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Nowadays, direct absorption solar collectors are a new concept of solar collectors which have attracted special attention. The type of heat transfer fluid (HTF) has a significant influence on the efficiency of this kind of collector. Therefore, in this study, a wide range of working fluids including mono nanofluid (Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$ and CuO), binary nanofluid, and especially the incorporation of a new hybrid combination of nanofluid and microencapsulated phase change material (MPCM), are used as the working fluids of a triple‐walled direct absorption evacuated tube solar collector. The computational fluid dynamics (CFD) method is used for simulating the collector and investigating the effect of different parameters including volume fraction, base fluid, mass flow rate, and type of absorber tube structure (double‐ and triple‐walled) on collector thermal performance. Results show that binary nanofluids of 0.06% Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/0.002% CuO/water and 0.06% Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/0.002% CuO/ethylene glycol (EG) have the largest working fluid temperature differentials equal to 48.31 and 66.5 K, respectively. It was inferred that, at the mass flow rate of 2.7 kg/h $\mathrm{kg}/{\rm{h}}$, the efficiency is obtained to be 60.29% employing binary/EG nanofluid, which is 8.68% and 15.31% higher than CuO/EG and Al2O3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/EG nanofluids, respectively. Inserting the hybrid CuO nanofluid/MPCM leads to an improvement of 1.14% and 1.22% in the efficiency of triple‐ and double‐walled collectors, respectively, with respect to the individual usage of the nanofluid. The thermal efficiency of the double‐walled structure is higher than triple‐walled considering all HTFs. [ABSTRACT FROM AUTHOR]

In this study, a technique is suggested to enhance the temperature difference for cooling and energy efficiency of thermoelectric cooler (TEC) used in cooled detectors when subjected to high current conditions. Embedding a structure for storing heat during phase change is the basis of this method at the heat sink. A simulation model was created for a common two‐stage series TEC with an asymmetrical design, which is coupled with a structure for storing heat through phase change. The research examined how phase transition heat storage impacts the coefficient of performance (COP) and refrigeration temperature difference across various phase‐change substances, heat transfer coefficients at the hot end, currents, and the height of the phase‐change material (PCM). The findings suggest that the suggested approach of combining PCM with TEC can efficiently lower the cold end temperature of TEC by a maximum of 20 K, enhance the temperature gap by a maximum of 16 K, and preserve the consistency of the optimized quantity across various hot end heat transfer coefficients. During the phase‐change process of PCMs, the COP of TECs integrated with PCM is found to increase by an average of 2%–3% compared to TECs without PCM integration. Under the maximum current operating condition, the cryogenic temperature can be optimized to a minimum of 238 K. In summary, the proposed method of integrating phase‐change heat storage with TECs provides a promising solution for improving their cooling performance and energy efficiency in cooled detectors under high current conditions. Additional investigation can be conducted to explore the practical application of this approach and enhance the design parameters for various uses. [ABSTRACT FROM AUTHOR]

Drinking water is a crucial need for human survival and solar stills (SSs) have emerged as a cost‐effective solution to meet this need from an economic point of view. In this work, the working of various SSs, their productivity factors, and various devices that can be integrated to improve their efficiency have been studied. The conversion of saline water into freshwater water using SSs has the potential to address the issue of drinking water. This study highlights the importance of SSs as a viable and sustainable solution for drinking water access. On the basis of various parameters correlating to the performance of the SSs, energy, exergy, economics, exergoeconomics, exergoenvironment, and enviroeconomics analysis has been analyzed in this study. To improve the performance and sustainability of SSs, various combinations were studied. These combinations include SSs with different nanoparticle coatings, phase‐change materials, photovoltaic modules, external condensers, wick materials, and reflectors. It is concluded that a comprehensive framework that integrates thermodynamic, economic, and environmental criteria can guide the development of more efficient and sustainable SS technologies. [ABSTRACT FROM AUTHOR]

Hungary is not only dependent on imports of natural gas and fossil fuels, but Hungary is also the lowest in renewable energy utilization; otherwise, only 11.3% compared to other Central European countries in renewable energy utilization, above 13%. The percentage of renewables in power generation quadrupled from 8% to 16% between 2010 and 2020, with most of the gains coming from the rapid expansion of solar energy, particularly after 2016. Regarding solar energy resource potential, Hungary has a daily total of around 3.2–3.6 kWh/m2 and a yearly total of about 1168–1314 kW.h/m2. This makes it a suitable location for putting solar thermal collectors in conjunction with an organic Rankine cycle (ORC) system. In this study, the authors analyzed solar thermal as a heat source to generate electricity with ORC using two types of working fluids (R245fa and R123). Hungary's weather data for a whole year is used as primary data to look for solar radiation characteristics and ambient temperature. Based on the general solar collector equation, the parabolic tube collector was selected as the best solar collector to utilize solar radiation by producing a maximum heat of around 654.68 kW. Therefore, the evacuated flat plate collector was selected as the solar collector that can produce the maximum outlet temperature of around 372.15 K with a similar size aperture area. Producing a temperature output from the solar collector for heat transfer in the ORC system and from the performance showed that R245fa resulted in better Wnet performance compared with R123 with values of 45.82 and 28.17 kW, respectively, under the same solar collector. Meanwhile, the material suitable for the thermal energy storage‐evaporator combination is organic phase change material using N‐Octacosane, which in the same temperature range (350–375 K) has the smallest ζ(T) value (1.08–1.103), so the mass required for the system is very efficient. [ABSTRACT FROM AUTHOR]

Abstract In this study, the effect of fin number and size on the solidification output of a double‐tube container filled with phase change material (PCM) was analyzed numerically. By altering the fins' dimensions, the PCM's heat transfer performance is examined and compared to finless scenarios. To attain optimal performance, multiple inline configurations are explored. In addition, the initial conditions of the heat transfer fluid (HTF), including temperature and Reynolds number, are considered in the analysis. The research results show a significant impact of longer fins with higher numbers on improving the solidification rate of PCM. The solidification rate increases by 67%, 170%, 308%, and 370% for cases with 4, 9, 15, and 19 fins, respectively, all with the same fin length and initial HTF boundary condition. The best case results in a solidification time that is 4.45 times shorter compared to other fin number and dimension scenarios. The study also found that moving from Reynolds numbers 500 to 1000 and 2000 reduced discharging times by 12.9% and 22%, respectively, and increased heat recovery rates by 14.4% and 27.9%. When the HTF entrance temperature was 10°C and 15°C, the coolant temperature showed that the entire discharging time decreased by 37.5% and 23.1% relative to the solidification time when the initial temperature was 20°C. Generally, this work highlights that increasing the length and number of fins enhances thermal efficiency and the phase change process.

Optimizing the efficiency of conventional heat exchangers is critical for improving the performance of various processes. This study proposed increasing the heat dissipation buffer space of heat exchangers by filling the gap between the heat exchanger and the shell with phase‐change materials for optimizing phase‐change heat exchangers. Comparative simulation analyses were performed by investigating the difference between the internal and external diameters of the inner ring ribs of the heat exchanger, the flow rate of the cooling liquid, the spacing distance, and the number of the inner ring ribs as independent variables. The results revealed that the heat transfer efficiency of heat exchangers can be improved by adding the inner ring rib structure to the heat exchange copper tube. The difference between the inner and outer diameters of the inner ring rib considerably influences heat dissipation. Furthermore, a sensitivity coefficient of 0.2457 can be obtained. The distance and number of inner ring ribs and the flow rate of cooling liquid exhibit certain effects on the heat transfer efficiency of the heat exchanger. The sensitivity coefficients were 0.1477 and 0.0935. The heat dissipation efficiency of the coil heat exchanger was improved by 3.8% by adding inner ring ribs in the coil heat exchanger channel. [ABSTRACT FROM AUTHOR]

In this study, the effect of fin number and size on the solidification output of a double‐tube container filled with phase change material (PCM) was analyzed numerically. By altering the fins' dimensions, the PCM's heat transfer performance is examined and compared to finless scenarios. To attain optimal performance, multiple inline configurations are explored. In addition, the initial conditions of the heat transfer fluid (HTF), including temperature and Reynolds number, are considered in the analysis. The research results show a significant impact of longer fins with higher numbers on improving the solidification rate of PCM. The solidification rate increases by 67%, 170%, 308%, and 370% for cases with 4, 9, 15, and 19 fins, respectively, all with the same fin length and initial HTF boundary condition. The best case results in a solidification time that is 4.45 times shorter compared to other fin number and dimension scenarios. The study also found that moving from Reynolds numbers 500 to 1000 and 2000 reduced discharging times by 12.9% and 22%, respectively, and increased heat recovery rates by 14.4% and 27.9%. When the HTF entrance temperature was 10°C and 15°C, the coolant temperature showed that the entire discharging time decreased by 37.5% and 23.1% relative to the solidification time when the initial temperature was 20°C. Generally, this work highlights that increasing the length and number of fins enhances thermal efficiency and the phase change process. [ABSTRACT FROM AUTHOR]

Due to the low thermal conductivity of the phase change material and low thermal diffusion inside the phase change material, this study seeks to improve the melting response of a triple‐tube latent heat storage system via employing annular fins by optimizing their structural parameters, including the fin number, location, and dimensions. Natural convection effects are numerically evaluated considering different numbers and the locations of the fins, including fin numbers of 4, 10, 16, 20, and 30 in a vertical system orientation. The fins are attached to the inner and outer sides of the annulus, accommodating the phase change material between the inner and center tubes. The fins' number and location are identical on both sides of the annulus, and the volume of the fins is the same across all scenarios evaluated. The results show that the higher the number of fins used, the greater the heat communication between the fins and the phase change material layers in charge, resulting in faster melting and a higher rate of heat storage. Due to the limited natural convection effect and lower heat diffusion at the heat exchanger's bottom, an additional fin is added, and its thickness is assessed. The results show that the case with equal fin thickness, that is, both original fins and the new fin, performs the best performance compared with that for the cases with an added fin with thicknesses of 0.5, 1, and 2 mm. Eliminating an extra fin from the base of the system for the case with 30 fins increases the charging time by 53.3%, and reduces the heat storage rate by 44%. The overall melting time for the case with an added fin to the bottom is 1549 s for the case with 30 fins which is 85.8%, 34.2%, 18%, and 8.8% faster than the cases with 4, 10, 16, and 20 fins, respectively. This study reveals that further attention should be given to the position and number of annular fins to optimize the melting mechanism in phase‐changing materials‐based heat storage systems. [ABSTRACT FROM AUTHOR]

Recently, phase change materials (PCMs) are acquiring much attention for the overall enhancement of photovoltaic (PV) systems' performance, because of their extraordinary property in temperature management. Many researchers have been incorporating PCMs in PV systems. However, the tested materials are principally organic PCMs. In this review, a comprehensive literature of PV systems with utilization of inorganic PCMs is introduced. Salt hydrates are the focus materials. They, in general, have comparative properties as organic PCMs and are better from safety and environmental standpoints. The characterization, properties, and applications of the salt hydrates in PV‐PCM research are discussed in this paper. Indeed, even most research shows promising outcomes, there is still need in data collection for more detailed and accurate system performance evaluation. Therefore, the real‐life application of this type of PV‐PCM system is still a long way from clear due to the discovered challenges. Finally, the possibilities of future research on PV‐PCM systems are highlighted, innovative technologies are to be discovered and addressed to defeat the current issues including system reliability and economic attainability. [ABSTRACT FROM AUTHOR]

An experimental setup is built to improve the charging process of a bio‐based phase change material inside a rectangular latent heat thermal energy storage (LHTES) system. In addition to experimenting with different porosities of full‐coverage wire mesh, a novel method of partial wire mesh placement at a proper location is used for improving conduction and maintaining natural convection, proven by the particle image velocimetry (PIV) method. Although acquiring PIV images from coconut oil is challenging because of the laser reflection, the image capturing and processing have been completed successfully. Temperatures inside the enclosure were measured using four K‐type thermocouples, and the melt fraction was calculated using captured images. The full‐size mesh results in a more uniform temperature distribution, and its charging time for porosities of 88% and 82% is decreased by 41% and 52%, respectively. The results of partial wire mesh placements indicate that a top‐only approach leads to a time reduction of only 7%. However, the bottom‐only approach yields a time reduction of 34% and the value of 3.8 for the charging time reduction over the porosity reduction parameter, which is the highest among all experiments. Additionally, this placement eliminates sudden temperature spikes, which improves the performance of the LHTES system and results in an economical and practical configuration. Moreover, the PIV test shows sustained convective velocities at the top half of the enclosure with a partial mesh at the bottom, demonstrating improved natural convection compared to that of a full‐size mesh implementation which weakens convection. Therefore, contrary to full‐size meshes used in previous works, a bottom‐only mesh placement can enhance conduction and convection simultaneously, which can be utilized in practical applications. [ABSTRACT FROM AUTHOR]

This paper studies the heat storage system's influence on a solar chimney's power production. This study considers several material types, including solid and phase change materials, at the bottom section of a solar chimney for energy storage, and evaluates their effects on the energy yield and capacity to prolong the power output during the absence of the sun. A computational fluid dynamic model using COMSOL Multiphysics is performed to carry out this work. An initial steady‐state analysis using average monthly irradiance is implemented, after which the top two solid and phase change material options are selected. Subsequently, a time‐dependent simulation using a typical summer day is carried out for the chosen storage materials. The overall performance results are comparatively assessed in terms of average temperature, power generation, and efficiency. As a result, bismuth‐led‐tin‐cadmium and magnesium chloride hexahydrate present the highest power production among the phase change materials, giving a yearly average power output of 27.46 kW and a storage temperature of about 346 K. On the other hand, sandstone offers the highest overall annual average power production, yielding 31.49 kW, and a storage temperature of 352.17 K. This material also reflects the highest yearly average energy and exergy efficiencies with 0.122% and 0.128%, respectively. [ABSTRACT FROM AUTHOR]

In order to attain an efficient path into the enhancement of the sustainable conservation and management of energy resources in the buildings and residential sections, efforts by all relevant institutions in the area of energy are essential and primitive. Hence, the development of the energy supply model in the building and the provision of fundamental solutions in this area is rudimentary. The key to any program related to this matter is to boost and extend energy efficiency and energy resource management. According to the global statistics and processed data, the residential sector accounts for 34 percent of the total energy consumption in Iran, which is the highest energy consumption compared to all existing sectors; therefore, immeasurable research has been done on optimizing energy usage in the building sector. One of the most efficient energy optimization methods can be achieved by using energy storage materials in the outer walls of the buildings. In this project, a research‐based residential building is considered as a case to investigate for energy optimization. In the first stage, the building is simulated and the energy consumption of the building is measured. Afterward, with actual measurements, real consumption is approximated and compared with the results of the software. After verifying the software data, the insulation is simulated in the software and the outcomes of using this insulator are investigated to reduce energy consumption. Energy storage materials are considered as a type of phase‐change material. These materials have the same characteristics which is having a different melting point and, by capturing and losing heat at design temperatures, they can help maintain energy inside the building that is how they can be considered as an insulator. Within the appropriate software which is Design‐Builder, miscellaneous types of these materials are available with various features. The final results point out that the use of this material saves up to 30% of the heating energy and about 8% in the cooling load of the building. [ABSTRACT FROM AUTHOR]