This work focuses on developing a Low-cost, low-grade electrical-thermal solar humidification system, as a promising solution for freshwater production. To increase the air humidity ratio at the humidifier exit, a designed and instrumented solar humidifier harnesses solar radiation and receives both a forced hot air stream from a solar air collector and water droplets falling onto its absorber plate, where the droplets evaporate. The solar humidifier dimensions were 330 × 50 × 1000 mm. PV panels supplied electrical power to circulate water and air for preheating by a flat-plate and an air solar collector. Key factors influencing air’s relative humidity (RH) are air flow rates (0.5 m3/min to 1.5 m3/min), water drip rate (4 to 10 drops/s), and the solar humidifier’s absorber surface geometry (flat or dimpled). Tests were extended from 8:00 to 17:00 to evaluate air RH and temperature on clear-sky days in Baghdad, Iraq. Results showed that the highest outlet air RH was 61.2%, 72.4%, and 69.9% for water dripping rates of 4, 7, and 10 drops/s, corresponding to 0.167, 0.297, and 0.423 g/s, respectively, with a constant airflow rate of 0.5 m3/min. The best dripping rate was 7 drops/s. The outlet air RH from the humidifier was 72.4% and 85.6% for flat and dimpled absorbers, respectively, at an airflow rate of 0.5 m3/min and 7 water drops/s (0.297 g/s). The humidifier’s effectiveness was 85% and 70%, respectively. It is concluded that the dimpled absorber achieves significantly better humidification performance than the flat-plate absorber across all airflow rates. The humidifier pressure drops increases from 0.13 Pa to 0.36 Pa for the flat plate and dimpled plate, respectively, at solar noon, for a flow rate of 0.5 m3/min.

Solar distillers are a sustainable and simple solution for addressing water scarcity, but their limited productivity restricts their effectiveness. This work aimed to assess the thermal performance of a novel tracked, tilted, hexagonal tubular solar still (HTSS) of four-sectioned U-channel receiver. Two identical HTSSs were side-to-side tested in Baghdad-Iraq (33.3 degrees N, 43.3 degrees E) from June to September 2024. The thermal evaluation of single-axis tracking solar still, tilted at (5 degrees to 15 degrees) with the horizontal axis and charged with and without hydrogel beads for water depth of 60 mm. The still's thermal performance is assessed by analyzing heat transfer coefficients, energy and exergy efficiencies, as well as conducting cost and environmental impact analyses. A considerable improvement in still yield is achieved as hydrogel is charged in. Results showed that the still thermal efficiency is uplifted by (87.79, 96.24, and 108.26 %) for (2000, 4000, and 6000 beads), respectively, as the tilt angle increases from 5 degrees to 15 degrees. It was found that the present still (with 6000 hydrogel beads, and tilted at 15 degrees) has the best thermal and exergy efficiencies and produces 16.72 l/m(2), accompanied by 9.91 ton/year emission reduction of CO2, with a competitive cost for water production of 0.039 $/liter.

The deficiency of potable water resources and energy supply is emerging as a significant and concerning obstacle to sustainable development. Solar and waste heat-powered humidification dehumidification (HDH) desalination systems become essential due to the severe impacts of global warming and water shortages. This problem highlights the need to apply boosted water desalination solutions. Desalination is a capital-intensive process that demands considerable energy, predominantly sourced from fossil fuels worldwide, posing a significant carbon footprint risk. HDH is a very efficient desalination method suitable for remote areas with moderate freshwater requirements for domestic and agricultural usage. Several operational and maintenance concerns are to blame. The flow and thermal balances of humidifiers and dehumidifiers under the right conditions are crucial for system efficiency. These systems comprise a humidifier and dehumidifier, energy foundations for space or process heating and electricity generation, fluid transfer or efficiency enhancement accessories, and measurement-control devices. All technologies that enhance the performance of HDH systems are elucidated in this work. These are utilizing efficient components, renewable energy, heat recovery via multi-effect and multi-stage processes, waste heat-powered, and accelerating humidification and dehumidification processes through pressure variation or employing heat pumps, in addition to exergy and economical analyses. According to the present work, the seawater HDH system is feasible for freshwater generation. Regarding economics and gain output ratio, humidification–dehumidification is a viable approach for decentralized small-scale freshwater production applications, but it needs significant refinement. System productivity of fresh water is much higher with integrated solar water heating than with solar air heating. The HDH offers the lowest water yield cost per liter and ideal system productivity when paired with a heat pump. The suggested changes aim to enhance system and process efficiency, reducing electrical energy consumption and cost-effective, continuous, decentralized freshwater production. This thorough analysis establishes a foundation for future research on energy and exergy cycles based on humidification and dehumidification.

Freshwater scarcity poses a global challenge, particularly in regions where conventional water resources are limited. Solar stills offer an economical, sustainable solution; however, their yield is limited. This study aims to evaluate a new tracking concentrated tilted tubular solar still equipped with a heat-pipe TTSS-HP. The novelty of the present work lies in four aspects: a novel trough U-channel design that improves the interception of reflected solar radiation, a novel hexagonal glass cover design. A receiver formed of four-sections, combined with a heat-pipe and dual trough concentrators. Outdoor experiments are carried out in Baghdad, Iraq (33.27 degrees N, 44.37 degrees E), to test the water depth (55 mm, 65 mm) and still tilt angles (10 degrees, 15 degrees) impact on stills' yield and efficiency. The reported yield for TTSS-HP was enhanced by 62.1% and 46.3% for water heights of 55 and 65 mm, respectively, when the still is tilted at 10 degrees compared to the still with no heat pipe. While that for the still tilted at 15 degrees was 41.6% and 29.3%. It has been found that increasing the water content of the still from 55 to 65 mm increases the freshwater yield by 14.9% for the still tilted at 10 degrees and 21.3% for the still tilted at 15 degrees. The optimum thermal efficiency was 21.6% for a maximum water depth of 65 mm and a still tilt angle of 15 degrees. TTSS-HP achieves the highest daily yield of 5.34 L at a 15 degrees tilt angle and 65 mm water depth, while the still without a heat-pipe HSS yields 3.31 L at a 10 degrees tilt angle and a 65 mm water depth. It is concluded that TTSS-HP with trough reflectors improved freshwater yield by 62.1% and thermal efficiency by 49.12% compared to the baseline HSS.

The Humidification-Dehumidification (HDH) desalination technique offers a viable solution for providing freshwater to populations in water-scarce, remote areas. This study experimentally investigates a novel humidifying method by cross airflow over water-wetted pottery tubes, which function as a humidifier, incorporating a thermoelectric cooler to condense water vapor for freshwater production. To optimize freshwater production and thermal efficiency, meticulous design of these components and appropriate operational parameters are selected. Experiments were performed in three environments with differing temperatures and relative humidity levels, while air velocity varied from 1.02 to 1.89 m/s, and thermoelectric cooler voltage ranged from 6 to 12 V. These measures include GOR, COP, fresh water production, and dehumidifier efficiency. Air, saline water, and thermoelectric cooler voltage volume flow rates greatly affected system performance, according to the findings. The obtained optimal freshwater yield, COP, humidification efficiency, evaporation efficiency, and GOR were 1.7 L/hr, 4.3, 71 %, 65 %, and 4.6, respectively. Higher water productivity is indicated for low saline water flowrate supplied. Results show 71 % efficiency of the pottery tube humidifier for air speed lower than 1.02 m/s. Increasing the air flow rate from 38.88 m3/hr to 72 m3/hr decreases the system's freshwater yield from 1.7 L/hr to 0.7 L/hr. A 55.8 % reduction in COP is found as the thermoelectric voltage increases from 6 to 12 volts for the same air flow rate (38 m3/hr). The results indicate that pottery tubes and air velocity significantly influence freshwater yield and energy efficiency, thereby promoting cost-effective and sustainable atmospheric water harvesting.

This work explores the advancement and potential of solar-powered humidification-dehumidification (HDH) desalination systems, addressing the critical challenge of global water scarcity. Emphasizing solar-powered humidifiers in HDH systems presents an innovative solution per the urgent demand for sustainable freshwater sources utilizing abundant energy resources. This work reviews various humidifier designs, pointing out their crucial role in the efficiency and yield of HDH desalination units and their operational, maintenance, and scaling issues. Key factors, such as design effectiveness, water-vapor capacity, and material selection, are assessed to understand their impact on the system's overall performance and energy consumption. Moreover, recent advancements in solar technology, particularly in solar collectors and heat exchange mechanisms, present significant improvements in humidifier functionality. By synthesizing current research findings, this paper identifies pivotal factors for optimizing humidifier design and operation, underscoring the growing importance of solar desalination technologies in combating freshwater scarcity. This comprehensive overview not only advertised the current technological capabilities but also outlined future research directions, aiming to enhance the viability and accessibility of solar-HDH systems for widespread application.

Solar energy is still commonly used to produce clean drinking water due to its simple construction, low maintenance, and ecofriendliness. This work aims to experimentally investigate the yield upgrade and the thermal performance of a novel concentrated single-axis tracking trough tubular solar still (TSS). This tubular still is identified by three baffles that generate four interrupted sections in the U-receiver, which is inserted with copper mesh and fitted in a hexagonal-shaped glass cover. Two identical TSS models were side-by-side outdoor tested in Baghdad-Iraq 33.3 degrees N and 43.3 degrees E from January to March 2024. The first is inserted with black copper mesh (Model I), and the other has no insertion (Model ll). The effect of the inserted copper mesh (60, 120, and 180 g) and the receivers' tilt angle (5 degrees, 10 degrees, and 15 degrees) on the still performance are involved. The still thermal performance is analyzed per heat transfer coefficients, energy, and exergy efficiencies. The results revealed that the accumulated daily yield is enhanced for Model I by 78.9%-194.8% while the thermal efficiency is enhanced by 68.3%-206.4% when it is tilted at 15 degrees with the insertion of 60-180 g copper mesh, respectively, compared with Model II. It is concluded that an effective improvement in the solar still yield is obtained by using copper mesh.

A new, easy-to-manufacture, and low-cost integrated cubical solar collector tank for domestic usage is concerned in this work. Three models are prepared, side by side, and tested to point out their seasonal performance. Tank Model I has three vertical sides, black painted and glazed to act as an absorber; the other sides are insulated. Tank Model II has two black painted and glazed sides, with four insulated surfaces. The models are south-oriented at different positions and tested versus the conventional tank (Model III) to validate and assess their performance in summer and winter. In summer, the temperatures in Models I and II are lower than those for Model III since they have insulated sides. Their glazed sides absorb a small amount of solar radiation since they are almost parallel to the incident solar radiation in summer. In winter, the water temperature in these models rises higher than that for Model III since their glazed sides work as solar collectors and have much lower heat loss to ambient. Therefore, the new design can provide a moderate temperature for summer and winter for residential use. Their water temperature does not exceed the ambient temperature at night in summer. It was higher than the ambient temperature in winter. The thermal efficiency for Models I and II in summer was 10.93% and 15.62%, respectively. While in winter, they were 15.09% and 19.46%, respectively.

In this paper thermo-hydrodynamic characteristics were investigated experimentally for a new type shell-helical coiled tube heat exchanger used as a storage tank of closed loop solar water heater system. Triple concentric helical coils were made of copper tubes of (12.5mm OD and 10mm ID) with coils diameter of (207, 152.2, 97mm) for outer, middle and inner coils respectively. The experiments were carried out during a clear sky days of (March and April 2012). The parameters studied in this work are: history of average temperature of shell side of the storage tank, collector heat gain, heat rejected from coils to shell side of the storage tank, collector efficiency, thermal effectiveness of the heat exchanger (storage tank), and pressure drop. These parameters were studied at four different circulating mass flow rates of (1.8, 3, 6, 9 l/min) and for two consuming modes of supply water namely no withdrawal, and continuous withdrawal of (1 l/min). The results show that stratification temperature in the storage tank is increased for no withdrawal compared with water withdrawal, also the shell side average temperature increases with increased solar time. Collector efficiency is increased with increasing circulation flow rates, also increases with water withdrawn from storage tank. The pressure drop decreases with the increase of solar radiation .

The aim of this work is to explore the thermal performance of a tracked tubular solar still (TSS) with a parabolic trough concentrator in Baghdad (33.27 degrees N, 44.37 degrees E) in September 2022. The present tubular still is distinguished by its hexagonal glass cover. The effect of integrating the TSS with a heat pipe, the still tilt angle (10 degrees, 15 degrees), and the depth of saline water inside the still partitions on the productivity of freshwater are investigated. The results showed that using heat pipe enhances the freshwater productivity by 25%-40% and the efficiency by 25%. For the still integrated with heat pipe, as the water depth is increased from 5.5 to 6.5 cm the productivity of freshwater is increased by 16% and 20% for tilt angles 10 degrees and 15 degrees, respectively.

In this study, thermal characteristics of a two-phase closed heat pipe were investigated experimentally and theoretically. A two-phase closed heat pipe (copper container, Fluorocarbon FC-72 (C6F14) working fluid) was fabricated to examine its performance under the effect of input heat flux range of 250–1253 W/m2 , 70% fill charge ratio and various tilt angles. The temperature distribution along the heat pipe, input heat to evaporator section, and output heat from condenser were monitored. A comprehensive mathematical model was developed to investigate the steadystate heat transfer performance of a two-phase closed heat pipe. A steady state analytical model, is presented to determine important parameters on the design of two-phase closed heat pipe, including temperature levels and heat transfer coefficients for condenser and evaporator. The experimental and simulation results of this work are found in good agreement. The experimental boiling heat transfer coefficients were compared with existing previously reported correlations.

Determining the aerodynamic characteristics of iced airfoil is an important step in aircraft design. The goal of this work is to study experimentally and numerically an iced airfoil to assess the aerodynamic penalties associated with presence of ice on the airfoil surface. Three iced shapes were tested on NACA 0012 straight wing at zero and non-zero angles of attack, at Reynolds No. equal to (3.36*105). The 2-D steady state continuity and momentum equations have been solved utilizing finite volume method to analyze the turbulent flow over a clean and iced airfoil. The results show that the ice shapes affected the aerodynamic characteristics due to the change in airfoil shape. The experimental results show that the horn iced airfoil consumes more power than the other shapes of ice, its value was (44.4W). The horn iced shape has the worst effect on the airfoil than the other shapes. The present results are compared with previously reported results; it is found there is a very good agreement between them. A comparison between the experimental and computational results of the presented work were pursing the same behavior.

Heat transfer process and fluid flow in a solar chimney used for natural ventilation are investigated numerically in the present work. Solar chimney was tested by selecting different positions of absorber namely: at the back side, front side, and at the middle of the air gap. CFD analysis based on finite volume method is used to predict the thermal performance, and air flow in two dimensional solar chimney under unsteady state condition, to identify the effect of different parameters such as solar radiation. Results show that a solar chimney with absorber at the middle of the air gap gives better ventilation performance. A comparison between the numerical and previous experimental results shows fair agreement.

The present work describes numerical and experimental investigation of the heat transfer characteristics in a plate-fin, having built-in piezoelectric actuator mounted on the base plate (substrate). The geometrical configuration considered in the present work is representative of a single element of the plate-fin and triple fins. Air is taken as the working fluid. A performance data for a single rectangular fin and triple fins are provided for different frequency levels (5, 30 and50HZ) , different input power (5,10,20,30,40 and 50W) and different inlet velocity (0.5, 1, 2, 3, 4, 5 and 6m/s) for the single rectangular fin and triple fins with and without oscillation. The investigation was also performed with different geometrical fin heights ( 50mm and 35mm) and distance between the fins (3mm and 6mm). It is observed that the heat transfer increases with the increase in the frequency and Reynolds number. It is further observed that triple fins with (height=50mm and distance between the fins=3mm) gives better enhancement as compared to othercases, The study shows that the piezoelectric actuator when mounted on the rectangular fins gives great promise for enhancing the heat transfer rate

Heat transfer around a flat plate fin integrated with piezoelectric actuator used as oscillated fin in laminar flow has been studied experimentally utilizing thermal image camera. This study is performedfor fixed and oscillated single and triple fins. Different substrate-fin models have been tested, using fins of (35mm and 50mm) height, two sets of triple fins of (3mm and 6mm) spacing and three frequenciesapplied to piezoelectric actuator (5, 30 and 50HZ). All tests are carried out for (0.5 m/s and 3m/s) in subsonic open type wind tunnel to evaluate temperature distribution, local and average Nusselt number (Nu) along the fin. It is observed, that the heat transfer enhancement with oscillation is significant compared to without oscillation for low air inlet velocity. Higher thermal performance of triple fins is obtained compared to the single rectangular fin, also triple fins with (height=50mm and finspacing=3mm) gives better enhancement as compared to other cases. This work shows that the piezoelectric actuator when mounted on the rectangular fins shows great promise for enhancing the heat transfer rate.

The thermal and electrical performance of different designs of air based hybrid photovoltaic/thermal collectors is investigated experimentally and theoretically. The circulating air is used to cool PV panels and to collect the absorbed energy to improve their performance. Four different collectors have been designed, manufactured and instrumented namely; double PV panels without cooling (model I), single duct double pass collector (model II), double duct single pass (model III), and single duct single pass (model IV) . Each collector consists of: channel duct, glass cover, axial fan to circulate air and two PV panel in parallel connection. The temperature of the upper and lower surfaces of PV panels, air temperature, air flow rate, air pressure drop, wind speed, solar radiation and ambient temperature were measured. The power produced by solar cells is measured also. A theoretical model has been developed for the collector model IV based on energy balance principle. The prediction of the thermal and hydraulic performance was obtained for the fourth model of PV/T collector by developing a Matlab computer program to solve the numerical model. The experimental results show that the combined efficiency of model III is higher than that of models II and IV. The pressure drop of model III is less than that of models I and IV, by (43.67% and 49%). The average percentage error between the theoretical and experimental results was 9.67%.

In this study, the turbulent buoyancy driven fluid flow and heat transfer in a differentially heated rectangular enclosure filled with water is quantified numerically. The two dimensional governing differential equations are discretized using the finite volume method. SIMPLE algorithm is employed to obtain stabilized solution for high Rayleigh numbers by a computational code written in FORTRAN language. A parametric study is undertaken and the effect of Rayleigh numbers (1010 to 1014), the aspect ratio (30, 40 and 50), and the tilt angle (10o to 170o ) on fluid flow and heat transfer are investigated. The results of the adopted model in the present work is compared with previously published results and a qualitative agreement and a good validation is obtained. Results show that the fluid circulation and temperature fields are strongly affected by the enclosure tilt angle and Rayleigh Number.

In this study, the optical and thermal performance of a Parabolic Trough Collector PTC system is investigated theoretically. A series of numerical simulations and theoretical analysis has been conducted to investigate the effect of the receiver geometry and location relative to the focal line on its optical performance. The examined receiver geometries are circular, square, triangular, elliptical and a new design of circular-square named as channel receiver. The thermal performance of PTC is studied for different flow rates from (0.27 to 0.6 lpm) theoretically. Results showed that the best optical design is the channel receiver with an optical efficiency of 84% while the worst is the elliptical receiver with an optical efficiency of 70%. Thermally the best design is the elliptical receiver with a thermal efficiency of 85% while the worst is the circular receiver with a thermal efficiency of 82%.

Fresh water production from saline or waste water utilizing solar stills is the secured future approach in water industry with low cost and no environmental pollution accompanied with low productivity. In this work, the effect of inserting different available materials in a passive Single Slope Solar SSS stills on their productivity is accomplished. Side by side tests are performed on a conventional still, and three SSS stills inserted with carbon filter media, Copper wire mesh, and Cellulose sheets. All these stills are symmetrical in dimensions with 0.5 m2 base area tested for 20mm water level. The stills have been manufactured, instrumented, and tested in July 2021 under DhiQar-Iraq climate conditions (latitude 31.2° N, longitude 46.34° E). The effect of sunny days ambient conditions on the hourly thermal performance including temperature, pressure, heat transfer coefficients, and still efficiency are explored. Results have showed that these materials store energy from the incident solar radiation during the daytime and have extended their yield at first night hours so increasing the still daily distillate output. The freshwater daily yield has reached 4753g, 2465 g, and 2080 g, for stills inserted with copper wire mesh, carbon fiber, and cellulose sheets respectively compared with (1000 g) for the conventional still.