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CFD modeling of a triple-walled direct absorption evacuated tube solar collector based on hybrid nanofluid/microencapsulated pcm

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ENERGY SCIENCE & ENGINEERING 2024年第5期12卷 2297-2318页

作者： Shahini, Niloofar Karami, Maryam Akhavan-Behabadi, Mohammad Ali Univ Tehran Coll Engn Sch Mech Engn Tehran Iran Kharazmi Univ Fac Engn Dept Mech Engn Tehran Iran Kharazmi Univ Fac Engn Tehran Iran

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 (Al 2 O 3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$ 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% Al 2 O 3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/0.002% CuO/water and 0.06% Al 2 O 3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/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 Al 2 O 3 ${\text{Al}}_{2}{{\rm{O}}}_{3}$/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. Nanofluid/microencapsulated phase change material (Mpcm)-based triple-wall direct absorption evacuated tube collector. image

关键词： computational fluid dynamics direct absorption solar collector evacuated tube hybrid nanofluids microencapsulated pcm

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Thermal management of electronic devices using pin-fin based cascade microencapsulated pcm/expanded graphite composite

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2020年 149卷

作者： Ren, Qinlong Guo, Penghua Zhu, Jianjun Xi An Jiao Tong Univ Sch Energy & Power Engn Key Lab Thermofluid Sci & Engn MOE Xian 710049 Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn Dept Fluid Machinery & Engn Xian 710049 Peoples R China

microencapsulated phase change material (MEpcm) could be used for effective thermal management of electronic devices due to its large latent heat, phase change at nearly constant temperature, low volume expansion, and anti-leakage characteristics. Unfortunately, the low thermal conductivity of MEpcm hinders the heat dissipation rate from electronic devices especially at high heat flux conditions. Although the heat transfer capability of MEpcm could be accelerated by adding expanded graphite (EG) or inserting high thermal conductivity pin-fins, the latent heat energy storage capacity of MEpcm composite becomes less which reduces the corresponding operating time of limiting the electronic device temperature rise through solid-liquid phase change. In purpose of clarifying and optimizing this tradeoff effect on electronic device thermal management using MEpcm-EG composite with pin-fins, a numerical study is carried out through 3D lattice Boltzmann method with respect to different pin-fin configurations, EG content, pcm melting temperature, and heat flux conditions. The results indicate that the pin-fin array with medium fin number and fin thickness is beneficial for balancing the increased heat transfer capability and the decreased latent heat of MEpcm so that its optimum thermal performance is achieved. At the early working stage of electronic device, the pin-fin based MEpcm is demonstrated to be more effective than MEpcm-EG composite for controlling the electronic device temperature rise because of the direct contact between pin-fins and electronic heat sink base. However, as the electronic device working time evolves, the MEpcm-EG composite with network heat transfer channel is found to be more efficient for dissipating heat out of electronic device due to the relatively high average thermal conductivity throughout the whole heat sink system. Furthermore, the thermal performance of electronic device is found to be improved by inserting MEpcm-EG composite with cascade

关键词： Electronic thermal management microencapsulated pcm Pin-fins Expanded graphite GPU-based lattice Boltzmann modeling

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Glass fiber reinforced gypsum composites with microencapsulated pcm as novel building thermal energy storage material

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CONSTRUCTION AND BUILDING MATERIALS 2022年 340卷

作者： Gencel, Osman Hekimoglu, Gokhan Sari, Ahmet Ustaoglu, Abid Subasi, Serkan Marasli, Muhammed Erdogmus, Ertugrul Memon, Shazim Ali Bartin Univ Fac Engn Architecture & Design Civil Engn Dept TR-74100 Bartin Turkey Karadeniz Tech Univ Met & Mat Engn Dept TR-61080 Trabzon Turkey King Fahd Univ Petr & Minerals KFUPM Res Inst Ctr Res Excellence Renewable Energy CORERE Dhahran 31261 Saudi Arabia Bartin Univ Fac Engn Architecture & Design Dept Mech Engn TR-74100 Bartin Turkey Duzce Univ Fac Engn Civil Engn Dept TR-81620 Duzce Turkey Fibrobeton Inc TR-34810 Istanbul Turkey Bartin Univ Fac Engn Dept Environm Engn Architecture & Design TR-74100 Bartin Turkey Nazarbayev Univ Sch Engn & Digital Sci Dept Civil & Environm Engn Nur Sultan Kazakhstan

A comprehensive study involving the fabrication and characterization of gypsum plasterboards combined with microencapsulated phase change material (mpcm) is introduced to evaluate their benefits regarding thermoregulation management and energy saving performance in buildings. For this purpose, the produced new type of gypsum plasterboard was subjected to the detailed chemical, morphological, mechanical, physical and thermal tests. The gypsum plasterboard incorporated with mpcm (7.5 wt%) and reinforced by glass fiber has latent heat capacities as high as 16.7 and 16.6 J/g at onset melting and solidification temperature of 11.90 ? and 12.09 ?, respectively. TGA analyzes revealed high thermal stability of gypsum plasterboard up to about 140 ?. Outcomes exhibited that mpcm-gypsum plasterboard can substantially diminish cooling load of a building during the daytime even at the high room temperature and offer decline in heat necessity of a house during night-time. During peak room temperature hours, the mpcm-gypsum plasterboard achieved 3 ? lower temperatures than the reference room, and it provided a cooler room temperature for about 7 h during the daytime while a warmer temperature of 0.3 ? was achieved at the cold weather. As a result, the produced gypsum-based composites can be considered as an energy-saving and indoor temperature regulating material in buildings.

关键词： Gypsum Glass fiber microencapsulated pcm Thermal energy storage

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Influence of the Physical State of microencapsulated pcm on the Pressure Drop of Slurry in a Circular Channel

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MATERIALS 2022年第19期15卷 6719页

作者： Dutkowski, Krzysztof Kruzel, Marcin Kaczmarek, Dominika Nalepa, Bartlomiej Zajaczkowski, Bartosz Valicek, Jan Harnicarova, Marta Koszalin Univ Technol Fac Mech Engn Ul Raclawicka 15-17 PL-75620 Koszalin Poland Wroclaw Univ Sci & Technol Dept Thermal Sci PL-50370 Wroclaw Poland Inst Technol & Business Ceske Budejovice Fac Technol Dept Mech Engn Okruzni 10 Ceske Budejovice 37001 Czech Republic Univ Agr Nitra Fac Engn Dept Elect Engn Automat & Informat Tr A Hlinku 2 Nitra 94976 Slovakia

Phase Change Material (pcm) is mainly used in thermal energy storage. The addition of small pcm particles to the working fluid circulating in the heat exchange systems allowed to increase the amount of transported energy thanks to the use of latent heat-the heat of phase change. Encapsulating pcm in microcapsules avoids the disadvantages of pcm emulsions and makes the resulting slurry an attractive heat energy carrier. The paper presents the effect of the aggregate state of pcm enclosed in microcapsules on the flow resistance of the slurry through a rectilinear tubular channel. The tests were carried out with the use of a tube with an internal diameter of 4 mm and a measuring section length of 400 mm. A slurry of 21.5 wt.% pcm microcapsules (Mpcm) was used as the working fluid in distilled water. A slurry with temperatures of 18.4 degrees C (pcm encapsulated in a solid state), 26.1 degrees C (pcm is in a phase change), and 30.5 degrees C (pcm in a liquid state) flowed through the measuring section. The mass flow rate of the Mpcm slurry reached 70 kg/h (Re-max = 2150). It was shown that the higher the Re number, the higher the value of the flow resistance, and the more clearly this value depended on the temperature of the slurry. Detailed analyses indicate that the observed changes were not the result of a change in the viscosity of the slurry, but its density depending on the state of the pcm. Significant changes in the density of the slurry in the range of the phase transition temperature are the result of significant changes in the volume of the microcapsule containing the phase change material in different aggregate states.

关键词： experimental investigation pressure drop microencapsulated pcm slurry phase change

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Evaluation of thermal kinetics of microencapsulated pcm for low-temperature thermal energy storage application

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MATERIALS LETTERS-X 2022年 14卷

作者： Amim, Atif Priyadarshi, Gaurav Babre, Tirtharaj Purushottam Naik, B. Kiran Natl Inst Technol Rourkela Dept Mech Engn Sustainable Thermal Energy Syst Lab STESL Rourkela 769008 Odisha India

In the present investigation, the microencapsulated phase change material (pcm) thermal kinetics for low-temperature thermal energy storage applications (32 degrees C-53 degrees C) is analysed. microencapsulated pcms selected are CaCl2 center dot 6H(2)O, n-Hexadecane, n-Octadecane, n-Eicosane, Capric/Lauric acid, Paraffin wax (C30H62), and Palmitic acid (C16H32O2), respectively. Ambient air is selected as the external/heat transfer fluid which interacts with pcm materials. The thermal kinetics of microencapsulated pcms is evaluated by selecting the solid-liquid interface position with melting time and molten fraction as the performance evaluation parameters. Among all the phase change materials, the best pcm is found to be CaCl2 center dot 6H(2)O with 4 cm of pcm diameter, 53 degrees C of external fluid temperature, and 106 min of melting time.

关键词： microencapsulated pcm Energy storage and conversion Thermal analysis Simulation and modelling Thermal properties Thermodynamics Kinetics of processes in materials

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Validation of different numerical models with benchmark experiments for modelling microencapsulated-pcm-based applications for buildings

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INTERNATIONAL JOURNAL OF THERMAL SCIENCES 2021年 159卷

作者： Soares, N. Rosa, N. Costa, J. J. Lopes, A. G. Matias, T. Simoes, P. N. Duraes, L. Univ Coimbra Dept Mech Engn ADAI Coimbra Portugal Univ Coimbra Dept Chem Engn CIEPQPF Coimbra Portugal

This paper assesses the thermal performance of four microencapsulated-pcm-based samples that can be used in the design of new thermal energy storage systems for buildings: a pcm-enhanced plasterboard;three different fin-enhanced aluminium containers filled with the pcm. The methodology covers: the thermophysical characterization of the pcm-based products;the development of charging and discharging experiments to provide data for numerical validation purposes;the numerical modelling considering five different methods dispersed in literature, and a new-improved method. The main goals are to validate the numerical predictions against reliable experimental results and to find out which method is preferable for future simulations. The 3D numerical simulations were based on the effective heat capacity (EHC), additional heat source (AHS) and enthalpy (H-P) approaches. The first two methods were implemented in ANSYS CFX (R);the other in ANSYS FLUENT (R). For the EHC method, four different ways to specify the variation of the effective specific heat with temperature were assessed. While the H-P commercial code already implemented in ANSYS FLUENT (R) was used, the other two methods implemented in ANSYS CFX (R) were developed and validated for the purpose of this study. Good agreement between numerical and experimental results was achieved for all numerical approaches. In fact, it was concluded that the six numerical methods can be used to simulate heat diffusion with solid-liquid phase-changes. However, it was verified that the EHC method with the triangular or the self-adjusted triangular profiles is preferable for both charging and discharging simulations, since it can be drawn based on few information about the pcm-based products;it ensures good predictions of both charging/discharging kinetics and stored/released energy;it can be used without compromising computation time in comparison to other methods. The EHC method with the rectangular profile, recurrently used in lite

关键词： Phase change material microencapsulated pcm Numerical modelling Effective heat capacity method Additional heat source method Enthalpy method

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Harnessing meta-heuristic, Bayesian, and search-based techniques in optimizing machine learning models for improved energy storage with microencapsulated pcms

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2025年 162卷

作者： Ben Said, Lotfi Basem, Ali Sultan, Abbas J. Singh, Pradeep Kumar Jasim, Dheyaa J. Anqi, Ali E. Rajab, Husam Ahmed, Mohsen Rajhi, Wajdi Univ Hail Coll Engn Dept Mech Engn Hail City Saudi Arabia Warith Al Anbiyaa Univ Fac Engn Karbala Iraq Univ Technol Iraq Dept Chem Engn Baghdad Iraq GLA Univ Inst Engn & Technol Dept Mech Engn Mathura India Al Amarah Univ Coll Dept Petr Engn Maysan Iraq King Khalid Univ Coll Engn Dept Mech Engn Abha 61421 Saudi Arabia Najran Univ Coll Engn Dept Mech Engn King Abdulaziz RdPOB 1988 Najran Saudi Arabia Imam Abdulrahman Bin Faisal Univ POB 1982 Dammam 31441 Eastern Provinc Saudi Arabia

In recent years, systems based on microencapsulated phase change materials (Mpcms) have found applications in thermal energy storage, smart building construction, and battery thermal management. Despite their growing utility, there has been limited focus on modeling their thermophysical properties. This study aims to bridge this gap by developing optimized models to enhance understanding of the thermal conductivity of Mpcm-based suspensions, with and without 2D MXene nanomaterials. The approach involves employing three key machine learning algorithms-multilayer perceptron neural network (MLPNN), random forest (RF), and support vector machine (SVM). To maximize their performance, hyperparameters are fine-tuned using various optimization algorithms such as genetic algorithm (GA), Bayesian optimization (BO), random search (RS), and grid search (GS). SVM models displayed superior accuracy, followed by MLPNN models, and then RF models with the lowest accuracy. The GS-ANN model emerged as the top performer among MLPNN models, with a MAPE of 0.90713 % and an R-value of 0.99668. It was quick and had a simple architecture. In contrast, GA-ANN was significantly slower, resulting in a more complex structure. On the other hand, despite the higher accuracy of the GA-RF model, the RS-based model was 17 times faster. Finally, the GA-SVM model excelled overall, with impressive statistical metrics (MAPE = 0.45 % and R-value = 0.99949) and success in performance evaluation.

关键词： microencapsulated pcm Solar energy storage Thermal conductivity ANN SVM

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Thermal performance evaluation of pcm-integrated interior shading devices in building glass facades

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JOURNAL OF ENERGY STORAGE 2025年 113卷

作者： Celik, Ali Mandev, Emre Ersan, Orhan Muratcobanoglu, Burak Ceviz, Mehmet Akif Kara, Yusuf Ali Erzurum Tech Univ Dept Mech Engn Erzurum Turkiye Erzurum Tech Univ Inst Nat Sci Erzurum Turkiye Bursa Tech Univ Dept Mech Engn Bursa Turkiye

This study investigates the thermal performance and energy efficiency potential of Phase Change Material (pcm)-integrated interior shading devices installed within double and triple-glazed facades. The primary aim is to explore how these systems can enhance indoor thermal comfort, reduce energy consumption, and impact natural lighting levels. A test cabin was designed to evaluate these parameters, featuring double and triple-glazed panels with integrated shading devices containing microencapsulated pcms. The pcms, known for their ability to store and release thermal energy through phase changes, were utilized to mitigate indoor temperature fluctuations by absorbing excess solar heat during the heating period and releasing it during the cooling period. Experimental results revealed that the combination of triple glazing, shading devices, and pcm led to significant improvements in thermal performance, reducing temperature peaks and extending the cooling period compared to systems without pcm. The integration of pcm reduced the maximum temperature difference caused by heating and cooling cycles from 26.9 degrees C to 20.1 degrees C in double-glazed windows and from 19.8 degrees C to 12.4 degrees C in triple-glazed windows. Furthermore, pcm integration was shown to delay temperature rises by acting as a thermal buffer, thus stabilizing indoor conditions and reducing the load on cooling systems. Additionally, light intensity measurements were conducted to assess the impact of the shading devices on natural daylight levels. Despite the 35 % reduction in natural lighting caused by the shading devices, the overall thermal performance and energy saving potentials were substantial, highlighting the effectiveness of pcm as a passive thermal regulation material. This study provides valuable insights into the potential of pcm-enhanced shading devices as a solution for improving energy efficiency and occupant comfort in modern buildings.

关键词： Glass facade Shading device microencapsulated pcm Thermal energy storage Thermal comfort Indoor lighting

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Experimental Studies on the Critical Reynolds Number in the Flow of a microencapsulated Phase Change Material Slurry

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ENERGIES 2025年第6期18卷

作者： Dutkowski, Krzysztof Kruzel, Marcin Koszalin Univ Technol Dept Mech & Power Engn PL-75453 Koszalin Poland

The disadvantage of phase change materials (pcms) that store thermal energy is their low thermal conductivity. The macro-, micro-, and nanoencapsulation of pcms are some of the ways to eliminate this drawback. Liquids with micro- and nanometer-sized capsules containing pcms have become innovative working fluids for heat transfer-a slurry of encapsulated pcms. This paper shows the results of in-depth studies on the nature of fluid movement (slurry of microencapsulated pcms) in pipe channels. The slurry flowed inside a tube with a diameter of 4 mm in the range of Re = 350-11,000. The pcm microcapsule (mpcm) concentration ranged from 4.30% to 17.2%. A pressure loss measurement was carried out on a section of 400 mm. The temperature of the flowing slurry was selected so that the pcms in the microcapsules were in a liquid state and were solid during subsequent measurement series after undergoing a phase transformation. It was found that the boundary of the transition from laminar to turbulent flow is influenced by both the mpcm concentration in the slurry and the state of matter of the pcms in the microcapsules. The influence of the slurry concentration and the state of matter of the pcms in the microcapsules on changes such as fluid movement is presented (in terms of the critical Reynolds number).

关键词： experimental research microencapsulated pcm mpcm slurry flow resistance critical Reynolds number

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Heat transfer within mortar containing micro-encapsulated pcm: Numerical approach

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CONSTRUCTION AND BUILDING MATERIALS 2019年 210卷 422-433页

作者： El Ouali, A. El Rhafiki, T. Kousksou, T. Allouhi, A. Mandaoui, M. Jamil, A. Zeraouli, Y. Univ Moulay Ismail UMI Marjane II ENSAM BP 4024 Meknes Ismailia Morocco Univ Pau & Pays ADOUR Lab Sci Ingn Appliquees Mecan & Genie Elect Feder EA4581 E2S Uppa F-64000 Pau France Univ Sidi Mohamed Ibn Abdelah Ecole Super Technol Fes Route Imouzzer BP 2427 Fes Morocco Univ Abdelmalek Essaddi Tanger Equipe Rech Transferts Therm & Energet UAE Dept Phys FST E14FST Tangier Morocco

An axisymmetric physical model based on the porous medium approach was performed to quantify the thermal gradients inside a building material containing microencapsulated phase change material (pcm) in the differential scanning calorimeter cells. The conservation equations are solved numerically using finite difference method. The general expressions of the specific enthalpy, the apparent heat capacity and the equivalent heat capacity are exposed. The influence of various parameters like the heating/cooling rate, the volume fraction of the pcm and the sample masse on the thermal behavior of these materials is investigated and discussed. Despite the small dimensions of the differential scanning calorimeter samples, important temperature gradients were observed during the phase change process of the pcm. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： microencapsulated pcm Heat transfer Building DSC Hysteresis phenomenon

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