Phase Change Heat Storage Research Articles

Study on the thermal storage properties of a spiral tube heat storage tank based on numerical analysis

IntroductionThe spiral tube heat storage tank is a highly efficient device designed for storing and releasing heat, utilizing a spiral tube structure. Its key advantages include efficiency, reliability, and flexibility, making it suitable for a wide range of conditions, from high temperatures and pressures to low temperatures and high vacuums.MethodsThis study aims to analyze phase change heat storage in spiral tube heat storage tanks using numerical simulation.ResultsIt explores the impact of varying water supply temperatures on heat transfer efficiency and the melting behavior of phase change materials within the tanks. Proposed enhancements, informed by numerical simulation results, seek to improve heat transfer efficiency. Simulation findings indicate that charging efficiency rises with increased temperature differentials, akin to sleeve-type heat exchangers.DiscussionCalculations suggest faster melting of phase change materials at the central position of the tank’s spiral tube, with slower melting near the vessel wall. Consequently, reducing the number of spiral tubes in the middle is suggested for future structural optimization.

The innovative application of phase change materials in heat storage products: warmer pads

As the issue of energy shortage becomes increasingly severe, energy storage technology has gradually attracted global attention, with the application of phase change materials (PCMs) being particularly widespread. This paper focuses on a common daily product: the warmer pad, and investigates the selection and ratio of suitable PCMs to achieve a recyclable heat storage solution. The study first outlines the research background, significance, and methods, then summarizes the basic principles of phase change and the role of differential scanning calorimetry (DSC) in the study of phase change heat storage. Finally, the properties of PCMs with different proportions were tested, and the DSC curves were analyzed. The results showed that the phase change material mixture with a ratio of paraffin: OBC: expanded graphite = 77:20:3 exhibits excellent performance in heat storage, with a thermal conductivity of 0.547 W/mK, a phase change latent heat of 150 J/g, and a phase change temperature of 41.9C. The warmer pad achieved a surface temperature close to 40C and a heat release duration of nearly one hour. This study aims to promote the industry's transformation towards sustainable development and provide a reference for research in the field of daily-use products with phase change heat storage.

Investigation on heat transfer enhancement of PCM by tree-like fins

Abstract The limited thermal conductivity of PCM significantly hampers the potential applications of phase change heat storage. To enhance heat transfer efficiency, fins can be incorporated into the phase change unit. In this study, two tree-like fins were designed based on fractal principles, and a transient model for fin-lauric acid phase change was established. Through numerical simulations, we investigated and compared the variations in liquid fraction of units equipped with fractal fins, traditional rectangular fins, and without any fins. In order to explore the variation of the heat transfer process in the units, the solid-liquid interface and temperature distribution were analyzed. The results demonstrate that due to their superior enhancement effect on heat conduction outweighing any inhibitory effects from natural convection, fractal fins exhibit significant improvements in heat transfer performance by shortening the complete melting time by 33.72% and 29.17%, respectively, for each type of tree-like fin.

Optimization of the annular fin arrangement in phase change heat storage units based on response surface methodology

Latent heat thermal energy storage (LHTES) technology is of increasing industrial interest due to its advantages such as high heat storage density and near-constant temperature during the phase change process. However, the latent heat storage technology is impacted by the low thermal conductivity of the phase change material (PCM), leading to delays and heat loss in the heat transfer process within LHTES. This limitation reduces the efficiency of heat transfer and diminishes the performance of the heat storage unit. To address this issue, this paper employs numerical simulation and response surface methodology to investigate different types of annular fin phase change heat storage units, aiming to derive the optimal configuration for enhancing unit performance. Therefore, the effect of fin type and number on the melting and solidification process is analyzed in detail. The research results indicate that among the five different types of fins studied, the total time required for the unit to complete melting and solidification is the least with type “e” fins, only 51.78 h, demonstrating that type “e” fins have the best effect on improving unit performance. For type “e” fins, when the number of fins n is 15, it can most effectively shorten the melting and solidification time of the phase change heat storage unit, reducing it to only 47.81 h. In addition, the response surface methodology was utilized to derive the optimal fitting formulas for different types of annular fins and to validate these formulas, and the error between the validation analysis and the numerical simulations was within 5%, which confirms the reliability of the fitting formulas developed in this study. This approach facilitates the selection of various annular fin models for subsequent experimental and simulation studies, thereby reducing the time and cost associated with model selection.

Recent Progress of Phase Change Materials and Their Applications in Facility Agriculture and Related-Buildings—A Review

Facility agriculture, which involves agricultural production in controlled environments such as greenhouses, indoor farms, and vertical farms, aims to maximize efficiency, yield, and quality while minimizing resource consumption and environmental impact. Energy-saving technologies are essential to the green and low-carbon development of facility agriculture. Recently, phase change heat storage (PCHS) systems using phase change materials (PCMs) have gained significant attention due to their high thermal storage density and excellent thermal regulation performance. These systems are particularly promising for applications in facility agriculture and related buildings, such as solar thermal utilization, greenhouse walls, and soil insulation. However, the low thermal conductivity of PCMs presents a challenge for applications requiring rapid heat transfer. This study aims to provide a comprehensive review of the types, thermophysical properties, and various forms of PCMs, including macro-encapsulated PCMs, shape-stabilized PCMs, and phase change capsules (PCCs), as well as their preparation methods. The research methodology involves an in-depth analysis of these PCMs and their applications in active and passive PCHS systems within facility agriculture and related buildings. The major conclusion of this study highlights the critical role of PCMs in advancing energy-saving technologies in facility agriculture. By enhancing PCM performance, optimizing latent heat storage systems, and integrating intelligent environmental control, this work provides essential guidelines for designing more efficient and sustainable agricultural structures. The article will serve as the fundamental guideline to design more robust structures for facility agriculture and related buildings.

Performance investigation of a solar-driven cascaded phase change heat storage cross-seasonal heating system for plateau applications

The mismatch between solar radiation resources and building heating demand on a seasonal scale makes cross-seasonal heat storage a crucial technology, especially for plateau areas. Utilizing phase change materials with high energy density and stable heat output effectively improves energy storage efficiency. This study integrates cascaded phase change with a cross-seasonal heat storage system aimed at achieving low-carbon heating. The simulation analyzes heat distribution and temperature changes from the heat storage system to the heating terminal. The results indicate that although the solar collectors operate for 26.3% of the total heat storage and heating period, the cumulative heat stored is 45.4% higher than the total heating load. Heat transferred by the cross-seasonal heat storage system accounts for up to 61.2% of the total heating load. Therefore, the system reduces fuel consumption by 77.6% compared to conventional fossil fuel heating systems. Moreover, radiant floor heating terminals, with a wide range of operating temperatures, match well with cascaded phase change heat storage and can reduce operation time by 19.5% and heat demand by 5.2% compared to conventional radiators. In addition to demonstrating the feasibility of applying cascaded phase change technology in cross-seasonal heat storage heating, this study reveals the lifecycle sustainability due to the shortened heat storage period. The configuration, parameters, and simulation results provide a reference basis for system application and design.

Application of bionic topology to latent heat storage devices

Latent heat storage is employed to address the intermittent supply of renewable energy, and enhancing heat transfer in phase change materials (PCMs) is pivotal for achieving effective heat storage. Currently, the predominant method for improving heat transfer is through the integration of high thermal conductivity fins into heat storage devices. This study introduces an innovative design of a three-tube phase change heat storage device created through bionic topology optimization. The impact of parameters such as penalty factors and filtering radius on the topology structure is analyzed, and the optimal range of fin volume fraction is determined based on energy storage density and energy storage time. Considering the influence of natural convection on heat transfer properties, four distinct heat storage models, including topology-optimized fins, are compared. The heat transfer and flow properties during the processes of melting and solidification, as well as their field synergy, are investigated. The study reveals that the optimized fins exhibit more bionic fractal structures and a larger, more uniform heat transfer contact area. Compared to traditionally optimized fin structures, this research reduces the heat storage time of the three-tube heat storage device by 21.96 % and the heat release time by 38.13 % without compromising the maximum heat storage capacity. The topology-optimized fins demonstrate a fractal dimension similar to natural fractal structures such as branches, leaf veins, antlers, and snowflakes. This study presents a novel bionic structural design approach for high-performance latent heat storage systems.

Preparation of Al[sbnd]Si microcapsules with high latent heat and durability via control of shell thickness

Microencapsulation of the AlSi alloy is an effective approach to overcome the challenges of corrosion and oxidation during high temperature operational service when used as phase change heat storage material. Research to date has shown that the prepared microcapsules was not able retain the high latent heat of AlSi alloy and achieve excellent thermal cycling performance at the same time. In this work, AlSi alloy microcapsules with adjustable shell thickness were successfully prepared through hydrothermal reaction, in situ polymerization and heat treatment at different oxygen contents. The phase composition and microstructure of the microcapsules were characterized in detail by XRD and electron microscopy. The thermal performances were tested through thermal cycling and thermal analysis. The results demonstrated that the outer protective shell layer of microcapsules was composed of dense α-Al2O3 and the thickness was adjustable from 372 to 1504 nm by controlling the oxygen content during heat treatment. Meanwhile, the regulation mechanism of shell thickness was analyzed. According to thermal analysis, the latent heat of microcapsules could achieve 450 J·g−1, and the latent heat retention was 100 % after 5000 thermal cycles from 500 °C to 650 °C. This work provides new method of adjusting the shell thickness of AlSi microcapsules to achieve an ultra-high thermal performance in terms of latent heat and retention, which promotes the development of applications for metal-based heat storage materials.

Simulation study on thermal performance of solar coupled air source heat pump system with phase change heat storage in cold regions

The development of efficient and clean heating technologies is profoundly significant for the reduction of carbon emissions in cold regions. This paper puts forth a novel solar-coupled air source heat pump system integrated with phase change heat storage technology, which is well-suited for regions with such climatic conditions. A numerical model of the components and coupled systems is established using the lumped parameter method, and an iterative method is employed for the computational solution in MATLAB software. A variety of system performance aspects are then simulated and analysed following the configuration of component structural parameters and initial operating conditions. The results of the simulations indicate that an increase in the phase change temperature interval of the phase change materials leads to a higher average heat release power. In particular, a 2 °C increase in the phase change temperature interval results in an increase in the heat release power of over 10 %. Furthermore, when the system is applied in typical cold regions, including Kunming, Hangzhou, Lhasa, and Harbin, the average coefficient of performance is 10.23, 8.87, 8.49, and 7.70, respectively. The proportion of solar energy input contributes to an increase in system efficiency across all regions. A case study of Hangzhou reveals that the incorporation of solar energy into the system results in an increase in efficiency of 70.91 %. This research provides valuable operational methods and site selection recommendations for engineering practices, laying a theoretical foundation for its widespread application in cold regions.

Preparation and characterization of Al-12Si/ceramic composite phase change heat storage material

Preparation and characterization of Al-12Si/ceramic composite phase change heat storage material

Thermal performance of cascaded latent heat thermal energy storage units constructed based on solid-liquid interface information

A novel approach to constructing cascaded latent heat thermal energy storage units is proposed to enhance the thermal performance of horizontally placed shell-and-tube phase change heat storage systems. This method is based on the solid-liquid interface variation patterns during the solidification and melting processes. It creates interfaces between different phase change materials within the cascaded latent heat thermal energy storage unit to shorten melting time and increase thermal performance by optimizing the unit's internal structure to balance heat transfer rates across all areas. The enthalpy-porosity method was used to numerically study the phase change phenomenon. The inner tube of the units was set as an isothermal boundary, and the outer shell was insulated. Findings from this cascaded latent heat thermal energy storage system demonstrate that, compared to single-latent heat thermal energy storage units, the average heat transfer rates during solidification and melting increased by 27.3% and 36.7%, respectively. The average heat transfer rate during solidification improved by 11.7% compared to traditional concentric circular cascaded latent heat thermal energy storage units. These results indicate that this method can significantly enhance the thermal performance of latent heat thermal energy storage units, providing valuable insights for future structural optimization.

Study on the Coupling of Air-Source Heat Pumps (ASHPs) and Passive Heating in Cold Regions

Air-source heat pumps (ASHPs), as an active device, are widely used in building heating and cooling processes. However, in severe cold regions, they face reduced heating efficiency and frosting problems in winter. This paper proposes a new heating solution by coupling an ASHP with passive heating systems. It combines an ASHP with passive sunrooms and heat storage systems for heating. Through software simulations and mathematical modeling, the new scheme is compared and analyzed against traditional ASHP solutions to explore the performance of this scheme in rural houses in severe cold regions of China during winter. According to simulation and calculation analysis, on the coldest day of winter, the coupling scheme can provide approximately 99.41 kWh of heat to the indoors, which exceeds the 86.67 kWh required to maintain an indoor temperature of 20 °C. The system’s power consumption is 36.96 kWh, which is 66.88% lower than that of traditional heat pump heating. The study shows that the coupling system of an ASHP and passive heating has a good heating effect in severe cold regions. For the situation of insufficient solar energy at night, the design of phase-change materials and heat storage media can meet heating needs throughout the day.

Novel modular PCM wall board for building heating energy efficiency: Material preparation, manufacture and dynamic thermal testing

With the comprehensive implementation of China’s “dual carbon” goals, the building heating sector, characterized by high energy consumption and emissions, urgently requires low-carbon transformation. However, energy-saving measures for plateau regions are scarce and face challenges due to harsh climates. This study proposes an innovative heating method utilizing composite phase change materials. A new modular phase change thermal storage electric heating terminal integrated with a photovoltaic thermal system has been designed to address issues of high building energy consumption and problems related to heating system freezing and leakage in the Tibetan Plateau (Qinghai-Xizang Plateau). Laboratory tests were conducted on six groups of samples with different structures and placements to examine their heat storage and release characteristics. Results indicate: The system’s temperature stabilization time totals 14.6 h; Horizontally placing the terminal reduces melting time by up to 2.7 h, enhancing heat storage performance; Structure three shortens solidification time by up to 2.2 h compared to structure one, improving heat release performance; Vertically placed terminals have better heat release performance than horizontally placed ones, resulting in more effective indoor heating. This study proposes a modular design for phase change heat storage electric heating walls, simplifying installation and maintenance while maintaining aesthetic appeal. Detailed temperature measurements of different wall surfaces revealed excellent cyclic heat storage and release performance. The developed phase change heat storage electric heating terminal is expected to significantly reduce heating energy consumption in the Tibetan Plateau (Qinghai-Xizang Plateau), enhancing building energy efficiency and providing valuable insights for further applications of phase change materials in building design.

Study on the Influence of Phase Change Process on the Desorption Characteristics of Gas-Containing Anthracite in Phase Change Heat Storage Materials

Study on the Influence of Phase Change Process on the Desorption Characteristics of Gas-Containing Anthracite in Phase Change Heat Storage Materials

Thermo-economic assessments on building heating by a sewage source heat pump coupled with heat storage system

To enhance the economic feasibility of building heating systems, phase change heat storage materials are often utilized to utilize renewable energy and address system peak loads. This article presents an innovative method of integrating a sewage source heat pump with a heat storage device. Upon an industrial building in Xilinhot as a case study, numerical models for the heat accumulator coupled with the energy consumption of buildings are established, taking into account dynamic hourly loads and meteorological conditions. Through a comprehensive analysis, the thermophysical properties of the heat accumulator as well as the economic implications of the multi-energy complementary heating system are investigated. Results demonstrate that the complete melting time for a 95 % filling rate is significantly reduced, 87.11 % shorter than that of pure phase change material, achieving the highest heat storage efficiency. Furthermore, the phase change storage device with a 75 % filling rate had the shortest investment payback period, requiring only 6 years. These findings have significant implications for guiding green renovation projects in building heating systems.

Phase change heat storage and enhanced heat transfer based on metal foam under unsteady rotation conditions

Phase change heat storage technology is an essential method for balancing supply and demand in solar energy heat utilization. In this study, a numerical model of the phase change heat storage process is built to explore the impact of non-constant rotation, with and without metal foam. Subsequently, an investigation into the influence of metal foam pore density and porosity on heat storage performance is conducted, with a focus on Taguchi design for statistical analysis. The research delves into the effects of foam parameters on heat storage rate, temperature response, heat storage time, and heat storage properties. Findings reveal significant resolidification in the melting process of this thermal storage structure without metal foam, due to periodic rotation speed hindrance in transferring heat to the outside. Taguchi design results underscore the greater influence of porosity on the melting time and average heat storage rate compared to pore density. Specifically, a reduction in melting time by 62.21 % and 30.49 %, and an increase in average heat storage rate by 237.56 % and 51.19 % is observed when pore density and porosity are 40 PPI and 0.97, compared with the ones with porosities of 0.99 and 0.98, demonstrating minimal impact on total heat absorption.

Preparation of phase change Heat storage wood with in-situ generation of thermal conductive particles to improve photothermal conversion efficiency

Wood has been developed with phase change heat storage function using balsa as a natural packaging material, and PEG was employed as a material for phase change heat storage (PCHS). Moreover, the thermal conductivity efficiency of the wood was be improved by in-situ synthesizing Fe3O4 in wood. The prepared PCHS wood was characterized by high solidification and melting enthalpies. The temperature of phase change ranged from 21.47 °C to 35.30 °C, consistent with the temperature range that makes humans comfortable in their body. The in-situ generation of Fe3O4 not only improves the PCHS wood's thermal conductivity efficiency, but also forms a 3D network structure with PCHS materials, thereby improving the dimensional stability. Comparing with original wood, PCHS wood shows good temperature regulation function, which can quickly convert light energy into internal energy and has a longer period of thermal radiation at low temperatures. The generated PCHS wood shows a promising application as indoor temperature regulating materials to promote building energy conservation.

Solar-heat pump combined drying with phase change heat storage: Multi-energy self-adaptive control

Due to the various uncertainties in multi-energy drying systems, traditional condition control struggles with the rational matching of multiple heat sources and precise temperature regulation. In order to automatically switch energy utilization modes based on current parameters to reduce energy consumption, this paper developed a fuzzy control system for a kelp multi-energy drying device. An automatic switching strategy between different operating modes and the action processes of various actuators were established for matching multiple energy sources. The system hardware and software were designed and installed, including a remote monitoring devices and human-machine interface. Drying experiments of kelp were conducted in solar, solar-heat pump, heat pump and Heat storage-heat pump mode using both the fuzzy control system and the original. The fuzzy control system showed a temperature overshoot of 2.57 %–3.95 %, temperature deviation within ±1.5 °C, which were superior to the original control system. The energy consumption in solar-heat pump mode was 0.398 kW h/kg, only 43 % of the original control system. BP neural networks prediction model of kelp moisture content under different drying modes was established to prevent over-drying. The model can accurately describe the pattern of moisture content variation with RMSE of 2.36–4.27.

Application of phase change material on solar-greenhouse back wall and its effects on indoor thermal environment and cucumber production in winter

The configuration of the solar greenhouse building wall and the thermal properties of the building materials directly impact wall insulation, heat storage characteristics, and, consequently, the thermal environment within the greenhouse. To address the variations in wall heat storage during the design and construction of solar greenhouses, this study aims to integrate solar energy effectively with phase change heat storage technology. Utilizing Energy Plus, the study simulates and verifies the heat storage and release performance of phase change materials on the greenhouse's back wall. The research also explores the warming effect of these materials on cucumber growth. The findings reveal that the composite phase change greenhouse (PC) wall exhibits an average heat release of 60.47 W/m2, maintaining an average temperature of 21.09 °C. In comparison, the heat release from the back wall of the traditional greenhouse (CK) increases by 14.03 W/m2, resulting in a temperature rise of 1.91 °C. Additionally, the substantial heat released by the phase change wall raises the average ground temperature to 18.26 °C through heat conduction, exceeding CK by 3.07 °C. Despite this, the maximum temperature remains below 25 °C, creating an ideal growth temperature for cucumbers and fostering vigorous growth. Furthermore, cucumber quality indicators, such as soluble sugar and VC content, significantly improve, demonstrating a 28.5 % increase in the single fruit weight of cucumbers. In conclusion, the composite phase change greenhouse outperforms the traditional greenhouse in heat storage capacity. The heat storage wall effectively enhances the overall thermal environment, insulation, and heat storage performance, ultimately leading to increased cucumber yield and quality.

Effect of composite fin structure on phase change heat storage tank: A numerical investigation

This study investigates the phase change heat storage process in the hot water displacement system. The PCHS unit incorporates V-shaped fins and straight fins to enhance heat transfer, with the additional enhancement of annular fins. Numerical simulation is used to examine the impact of fin structure and quantity on the evolution of internal flow rate, liquid phase, and temperature during the heat charging process. The response of different fin structures to parameters such as melting time, heat storage rate, storage capacity, and dimensionless temperature is analyzed. The results indicate that Model-6 (4 V-shaped fins + annular fins) exhibits the shortest melting time, reduced by 52.13 % compared to Model-1 (initial structure). The melting time of Model-4 (4 straight fins + annular fins) and Model-6 shows little difference, during the final melting stage, attributed to the good heat transfer performance of the bottom fin in Model-4. Furthermore, the total heat absorption of Model-4 and Model-6 is decreased by 3.92 % and 3.20 % respectively compared to Model-1, while the mean rate of heat storage is increased by 100.20 % and 102.21 % compared to Model-1, demonstrating the significant improvement in heat storage performance with annular fins. Additionally, the same number of V-shaped fins and straight fins, when paired with annular fins, exhibit minimal differences in their strengthening effects, with V-shaped fins enhancing pre-melting and mid-melting, and straight fins showing advantages for end-melting.