Phase Change Thermal Storage Device Research Articles

Numerical simulation of heat transfer performance and convective vortex evolution in a phase change thermal storage device with dispersed heat sources

Numerical simulation of heat transfer performance and convective vortex evolution in a phase change thermal storage device with dispersed heat sources

Multi-objective optimization of a novel phase-change thermal storage unit based on theoretical modeling and genetic algorithm

Phase-change thermal storage technologies are becoming increasingly indispensable in the field of renewable energy, and researchers have been striving to achieve high thermal storage performance in storage devices. To enhance the application potential of phase-change thermal storage units based on micro heat pipe arrays, theoretical analysis is applied to optimize the operating parameters and the fin structure, addressing the research gap caused by insufficient theoretical analysis. Therefore, an accurate thermal resistance network model is developed, and machine learning algorithms are employed for the multi-objective optimization of the fin structure. The optimal heights, widths, and thicknesses in two directions of the fins are 42.2, 3.7, 0.3, and 0.8 mm, respectively, resulting in a 15.8 % increase in charging power compared to the initial structure without increasing metal consumption. Additionally, it is recommended that the design flow rate be increased by 26 kg/h for each additional thermal storage unit connected in series. Finally, a phase-change thermal storage device is designed for a solar water heating system, and its applicability is simulated and analyzed. This study provides design guidance for this novel thermal storage device and promotes its application in the field of renewable energy.

Performance simulation of novel heat pipe type phase change thermal storage device

Given that the performance of the phase change thermal storage device (PCTSD) is limited by the low thermal conductivity of the phase change material, more effective heat transfer structures should be developed to improve the thermal storage rate. In this paper, a novel micro heat pipe array (MHPA)–PCTSD with a highly rational heat transfer structure is proposed to understand the influence mechanism of the relative positions of the MHPA and heat transfer channel. The arrangement of the heat transfer fluid (HTF) channels on both sides of the MHPA (Type A) and the arrangement of the MHPA on both sides of the HTF channel (Type B) are numerically modeled in three dimensions, and the thermal storage performance is analyzed. Results show that Type B has a significant advantage over the traditional heat pipe PCTSD and Type A, which can obtain better temperature uniformity and more reasonable thermal resistance distribution. Moreover, its total thermal resistance and melting time are 17.4% and 21% lower than those of Type A, thus confirming its higher optimization potential.

Experimental and Numerical Optimization Study on Performance of Phase-Change Thermal Energy Storage System

Promoting the use of solar energy resources has always involved the challenges of instability and supply–demand mismatch. The key to solving these issues is to efficiently store and utilize solar energy resources using high-performance heat storage devices. This study designed a high-performance shell-and-tube phase-change thermal storage device and established a numerical model using ANSYS software to summarize the device’s dynamic melting law. To verify the accuracy of the numerical simulation, a performance testing platform for the phase-change thermal storage device was built to investigate the impact of various factors, such as the inlet water temperature, inlet water flow rate, type of heat storage, and initial temperature of the device, and to reveal the change law of the device’s performance. The results show that the inlet water temperature has the most significant impact on the device’s heat storage and release performance. When the device’s heat storage or release is used for heating, changing the inlet water flow rate has a weak and limited effect on the device’s performance. However, when the device’s heat release is used to provide domestic hot water, increasing the make-up water temperature and reducing the inlet water flow rate can significantly improve the device’s effective heat release. Furthermore, based on the experimental validation of the model’s correctness, this study further simulated and studied the impact of different factors on the device’s heat storage process to optimize its structural design and provide technical references for the device’s actual operation and installation. The results show that the placement of fins has a negligible effect on the performance of the heat storage device while reducing the fin spacing and increasing the fin thickness can significantly improve the melting efficiency of the phase-change material (PCM). Additionally, the heat storage characteristics of the device are significantly better in the vertical installation mode than in the horizontal installation mode. This study provides theoretical guidance and technical references for the design and use of phase-change thermal storage devices.

Performance and optimisation of a novel phase change thermal storage device

To apply phase-change thermal storage in heat-pump systems, a low heat-transfer temperature difference is required. The typical temperature material requirements for phase change limit the application of its thermal storage in heat pump energy supply systems. This study introduces a novel phase-change thermal storage device suitable for a renewable energy supply system composed of multichannel flat tubes and closed rectangular fins. Performance experiments and optimisation of the connection geometry of the thermal storage units under low heat-transfer temperature differences were carried out. When the inlet temperature of the heat transfer fluid was 55 °C (the melting point of the phase change material is 50 °C), the energy storage density and gravimetric specific power can reach 175.16 kJ/kg and 27.93 W/kg respectively, which has obvious advantages compared to relevant devices in the literature. A dimensionless energy-efficiency ratio was used to optimise the device. It was shown that the series type can significantly increase pressure loss while improving heat storage performance, and optimising the structure and operation design parameters of parallel components is more beneficial in terms of device performance improvement. The optimal operating flow corresponding to different heights of the novel thermal storage unit in parallel was provided, thus laying a theoretical foundation for practical applications.

Studies on performance enhancement of heat storage system with multiple phase change materials

This paper aims to improve the heat storage system's performance by using multiple phase change materials (PCMs). A heat storage device is designed with multiple PCMs firstly. The heat storage device consists of three identical shell-tube phase change thermal storage units. The numerical method is developed and verified experimentally. Two parameters, namely the latent heat utilization of PCM (ω) and the heat transfer effectiveness of heat storage device (ε), are introduced to evaluate the performance of energy storage and the heat exchange of the heat storage system with multiple PCMs. The effects of factors on ω and ε are studied, including the thermal conductivity, latent heat and melting temperature difference of PCMs, and the inlet velocity and temperature of heat transfer fluid. Results indicate that increasing the inlet velocity and temperature of HTF can greatly improve ω, but reduce ε. Increasing the thermal conductivity of PCM can obviously improve ω, but it has little effect on improving ε. Multiple PCMs with suitable melting temperature difference can improve both ω and ε. In practice, multiple PCMs can be associated with the above methods to improve the overall performance of the phase change thermal storage system. This research is used to optimize the design of phase change thermal storage device and improve its performance.

Experimental Research of the Heat Storage Performance of a Magnesium Nitrate Hexahydrate-Based Phase Change Material for Building Heating

Phase change heat storage material is a preferred material in solar building heating or off-peak electric-heat storage heating technology and is the research focus. A compact phase change thermal storage device has been designed and experimentally studied for improving heating system load in this work. A new type, magnesium nitrate hexahydrate-based phase change material has been studied to improve the cooling degree and crystallization difficulty. The focus of this study is on the heat charging and discharging characteristics of this new phase change material. The heat storage device has two groups of coils, the inner side which carries water and the outer side which is the phase change material. A testing system was built up to value the thermal cycling performance of the heat storage device. The measurement data include phase change material temperature field, water inlet and water outlet mean temperature, heat charging and heat discharging depth, and flow rates over the operating period. The results show the phase change material has a quick response with the operating temperature range of 20–99 °C. Its latent heat is 151.3 J/g at 91.8 °C. The heat storage density of this phase change material is about 420 MJ/m3. The thermal performance degradation is about 1.8% after 800 operation cycles. The phase change thermal storage device shows flexibility and a great potential to improve the capacity and economy of heating systems.

Study on Thermal Performance of a Phase Change Thermal Storage Device by Utilizing Off-peak Power

Based on the background of peak load shifting, this paper proposes a phase change thermal storage device by utilizing off-peak power. Experimental investigations on its thermal performance is conducted, it shows that the regenerator has high density of thermal storage and good thermal storage efficiency of 91.3%. At the same time, numerical simulations of the heat transfer enhancement by using fins are performed on the exothermic process, the results show that the addition of fins can effectively improve the exothermic efficiency to 80%. The experimental and simulation results have some reference value for exploring the application of latent heat thermal storage in real life.

Experimental study on random heat transfer of phase change heat storage device

In the study of the heat conduction of phase change materials, due to the inherent properties, the deviation of the measured data and the processing technology of the phase change material, the uncertainty of the parameters of the material properties and geometric properties of the phase change materials exist inevitably. But at the present stage, there are very few experimental researches content of uncertain heat transfer in phase change thermal storage devices. The purpose of this paper is to study the uncertain heat transfer process of phase change heat transfer experimentally. The influence of latent heat of phase transition on the heat transfer process is mainly analyzed. The latent heat of different phase transitions is transformed into internal heat sources, and simulated by electric heating. The thermal response of phase-change heat transfer is analyzed by constructing the electric heating quantity under different probability distribution and uncertainty. The experimental results show that when the uncertainty is the same as 1/7, the difference of the standard deviation between two mean values (560 W and 630 W) is not large. The standard deviation and the mean correlation of the experimental values are not significant under the same uncertainty.

Numerical simulation on heat transfer enhancement of phase change thermal storage devices for low-middle temperature

Using Ba(OH)2·8H2O as phase change material (PCM) and water as heat transfer fluid (HTF), we numerically simulated annular finned-tube heat exchangers. In order to measure and analyze the impact of parameters in the heating/cooling process, temperature changes of different monitoring points, fin widths, and fin pitches as key parameters were considered and applied. The experimental results show that the heat exchange process can be divided into three stages within a certain time. The faster heat transfer rate is associated with the greater temperature difference between PCM and HTF. Furthermore, fins width and pitch affect dramatically the heat charging/discharging rate. The large fins width or small fins pitch is beneficial for extending the heat exchange surface, leading to improve heat transfer efficiency.

Characterization and numerical simulation on heat transfer performance of inorganic phase change thermal storage devices

Inorganic hydrated salt Ba(OH)2⋅8H2O is one of most potential thermal storage materials in the low–medium temperature range due to its highest latent heat per unit volume. Thermal stability tests, super-cooling and corrosion investigations of Ba(OH)2⋅8H2O on four metal materials were conducted, thermal cycling tests revealed that Ba(OH)2⋅8H2O as PCM had a good thermal reliability, the super-cooling increased and then stabilized after 300 thermal cooling cycles, the corrosion investigations showed that the copper had the strongest resistance corrosion performance. Furthermore, using copper as finned-tube and cylindrical shell and Ba(OH)2⋅8H2O as phase change material (PCM), numerical simulation of heat exchangers was carried out. The simulation results showed higher heat transfer efficiency was associated with the greater temperature difference between PCM and heating/cooling wall. The large fin width or small fin pitch could help extend the surface of the heat exchange, and contribute to improving the heat transfer efficiency.

Study of solar heated biogas fermentation system with a phase change thermal storage device

A new technique of solar heating biogas fermentation system integrated with a phase change thermal storage device is introduced for improving the low efficiency of the traditional biogas fermentation devices during winter. For a designed solar heated biogas system, its performance of anaerobic fermentation process under the different natural cooling conditions has been assessed by varying the thicknesses of insulation materials. And the optimum relative proportion between the heat supplied by solar and that stored in phase change heat storage device has been also investigated. The preliminary results based on the numerical simulations performed with meteorological data from Anhui Province, China show that the proposed PCM device with 3 m3 paraffin wax as phase change material (PCM) and 20 m2 solar collector areas can satisfy the heat required by producing 5 m3 biogas per day corresponding to a solar fraction (f) of 0.8 in winter. It indicates that the proposed solar heating system could be a promising approach for promoting biogas technology applications in cold rural regions of China.

Modeling a Phase Change Thermal Storage Device

A numerical model of a rapid response phase change heat exchange module has been developed and challenged with experimental data taken on a flow bench with multiple temperatures and flow rates for two different phase change thermal storage devices (PTSDs). The model requires an a priori knowledge of an effective overall heat transfer coefficient. A single test was used to establish a value for an effective overall heat transfer coefficient. With this information the model will predict the power removed from a fluid being cooled to closer than 15% of the peak power and the temperature of the fluid exiting the device to within 2 °C over the entire fluid discharge temperature range. This model, developed for potential use in feedback control algorithms, requires a real-time execution speed, and this goal has been achieved with a desktop quad-core computer (four times faster than real time). While 3D models with millions of cells can provide greater resolution, the large computational resources and run times required for these simulations precludes their use as a part of feedback control algorithms.

The Heat Charge and Discharge Characteristics Simulation of Phase Change Thermal Storage Device

The two-dimensional unsteady heat transfer model is been established. Analyzing on heat storage-release property of phase change thermal storage device within the fluid parallel spiral pipes in various conditions, suggestions are put forward to strengthen thermal storage for the device.