ABSTRACT Across the arid and semi‐arid regions, the scarcity of fresh water is a critical problem. The demand for fresh water can be solved using conventional desalination plants; however, their high energy demand and initial capital cost remain their constraint. A solar still is such an alternative, as it is a sustainable and low‐cost solution and uses solar heat as a renewable form of energy. However, solar stills are less attractive than conventional desalination plants due to their low thermal efficiency and poor heat retention. To address these constraints, the present work reports the use of agro‐industrial waste (walnut shells) as thermal energy storage (TES) in a tubular solar still (TSS) in a flat absorber. Walnut shells have been used as a thermal energy storage in conical geometries, but still their influence on the mass of TES loading has not been studied so far. In the present experimental investigation, three identical solar stills, namely traditional TSS (TTSS) and solar stills with 5 and 10 kg mass of walnut shell, are tested under the identical outdoor conditions, and their thermal performance (energy and exergy), economic performance, and environmental performance (4E) analysis are studied. The experimental findings revealed that walnut shell with 10 kg mass as thermal energy storage produced a maximum cumulative yield of 8.01 kg/m 2 /day which is 31% higher compared to the TTSS. Similarly, the mean energy and exergy efficiencies are improved from 49.13% to 64.41% and 3.23% to 5.81%, respectively, compared to the TTSS. Compared to the baseline (TTSS), the solar still with 10 kg walnut shell extended the water temperature for an effective evaporation rate, especially during the off‐sunshine period due to their higher porosity and higher carbon content. Economic analysis revealed that the cost of fresh water produced from the modified solar still decreased to 0.0069 from 0.0085 $/L, with a reduction in the payback period to 33 days. Similarly, the CO 2 mitigation reached 21,413 kg. These findings establish walnut shells as a low‐cost, circular‐economy‐aligned TES that materially improves the technical and financial viability of solar‐driven desalination.
ABSTRACT Waste heat rejected from gas turbine exhaust represents a substantial and largely unexploited energy resource, and the organic Rankine cycle (ORC) is the established means of recovering it. The selection of a working fluid for this duty is, however, increasingly constrained by environmental regulations, and the introduction of an internal heat exchanger (IHX) alters the thermodynamic and economic balance of the cycle in ways that have not been assessed consistently for conventional and next‐generation fluids under a common set of conditions. The present study addresses this gap. Its objectives are threefold: to quantify the thermodynamic and thermo‐economic penalty associated with substituting low global warming potential (GWP) fluids for conventional hydrocarbons; to determine the extent to which internal recuperation offsets that penalty; and to establish whether the resulting fluid ranking is governed by thermodynamic or by economic criteria. Eight working fluids—toluene, cyclohexane, cyclopentane, isopentane, n‐pentane, R1233zd(E), R245fa, and Novec 649—are compared in basic and regenerative configurations using a model implemented in Python with CoolProp, validated against published gas turbine and ORC data to within 1.5% and 2.1%, respectively. The analysis combines first‐ and second‐law performance, component‐level exergy destruction, capital cost estimation, and uncertainty propagation, with the ORC evaporation temperature coupled to the exhaust‐gas exit temperature through the pinch‐point constraint. Regeneration raises the thermal efficiency by 41.7%–53.2%, with the largest relative gains accruing to the low‐GWP fluids, which narrows the performance spread between fluid families from a factor of 2.01 to 1.86; total exergy destruction falls by 44.5% for toluene at unchanged net work output. Toluene attains the highest thermal efficiency (26.44% basic, 37.46% regenerative) and the lowest specific investment cost ($374/kW), while Novec 649 is the least favorable on both counts ($1471/kW). The economic ranking is shown to follow specific work rather than thermal efficiency, and the heat exchangers are found to dominate both the irreversibility and the capital cost. All configurations remain economically viable, with levelized costs of ¢0.59–2.31/kWh against an assumed selling price of ¢8/kWh.
ABSTRACT The present investigation aims to explore the nonsimilar stagnation‐point flow and heat transfer characteristics of a Williamson nanofluid over a stretching cylinder. This study investigates the coupled influences of magnetic field, viscous dissipation, nonlinear radiative heat flux, Joule heating, Brownian motion, and thermophoresis on the hydrodynamics and heat transfer characteristics. This mathematical modeling of the phenomenon is achieved by using basic conservation laws of mass, momentum, energy, and concentration. To enable a more efficient and insightful analysis of the underlying physical phenomena, the original dimensional nonlinear partial differential equations are transformed into dimensionless form using suitable nonsimilar transformations. After that, these equations are numerically solved by using the Finite difference method to investigate how different physical parameters affect the profiles of temperature, velocity, and nanoparticle concentration. The obtained results are compared with previously published work, and the close agreement confirms that the numerical scheme is accurate and reliable. Key findings show that the Williamson fluid parameter raises the velocity profile. Viscous dissipation and thermal radiation both increase heat transfer. The streamwise coordinate shows increasing effects on the velocity and temperature profiles, but dual effects on the concentration profile. The obtained findings can contribute to the understanding of nanofluid transport phenomena in engineering systems involving simultaneous heat and mass transfer, particularly in material processing and biomedical applications.
ABSTRACT This study systematically investigates the evolution mechanism of Rayleigh–Taylor instability (RTI) in porous media using a lattice Boltzmann model at the representative elementary volume (REV) scale. The results indicate that miscible RTI in REV‐scale porous media is governed by a structural–transport–force coupling mechanism. Porosity mainly regulates the effective flow area and structural resistance, whereas the Darcy number controls permeability‐related resistance and inertial flow reorganization. The Rayleigh number mainly reflects the intensity of buoyancy‐energy input. By analyzing the distributions of the horizontal and vertical force components, Fx and Fy , respectively, the present study shows that force‐field symmetry breaking is closely associated with vortex formation, interface deformation, and fingering development. Under the present numerical configuration, the transition from resistance‐limited diffusion to buoyancy‐driven convection appears around ε ≈ 0.35, Da ≈ 10 −4 , and Ra ≈ 10 5 . These values are interpreted as case‐dependent transition ranges rather than universal critical constants. The findings may provide useful guidance for controlling mixing and heat/mass transfer in porous‐media systems, including CO 2 geological storage, miscible displacement, catalytic porous layers, and porous heat‐transfer structures.
ABSTRACT This paper experimentally investigates the use of Nano‐Coating materials (TiO 2 and SiO 2 ) to analyze their effects on solar PV cells and identify the optimal ratio for enhancing solar panel performance. The study includes an experimental module to measure voltage, current, temperature, and other relevant data, comparing average electrical energy production before and after applying the coating. Panels coated with a 30% TiO 2 and 70% SiO 2 mixture demonstrated improved efficiency across all types. Uncoated panels showed a 6% efficiency increase with cleaning, while single‐layer nano‐coated panels achieved a 9% increase without cleaning and a 13% increase with cleaning, marking the highest recorded improvement. Two‐layer nano‐coated panels exhibited an 8% efficiency gain without cleaning and a 10% increase with cleaning, slightly lower than the cleaned single‐layer coating. Additionally, water consumption for cleaning was reduced, with single‐layer coated panels requiring 30% less water and double‐layer coated panels using 20% less compared to uncoated panels. The application of TiO 2 and SiO 2 nanofluids enhances the panels' self‐cleaning properties, reducing dust accumulation and leading to higher output power and improved overall efficiency.
ABSTRACT This work investigates the thermal performance of roof systems integrated with phase‐change materials (PCMs) to mitigate cooling loads under severe hyper‐arid climatic conditions. The primary objective is to evaluate the capacity of paraffin wax to enhance the thermal inertia of roofs and successfully shift cooling demands during peak solar hours. Dual custom‐built experimental test cells were deployed in Baghdad, Iraq, to conduct the field evaluations. To ensure a strict one‐dimensional (1D) downward heat flux through the roof and eliminate lateral thermal interference, the vertical walls of both cells were comprehensively insulated. The experimental data demonstrate that the PCM‐integrated roof effectively stabilized the indoor thermal environment, achieving a 40.5% reduction in the thermal load leveling rate (TLLR). Furthermore, a 3.3°C reduction in the peak indoor air temperature alongside a significant time lag of 4.5 h was recorded, thereby successfully shifting the cooling load to off‐peak periods. From an economic perspective, the system yielded an average daily electricity cost saving of 213.3 IQD and a carbon emission reduction of 1.73 kg of CO 2 per day. Given a calculated payback period of 2.05 years, these findings conclusively demonstrate the technical viability and economic feasibility of the proposed PCM‐roof configuration for building energy efficiency in extreme desert environments.
ABSTRACT The article expounds on forced convective flow over an annular region with an irregular boundary in a diverging channel and on the fluid properties. The nanosized particles are used in the inner nanofluid region and the base fluid in the annulus region. The nonlinear governing equations for the inner and annulus regions are converted into nondimensional partial differential equations using similarity transformations, which are then simplified to linear form by the quasilinearization method. The system of linear equations is then solved using the finite‐difference method. Results are obtained and expressed in terms of velocity, temperature, and concentration profiles, including magnetic and dissipation parameters, the Nusselt number, and skin friction, and are discussed using graphical aids. The findings suggest that the nanofluid region yields significant changes in velocity profiles in the presence of the magnetic parameter (). In the case of temperature profiles, the annulus region has a lower heat‐transfer rate. The diameter of the annulus region has a dominant impact on fluid behavior. Pressure drop and resistance are higher in the annulus region than in the inner region in terms of skin friction. The temperature profile overshoots in the annulus region for viscous dissipation (). In the case of the inner region, the reverse trend is observed; the mass transfer rate () increases by approximately 45% as the Lewis number rises from 1.0 to 2.0 in the inner region. An increase in Lewis number strengthens mass transfer characteristics by lowering mass diffusivity relative to thermal diffusivity, resulting in a thinner concentration boundary layer. As a result, the concentration gradient at the surface steepens, increasing the mass transfer rate.
ABSTRACT Freshwater scarcity remains one of the most pressing humanitarian and environmental challenges of the 21st century, driving urgent demand for decentralized, low‐energy purification technologies. Among passive solar desalination systems, solar stills have attracted sustained research attention; however, their characteristically low distillate yield has long constrained practical adoption. Vertical wick integration—encompassing both standard vertical wick solar stills (VWSS) and the more advanced vertical corrugated wick solar still (VCWSS)—has emerged as a transformative design strategy that simultaneously amplifies evaporation surface area, exploits capillary‐driven feedwater transport, and feeds pre‐heated brine into a coupled primary still, creating a synergistic thermal cascade. This review critically analyses 10 experimental investigations spanning eight distinct still geometries—conventional, coiled, pyramid, stepped, tray, hemispherical, spherical, tubular, and concave—each augmented with vertical wick subsystems and evaluated alongside co‐applied enhancements such as silver nanoparticle‐enriched phase change materials (Ag‐PCM), corrugated absorbers, internal reflectors, extended fins, and magnetic field application. The results are striking: VCWSS‐integrated configurations consistently outperform their VWSS counterparts, with the fully optimized concave‐VCWSS‐Ag‐PCM system achieving a peak daily productivity of 13,650 mL/m 2 /day—a 326% gain over a conventional baseline—and a thermal efficiency ceiling of 76.4%, the highest recorded across all reviewed configurations. Even the most modest wick‐integrated hybrid, a pyramid still coupled with VWSS and nanocomposite PCM, delivered an 84% productivity uplift and reduced water production cost from USD 0.019 to USD 0.0142 per liter, underscoring the economic accessibility of wick‐based retrofits across still geometries. Across the full dataset, freshwater production costs span USD 0.0048 to USD 0.012 per liter—competitive with many decentralized purification alternatives—while annual avoided CO 2 emissions reach up to 29.3 tons per installation, affirming meaningful environmental co‐benefits. Isolated performance attribution reveals that the vertical wick subsystem alone contributes 107%–117% incremental yield gains beyond the improvements already achieved by geometric and material modifications, confirming its role as the dominant driver of hybrid system performance. Despite these advances, the review identifies four persistent research gaps: the restriction of nearly all studies to single‐day, lab‐scale experiments; the absence of long‐term wick durability and salt‐fouling data beyond bi‐annual maintenance cycles; insufficient investigation of real industrial or agricultural wastewater feeds; and limited interdisciplinary coupling with photovoltaic, wind, or adsorption‐based energy subsystems. To bridge these gaps, future work is directed toward machine‐learning‐assisted multi‐variable optimization, CFD‐guided wick geometry refinement, next‐generation metamorphic fabric absorbers, and pilot‐scale field deployment targeting 8–10 L/m 2 /day in arid regions at a capital cost below USD 50/m 2 . By consolidating quantitative performance evidence, economic benchmarks, and a forward‐looking research roadmap, this review provides a definitive reference for engineers and scientists advancing scalable, sustainable solar desalination.
ABSTRACT This manuscript investigates the transient thermal characteristics of graded longitudinal fins subjected to boundary conditions of a step change in root temperature and convective tip at the extremities of fin. Herein, the spatially varying heat conductivity of graded fin is treated as a polynomial function of temperature, and the convection coefficient of environment fluid is considered as a power law function of temperature. The non‐linear governing equation is explicitly solved to determine the numerical solution using the mesoscale Lattice Boltzmann (LB) solver coupled with in‐house source code. The transient thermal characteristics , namely instantaneous temperature , steady‐state temperature, threshold time , and instantaneous efficiency of homogeneous material ( HM ) and linearly graded material ( LGM ) fins, have been investigated. The threshold time ( τ th ) required to attain the steady‐state temperature (θ ss ) is obtained for a stipulated location for HM and graded LGM longitudinal fins. The reported results reveal that owing to their tailored material composition, LGM quickly dissipates the heat as compared to the uniform composition of HM material for the same value of equivalent thermal conductivity. Increasing the value of the grading factor ( β ) from β = 1.0 to β = 3.0 significantly enhances the magnitude of the relative improvement percentage ( ϕ th ) for instantaneous normalized temperatures ( ϕ in ) approximately from 2.324% to 13.178 and steady‐state temperature ( ϕ ss ) from 2.314% to 11.051%, whereas it decreases the threshold time ( ϕ th ) from 2.500% to 15.789%. Consequently, the relative improvement percentage(ϕ th ) of ( IE ) can be improved up to 12.598%. Rapid attainment of a steady state indicates that LGM fins quickly dissipate the heat, consequently lessening the impact of thermal deformation and stress on the material. Hence, comprehending the material grading significance facilitates material selection for applications wherein temperature management is paramount. The reported data set can be utilized as design references for practicing engineers.
ABSTRACT In aerospace and defense industries, high‐power radar transmit/receive modules (TRMs) are often operated under extreme heat flux conditions, demanding compact and highly efficient thermal management solutions under size, weight, and power (SWaP) constraints. Due to high surface‐area‐to‐volume ratio and superior heat removal capability, microchannel heat sinks (MCHS) have emerged as a promising approach. Although MCHS provide enhanced heat transfer capability, pressure drop, substrate material sensitivity and long‐term operational reliability remain critical challenges in many cooling systems. This paper presents a combined analytical and computational investigation of the thermal and hydraulic performance of straight and zigzag microchannel heat sinks subjected to a 200 W heat load. Temperature dependent water properties are considered under laminar flow conditions (Re = 58–76). The influence of three substrate materials (Copper, Al6061, and SiC) on base temperature distribution and thermal spreading is evaluated. Numerical simulations are validated against analytical calculations, showing deviations below 1%. Results indicate that zigzag channels enhance local heat transfer but increase pressure drop by approximately 8% compared to straight channels due to bend‐induced flow resistance. Copper substrates reduce peak base temperature by up to 8% relative to Al6061 owing to superior thermal conductivity. A conceptual AI‐based condition‐based monitoring (CBM) framework is further proposed to enable predictive fault detection using pressure drop and thermal‐resistance indicators. The findings provide a physics‐based design reference for intelligent microchannel cooling architectures in high‐power radar systems.
This study investigates the cilia-driven transport of an incompressible micropolar fluid through a porous ductuli efferentes channel under the combined effects of thermal radiation, heat generation, mixed convection, and activation energy. The mathematical model governing momentum, microrotation, energy, and concentration transport is developed using lubrication approximation theory, resulting in a coupled nonlinear system of differential equations. The reduced equations are solved numerically through a second-order finite difference method (FDM). To accelerate the prediction process and reduce computational cost, an artificial neural network (ANN) model based on TensorFlow is developed using the numerical data set generated from the FDM solutions. The data set is divided into training, validation, and testing subsets to ensure accurate learning and prediction performance. The influence of important physical parameters, including Brinkman number, radiation parameter, Schmidt number, porous-medium parameter, Grashof number, micropolar parameters, and activation energy, on velocity, temperature, concentration, pressure gradient, pressure rise, and trapping phenomena is examined in detail. The results reveal that thermal radiation reduces fluid temperature, whereas heat generation and viscous dissipation significantly enhance thermal transport. Increasing activation energy elevates the concentration profile due to reduced chemical reaction strength, while larger Schmidt numbers suppress mass diffusion. The ANN predictions exhibit excellent agreement with the numerical solutions with very small prediction errors, confirming the reliability and efficiency of the proposed intelligent computational framework. The present analysis provides important insights into seminal fluid transport mechanisms in the male reproductive tract and offers potential applications in biomedical engineering, reproductive biomechanics, and bio-inspired microfluidic systems.
The present study investigates the heat transfer in Darcy-Forchheimer flow of carbon-nanotubes (CNTs) including thermal radiation, viscous dissipation, and Joule heating over exponential curved stretching surface. Nanoparticle transport is modeled using the Xue formulation. The governing nonlinear partial differential equations are transformed through suitable similarity variables and solved numerically via the Maple ODE solver technique. The highlights of the present work are: Excellent agreement has been achieved between the current numerical results and the previous findings under limiting conditions. Taguchi method was used to recognize the impacts of key parameters on heat transfer performance. This statistical approach reduces the computational and empirical efforts and is very much accurate with an assessed error of 0.01%. Multivariate linear regression analysis and Pearson correlation coefficients are utilized to find the individual influence of parameters and found very good observations. Thus, the current study explores the combined thermal effects with three statistical approaches and the findings of the study have applications in biomedical and environmental technologies.
This study examines a compact latent heat thermal storage system featuring a finned-tube helical heat exchanger and two phase change materials: pure beeswax and a beeswax-paraffin eutectic mixture. Experimental charging and discharging processes were performed at flow rates ranging from 40 to 100 L/h to evaluate the influence of operational parameters on the system's thermal behavior. The system would demonstrate high reliability, with temperature deviations below +/- 1.1%, and melting time would be cut by up to 50% at higher flow rates. Although faster melting would come at the cost of lower effectiveness, solidification would remain highly efficient, reaching up to 0.93. The study would also highlight a clear shift from convective limitations at low flow rates to PCM-conductivity limitations at higher ones. Throughout all tests, natural beeswax would offer superior thermal stability and outlet-temperature uniformity. With efficiencies near 0.9 and C-factors around 0.019, the compact finned-tube design would outperform conventional systems, suggesting that such enhanced geometries coupled with natural PCMs could offer a highly effective and sustainable solution for low-temperature thermal energy storage.
ABSTRACT Conventional cooling systems are major energy consumers in hot climates, directly contributing to increased carbon emissions and placing a significant strain on Iraq's national electricity grid. This study aims to explore and evaluate clean and sustainable alternatives to conventional systems. The methodology is based on a comparative analysis of various cooling technologies, including mechanical, absorption, adsorption, drying, and hybrid systems, using key performance indicators such as the coefficient of performance (COP), energy consumption, carbon emissions, and system cooling capacity. The results show that innovative solar cooling technologies offer superior operational efficiency and significantly lower carbon emissions compared to mechanical systems. Single‐effect absorption systems are the optimal choice for the local climate, as they can operate efficiently at operating temperatures (80°C–85°C) achievable with evacuated solar collectors. Furthermore, integrating thermal storage (PCM) technologies reduces system performance fluctuations, reaching approximately 33.5% [1], thus ensuring cooling stability. Based on an in‐depth analysis of the latest available literature, it is possible to save up to approximately 45% [2, 3] of the energy consumed by harnessing the abundant solar radiation in Iraq for most days of the year, depending on the type and efficiency of the system used.
ABSTRACT This study investigates steady two‐dimensional flow of a viscous, electrically conducting fluid over a vertical permeable surface under a transverse magnetic field. The analysis incorporates induced magnetic field effects corresponding to a high magnetic Reynolds number, along with viscous dissipation, chemical reaction, and internal heat generation or absorption. Using suitable similarity transformations, the governing nonlinear partial differential equations are reduced to a system of coupled ordinary differential equations, which are solved numerically. The effects of key parameters such as magnetic parameter, permeability, Prandtl number, Schmidt number, Eckert number, magnetic Reynolds number, chemical reaction parameter, and heat source or sink parameters on velocity, temperature, concentration, and induced magnetic field profiles are investigated. The results reveal that magnetic effects tend to slow down the fluid motion, while viscous dissipation enhances the temperature distribution. Increasing chemical reaction and Schmidt number reduces concentration, whereas heat generation and absorption exhibit opposite influences on thermal behavior. The numerical results show strong agreement with available benchmark solutions under limiting conditions, confirming the accuracy and reliability of the present analysis. The novelty of the present study lies in incorporating induced magnetic field effects at finite magnetic Reynolds number along with viscous dissipation, chemical reaction, and heat source or sink mechanisms in a unified model. The results reveal that the magnetic parameter significantly reduces velocity while enhancing temperature, whereas chemical reaction reduces concentration profiles. These findings provide useful insights for applications in thermal management and energy systems.
ABSTRACT With many challenges casting a shadow on the amount of fresh water available for human use. It has become essential to develop real solutions to produce fresh water in various ways, including using solar energy. The outputs and efficiencies available for conventional solar stills are somewhat limited. Many researchers have studied the possibility of modifying the design of solar stills to increase efficiency and productivity. In the present study, several modified designs were examined. The studies showed that the use of a Fresnel lens coupled with a single‐slope, single‐basin design gives the best possible improvement in productivity of about 638.02%. While the remaining productivity improvements ranged from 24.8% to 370%, this review also concludes that the most suitable design for solar stills in industrial applications is the tubular type with a wick, while the single‐slope type is most suitable for domestic and personal use. The reviewed modifications demonstrated productivity enhancements ranging from 15% to 676% relative to the conventional solar still.
ABSTRACT Rapid industrialization and urban expansion have intensified the discharge of toxic heavy metals and persistent synthetic dyes into aquatic systems, posing severe ecological and human health risks. Conventional remediation technologies, while effective at high contaminant concentrations, often suffer from sludge generation, limited selectivity, and high operational costs. This review critically examines recent advances in nanocomposite adsorbents as next‐generation materials for sustainable wastewater treatment. Emphasis is placed on carbon‐based nanomaterials (graphene derivatives, carbon nanotubes, nano‐activated carbon), metal–organic frameworks (MOFs), polymer‐based nanocomposites, layered double hydroxides, molecularly imprinted polymers (MIPs), and zeolite‐based hybrids. They exhibit desirable physicochemical properties including ultrahigh specific surface areas (> 500 m 2 g −1 ), finely tuned pore structures, and tailored functional groups (–NH2, –SH, –COOH), that lead to exceptionally high adsorption capacities (generally > 500–1000 mg g ‐1 ) for Pb2 + , Cd2 + , Cr(VI), As(V), and dyes (methylene blue, Congo red). The adsorption mechanisms encompassing electrostatic attraction, surface complexation, ion exchange, π–π interactions, redox reactions, and size‐selective confinement are well interpreted by Langmuir/Freundlich isotherms and pseudo‐second‐order kinetic models. Efficient regeneration techniques involving chemical elution, thermal treatment, magnetic separation, and electro‐assisted desorption allow 5–15 reuse cycles with > 85%–99% capacity retention. Notwithstanding, these nanoadsorbents face nanoparticle release, energy‐intensive synthesis, environmental impacts of lifecycle, and lack of stringent regulations. Future directions should focus on green nanomaterial synthesis, multifunctional nanocomposites, holistic regeneration systems, and pilot‐scale applications for cost‐effective and environmentally friendly nanomaterial‐enabled water purification.
ABSTRACT Low efficiency is the primary disadvantage of using solar stills (SSs). The efficiency is based on the SS's daily yield, which is strongly influenced by the cover temperature. Lowering the SS cover temperature increases the temperature difference between the SS cover and the basin water, and enhances the condensation process of the water vapor. Numerous technologies were employed and examined to improve the SS's performance through cover cooling. Water and air cooling are the most well‐known technologies for SS cover cooling. Also, thermoelectric technology is used to cool the cover plate via the Peltier effect. Other methods for SS cover cooling are being investigated, including integrated fins, nanoparticles, and an external heat exchanger. This review's objective is to examine the impact of cooling the SS cover on freshwater productivity. The results of the discussion showed that the water‐cooling technique increased freshwater productivity and energy efficiency by 107.7% and 103.4%, respectively, while reducing the cost of generated water by 38.4%. Utilization of air cooling with a velocity of 4 m/s raised the water productivity to 104%, while forced air (FA) cooling at a velocity of 5 m/s can provide a temperature difference of 21°C between the cover and basin water. When the external condenser was combined with the SS, the energy efficiency and freshwater productivity rose by 18.2% and 33.12%, respectively. Although the initial cost and energy consumption were higher, thermoelectric cooling increased water output by 74% and reported a cost of 0.0326 $/L. According to computational research, using nanofluid cooling increased water productivity by 11.09%. Also, the phase‐change material and nano‐phase‐change material augmented the freshwater productivity by 27.7% and 60.37%, respectively. This review is useful for researchers to expand their knowledge and help them select the best technique for enhancing SS cover cooling, taking economic and environmental feasibility into account.
A comprehensive numerical investigation is presented for steady free convection of a micropolar fluid along an isothermal vertical plate embedded in a saturated porous medium, incorporating Darcy-Forchheimer resistance and viscous dissipation effects. The governing equations for continuity, linear momentum, microrotation, and energy are formulated within the framework of micropolar fluid theory and reduced to a coupled system of nonlinear ordinary differential equations using a local similarity transformation. Despite extensive studies on micropolar convection and porous-media transport, the combined influence of Darcy-Forchheimer resistance and viscous dissipation on micropolar free convection remains insufficiently understood. The primary objective of this study is to investigate the coupled effects of Darcy-Forchheimer resistance and viscous dissipation on momentum and heat transfer in micropolar free convection within porous media. The novelty of the present work lies in the simultaneous incorporation of micropolar fluid microstructure, nonlinear porous resistance, and viscous dissipation within a unified similarity-based framework. Therefore, the resulting boundary-value problem is solved numerically using the MATLAB Boundary Value Problem Solver (bvp5c) collocation-based solver. A systematic parametric study is conducted to elucidate the individual and coupled influences of porous-medium resistance, inertial drag, micropolar viscosity ratio, microrotation boundary condition, microrotation coupling and diffusion parameters, effective Prandtl number, porosity, and viscous dissipation on the skin-friction coefficient and local Nusselt number. The findings reveal that both the Darcy and Forchheimer resistance forces strongly influence heat- and momentum-transfer processes due to the restriction of fluid flow in the porous medium. In comparison, both micropolar viscosity and wall micromotion significantly enhance near-wall momentum and convective heat transfer, underscoring the importance of microstructure effects. The influence of viscous dissipation on the thermal fluid dynamics is found to increase temperatures and reduce wall temperature gradients, thereby decreasing heat transfer without substantially affecting the skin friction characteristics. Furthermore, there is a clear distinction between the parameters affecting momentum transfer and those influencing heat transfer. In summary, this investigation presents important physical understanding of the influence of micropolar microstructure, porous resistance, and viscous dissipation on the free-convection heat-transfer process.
ABSTRACT The integration of phase change materials (PCMs) into building walls is considered a promising passive solution for reducing thermal loads under autumn climatic conditions. However, under transient climatic conditions, the respective effects of PCM type, PCM quantity, and PCM location inside hollow bricks are still not fully clarified. In this work, a two‐dimensional 2D transient Computational Fluid Dynamics (CFD) study was carried out to analyze the thermal behavior of PCM‐integrated hollow brick walls under the climatic conditions of Kairouan, central Tunisia (35°40'N, 10°05'E), on October 10, 2025. Ten configurations were examined from a reference eight‐cavity hollow brick by varying the type of PCM and its position inside the cavities. The novelty of the present study lies in the isolation of the impact of PCM location within the same eight‐cavity hollow brick, comparing external‐side placement, internal‐side placement, and a fully filled cavity configuration for three melting temperatures under the same transient climatic conditions. Three PCMs were considered, namely RT26, RT30, and RT34, and three placement strategies were studied: external‐side placement, internal‐side placement, and a fully filled cavity configuration. The numerical model was developed in ANSYS Fluent R19 using the enthalpy‐porosity method. The results show that PCM position has a stronger influence on wall thermal response than PCM quantity under the conditions considered. For RT26, placing PCM in the external cavities led to premature melting and poor thermal performance, whereas internal placement reduced the daytime heat flux by 82.5% compared with the reference case. Among the three paraffins, RT30 gave the most balanced response, with a 51.5% reduction in daytime heat flux and a thermal time lag of up to 11 h. The results also show that PCM integration strongly reduces natural convection inside the cavities and shifts the thermal behavior toward a conduction‐dominated regime.
