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Solar-driven water desalination technologies are rapidly developing with various links to other renewable sources. However, the efficiency of such systems severely depends on the design parameters. The present study focused on using graphene oxide (GO) with the Φ = 0.2, 0.4 and 0.6 wt.% dispersed in paraffin, as phase-change materials (PCMs), to improve the productivity of a solar still for desalination applications. The outcomes showed that by adding more graphene oxide to paraffin, the melting temperature got reduced. Solar still with GO/paraffin showed 25% productivity improvement in comparison with the solar still with only PCM. The obtained Nusselt number during the melting time also represented that free convection heat transfer into the melted region of the solar still has been enhanced by adding dispersed GO to the PCM, compared to the base paraffin. Also, increasing the hot wall temperature augments the Nusselt number. Finally, an empirical equation was derived to correlate the average Nusselt number as a function of Rayleigh number (Ra), the Stefan number (Ste), the subcooling factor (Sb), and the Fourier number (Fo). The obtained correlation depicted that Nusselt number enhancement has a reverse relation with Fourier number.

This paper shows the results of a novel research conducted with the overall aim of developing a system that can provide continuous desalination. Productivity enhancement of solar stills is regarded as the main purpose of the investigators in desalination field. This paper represents the experimental results in a new approach of paraffin + graphene oxide nanoparticles mixture. The paraffin mixture in a semicircular, triangular and rectangular absorber with paraffin + graphene oxide of 0.1, 0.3 and 0.5 mass% has been investigated. The finding indicated that for all absorbers, the use of paraffin + graphene oxide in higher mass fractions enhances daily freshwater production. The results showed that the thermal performances are greater applying graphene oxide + paraffin of 0.5 mass% with semicircular absorber compared to triangular and rectangular absorber. The achievement of the present paper can be implemented to design more efficient absorbers for solar still parts.

The heating and cooling industry underpins everything we do, e.g., manufacturing, commercial and residential applications. Many of these applications invariably use mechanical refrigeration technologies, consequently contributing significantly to the environmental impacts of the refrigeration, air conditioning, and heat pump (RACHP) industry both through direct and indirect emissions of CO2. To reduce these emissions, research and development worldwide aim to improve the performance of conventional systems and the development of new refrigeration technologies of potentially much lower environmental impacts. As we transition to a low carbon economy, there are sizable environmental and economic benefits from developing and using efficient, innovative, low carbon heating and cooling technologies that reduce energy use and carbon emissions. This paper provides an up-to-date and comprehensive critical review and evaluation of recent advances in emerging alternative heating and cooling technologies that have the potential to reduce the environmental impacts of refrigeration in the RACHP sector. The paper highlights the basic working principle of operation, its main applications, the challenges and opportunities in penetrating the market. The paper also highlights further research and development needed to accelerate the development and adoption of these alternative refrigeration technologies by the sector. Most of the technologies reviewed have a Technology Readiness Level (TRL) of 3–4, except electrocaloric technology which is less ready compared to its counterparts with a TRL of 1–2 at this stage. Furthermore, most technologies have capacities ranging between a few kilowatts to a maximum of 7 kW with a coefficient of performance COP between 1 and 10 reported in the literature.

This article discusses a focused study on visualizing the flow patterns in a two-phase pulsating heat pipe (PHP) using Fe 3 O 4 /water as the working fluid at 3 V/V% concentration. The research also aims to meticulously examine phase change phenomena in the heating section, particularly focusing on bubble formation and expansion processes. A high-speed video camera was utilized to capture dynamic insights into the behavior of the Fe 3 O 4 /water mixture. Based on the findings, a straightforward model was developed to explain bubble generation and growth in the mixture, serving as a useful reference for future PHP designs and optimizations. Visual observations also noted the stable nature of the Fe 3 O 4 /water nanofluid over a 4-day period, confirming its consistency throughout the experiments. Moreover, the impact of heat load variation on the evaporator section was assessed using controlled heat inputs ranging from 10 to 80 W. Observations on the arrangement of slugs and plugs at a 50% filling ratio revealed interesting self-adjusting flow patterns in response to increasing heat inputs, providing valuable insights into PHP operational dynamics. Notably, the oscillatory flow behavior of Fe 3 O 4 /water, the chosen working fluid, exhibited greater activity in comparison to water. This distinctive flow behavior contributed to achieving heightened thermal performance efficiency for the Fe 3 O 4 /water system, attributed to its faster attainment of the annular flow condition.

This paper presents a novel study on the performance of closed-loop oscillating heat pipe (CLOHP) using iron oxide (Fe3O4) as the working fluid for three types of condensers. The tested CLOHP consists of six turns made of copper tubes, 4.5 mm outer diameter and 3 mm inner diameter with heating power input in a range of 0–200 W. The experimental results showed that the thermal performance of the CLOHPs has been improved when the corrugated horizontal condenser was used compare to straight and corrugated vertical condensers. Based on 800 sets of available experimental data, the results show that the CLOHPs with corrugated horizontal condenser had better thermal performance when charged with Fe3O4/water at 2% mass concentration.

Natural ventilation is gaining more attention from architects and engineers as an alternative way of cooling and ventilating indoor spaces. Based on building types, it could save between 13 and 40% of the building cooling energy use. However, this needs to be implemented and operated with a well-designed and integrated control system to avoid triggering discomfort for occupants. This paper seeks to review, discuss, and contribute to existing knowledge on the application of control systems and optimisation theories of naturally ventilated buildings to produce the best performance. The study finally presents an outstanding theoretical context and practical implementation for researchers seeking to explore the use of intelligent controls for optimal output in the pursuit to help solve intricate control problems in the building industry and suggests advanced control systems such as fuzzy logic control as an effective control strategy for an integrated control of ventilation, heating and cooling systems.

Photovoltaic (PV) panels play a pivotal role in advancing renewable energy adoption by offering a clean and sustainable alternative to fossil fuels. However, elevated operating temperatures diminish PV cell performance, reducing energy output and accelerating material wear. This research evaluates the cooling efficiency of a PV panel equipped with a three‐dimensional oscillating heat pipe (3D‐OHP) integrated with hybrid nanofluids consisting of graphene oxide–copper oxide (GO–CuO), carbon nanotube–CuO (CNT–CuO), and multiwalled CNT–CuO (MWCNT–CuO). The OHP is charged with two concentrations of each nanofluid, specifically 0.1 and 0.2 g/L, to evaluate their impact on the thermal management of the PV panel. The study involved experimental tests using two PV panels: one equipped with a 3D‐OHP as the cooled panel and the other as a reference panel under identical environmental conditions. Hybrid nanofluids were prepared by dispersing nanoparticles in a base fluid, and their thermal properties were characterized prior to use. Energy and exergy analyses quantify the enhancements in thermal efficiency and the reduction in entropy generation. Experimental results reveal that CNT–CuO with a concentration of 0.2 g/L remarkably improves the electrical power output by 12.07%, outperforming other studied systems with the maximum exergy efficiency of 31.2%. The findings also highlight notable gains in first‐law efficiency. Furthermore, the levelized cost of energy (LCOE) and levelized cost of storage (LCOS) are analyzed, demonstrating the economic feasibility of hybrid nanofluid‐based cooling for PV systems.

Nowadays, there has been a growing trend toward using photovoltaic systems due to their high efficiency and cost-effectiveness; nevertheless, an inevitable side of solar panels is that their efficiency and life span experience a reduction when they are exposed to high intensity of solar irradiance and warm-up. In other words, when they are cooled, the electrical efficiency is promoted. Using oscillating heat pipes is a creative and practical approach to enhance PV efficiency. Furthermore, applying nanofluid as a working fluid can play an important role in maximizing panel productivity. The main objective of this investigation is to explore the cooling effect of a three-dimensional oscillating heat pipe on a photovoltaic panel, while graphene oxide nanofluid and distilled water are used as coolants. For this purpose, a novel three-dimensional oscillating heat pipe has been designed. The significant result from the study is that the cooling system was able to lower the temperature and improve the power output of the PV by 8.6 °C and 2.78 (W), respectively, in the warmest time of the day, when graphene oxide nanofluid was used as a coolant.