Thermal Energy Transfer and Storage

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closed (31 October 2024)

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Topic Information

Dear Colleagues,

The energy crisis, environmental deterioration, and global greenhouse effect have become increasingly more serious in recent decades, leading to rapid-growing demand for the utilization of renewable energy. Currently, their transience and intermittency have been concerns affecting further development and commercialization on device levels. Therefore, thermal energy storage has been widely used to provide a reliable thermal performance and stable power production. There are three kinds of TES technologies, including sensible heat storage (SHS), latent heat storage (LHS), and thermochemical heat storage (TCHS). In recent years, various scholars have placed emphasis on the improvement of energy storage tanks, including novel structures and composite PCM by installing fins and adding high thermal conductivity materials. Thus, we are committed to providing a platform for high-quality papers in the field of thermal energy storage. This issue focuses on fundamental and applied research which could help to augment charging/discharging performance of thermal energy storage.

Prof. Dr. Xiaohu Yang
Prof. Dr. Kamel Hooman
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Designs designs	-	3.9	2017	21.7 Days	CHF 1600
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600
Materials materials	3.1	5.8	2008	13.9 Days	CHF 2600
Nanomaterials nanomaterials	4.4	8.5	2010	14.1 Days	CHF 2400
Sustainability sustainability	3.3	6.8	2009	19.7 Days	CHF 2400

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Published Papers (30 papers)

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10 pages, 2136 KiB  

Open AccessArticle

Pool Boiling Heat Transfer Characteristics of SiO₂ and BN Nanoparticles Dispersed Mono and Hybrid Nanofluids

by Wagd Ajeeb and S M Sohel Murshed

Nanomaterials 2023, 13(19), 2625; https://doi.org/10.3390/nano13192625 - 23 Sep 2023

Cited by 7 | Viewed by 1275

Abstract

This study reports an experimental investigation of pool boiling (PB) heat transfer performance of hybrid (two types of particles) and mono (single-particle) nanofluids consisting of Boron nitride (BN) and Silicon dioxide (SiO₂) nanoparticles (NPs). While hybrid nanofluids (HNFs) were prepared in [...] Read more.

This study reports an experimental investigation of pool boiling (PB) heat transfer performance of hybrid (two types of particles) and mono (single-particle) nanofluids consisting of Boron nitride (BN) and Silicon dioxide (SiO₂) nanoparticles (NPs). While hybrid nanofluids (HNFs) were prepared in a total particle concentration of 0.05 vol.% with four different percentages of these two types of NPs (are 0.01/0.04, 0.02/ 0.03, 0.03/0.02, and 0.04/0.01 (BN vol.%/SiO₂ vol.%)), two mono nanofluids (MNFs) of BN and SiO₂ nanoparticles were prepared at the same total concentration of 0.05 vol.% for each NP type. Both nanofluids (NFs) were prepared in the base fluid (BF), which is the mixture of 15 vol.% of ethylene glycol (EG) and 85 vol.% of distilled water (DW). Then, the boiling heat transfer performance of these MNFs and HNFs was assessed by experimentation in a pool boiling test rig. The obtained results demonstrated good improvements in critical heat flux (CHF) and burnout heat flux (BHF) of both types of NFs. The CHF increased by up to 80% for BN-based MNF and up to 69% for HNF at 0.04 vol.% BN, which is the maximum percentage of BN into HNF, while the lowest improvement in CHF was 48% for the SiO₂-based MNF compared to the BF. Similarly, the BHF was found to increase with the increasing in the loading of BN nanoparticles and a maximum enhancement of BHF of 103% for BN-based MNF was observed. These HNFs and MNFs exhibited significantly improved pool boiling heat transfer performance compared to this BF, and it became lower by increasing the percentage of SiO₂ NPs in the HNFs. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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14 pages, 7975 KiB  

Open AccessArticle

Abrasion Effect on Heating Performance of Carbon Nanotube/Epoxy Composites

by Byung-Wook Kim, Seung-Jun Lee, Sung-Hwan Jang and Huiming Yin

Nanomaterials 2025, 15(5), 337; https://doi.org/10.3390/nano15050337 - 21 Feb 2025

Viewed by 409

Abstract

The effects of abrasion on the heating performance of carbon nanotube (CNT)/epoxy composites were investigated in terms of Joule’s heat, convective heat, and radiative heat under moderate-to-severe and localized abrasive conditions. While the overall heating behavior was characterized by the heating rate and [...] Read more.

The effects of abrasion on the heating performance of carbon nanotube (CNT)/epoxy composites were investigated in terms of Joule’s heat, convective heat, and radiative heat under moderate-to-severe and localized abrasive conditions. While the overall heating behavior was characterized by the heating rate and the curvature of the transient response, a numerical solution of the heat equation was used to quantify convective and radiative heat transfers, incorporating the specific heat of each component, the convective heat transfer coefficient, and the Biot number. CNT reinforcement significantly improved wear resistance at a CNT concentration of 0.31 vol. %, but the presence of micro-voids led to a slight increase in wear rate with additional CNT inclusion. Using an equivalent circuit model, local and severe abrasion scenarios were analyzed to determine the variation in electrical conductivity with temperature at different degrees of abrasion, indicating the impact of scattering effects. This analysis provides valuable insights for estimating both wear resistance and the heating performance of self-heated surface materials, with potential applications in future space technologies. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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35 pages, 5019 KiB  

Open AccessReview

Beyond Thermal Conductivity: A Review of Nanofluids for Enhanced Energy Storage and Heat Transfer

by Ali Mirahmad, Ravi Shankar Kumar, Breogán Pato Doldán, Cristina Prieto Rios and Javier Díez-Sierra

Nanomaterials 2025, 15(4), 302; https://doi.org/10.3390/nano15040302 - 16 Feb 2025

Cited by 1 | Viewed by 1197

Abstract

The development of nanofluids (NFs) has significantly advanced the thermal performance of heat transfer fluids (HTFs) in heating and cooling applications. This review examines the synergistic effects of different nanoparticles (NPs)—including metallic, metallic oxide, and carbonaceous types—on the thermal conductivity (TC) and specific [...] Read more.

The development of nanofluids (NFs) has significantly advanced the thermal performance of heat transfer fluids (HTFs) in heating and cooling applications. This review examines the synergistic effects of different nanoparticles (NPs)—including metallic, metallic oxide, and carbonaceous types—on the thermal conductivity (TC) and specific heat capacity (SHC) of base fluids like molecular, molten salts and ionic liquids. While adding NPs typically enhances TC and heat transfer, it can reduce SHC, posing challenges for energy storage and sustainable thermal management. Key factors such as NP composition, shape, size, concentration, and base fluid selection are analyzed to understand the mechanisms driving these improvements. The review also emphasizes the importance of interfacial interactions and proper NP dispersion for fluid stability. Strategies like optimizing NP formulations and utilizing solid–solid phase transitions are proposed to enhance both TC and SHC without significantly increasing viscosity, a common drawback in NFs. By balancing these properties, NFs hold great potential for renewable energy systems, particularly in improving energy storage efficiency. The review also outlines future research directions to overcome current challenges and expand the application of NFs in sustainable energy solutions, contributing to reduced carbon emissions. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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19 pages, 10158 KiB  

Open AccessArticle

Investigation on Melting Process of Finned Thermal Energy Storage with Rotational Actuation

by Yi Liu, Xiankun Meng, Xuanzhi Lv, Junfei Guo and Xiaohu Yang

Energies 2024, 17(17), 4209; https://doi.org/10.3390/en17174209 - 23 Aug 2024

Cited by 1 | Viewed by 789

Abstract

Phase-change thermal storage is essential for renewable energy utilization, addressing spatiotemporal energy transfer imbalances. However, enhancing heat transfer in pure phase-change materials (PCMs) has been challenging due to their low thermal conductivity. Rotational actuation, as an active method, improves heat transfer and storage [...] Read more.

Phase-change thermal storage is essential for renewable energy utilization, addressing spatiotemporal energy transfer imbalances. However, enhancing heat transfer in pure phase-change materials (PCMs) has been challenging due to their low thermal conductivity. Rotational actuation, as an active method, improves heat transfer and storage efficiency. This study numerically examined the melting behavior of finned thermal storage units at various rotational speeds. The influence of speed was analyzed via melting time, rate, phase interface, temperature, and flow distribution. Results showed that rotational speed effects were non-monotonic: excessive speeds may hinder complete melting or reduce efficiency. There existed an optimal speed for the fastest melting rate and a limited speed range for complete melting. At the preferred rotation speed of 2.296 rad·s⁻¹, the utilization of PCMs in a finned tube could mitigate the risk of local overheating by 97.2% compared to a static tube, while improving heat storage efficiency by 204.9%. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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15 pages, 6243 KiB  

Open AccessArticle

Thermal Energy Storage in Concrete by Encapsulation of a Nano-Additivated Phase Change Material in Lightweight Aggregates

by Iván Carrillo-Berdugo, Juan Jesús Gallardo, Nazaret Ruiz-Marín, Violeta Guillén-Domínguez, Rodrigo Alcántara, Javier Navas and Juan Antonio Poce-Fatou

Nanomaterials 2024, 14(14), 1180; https://doi.org/10.3390/nano14141180 - 11 Jul 2024

Cited by 1 | Viewed by 2038

Abstract

This work discusses the applicability of lightweight aggregate-encapsulated n-octadecane with 1.0 wt.% of Cu nanoparticles, for enhanced thermal comfort in buildings by providing thermal energy storage functionality to no-fines concrete. A straightforward two-step procedure (impregnation and occlusion) for the encapsulation of the [...] Read more.

This work discusses the applicability of lightweight aggregate-encapsulated n-octadecane with 1.0 wt.% of Cu nanoparticles, for enhanced thermal comfort in buildings by providing thermal energy storage functionality to no-fines concrete. A straightforward two-step procedure (impregnation and occlusion) for the encapsulation of the nano-additivated phase change material in lightweight aggregates is presented. Encapsulation efficiencies of 30–40% are achieved. Phase change behavior is consistent across cycles. Cu nanoparticles provide nucleation points for phase change and increase the rate of progression of phase change fronts due to the enhancement in the effective thermal conductivity of n-octadecane. The effective thermal conductivity of the composites remains like that of regular lightweight aggregates and can still fulfil thermal insulation requirements. The thermal response of no-fines concrete blocks prepared with these new aggregates is also studied. Under artificial sunlight, with a standard 1000 W·m⁻² irradiance and AM1.5G filter, concrete samples with the epoxy-coated aggregate-encapsulated n-octadecane-based dispersion of Cu nanoparticles (with a phase change material content below 8% of the total concrete mass) can effectively maintain a significant 5 °C difference between irradiated and non-irradiated sides of the block for ca. 30 min. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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19 pages, 11420 KiB  

Open AccessArticle

Performance Analysis of Vermiculite–Potassium Carbonate Composite Materials for Efficient Thermochemical Energy Storage

by Jianquan Lin, Qian Zhao and Haotian Huang

Energies 2024, 17(12), 2847; https://doi.org/10.3390/en17122847 - 9 Jun 2024

Cited by 3 | Viewed by 1405

Abstract

In this study, the preparation of the composite material consisting of expanded vermiculite (EV) and potassium carbonate (K₂CO₃) was conducted using a solution impregnation method. Sorption and desorption experiments were undertaken to investigate the dynamic and thermodynamic properties of [...] Read more.

In this study, the preparation of the composite material consisting of expanded vermiculite (EV) and potassium carbonate (K₂CO₃) was conducted using a solution impregnation method. Sorption and desorption experiments were undertaken to investigate the dynamic and thermodynamic properties of the EV/K₂CO₃ composites with varying salt contents. The findings suggest that the EV/K₂CO₃ composites effectively address the issues of solution leakage resulting from the deliquescence and excessive hydration of pure K₂CO₃ salt, thereby substantially improving the water sorption capacity and overall stability of the composite materials. The salt content plays a vital role in the sorption and desorption processes of EV/K₂CO₃ composites. As the salt content rises, the resistance to sorption mass transfer increases, resulting in a decline in the average sorption rate. Concurrently, as the salt content increases, there is a corresponding increase in the average desorption rate, water uptake, and heat storage density. Specifically, at a temperature of 30 °C and a relative humidity of 60%, the EVPC₄₀ composite with a salt content of 67.4% demonstrates water uptake, mass energy density, and volumetric energy density values of 0.68 g/g, 1633.6 kJ/kg, and 160 kWh/m³, respectively. In comparison to pure K₂CO₃ salt, the utilization of EV/K₂CO₃ composites under identical heat demand conditions results in a 57% reduction in the required reaction material. This study offers essential empirical evidence and theoretical backing for the utilization and development of EV/K₂CO₃ composites within thermochemical energy storage systems. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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18 pages, 1497 KiB  

Open AccessReview

A Review of the Characteristics of Light Pollution: Assessment Technique, Policy, and Legislation

by Ying Hao, Peiyao Wang, Zhongyao Zhang, Zhiming Xu and Dagong Jia

Energies 2024, 17(11), 2750; https://doi.org/10.3390/en17112750 - 4 Jun 2024

Cited by 5 | Viewed by 2633

Abstract

Light pollution from the use of artificial lighting poses significant impacts on human health, traffic safety, ecological environment, astronomy, and energy use. The advancement of characteristics of light pollution assessment technology has played a significant role in shaping prevention and control policies, thereby [...] Read more.

Light pollution from the use of artificial lighting poses significant impacts on human health, traffic safety, ecological environment, astronomy, and energy use. The advancement of characteristics of light pollution assessment technology has played a significant role in shaping prevention and control policies, thereby enabling measures, such as environmental standards and legislation and product procurement guidelines, but considerable variation in the definition, control strategies, and regulatory frameworks remains. Therefore, there is a need to review the characteristics of light pollution, including the assessment technique, policy, and legislation. Through the literature review, it can be found that technical standards are required to prevent light pollution. For example, light pollution is decreased by 6% in France through the legislation of artificial light. Key approaches are suggested to control global light pollution, including implementing ambient brightness zoning, regulating lighting product usage, and establishing dark sky reserves. Technology and policy should be integrated. The precise data coming from satellite imagery, drones, and balloons could provide guidance when making the policies. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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15 pages, 18899 KiB  

Open AccessArticle

Experimental Study on Paraffin Wax and Soya Wax Supported by High-Density Polyethylene and Loaded with Nano-Additives for Thermal Energy Storage

by Deepak Kumar Yadav, Pushpendra Kumar Singh Rathore, Rajeev Kumar Singh, Arvind Kumar Gupta and Basant Singh Sikarwar

Energies 2024, 17(11), 2461; https://doi.org/10.3390/en17112461 - 21 May 2024

Cited by 19 | Viewed by 2024

Abstract

Thermal energy storage technology has evolved as one of the prominent methods of storing thermal energy when it is available and utilized as per the requirements. In recent years, thermal energy storage has found a variety of applications for thermal management, such as [...] Read more.

Thermal energy storage technology has evolved as one of the prominent methods of storing thermal energy when it is available and utilized as per the requirements. In recent years, thermal energy storage has found a variety of applications for thermal management, such as buildings, batteries, electronics, cold storage, textiles, and solar thermal systems. Phase Change Material (PCM) has taken the lead among all other thermal energy storage materials because of various merits such as high energy density, ease of use, low cost, low volume change, environmental friendliness, easy availability, and chemical stability. However, limitations such as poor thermal conductivity and leakage during phase transformation limit their applicability. In this study, Shape Stabilized Composite PCM (SSCPCM) was developed to overcome these drawbacks. Paraffin wax and soya wax were used as PCMs and multi-walled carbon nanotubes and graphene oxide were used as nano-additives. High-Density Polyethylene (HDPE) is used as a supporting matrix. Leakage test suggest maximum loading of 40 wt% and 35 wt% of paraffin wax and soya wax in HDPE without any leakage at elevated temperature. The prepared SSCPCM shows substantially better thermal energy storage capacity along with improved thermal conductivity. A maximum rise of 260.8% in thermal conductivity was observed in paraffin wax supported by HDPE and loaded with 3 wt% of multi-walled carbon nanotube nanoparticles. The heating and cooling performance suggests an improvement in the heating and cooling rate by adding nano-additives. The prepared SSCPCM are also thermally stable at elevated temperatures up to 150 °C. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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15 pages, 2366 KiB  

Open AccessArticle

Computational Fluid Dynamics Heat Transfer Analysis of Double Pipe Heat Exchanger and Flow Characteristics Using Nanofluid TiO₂ with Water

by Abdulaziz S. Alhulaifi

Designs 2024, 8(3), 39; https://doi.org/10.3390/designs8030039 - 30 Apr 2024

Cited by 3 | Viewed by 2413

Abstract

A device called a heat exchanger is used to exchange heat transfer between two fluids with different temperatures. Because of its durability and ability to handle high-pressure application, the concentric double pipe heat exchangers are widely utilized for numerous industrial applications. To conserve [...] Read more.

A device called a heat exchanger is used to exchange heat transfer between two fluids with different temperatures. Because of its durability and ability to handle high-pressure application, the concentric double pipe heat exchangers are widely utilized for numerous industrial applications. To conserve pumping power energy, many researchers were involved in study of the nanoparticles to be embedded in the fluid, which will enrich the fluid thermal conductivity and surface area. This article demonstrates the flow characteristics and convective heat transfer of nanofluids containing 0.2, 0.4 and 0.6 of vol% TiO₂ nanoparticles dispersed in water under turbulent conditions, which mainly can be used for cooling nuclear reactors applications. Reynolds numbers varying from 4000 to 18,000 are examined numerically. The convective heat transfer coefficient results of the nanofluid agree well against experimental data, which are slightly more than that of base water at 1.94%. The results of the numerical model showed that the convective heat transfer coefficient of nanofluids will increase when the Reynolds and volume fraction increases. By increasing the temperature of the annular hot water, the heat transfer rate will increase, showing no major impact to the convective heat transfer coefficient of nanofluids. A generalised solution predicting the convective heat transfer coefficient for extensive nanoparticle materials is proposed. The conclusion of the empirical equation is tested among published data and the results are highly congruent, confirming the strength of the gamma equation. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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31 pages, 9949 KiB  

Open AccessArticle

Techno-Economic Optimization of Radiator Configurations in Power Transformer Cooling

by Aliihsan Koca, Oguzkan Senturk, Ömer Akbal and Hakan Özcan

Designs 2024, 8(1), 15; https://doi.org/10.3390/designs8010015 - 2 Feb 2024

Cited by 2 | Viewed by 3335

Abstract

In this research, a numerical approach is created to assess the effective parameters of power transformer thermal management and, as a result, improve their cooling systems. This study analyzes the radiator’s thermal performance across several arrangements and optimizes the dimensions and configurations for [...] Read more.

In this research, a numerical approach is created to assess the effective parameters of power transformer thermal management and, as a result, improve their cooling systems. This study analyzes the radiator’s thermal performance across several arrangements and optimizes the dimensions and configurations for varied cooling loads from a techno-economic perspective. The optimization criteria were the radiator’s height (L), fin spacing (D), and number of fins (N). Due to the great complexity of the generated models, the coupled thermo-hydraulic numerical simulations were carried out on a computer cluster. An in-house radiator test facility was constructed for the experiments in order to verify the numerical model. The simulation findings accord well with the empirically obtained values. A total of 76 radiator sets were investigated. Following that, the generated findings were used to perform an optimization analysis. Finally, the response surface method was used to establish an ideal radiator layout for the specified cooling capacity at the lowest possible cost. These findings reveal that the best cooling performance is obtained when the spacing between the fins is 50 mm. Cooling capacity per unit cost rises as radiator size decreases. The cost factor and geometric details were shown to have strong connections. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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16 pages, 3383 KiB  

Open AccessArticle

Impregnation of Activated Carbon with Organic Phase-Change Material

by Jiyeol Bae, Suho Kim, Kwangsoo Kim and Soyoung Baek

Materials 2024, 17(1), 67; https://doi.org/10.3390/ma17010067 - 22 Dec 2023

Cited by 2 | Viewed by 1450

Abstract

In this study, we developed a thermal storage medium comprising porous activated carbon filled with organic phase-change materials (PCMs) that utilizes the latent heat of phase-change to absorb heat during heating and release heat during cooling. For the activated carbon, we used both [...] Read more.

In this study, we developed a thermal storage medium comprising porous activated carbon filled with organic phase-change materials (PCMs) that utilizes the latent heat of phase-change to absorb heat during heating and release heat during cooling. For the activated carbon, we used both charcoal-based powdered activated carbon (250–350 mesh) and granular activated carbon. The organic phase-change materials used in the experiments were dodecane, tridecane, tetradecane, and pentadecane. Material properties such as thermal conductivity, latent heat, and melting temperature range were evaluated experimentally and theoretically, with the results observed to be consistent. The cyclic thermal performance of the proposed medium was also evaluated. Notably, filling the activated carbon with a mixture of organic PCMs resulted in the highest temperature-moderating effect. The procedure and results presented in this study are expected to aid in further improvement in the performance of thermal storage media containing PCM where stable temperatures are required, including building heating and cooling. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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17 pages, 5667 KiB  

Open AccessArticle

Design and Research of Heat Storage Enhancement by Innovative Wave Fin in a Hot Water–Oil-Displacement System

by Tao Ning, Xinyu Huang, Junwei Su and Xiaohu Yang

Sustainability 2023, 15(22), 15785; https://doi.org/10.3390/su152215785 - 9 Nov 2023

Cited by 2 | Viewed by 1495

Abstract

Energy storage technology provides a new direction for the utilization of renewable and sustainability energy. The objective of this study is to introduce a novel, wavy, longitudinal fin design, which aims to improve heat transfer in the melting process of a Latent Heat [...] Read more.

Energy storage technology provides a new direction for the utilization of renewable and sustainability energy. The objective of this study is to introduce a novel, wavy, longitudinal fin design, which aims to improve heat transfer in the melting process of a Latent Heat Thermal Energy Storage (LHTES) unit. The main goal is to mitigate the negative effects caused by the refractory zone at the end of the melting phase. A two-dimensional numerical model of LHTES unit is established by using the enthalpy porosity method and verified by experimental data. Through the quantitative comparison between the traditional rectangular fin and the innovative wave fin, the influence of wave fin on the heat transfer mechanism in the heat storage process is revealed. The results show that the average heat storage rate of five and six wave fins is 3.70% and 12.98% higher than that of conventional rectangular fins, respectively, and the average temperature response of six wave fins is 17.78% higher than that of conventional rectangular fins. The addition of the wave fin weakens the negative effect of the refractory zone, but prolongs the heating time of the initial melting point. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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19 pages, 761 KiB  

Open AccessEditor’s ChoiceArticle

A Stochastic Model of Anomalously Fast Transport of Heat Energy in Crystalline Bodies

by Łukasz Stępień and Zbigniew A. Łagodowski

Energies 2023, 16(20), 7117; https://doi.org/10.3390/en16207117 - 17 Oct 2023

Viewed by 1015

Abstract

In this work, a new method for constructing the infinite-dimensional Ornstein–Uhlenbeck stochastic process is introduced. The constructed process is used to perturb the harmonic system in order to model anomalously fast heat transport in one-dimensional nanomaterials. The introduced method made it possible to [...] Read more.

In this work, a new method for constructing the infinite-dimensional Ornstein–Uhlenbeck stochastic process is introduced. The constructed process is used to perturb the harmonic system in order to model anomalously fast heat transport in one-dimensional nanomaterials. The introduced method made it possible to obtain a transition probability function that allows for a different approach to the analysis of equations with such a disturbance. This creates the opportunity to relax assumptions about temporal correlations for such a process, which may lead to a qualitatively different model of energy transport through vibrations of the crystal lattice and, as a result, to obtain the superdiffusion equation on a macroscopic scale with an order of the fractional Laplacian different from the value of 3/4 obtained so far in stochastic models. Simulations confirming these predictions are presented and discussed. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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19 pages, 5730 KiB  

Open AccessArticle

Thermo-Economic Performance Analysis of Modified Latent Heat Storage System for Residential Heating

by Xinyu Gao, Ze Li, Jiabang Yu, Jiayi Gao, Xiaohu Yang and Bengt Sundén

Energies 2023, 16(19), 6915; https://doi.org/10.3390/en16196915 - 30 Sep 2023

Viewed by 1342

Abstract

Solar energy is a sustainable source that can be effectively utilized to address winter heating challenges in buildings. To ensure the efficient application of solar energy for heating purposes and to maintain reliable performance of the heating system, the integration of phase-change materials [...] Read more.

Solar energy is a sustainable source that can be effectively utilized to address winter heating challenges in buildings. To ensure the efficient application of solar energy for heating purposes and to maintain reliable performance of the heating system, the integration of phase-change materials (PCMs) in thermal energy storage (TES) systems has emerged as a crucial auxiliary approach. This study focuses on the design and simulation of four TES structures: smooth, finned, metallic foam, and metallic foam-finned tubes. It explores their thermal characteristics, such as complete melting time and heat flux, under various flow conditions. Additionally, a residential building in Xi’an is selected as the object, where the proposed solar energy phase-change TES system is employed to meet the heating demand. Economic indicators, including initial investment and investment payback period, are estimated using a static evaluation method. The results highlight that the complete melting time of the TES unit with a metallic foam-finned tube is 4800 s, which is 88.3% less than the smooth tube. Finally, based on the actual project, it is determined that the metallic foam-finned heating system, with an HTF flow rate of 0.25 m/s, requires the fewest TES devices (914) and has a payback period of 13 months. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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14 pages, 8651 KiB  

Open AccessArticle

Thermal Energy Storage Using a Hybrid Composite Based on Technical-Grade Paraffin-AP25 Wax as a Phase Change Material

by Hossam A. Nabwey and Maha A. Tony

Nanomaterials 2023, 13(19), 2635; https://doi.org/10.3390/nano13192635 - 25 Sep 2023

Cited by 4 | Viewed by 1572

Abstract

Thermal energy storage (TES) has a strong ability to store energy and has attracted interest for thermal applications such as hot water storage. TES is the key to overcoming the mismatch between energy supply and demand by using phase change materials (PCMs). However, [...] Read more.

Thermal energy storage (TES) has a strong ability to store energy and has attracted interest for thermal applications such as hot water storage. TES is the key to overcoming the mismatch between energy supply and demand by using phase change materials (PCMs). However, a common organic PCM characteristic is low thermal conductivity. This causes a slow thermal response for paraffin-AP25, which is not suitable for many applications. Hence, a search is underway for modifications to enhance its thermal properties. Thus, the current investigation introduces a novel PCM system based on the use of waste material as an economic and efficient system. In the current investigation, nanoparticles were added to a PCM; specifically, a technical-grade paraffin-AP25 wax (AP25 wax)/hybrid composite was synthesized via ultrasonic dispersion. The focus of this investigation is to assess the behavior of a PCM for energy storage via charging (melting process) and discharging (solidification process). Nanoparticles of magnetite were prepared via a simple, cost-efficient route, co-precipitation, augmented with aluminum and silicon derived from waste streams from a hydrothermal facility and mixed with paraffin-AP25 wax to form a hybrid composite PCM. Transmission electron microscopy and scanning electron microscopy (augmented with dispersive X-ray analysis, EDX) micrographs, in addition to X-ray diffraction (XRD), show the prepared composite. Different mass fractions of the composite, ranging from 1 to 10 weight %, were embedded in a paraffin-AP25 phase change material. The latent heat storage capacity of the PCM was enhanced by 8% when paraffin-AP25 was applied. Finally, the overall system efficiency was evaluated, and the yield increased by 64% for the 8% hybrid composite. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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28 pages, 7232 KiB  

Open AccessReview

Fractional-Order PID Controllers for Temperature Control: A Review

by Adeel Ahmad Jamil, Wen Fu Tu, Syed Wajhat Ali, Yacine Terriche and Josep M. Guerrero

Energies 2022, 15(10), 3800; https://doi.org/10.3390/en15103800 - 21 May 2022

Cited by 71 | Viewed by 7726

Abstract

Fractional-order proportional integral derivative (FOPID) controllers are becoming increasingly popular for various industrial applications due to the advantages they can offer. Among these applications, heating and temperature control systems are receiving significant attention, applying FOPID controllers to achieve better performance and robustness, more [...] Read more.

Fractional-order proportional integral derivative (FOPID) controllers are becoming increasingly popular for various industrial applications due to the advantages they can offer. Among these applications, heating and temperature control systems are receiving significant attention, applying FOPID controllers to achieve better performance and robustness, more stability and flexibility, and faster response. Moreover, with several advantages of using FOPID controllers, the improvement in heating systems and temperature control systems is exceptional. Heating systems are characterized by external disturbance, model uncertainty, non-linearity, and control inaccuracy, which directly affect performance. Temperature control systems are used in industry, households, and many types of equipment. In this paper, fractional-order proportional integral derivative controllers are discussed in the context of controlling the temperature in ambulances, induction heating systems, control of bioreactors, and the improvement achieved by temperature control systems. Moreover, a comparison of conventional and FOPID controllers is also highlighted to show the improvement in production, quality, and accuracy that can be achieved by using such controllers. A composite analysis of the use of such controllers, especially for temperature control systems, is presented. In addition, some hidden and unhighlighted points concerning FOPID controllers are investigated thoroughly, including the most relevant publications. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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16 pages, 3791 KiB  

Open AccessArticle

Two-Dimensional Modelling of Sludge Heat and Mass Transfer in a Paddle Dryer

by Wei Liu, Miao Gui, Fanghao Zhang, Yudong Zha and Zengyao Li

Energies 2023, 16(9), 3645; https://doi.org/10.3390/en16093645 - 24 Apr 2023

Cited by 1 | Viewed by 1789

Abstract

In this paper, we propose a concise but general two-dimensional model based on the penetration model in order to simulate the heat and mass transfer and drying kinetics of sludge in the paddle dryer. The sludge control equations were developed to simulate the [...] Read more.

In this paper, we propose a concise but general two-dimensional model based on the penetration model in order to simulate the heat and mass transfer and drying kinetics of sludge in the paddle dryer. The sludge control equations were developed to simulate the heat and mass transfer of sludge and the penetration model was introduced to describe the mixing of sludge. Compared to the experimental results in the existing literature, the drying kinetics simulated simulated by the present model were in good agreement with the experimental data under various operation conditions. The effects of four key parameters on drying kinetics in the paddle dryer were studied. The results showed that the water content increased with the increase of sludge flowrate and the decrease of wall temperature and sludge density. Furthermore, the stirring velocity had little effect on the drying kinetics of the sludge. The present study contributes to the better understanding of the sludge drying kinetics and provides guidance for the optimal design of industrial paddle dryers. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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13 pages, 3132 KiB  

Open AccessArticle

Anisotropic Metamagnetic Spin Reorientation and Rotational Magnetocaloric Effect of Single Crystal NdAlGe

by Keunki Cho, Wonhyuk Shon, Jaehan Bae, Jaewoong Lee, Seungha Yoon, Jinhee Kim, Jong-Soo Rhyee and Beongki Cho

Materials 2023, 16(7), 2771; https://doi.org/10.3390/ma16072771 - 30 Mar 2023

Cited by 2 | Viewed by 1920

Abstract

Magnetic anisotropy strongly influences the performance of the magnetocaloric effect. We investigated the magnetocaloric properties of the NdAlGe single crystal with I4₁md structure. The temperature-dependent magnetization revealed significant anisotropic properties; stable antiferromagnetic transition at T_N = 6 K for H [...] Read more.

Magnetic anisotropy strongly influences the performance of the magnetocaloric effect. We investigated the magnetocaloric properties of the NdAlGe single crystal with I4₁md structure. The temperature-dependent magnetization revealed significant anisotropic properties; stable antiferromagnetic transition at T_N = 6 K for H//a and meta-magnetic spin reorientation at low temperature (T ≤ 5 K) within an intermediate field (H = 2 T) for H//c. During the metamagnetic spin reorientation, the abrupt change of the magnetic entropy leads to a significant magnetocaloric effect with negative magnetic entropy change (∆S_M) by −13.80 J kg⁻¹ K⁻¹ at T_C = 5.5 K for H = 5 T along the H//c axis. In addition, the antiferromagnetic state for H//a shows the inverse magnetocaloric effect(I-MCE) by positive entropy change ∆S_M = 2.64 J kg⁻¹ K⁻¹ at T_N = 6 K for H = 5 T. This giant MCE accompanied by the metamagnetic transition resulted in a significantly large relative cooling power (158 J/kg at H = 5 T) for H//c. The giant MCE and I-MCE can be applied to the rotational magnetocaloric effect (R-MCE) depending on the crystal orientations. NdAlGe exhibits rotational entropy change ∆S_c−a = −12.85 J kg⁻¹ K at T_peak = 7.5 K, H = 5 T. With comparison to conventional MCE materials, NdAlGe is suggested as promising candidate of R-MCE, which is a novel type of magnetic refrigeration system. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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23 pages, 9560 KiB  

Open AccessReview

Critical Review of Ca(OH)₂/CaO Thermochemical Energy Storage Materials

by Yupeng Feng, Xuhan Li, Haowen Wu, Chaoran Li, Man Zhang and Hairui Yang

Energies 2023, 16(7), 3019; https://doi.org/10.3390/en16073019 - 25 Mar 2023

Cited by 16 | Viewed by 5273

Abstract

Thermal energy storage is an essential technology for improving the utilization rate of solar energy and the energy efficiency of industrial processes. Heat storage and release by the dehydration and rehydration of Ca(OH)₂ are hot topics in thermochemical heat storage. Previous studies [...] Read more.

Thermal energy storage is an essential technology for improving the utilization rate of solar energy and the energy efficiency of industrial processes. Heat storage and release by the dehydration and rehydration of Ca(OH)₂ are hot topics in thermochemical heat storage. Previous studies have described different methods for improving the thermodynamic, kinetic, and structural stability of Ca(OH)₂ to improve energy storage density, energy storage rate, and cycle stability, respectively. Here, the mechanisms and effects of different techniques on the performance improvement of Ca(OH)₂ and some common problems were reviewed. Specific problems were also clarified based on the characteristics of different technologies. Finally, suggestions for the future development of Ca(OH)₂ heat storage materials were provided. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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20 pages, 9135 KiB  

Open AccessPerspective

Solar Hot Water Systems Using Latent Heat Thermal Energy Storage: Perspectives and Challenges

by Nishant Modi, Xiaolin Wang and Michael Negnevitsky

Energies 2023, 16(4), 1969; https://doi.org/10.3390/en16041969 - 16 Feb 2023

Cited by 12 | Viewed by 4645

Abstract

Domestic water heating accounts for 15% to 27% of the total energy consumption in buildings in Australia. Over the past two decades, the latent heat thermal energy storage (LHTES) system has been widely investigated as a way to reduce fossil fuel consumption and [...] Read more.

Domestic water heating accounts for 15% to 27% of the total energy consumption in buildings in Australia. Over the past two decades, the latent heat thermal energy storage (LHTES) system has been widely investigated as a way to reduce fossil fuel consumption and increase the share of renewable energy in solar water heating. However, the research has concentrated on the geometric optimisation of the LHTES heat exchanger for the past few years, and this might not be sufficient for commercialisation. Moreover, recent review papers mainly discussed the development of a particular heat-transfer improvement technique. This paper presents perspectives on various solar hot water systems using LHTES to shift focus to on-demand performance studies, as well as structure optimisation studies for faster commercialisation. Future challenges are also discussed. Since the topic is an active area of research, this paper focuses on references that showcase the overall performance of LHTES-assisted solar hot water systems and cannot include all published work in the discussion. This perspective paper provides directional insights to researchers for developing an energy-efficient solar hot water system using LHTES. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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20 pages, 11071 KiB  

Open AccessArticle

Numerical Investigation on the Thrust Vectoring Performance of Bypass Dual Throat Nozzle

by Saadia Afridi, Tariq Amin Khan, Syed Irtiza Ali Shah, Taimur Ali Shams, Kashif Mehmood, Wei Li and David Kukulka

Energies 2023, 16(2), 594; https://doi.org/10.3390/en16020594 - 4 Jan 2023

Cited by 7 | Viewed by 2857

Abstract

Modern aircraft and missiles are gradually integrating thrust vector control systems to enhance their military capabilities. Bypass Dual-Throat Nozzle (BDTN) control is a new fluidic thrust vectoring technique capable of achieving superior performance with large vector angles and low thrust loss. In this [...] Read more.

Modern aircraft and missiles are gradually integrating thrust vector control systems to enhance their military capabilities. Bypass Dual-Throat Nozzle (BDTN) control is a new fluidic thrust vectoring technique capable of achieving superior performance with large vector angles and low thrust loss. In this study, we analyzed the flow characteristics and performance parameters of BDTN by varying the bypass angle, nozzle convergence angle, and bypass width. The flow governing equations are solved according to a finite volume discretization technique of the compressible RANS equations coupled with the Renormalization Group (RNG) k-ϵ turbulence model for Nozzle Pressure Ratio (NPR = 2~10) to capture the significance of under-expanded and over-expanded jets. Results show that by decreasing the bypass angle from 90° to 35°, there is a 6% increase in vectoring angle while the vectoring efficiency is enhanced by 18%. However, a decrease of 3% in the thrust and discharge coefficients is also observed. When the convergence angle was increased from 22° to 37°, vectoring angle, discharge coefficient, and thrust coefficient increased by 2%, 1%, and 0.26%, respectively. Moreover, vectoring efficiency is also enhanced by 8% by reducing the convergence angle from 37° to 22°. Based on the investigated parameters, it is determined that nozzle convergence angle does not significantly influence thrust vectoring performance, however, bypass width and bypass angle have a significant effect on thrust vectoring performance. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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15 pages, 4257 KiB  

Open AccessArticle

Investigation on the Melting Performance of a Phase Change Material Based on a Shell-and-Tube Thermal Energy Storage Unit with a Rectangular Fin Configuration

by Meng Yu, Xiaowei Sun, Wenjuan Su, Defeng Li, Jun Shen, Xuejun Zhang and Long Jiang

Energies 2022, 15(21), 8200; https://doi.org/10.3390/en15218200 - 3 Nov 2022

Cited by 4 | Viewed by 1718

Abstract

A case study on the melting performance of a shell-and-tube phase change material (PCM) thermal energy storage unit with a novel rectangular fin configuration is conducted in this paper. Paraffin wax and circulated water are employed as the PCM and heat transfer fluid [...] Read more.

A case study on the melting performance of a shell-and-tube phase change material (PCM) thermal energy storage unit with a novel rectangular fin configuration is conducted in this paper. Paraffin wax and circulated water are employed as the PCM and heat transfer fluid (HTF), respectively. It can be observed that the melting performance could be significantly improved by using rectangular fins. Melting photographs demonstrate that the melting of the PCM is firstly dominated by heat conduction; then, the melting rate is improved further due to natural convection. Moreover, the results illustrate that the influence of the inlet HTF temperature on the melting performance is significantly greater than that of the inlet HTF flow rate. The liquid fraction of paraffin wax in the PCM unit with a higher inlet HTF temperature is always higher than that with a lower inlet HTF temperature at the same time. The total charging time is reduced by 62.38% and the average charging rate is increased by 165.51% when the inlet HTF temperature is increased from 57 °C to 68 °C. As a result, a higher value of the inlet HTF temperature and a lower value of the HTF flow rate are able to improve the energy efficiency of the PCM unit with a rectangular fin configuration. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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9 pages, 2496 KiB  

Open AccessArticle

Thermal Energy Storage (TES) Prototype Based on Geopolymer Concrete for High-Temperature Applications

by Mohammad Rahjoo, Guido Goracci, Juan J. Gaitero, Pavel Martauz, Esther Rojas and Jorge S. Dolado

Materials 2022, 15(20), 7086; https://doi.org/10.3390/ma15207086 - 12 Oct 2022

Cited by 18 | Viewed by 2544

Abstract

Thermal energy storage (TES) systems are dependent on materials capable of operating at elevated temperatures for their performance and for prevailing as an integral part of industries. High-temperature TES assists in increasing the dispatchability of present power plants as well as increasing the [...] Read more.

Thermal energy storage (TES) systems are dependent on materials capable of operating at elevated temperatures for their performance and for prevailing as an integral part of industries. High-temperature TES assists in increasing the dispatchability of present power plants as well as increasing the efficiency in heat industry applications. Ordinary Portland cement (OPC)-based concretes are widely used as a sensible TES material in different applications. However, their performance is limited to operation temperatures below 400 °C due to the thermal degradation processes in its structure. In the present work, the performance and heat storage capacity of geopolymer-based concrete (GEO) have been studied experimentally and a comparison was carried out with OPC-based materials. Two thermal scenarios were examined, and results indicate that GEO withstand high running temperatures, higher than 500 °C, revealing higher thermal storage capacity than OPC-based materials. The high thermal energy storage, along with the high thermal diffusion coefficient at high temperatures, makes GEO a potential material that has good competitive properties compared with OPC-based TES. Experiments show the ability of geopolymer-based concrete for thermal energy storage applications, especially in industries that require feasible material for operation at high temperatures. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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16 pages, 2300 KiB  

Open AccessArticle

Thermo-Economic Assessments on a Heat Storage Tank Filled with Graded Metal Foam

by Gang Liu, Yuanji Li, Pan Wei, Tian Xiao, Xiangzhao Meng and Xiaohu Yang

Energies 2022, 15(19), 7213; https://doi.org/10.3390/en15197213 - 30 Sep 2022

Cited by 9 | Viewed by 2151

Abstract

To save and better deploy waste heat, the use of a mobilized heat storage system (MHSS) with phase change enhancement means is developed. In this paper, three kinds of gradient structures (positive gradient, negative gradient, and non-gradient) are designed in the MHSS system. [...] Read more.

To save and better deploy waste heat, the use of a mobilized heat storage system (MHSS) with phase change enhancement means is developed. In this paper, three kinds of gradient structures (positive gradient, negative gradient, and non-gradient) are designed in the MHSS system. The uniform porosity is 94% in the non-gradient structure, and the gradient porosities are 86%, 93%, and 98% in the gradient structure, respectively. Numerical models are developed to explore the contribution of the graded metal foam structure to the heat storage and release process. An economic analysis and comparison of MHSS systems with different heat transfer models are carried out. The results show that the positive gradient case can promote the thermal cycle of the melting and solidification process, while the negative gradient case inhibits the thermal cycle. The positive gradient case can reduce the melting time by 9.7% and the solidification time by 4.4%, while the negative gradient can prolong the melting time by 31.4% and the solidification time by 35.9%. Although graded metal foam increases the initial investment by 76.09%, the 1 KW·h heat cost of graded metal foam is reduced by 10.63% compared to pure phase change material (PCM). It is cost-effective in the long run of thermal cycles. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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28 pages, 4855 KiB  

Open AccessReview

Review and Techno-Economic Analysis of Emerging Thermo-Mechanical Energy Storage Technologies

by Khem Raj Gautam, Gorm Brunn Andresen and Marta Victoria

Energies 2022, 15(17), 6328; https://doi.org/10.3390/en15176328 - 30 Aug 2022

Cited by 22 | Viewed by 4136

Abstract

Thermo-mechanical energy storage can be a cost-effective solution to provide flexibility and balance highly renewable energy systems. Here, we present a concise review of emerging thermo-mechanical energy storage solutions focusing on their commercial development. Under a unified framework, we review technologies that have [...] Read more.

Thermo-mechanical energy storage can be a cost-effective solution to provide flexibility and balance highly renewable energy systems. Here, we present a concise review of emerging thermo-mechanical energy storage solutions focusing on their commercial development. Under a unified framework, we review technologies that have proven to work conceptually through project demonstration at a scale above 1 MW by describing the current state of commercial development, quantifying techno-economic parameters, outlining the challenges, and assessing each technology’s potential for commercial viability. The levelized cost of storage for thermo-mechanical energy storage at storage duration between 8 h and 1 week is cheaper than that of lithium-ion batteries and hydrogen storage; however, energy storage for such duration does not pay for itself at the current renewable penetration levels. For medium-term energy storage to be viable, at the realistic storage cost of 15 USD/kWh to 40 USD/kWh, the investment cost for power components should decrease to one-fifth of the current costs. Thermo-mechanical energy storage can be economically viable at the current investment costs in off-grid systems only when the marginal cost of alternative fuel exceeds 100 USD/MWh. We identified the cost ratio (charge power cost/discharge power cost) and the discharge efficiency as the critical technology-related performance parameters. Other external factors such as wind and solar fractions, demand, interconnections, sector coupling, and market structure play an important role in determining the economic feasibility of thermo-mechanical energy storage. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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28 pages, 10513 KiB  

Open AccessArticle

Repowering a Coal Power Unit with Small Modular Reactors and Thermal Energy Storage

by Łukasz Bartela, Paweł Gładysz, Jakub Ochmann, Staffan Qvist and Lou Martinez Sancho

Energies 2022, 15(16), 5830; https://doi.org/10.3390/en15165830 - 11 Aug 2022

Cited by 23 | Viewed by 4537

Abstract

In the first months of 2022, there was a sharp turn in the energy policy of the European Union, initially spurred by increasing energy prices and further escalated by Russia’s invasion of the Ukraine. Further transformation of the energy system will likely be [...] Read more.

In the first months of 2022, there was a sharp turn in the energy policy of the European Union, initially spurred by increasing energy prices and further escalated by Russia’s invasion of the Ukraine. Further transformation of the energy system will likely be accompanied by the gradual abandonment of natural gas from Russia and an increase of renewable and nuclear energy. Such a transition will not only increase energy security, but also accelerate the pace at which greenhouse gas emissions are reduced in Europe. This could be achieved more effectively if some of the new nuclear energy capacity is optimized to play an increased balancing role in the energy system, thus allowing for deeper market penetration of intermittent renewable energy sources with a reduced need for flexible fossil backup power and storage. A double effect of decarbonization can be achieved by investments in nuclear repowering of coal-fired units, with the replacement of coal boiler islands with nuclear reactor systems. Repowered plants, in turn, operate flexibly via integration with thermal energy storage systems using molten salt. This paper presents the results of a technoeconomic analysis for three cases of nuclear repowering of a 460 MW supercritical coal-fired unit in Poland. The first reference case assumes that three reactors are replacing the existing coal boilers, while the second reference leverages two reactors. The third uses two nuclear reactors equipped with a molten salt thermal energy storage system as a buffer for the heat produced by the reactor system. The analysis of the third case demonstrates how the TES system’s capacity varies from 200 to 1200 MWh, highlighting the possibility of obtaining a high degree of flexibility of the nuclear unit due to TES system without significant drops in the efficiency of electricity production. The economic analysis demonstrates that integration with TES systems may be beneficial if the current levels of daily variation in electricity prices are maintained. For current market conditions, the most attractive investment is a case with two reactors and a TES system capacity of 800 MWh; however, with the increasing price volatility, this grows to a larger capacity of 1000 or 1200 MWh. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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31 pages, 8540 KiB  

Open AccessArticle

Study on Heat Storage Performance of Phase Change Reservoir in Underground Protection Engineering

by Hongyu Zhang, Fei Gan, Guangqin Huang, Chunlong Zhuang, Xiaodong Shen, Shengbo Li, Lei Cheng, Shanshan Hou, Ningge Xu and Zhenqun Sang

Energies 2022, 15(15), 5731; https://doi.org/10.3390/en15155731 - 7 Aug 2022

Cited by 1 | Viewed by 1741

Abstract

In view of the main problems of the condensing heat discharge modes of the existing underground air-conditioning system, the technical scheme of using phase change heat storage modules to improve the heat storage capacity of the reservoir is proposed. By establishing a 3D [...] Read more.

In view of the main problems of the condensing heat discharge modes of the existing underground air-conditioning system, the technical scheme of using phase change heat storage modules to improve the heat storage capacity of the reservoir is proposed. By establishing a 3D flow and transient heat transfer model of the phase change reservoir, the effects of thermal property parameters, package size and arrangement of the phase change heat storage modules on the heat storage performance of the phase change reservoir were quantitatively analyzed based on three indexes: heat storage capacity per volume Δq, guaranteed efficiency coefficient η and slope of temperature rise per unit load ε. The results show that when the phase change temperature is 29 °C (23 °C increased to 33 °C) and the latent heat value is 250 kJ/kg (100 kJ/kg increased to 250 kJ/kg), Δq (110.92 MJ/m³, 112.83 MJ/m³) and η (1.22, 1.24) under both conditions are at their most, respectively, indicating that the phase change temperature should be less than 4 °C at the outlet temperature of the reservoir, and phase change materials with a high latent heat should be selected in engineering design whenever possible. When the size of the phase change module is 150 mm × 20 mm and the phase change reservoir adopts four intakes, ε (0.259, 0.244) under both conditions is the smallest, indicating that increasing the area of the phase change heat storage module and the fluid and increasing the inlet disturbance of the reservoir can enhance its heat storage capacity. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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22 pages, 4860 KiB  

Open AccessArticle

Study on the Coupling Effect of Heat Transfer and Refrigerant Distribution in the Flat Tube of a Microchannel Evaporator

by Wenju Hu and Xin Zhang

Energies 2022, 15(14), 5252; https://doi.org/10.3390/en15145252 - 20 Jul 2022

Cited by 2 | Viewed by 2313

Abstract

Refrigerant maldistribution severely deteriorates the heat transfer performance of a microchannel evaporator. Compared with the refrigerant distribution among flat tubes along the header, refrigerant distribution among microchannels in the flat tube in the airflow direction has barely been paid attention. In this paper, [...] Read more.

Refrigerant maldistribution severely deteriorates the heat transfer performance of a microchannel evaporator. Compared with the refrigerant distribution among flat tubes along the header, refrigerant distribution among microchannels in the flat tube in the airflow direction has barely been paid attention. In this paper, a heat transfer mathematical model of a microchannel evaporator’s flat tube composed of vertically placed parallel microchannels in the airflow direction was developed. The Refrigerant distribution among the microchannels was evaluated and its influence on heat transfer between air and refrigerant was analyzed. The results showed that the refrigerant distribution and heat transfer performance between air and refrigerant were interrelated and interacted with each other. The temperature of the air leaving the microchannel evaporator changed along the microchannel because of uneven refrigerant distribution among the microchannels, and the air temperature difference between air leaving out of the bottom and the top of the evaporator was approximately 2.13 °C. Ignoring the heat transfer from adjacent microchannels will lead to a small heat transfer deviation for the flat tube; thus, heat transfer among microchannels can be neglected. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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13 pages, 1230 KiB  

Open AccessArticle

Experimental Investigation on Latent Thermal Energy Storages (LTESs) Based on Pure and Copper-Foam-Loaded PCMs

by Morena Falcone, Danish Rehman, Matteo Dongellini, Claudia Naldi, Beatrice Pulvirenti and Gian Luca Morini

Energies 2022, 15(13), 4894; https://doi.org/10.3390/en15134894 - 4 Jul 2022

Cited by 6 | Viewed by 2536

Abstract

In this work, a commercial paraffin PCM (RT35) characterized by a change range of the solid-liquid phase transition temperature $T_{\mathrm{s}-\mathrm{l}}=29–36$ °C and the low thermal conductivity ${\lambda }_{\mathrm{SL}}=0.2$ W/m K is experimentally tested by [...] Read more.

In this work, a commercial paraffin PCM (RT35) characterized by a change range of the solid-liquid phase transition temperature $T_{\mathrm{s}-\mathrm{l}}=29–36$ °C and the low thermal conductivity ${\lambda }_{\mathrm{SL}}=0.2$ W/m K is experimentally tested by submitting it to thermal charging/discharging cycles. The paraffin is contained in a case with a rectangular base and heated from the top due to electrical resistance. The aim of this research is to show the benefits that a 95% porous copper metal foam (pore density $PD=20PPI$) can bring to a PCM-based thermal storage system by simply loading it, due to the consequent increase in the effective thermal conductivity of the medium (${\lambda }_{\mathrm{LOAD}}=7.03$ W/m K). The experimental results highlight the positive effects of the copper foam presence, such as the heat conduction improvement throughout the system, and a significant reduction in time for the complete melting of the PCM. In addition, the experimental data highlight that in the copper-foam-loaded PCM the maximum temperature reached during the heating process is lower than $20K$ with respect to the test with pure PCM, imposing the same heat flux on the top ($P=3.5$ W/m²). Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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27 pages, 2072 KiB  

Open AccessArticle

Dynamical System Scaling of a Thermocline Thermal Storage System in the Thermal Energy Distribution System (TEDS) Facility

by Ramon Yoshiura, Alexander Duenas and Aaron Epiney

Energies 2022, 15(12), 4265; https://doi.org/10.3390/en15124265 - 10 Jun 2022

Cited by 5 | Viewed by 1801

Abstract

The purpose of this study was to develop a process to convert input signals from one facility into another by reflecting geometric and environmental settings. The Dynamic Energy Transport and Integration Laboratory (DETAIL) is one facility in development that aims to emulate the [...] Read more.

The purpose of this study was to develop a process to convert input signals from one facility into another by reflecting geometric and environmental settings. The Dynamic Energy Transport and Integration Laboratory (DETAIL) is one facility in development that aims to emulate the daily interactions among power production industry systems and be capable of receiving real-time data from those systems as inputs. To convert signals and ensure that the temporal sequences and magnitudes reflect the laboratory settings, the ability to scale and project data is essential. To demonstrate this ability, Dynamical System Scaling (a methodology that enables systems to scale and project or extrapolate datasets to desired environments while conserving the observed transient behavior based on first principles) was applied to DETAIL’s thermocline thermal storage system in the Thermal Energy Distribution System. The thermocline system was successfully scaled and a test case was conducted to generate a doubly accelerated energy charge and discharge in reference to past experimental data from the facility. The accelerated data were determined as able to conserve the amount of energy stored and the associated test boundary conditions were charge line maximum temperature, charge line velocity, and thermocline maximum temperature at 354 °C, 0.458 m/s, and 418 °C, respectively. The research results represented a case that required signals to be accelerated without altering the stored energy. Full article

(This article belongs to the Topic Thermal Energy Transfer and Storage)

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