Processes Of Phase Change Material Research Articles

Numerical investigation of the effect of an air layer on the melting process of phase change materials

Numerical investigation of the effect of an air layer on the melting process of phase change materials

Evaluation of the melting process of phase change materials in a tilted rectangular container: Experimental study

Evaluation of the melting process of phase change materials in a tilted rectangular container: Experimental study

Heat transfer and fluid flow in a PCM-filled enclosure: Effect of heated wall configuration

A detailed numerical investigation was conducted to scrutinize the impact of heated wall configurations, serving as a primary heat source, on the melting process of phase change materials (PCM) within a rectangular cavity. The study explored various configurations, including square, rectangular, trapezoidal, and curvy, to understand their influence on the liquid fraction, melting time, and stored energy. Through employing the enthalpy-porosity method for the phase change, the analysis revealed that wall geometry significantly affects the melting process, where formation of local enclosed regions acting as heat sources enhance both conduction and convection heat transfer mechanisms. The investigation showed that the curvy wall configuration, by facilitating more effective free convection due to its smooth and continuous surface, markedly improves the melting process. This configuration minimizes flow separation and promotes uniform fluid motion, thereby enhancing convective heat transfer efficiency, particularly in the latter melting stages. The results underscore the superiority of the curvy configuration, with a 57.6 % decrease in melting time and a 16.3 % increase in energy storage capacity compared to the baseline case. These findings highlight the critical role of heated wall geometry in advancing the efficiency of PCM-based energy storage solutions.

Heat transfer performance of copper foam/paraffin composite phase change material under different centrifugal forces-A visual experimental study

Copper foam is used to enhance the heat transfer of phase change material (PCM) due to its high thermal conductivity. However, its porous structure can restrict the convection of PCM. The natural convection of PCM embedded in copper foam under external force remains unclear. A visual experimental system was established to investigate the effect of copper foam on the heat transfer process of PCM under external force. The phase interface, temperature distribution, and heat storage rate of composite PCM (CPCM) were conducted under centrifugal forces from -5 g to 5 g. Results indicate that there is a significant difference in the melting rate and temperature distribution of PCM under different forces. Under forward force, the convection of PCM is inhibited, and the isotherm is parallel to the end-state isobars line, increasing the total melting time of CPCM and creating a large temperature gradient near the heat source. Conversely, under the backward force, the melting rate of CPCM is increased due to the enhanced natural convection of liquid PCM. The development of isotherms is influenced by buoyancy, which results in a more uniform temperature distribution of CPCM. However, the enhancement effect of the backward force is limited when it exceeds -3 g. In general, CPCM exhibits more apparent improvement in heat transfer performance under the backward force. This article provides references for the optimization design of thermal management systems.

Energy and exergy analysis of a laboratory-scale latent heat thermal energy storage (LTES) using salt-hydrate in a staggered tube arrangement

The energy and exergy analyses were performed for a laboratory-scale latent heat thermal energy storage (LTES) using hexahydrate calcium chloride (CC6) as phase change material (PCM) in a staggered tube array configuration, placed horizontally. The PCM melting and solidification process within the tube array was investigated by performing a numerical analysis using transient two-dimensional Navier-Stokes equations and Realizable k-ɛ turbulence model to predict flow and heat transfer. The enthalpy-porosity technique was applied to model PCM melting and solidification. The accuracy of the numerical model was validated against experimentally obtained data where the numerically predicted and measured air temperature at the tube array outlet and PCM temperatures were compared. Additionally, the pressure drop in the array and the average peripheral heat transfer coefficient calculated from the numerical results were compared to the well-known Zukauskas correlation (Zu). The results show that the melting and solidification process of PCM in the tubes of the array is asymmetric in nature, with the PCM melting taking slightly longer compared to the solidification process. It was also observed that the energy quantity was higher compared to the exergy quantity, as exergy considers entropy generation and accounts for irreversibility within the system.

Artificial neural network-based optimization of heat absorption process of phase change materials in a novel-designed finned-plate latent heat storage system

As the world transitions to more renewable and clean energy sources, energy storage systems become crucial. They assist in storing surplus energy produced during peak production times and release it when there is a high energy demand. Phase change material (PCM) based latent heat storage systems are appropriate candidates for efficient thermal energy storage. Their ability to harness the latent heat of phase transitions provides energy density, temperature control, and reduced heat loss advantages, making them well-suited for various applications. In the current research, a novel plate latent heat storage system (P-LHS) inspired by plate heat exchangers was introduced to enhance heat absorption. Besides, to facilitate the limited thermal conductivity of the PCM and increase natural convection phenomena, several fins were applied within the P-LHS system. Artificial neural network (ANN) models were exerted to anticipate the duration needed for melting of 70 % (φ = 0.7) and 100 % (φ = 1) of the PCM. The input variables of the ANN models were the fin angle (β), the distance between two fins (D), and the fin's trail angle (α). This research examined different configurations of the fins within the P-LHS system to find the optimal one. In all the designed Tests, the heat absorption and temperature distribution within the PCM were accelerated; thereby, the melting time up to φ = 0.7 and φ = 1 was reduced remarkably compared to those in the fin-less P-LHS system. Besides, for the fastest full melting of the material in the P-LHS system, the optimal design 2 (OD2) was proposed, in which the fins should have the dimensions of α = 171.450°, β = 97.540°, and D = 27.545 mm. In OD2, the time needed until the melting of 70 % of the PCM was decreased by approximately 65.68 %. While, the necessary duration for the PCM to melt entirely was 1574 s, approximately 66.80 % less than the time needed for melting the substance in the system without fins (4741 s). This reduction in melting time was about 53 min, which is a significant amount of time in energy storage systems.

Preparation and thermal properties of nano-microcapsule and simulation heat storage application

The prevention of material leakage and improvement of thermal conductivity are very important for thermal energy storage application. In this work, nano-TiO2@n-docosane microcapsules were synthesized by the fine emulsion interface polymerization method using tetra-n-butyl titanate (TBT). This approach enhances the encapsulation rate and efficiency of phase change microcapsules. The microcapsules formation process was observed using a biological microscope. The diameter of the microcapsules decreased significantly with the increase of stirring rate. The phase transition temperature of the optimal microcapsules is 42.4 °C. The encapsulation rate and efficiency reach up to 90.7% and 91.0%, respectively. The average thermal conductivity of nano-TiO2@n-docosane microcapsules is 215% higher than that of n-docosane. SEM and infrared spectroscopy testing results confirm the successful coating of n-docosane by TiO2. Thermogravimetric analysis presents that TiO2 forms a shell, which reduces the leakage of n-docosane. The melting and solidification processes of n-docosane and nano-TiO2@n-docosane microcapsules were simulated numerically. In comparison to n-docosane, nano-TiO2@n-docosane microcapsules exhibit a 14.89% increase in peak storage power and a 12.47% increase in heat transfer coefficient during charging. Additionally, during discharging, these values rise by 3.23% and 6.46%, respectively. Nano-TiO2@n-docosane microcapsules enhance heat transfer and the charging/discharging process of phase change materials.

Temporal numerical analysis of beeswax PCM melting in a cube geometry subjected to a constant wall temperature condition

The ability of phase change materials (PCM) to store thermal energy has gained wide application area, like battery thermal management, solar water desalination and many other. The melting process of beeswax phase change material within the cube geometry with constant wall temperature (65 °C) boundary condition has been investigated using solidification and melting model. The fluid flow and heat transfer governing equations are solved using second order finite volume scheme. A PRESTO algorithm is applied for pressure-velocity coupling. The convergence criteria of 10−10 have been selected for energy equation, while 10−8 is selected for both momentum and continuity equations. The results like percentage variation along length-height and height-width plane for transient liquid fraction and temperature has been plotted, along with velocity streamlines within the cube geometry. From the obtained results it is concluded that the melting fraction and temperature of beeswax PCM is different in different planes and the major factors which affect the complete melting process is wall temperature, and the geometry. A difference of more than 0.1 °C in temperature has been recorded between mid-length-height and height-width plane while a difference of more than 2% in liquid fraction of PCM is observed. Even the uniformity of temperature and liquid fraction is notably influenced and vary along length, height, and width of cube geometry. Thus, it is concluded that melting process of PCM may affect the ability to store and release the heat energy which further affect the performance parameters of applied physical system.

CFD simulation of a solar collector integrated with PCM thermal storage

AbstractThermal energy storage is indeed a valuable solution for addressing the time lag or mismatch between energy supply and demand. The study aims to computationally model the melting and solidification processes of phase change material (PCM) using ANSYS Fluent that utilizes the finite volume technique. The simulations provide insights into the shapes of the liquid fraction, corresponding times, and temperature distribution of the PCM particles under the given conditions. The study considers factors such as solar radiation, thermal conductivity, density, latent heat, and the melting temperature of the PCM. The study finds that paraffin wax melts more quickly under a higher average maximum solar irradiance of 985 W/m2, while a lower solar radiation of 300 W/m2 has the opposite effect. Enhanced heat transfer resulting from conduction within the molten PCM, especially at a thermal conductivity of k = 0.25 W/m·K, accelerates the melting process. The thermal conductivity of the PCM affects the overall performance of the thermal energy storage system. The study highlights the potential application of thermal storage for drying purposes. Through the controlled release of stored heat energy, thermal storage enables the provision of heat in the absence of sunlight.

Thermal performance enhancement of lauric acid using nanomaterials as composite phase change material.

In the present work, lauric acid was taken as a phase change material (PCM), and different nanoparticles (NPs) such as SiO2, TiO2, CuO, and ZnO were taken as the supporting materials. CuO NPs were prepared through the co-precipitation technique; SiO2, TiO2, and ZnO NPs were synthesized via the sol-gel technique. These NPs with different weight fractions were dispersed into molten lauric acid, individually. The variations in thermal properties (phase change temperature and latent heat for solid and liquid) of the prepared composite PCMs due to the dispersion of NPs were observed by DSC analyses. An increase in thermal conductivity of the composite PCMs was observed with the increasing weight fraction of NPs. In order to ascertain the long-term utility, a thermal reliability test was conducted on the composite PCMs with repeated heating and cooling cycles. Also, the specific heats of the pure PCM and the composite PCMs were determined as a function of temperature. Further, the experimental investigation was performed on the pure PCM and the prepared composite PCMs to assess their phase change behavior, and the test results clearly proved that the time required for the complete melting and freezing process of the composite PCMs was less when compared to pure PCM. By considering the above facts, the newly prepared composite PCMs can be recommended as a potential candidate for low-temperature solar heating applications.

Study of melting behavior of phase change material in a square enclosure with constant and variable heat flux at different wall heating conditions: A numerical approach

Latent heat thermal energy storage system offers the most promising cost-effective solution in thermal energy storage applications like solar water heaters to building air conditioning, textile industries, pharmaceutical industries, etc. In this article, the melting process of phase change material (PCM) in a square enclosure with constant, linearly increasing, linearly decreasing and sinusoidal heat flux on different sides of the wall is studied. The result shows that double-wall heating has the highest melting rate followed by side-wall heating and bottom-wall heating. This happens because double-wall heating increases the heat transfer area. Between side-wall heating and bottom-wall heating with uniform heat flux, side-wall heating gives a higher melting rate due to the higher length of solid–liquid interface promoting the heat transfer to solid PCM, thus increasing the melting rate. Again, for different heat distributions of side-wall heating the linearly decreasing heat flux provides the highest melting rate. This type of heat distribution actually transfers more heat to the lower part of the container, which counters the effect of convection, resulting in an enhanced melting process. On the other hand, in the case of distributions at bottom-wall heating, linearly increasing heat flux shows the highest melting rate. In addition, for linearly increasing heat flux, the shape of the liquid cavity is triangular, which gives more space and thereby intense natural convective circulation. This enhanced convection heat transfer leads to a higher melting rate.

Empirical Investigation of Thermal Features of Phase Change Material as Thermal Storage System

This paper presents an empirical investigation of the melting processes of phase change material (PCM) in a tube and shell heating exchanger utilizing solar thermal energy. The experiments were conducted outdoors in Al-Mussaib city, Babylon, Iraq (Lat 32.5° North, long 44.3° East), utilizing a north-south (N-S) collector oriented at a tilt angle of 32.5° from the horizontal. This work utilized pure Iraqi black paraffin with 12 kg as PCM. The main empirical rig involves a vacuum tube solar collector (VTSC) utilizing a tube and shell heating exchanger to melt PCM in the shell regime. Different rates of water flow inside the internal heating exchanger's tube, namely (3.5, 5, and 8.5 L/m), were utilized for each season from August 2022 to January 2023. The empirical findings concluded that the internal tube inlet and surrounding temps significantly influence the melting process compared to the rates of water flow. It was found that the melting process of PCM needs about (3 to 4) hours in the summer season. Still, winter needs a longer time, about 14 to 16 hours. Increasing surrounding temp and solar radiation reduces the melting time of phase-change material. The findings of the present work were compared with the earlier investigations and agree with increasing the present work by 23.5 %. The findings from the present study are of practical importance for industries requiring storage materials to improve thermal storage system performance.

MELTING PROCESS SIMULATION OF PHASE CHANGE MATERIAL LAYER USED IN THE BUILDING ENVELOPE

The melting process of phase change material (PCM) for thermal energy storage purposes has been studied and simulated in this paper. Using the ANSYS (Fluent) 2023 R1 software, the melting of a rectangular PCM zone with left and right sides exposed to convection heat and the other sides adiabatic is simulated. The study also discusses the program specifications, numerical modeling equations, and assumptions. For a total melting duration of 360 min, the contours of the liquid fraction, temperature, density, and velocity of phase change material particles are shown at regular intervals of 30 min. The contours aid in identifying how the melting interface changes in shape and motion as melting time increases. It also describes how the melting fraction changes over time, which provides information regarding the amount of melted PCM at various points.

Transient analysis of PCM discharging in a rotary triplex tube with wave-shaped fins

Phase change material (PCM) based thermal storage units have attracted attention in energy storage technology. To improve its effectiveness, researchers have introduced various techniques. In this study, a novel rotary triplex tube with sinusoidal wave-shaped fin design is proposed as a PCM based thermal storage unit, and its performance is compared with a conventional straight fin design. A two-dimensional numerical model is developed for the transient analysis of discharging process of PCM. The discharging process is modelled using enthalpy porosity technique. The validation of the model is done against the experimental result from the literature. The discharging process of PCM is analyzed at different rotational speeds. Thermal performance and fluid flow dynamics are evaluated by analyzing the molten portion, temperature, and velocity variation. The result showed that an increase in rotational speed led to an increase in the discharging rate of the PCM. When there is no rotation or slow rotation (0.05 and 0.1 RPM), the discharging is faster in the unit with straight fins compared to the unit with wave-shaped fins. However, at higher rotational speeds (0.2, 0.3 and 0.4 RPM), discharging is faster in the unit with wave-shaped fins. Overall, this study provides insights into the design and performance of PCM based thermal storage unit and suggests the use of wave-shaped fins for higher rotational speeds to enhance the discharging rate of PCM.

Computational investigation of magnetohydrodynamic flow and melting process of phase change material in a battery pack using the lattice Boltzmann method

This study employs the lattice Boltzmann method to investigate the magnetohydrodynamic (MHD) flow and melting process of phase change material (PCM) in a battery pack. The inclusion of the MHD effect allows for an examination of its impact on PCM melting. We analyze fluid fraction diagrams, isothermal lines, and streamlines to assess how magnetic field strength (Ha number), battery heat generation, and MHD field angle influence PCM melting. The study considers a configuration with two batteries separated by PCM, presenting results for two scenarios: single-battery overheating and dual-battery overheating. Our findings reveal significant MHD-induced effects on flow dynamics and PCM melting, with implications for battery pack thermal management, performance, and safety. Increasing the Ha number results in a substantial, approximately 11 % reduction in the battery's maximum surface temperature when the Ha number increases from 0 to 100. Additionally, varying the MHD field angle can lead to a 5 % increase in the maximum temperature. Through a thorough examination of maximum temperature and a sensitivity analysis regarding the MHD field angle, we unequivocally establish the optimal orientation for MHD implementation as γ = 180. This research underscores the potential for leveraging MHD effects to enhance battery pack thermal management and performance. It provides valuable insights into controlling PCM melting, benefiting various battery system applications.

Three-dimensional numerical simulation of solid-liquid phase change in the cavity of composite structures based on TPMS

Solid skeletons will play an important role in improving the thermal properties of phase change materials. For this reason, the efforts should be dedicated to studying the heat transfer characteristics of solid-liquid phase change with different structural skeletons. In this paper, the composite structures spliced with Gyroid and Diamond skeletons in the horizontal or vertical directions were established by using the Triply Periodic Minimal Surface method. A three-dimensional dimensionless lattice Boltzmann model of the phase change material (PCM) cavity with the spliced skeleton was developed by using the two-region model for solid-liquid phase change in the mushy zone. Based on the pore scale, the phase change heat transfer characteristics under the thermal conductivity ratio of the skeleton to PCM of 100 were analyzed in depth with constant temperature heating at the left wall surface. The results showed that the skeleton spliced in different directions has different effects on the temperature field and heat transfer characteristics of the phase change process. The (G + D)H spliced skeleton which was arranged by Gyroid and Diamond skeletons in the horizontal direction led to a faster melting rate of the PCM than the (D + G)H spliced skeleton which was arranged by Diamond and Gyroid skeletons. The promotion effect of a large porosity skeleton on the melting process of PCM was less than that of a small porosity skeleton. The dimensionless complete melting time for the cavity containing skeleton with porosity ε = 0.915 was increased by 35.7 % and 19.4 % compared to the cavities containing skeletons with porosity ε = 0.826 and 0.871, respectively. This study lays the foundation for the development and application of TPMS spliced skeletons in phase change heat storage and enhanced heat transfer technologies.

An approach to improve the efficiency of cooling enhancement of a thermoelectric refrigerator through the use of phase‐change materials

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

Thermal energy storage control using phase change materials in a rectangular energy storage chamber with metal foam gradient and magnetic field

Considering the low thermal conductivity of phase change materials (PCM) and the slowness of the melting process in the thermal energy storage chamber (TESC), a comprehensive study on the use of magnetic field and porous foam gradient in the phase change process of PCM in a rectangular chamber with a cylinder is presented. The numerical solution is done using the finite volume method. PCM, metal foam and nanoparticles are respectively lauric acids, aluminum and iron oxide. Porosity coefficient changes have been examined in the positive and negative directions of the coordinate axes during melting and compared to a uniform porosity coefficient in the common case. As a result of a constant magnetic field, melting does not take place as much, but when a non-uniform magnetic field is used, the process of melting in the TESC increases by about 35 times, and the intensity of the magnetic field can be used between 0.025 and 0.05 mT. The average thawing fraction of the PCM has augmented by 5.046, 6.86, 7.66 and 7.819 %, respectively, compared to the no-field. The metal foam gradient has an imperative efficacy in enhancing the process of melting and up to about 97 % reduces melting time. When the porosity coefficient is higher near the active wall, the heat transfer and liquifying are quicker. In the chamber, temperature changes of the cylinder can have a momentous efficacy on the thawing process. The greatest effect is observed when the changes of cylinder temperature with time are stepwise. The sensitivity analysis was done based on the Sobol method, which shows that the porosity coefficient has the greatest effect on the melting rate.

Thermal storage process of phase change materials under high humidity and laminar natural convection condition: Prediction model and sensitivity analysis

The application of phase change materials (PCMs) in renewable energy storage and building temperature regulation is considered an effective method to reduce the use of fossil fuels and carbon emissions. However, issues concerning the utilization of PCMs in high-humidity environments remain to be addressed to fill the gap in real-world applications. This paper establishes a simplified novel two-zone model, comprehensively considering the natural convection on the surface of the PCP in high-humidity environments, as well as the formation, movement, and evaporation of water films on the surface. Subsequently, numerical solutions and experimental validation are conducted, and the influence of high-humidity environments on the heat and moisture transfer is elucidated. The results indicate that a high-humidity environment can significantly suppress the sensible heat transfer with a ratio range of latent heat to sensible heat typically around 1–4. Furthermore, the increase in the height of PCP leads to an increase in the proportion of sensible heat transfer. On the contrary, increasing the thermal conductivity of the PCM can amplify the latent heat transfer. The results can help further study the thermal storage and the dehumidification potential of phase change units in application on a large scale under high humidity conditions.

Toroidal tube latent heat exchanger: An experimental study

Concentric shell and tube latent heat exchangers integrated with phase change material (PCM) are widely used in many heat storage/transfer applications specially for building energy management due to their high energy storage density and fair simplicity in design. However, inadequate phase change in such systems reduces the thermal performance. The innovative geometric design is key in addressing this issue and accelerating the phase change process. The present work reports an experimental effort to investigate the progression of the melting process of PCM inside a novel design of toroidal tube embedded in the system as a shell and tube latent heat exchanger. The experimental setup consists of a toroidal enclosure filled with a bio-based PCM (i.e., coconut oil) and a constant temperature bath as a heat exchange environment. Digital images of melting progression and melting front at three different boundary temperatures (high, middle, and low temperature differences) are captured. Moreover, the time dependent temperature at a selected prob. point is also measured during the phase change process. As expected, decreasing temperature difference, decrease the melting rate, as the experiments show that the completed melting times are 20, 32, and 75 min for the high, middle, and low temperature differences. The melting front is sharper and more distinct to track for higher temperature differences as well. To observe the melting pattern and melting front inside the system (cross-sectional area of the tube) better, the melting progression in different selected times in a half-toroidal tube is also investigated. Furthermore, an extensive uncertainty analysis associated with measuring devices is reported.