tubes with sudden contractions. Small mass fractions of multi-walled carbon nanotubes (MWCNTs), functionalized multi-walled carbon nanotubes (FMWCNTs), and graphene nanoparticles were dispersed in a water-ethylene glycol mixture (50:50 by weight). These colloidal suspensions were directed through a closed conduit to a test section with an internal diameter of 14.29 mm and a length of 1700 mm. Three scenarios were evaluated: (1) nanofluid flowing inside a copper tube prior to entering the test section; (2) nanofluid flowing through a tube with an internal diameter of 20.64 mm; and (3) nanofluid flowing through a tube with an internal diameter of 26.99 mm. The mass flow rates ranged from 4.67 g/s to 157.4 g/s, with inlet temperatures of 25 degrees C and 45 degrees C. Nanofluid concentrations of 0.005 % wt. and 0.01 % wt. were tested under a constant heat flux of 10 kW/m2. This study investigates the influence of contraction ratios and nanoparticle types on flow behavior and thermal performance. Results indicate that graphene nanofluids achieve up to 17.85 % improvement in heat transfer, while functionalized MWCNTs enhance stability but increase viscosity and pumping power. These findings provide valuable insights for optimizing cooling systems in engineering applications.

The Canadian SWeeping Energetic Particle Telescope (SWEPT) targets an assessment of the pitch angle dependence of particular space radiation, and will address and characterize the energy and directional dependence of this space radiation in the lunar environment. The project focuses on an assessment of the fundamental plasma processes which accelerate the particles to create this severe radiation hazard for astronauts in deep space, and assess radiation risk mitigation. By using an innovative sweeping look direction to determine the angular and energy dependence of the radiation on the Lunar Gateway, the SWEPT can assess the temporally evolving solar energetic particle (SEP) radiation in the heliosphere, emitted in solar eruptions and accelerated at interplanetary shocks, as well as address the impacts of primary and secondary radiation hazards on the Lunar Gateway. The SWEPT will also contribute to the development of effective deep space radiation mitigation strategies, such as those based on the early arrival of solar energetic electrons in advanceof SEP protons for humans on the lunar surface or in the lunar vicinity.

Multiphase flow and heat transfer processes are involved in various applications, such as water desalination, sterilisation, and power generation. Environmentally friendly and sustainable system operation can be ensured through the utilisation of renewable energy resources. Furthermore, the thermal efficiency of these systems can be enhanced by using nanofluids. This study reports an experimental investigation of the photothermal conversion properties of polyethylenimine (PEI) functionalised Copper oxide (CuO) nano particles used in Lithium Bromide (LiBr) salt solutions. The nano particles were characterised by the dynamic light scattering (DLS), transmission electron microscope (TEM), ultraviolet visible (UV-Vis) spectrophotometer. The long-term stability of the prepared nanofluid was evaluated using a high-speed centrifuge analyser. The instability index of 0.071 +/- 0.002 indicated low agglomeration and sedimentation tendencies. Photothermal conversion efficiency for different concentrations of CuO was experimentally investigated under a solar simulator. The experiments were conducted with nanofluids containing 55 wt% of LiBr and PEI functionalised nanoparticles, with loading ranging from 0.05 to 0.15 wt%. The addition of nanoparticles resulted in an increase in surface temperature, up to 90.69 +/- 2.7 % higher than the base case tested with deionised water (DIW). Experimental results further confirms that the nanofluid tested in this study has the potential to significantly increase solar energy trapping efficiency and evaporation rate due to a localised solar energy harvesting by the surface of nanofluid. It was found that a 0.1 wt% CuO NP concentration is the optimum nanofluid concentration in terms of stability for enhanced sensible and latent heat efficiencies. (c) 2025 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

The present experimental study investigates the thermal and hydraulic performance of Ethylene Glycol (EG)-based ZnO nanofluids (NFs) in circular minichannel test sections, each of 330 mm in length and 1.0-2.0 mm inner diameters. The experiments were conducted under steady-state constant heat flux and laminar flow conditions. The stable ZnO/EG-based NFs were synthesized using a standard two-step method in varying nanoparticles (NPs) loadings (0.012-0.048 wt %). The morphological characteristics, crystal structure, and specific surface area (SSA) showed that the NPs were sized in nm, possessing excellent crystal structure and enhanced surface area. Thermal conductivity (TC) and viscosity (VC) of the NFs were examined in the 20-60 C-degrees temperature range. Both TC and VC possessed an increasing trend with the rise in concentration of the NPs. However, with the temperature rise, TC increased while the VC decreased and vice versa. The highest enhancements in TC and VC were 14.38 % and 15.22 %, respectively, at 40 C-degrees and 0.048 wt% of NPs loading. The highest enrichment recorded in the local and average heat transfer coefficient (HTC) were 14.80 % and 13.48% in a minichannel with 1.0 mm inner diameter, respectively. It was directly proportional to the NPs loading and volume flow rate of the NFs. The friction factor was also directly proportional to the test section's inner cross-sectional area, while the pressure gradient showed an inverse behavior. An inverse relationship was recorded for the volume flow rate of the NFs and vice versa. Maximum friction factor and the pressure drop for all three minichannel test sections were recorded as 34.58 % and 32.16 %, respectively. The wellknown Shah correlation predicted the local and average HTC within +/- 15.0 %, while the friction factor and the pressure gradient were well predicted by the Darcy correlation within the +/- 10.0 % range.

The solar-powered thermoelectric refrigerator (SPTR) is an innovative approach that uses solar energy to cool spaces. Its effectiveness relies on solar insolation rates and an intelligent dual-axis solar tracking system (STS) that maximizes solar energy capture. Performance analysis of SPTR with the fixed panel solar system (WST) and dual-axis STS by keeping the SPTR at a standard ambient temperature of 25 °C was carried out under local climate conditions. The experimental test setup includes a thermoelectric refrigerator (TER), thermoelectric module (TEM), solar panels, and STS. The experimental findings showed that the coefficient of performance (COP) of SPTR depends on the solar irradiance, the system's input power, the surface temperature of the solar panels, and the cooling rate. The maximum and minimum values of COPs were 1.19 and 0.27 for directly coupled SPTR with a WST and 2.07 and 0.39 for STS, respectively. Compared with the stand-still solar system, a COP enhancement of 44–75 % is achieved. The results also show that the cooling load is a function of the refrigerated space, and the products are to be cooled, which is affected by the thermoelectric properties of the TEM. The cooling rate is recorded at its maximum when the system is operated using an STS on a clear sunny day with a maximum solar insolation rate. The SPTR has proven to be environmentally friendly, the best alternative to conventional cooling systems, and sustainable due to the independence of traditional energy resources.

Experimental setup has been designed and tested for local heat transfer performance of mPCM slurry flow inside the microchannels under convective boundary condition following unique inverse method. The heat transfer data were collected at ninety-eight precise locations along the flow direction of mPCM slurry inside six microchannels. The experimental setup was validated for both pure water and mPCM slurry with available published literature and found to be in good agreement. The experiments were conducted with mPCM slurry for 5–10

The advancement of nanotechnology has demonstrated the ability of metal-oxide-based nanofluids (NFs) to produce high heat flux in microscale thermal applications. Convective heat transfer (HTC) and flow characteristics (pressure drop (ΔP) and friction factor (f)) of aqueous ZnO NFs' within a circular mini tube (Di = 1.0 mm, L = 330 mm) were analyzed. Experiments were carried out under steady-state and varying flow rates using 0.012–0.048 wt % of NFs and sodium hexametaphosphate (SHMP) and acetylacetone (ACAC) as surfactants (SFs). Laminar flow and constant wall heat flux conditions were used to assess NFs heat transfer properties, ΔP and f. The viscosity (VC) and thermal conductivity (TC) of NFs exhibited a strong dependence on the operating temperature and NFs concentration. VC and TC increased by increasing the NFs concentration and decreased by increasing the operating temperature. Maximum VC and TC enhancement of 16.75% and 23.70% were achieved for SHMP-stabilised NFs, respectively. The average HTC increased by increasing NFs loading and flow rate, with HTCmax of 17.0% noticed for ACAC-stabilised NFs. The ΔPmax and fmax were 16.0% and 12.0%, respectively. Experimental and theoretical results showed a maximum deviation of ±7.0% and ±4.0%, respectively.

Photovoltaic solar energy has emerged in Brazil in distributed generation due to affordable costs and its application in different segments of the market. However, the electric energy storage in the photovoltaic systems is only viable for certain conditions in which the installation does not have access to the electricity network and the thermal portion of the solar energy is lost to the ambient. Heliothermic power plant represents another system available for solar electricity generation, which has higher costs, but takes better advantage of the portion of thermal energy and allows energy storage efficiently to meet the demands during periods without incident solar radiation. Heliothermic and photovoltaic generation have great potential in the Southeast and Northeast regions of Brazil, but the costs of both technologies cannot meet the demands during periods without solar radiation. This work presents a conceptual analysis of compound parabolic solar concentrators along with hybrid of photovoltaic and thermal collector systems to meet both the demand during sunlight hours and without solar radiation. The investigation consisted of implementing an organic Rankine cycle with different heliothermic plant configurations and the analysis of the diode model to examine different commercial photovoltaic cells operated in the Rankine cycle evaporation region. The results showed that the best working fluid for the application is R245fa with Urea-NaCl as molten salt for the thermal energy storage. The expected electrical power for the hydride cycle is 1580W at 2600 rpm and at 80°C of evaporation temperature, enabling a power generation for 1 hour and 20 min without solar radiation.

The brick kiln industry is one of the largest and most highly unregulated industrial sectors in developing countries. Most of the kilns use low-quality coal as primary fuel along with small quantities of bagasse, rice husk, and wooden chips. As a result of inefficient methods of combustion in conventional brick kilns, such as fixed chimney Bull's trench kilns (FCBTKs), harmful pollutants are emitted in high quantities, which ultimately deteriorate the environment and are widely in operation in Pakistan. The most prominent harmful pollutants include carbon dioxide (CO2), carbon monoxide (CO), sulphur dioxide (SO2), black carbon (BC), and particulate matter less than 2.5 microns (PM2.5). Over the years, new technologies have been adopted by developed countries for the reduction of environmental burdens. One of these technologies is induced draught zigzag kilns (IDZKs), or zigzag kilns (ZZKs), technology, which effectively improves the combustion across the path of bricks stacked in a zigzag pattern. For the mass adoption of this technology, environmental assessment and comparison of both technologies is a crucial step. Both types of kiln sites are investigated for the analysis of their emissions and their environmental impact in this work. Carbon mass balance equations are used for the calculation of emission factors. Collected inventory data is then used for the life cycle assessment of both types of kilns using open LCA (version 1.10.3) and the Eco-invent database. According to the study, ZZK technology outperforms FCBTK in all aspects. The analysis of the specific energy consumption (SEC) of fired bricks for each kiln type reveals that ZZKs require 30% less energy than the conventional FCBTK. This implies that ZZKs demand lesser fuel than FCBTKs. The zigzag technology adoption scenario, in particular, can lead to approximately 30% lower CO2 emissions, which can be further reduced by up to 80% when taking into account black carbon (BC) emissions. Additionally, the adoption of zigzag technology can result in a 35% decrease in PM2.5 emissions. The study shows that adopting ZZK technology significantly reduces impact categories, such as particulate matter formation (PMF), photochemical oxidant formation (POF), and terrestrial acidification (TA) by 63%, 93%, and 95%, respectively.

This research presents the numerical and empirical efforts to investigate the effect of friction stir welding (FSW) parameters on the weld temperature, weld strength, and weld hardness for novel brass known as yellow brass 405-20. The numerical approaches used to measure the weld temperature and weld strength were studied for the first time for yellow brass 405-20 and their validations via empirical studies. Two numerical models were simulated including transient thermal analysis and static structural analysis. Thermal distribution leading to maximum weld temperature during FSW of yellow brass was investigated via both simulations and experiments. Moreover, the ultimate tensile strength, namely the weld strength, was measured numerically and validated from its empirical counterpart. Finally, weld hardness was measured empirically to explore the joint health. A maximum temperature of 598 °C was recorded, which was much below the melting point of brass. Joint strength of 228 MPa was observed, which is 83% of the base brass strength. Microscopic examination of the weldment revealed the underlying mechanisms of less weld strength as compared to the parent brass material strength.

EDITORIAL article Front. Energy Res., 13 December 2023Sec. Bioenergy and Biofuels Volume 11 - 2023 | https://doi.org/10.3389/fenrg.2023.1339666