Melting Of Phase Change Material Research Articles

A novel design of lithium-polymer pouch battery pack with passive thermal management for electric vehicles

This study investigates the thermal characteristics of a lithium polymer pouch battery thermal management system using phase change material (PCM) during the discharge. The research provides a detailed discussion of various factors influencing the system. The novelty aspect of this study involves evaluating thermal changes in the battery at 40 °C through hot soaking experiments comparing with both PCM-integrated modules and without PCM modules. The study further aims to identify the optimal PCM for both normal and high ambient conditions. Thermal parameters, including maximum temperature Tmax, average temperature Taverage and thermal gradient ΔT were evaluated at 25 °C and hot soaking performance at 40 °C temperature during discharge was analysed. Simulation were conducted to compare module behavior, especially at high-temperature conditions. Furthermore, a thorough examination of PCM melting and solid-phase transitions at high temperatures were performed that significantly impact the cooling performance of the PCM system. Our findings reveal that expanded graphite PCMs offers effective thermal performance with observed improvement of 27 %. Therefore, we recommend employing EG26 and EG28 PCMs for real-world application electric vehicle battery pack systems.

Magnetically- regulated close contact melting for high-power-density latent heat energy storage

Rapid melting of solid-liquid phase change materials (PCMs) is critical to the high-power-density latent heat energy storage and efficient thermal management. The pressure-enhanced close contact melting is seen as a promising method because of the suppressed heat transfer resistance between the heating surface and the melt front during thermal charging, but it remains a key challenge how to tactfully apply external pressure for a practical device. Herein, we present a magnetically-regulated close contact melting strategy for rapid melting of PCMs from the perspective of the practical application. In this method, a PCM and a permanent magnet are contained inside a highly thermally conductive vessel, and the magnet regulated by another one can push the solid PCM toward the heating surface. Consequently, the superheated molten PCM can be instantly removed from the heating surface due to the magnetic force so as to achieve the suppressed thermal resistance. The temperature-control performance of paraffin wax is evaluated under various applied external forces and heat loads. Experimental results indicate that the heating surface temperature can be controlled near the melting temperature of PCM even under a relatively high heating flux. With applying the external pressure of 900 Pa, the average heat transfer resistance is reduced to lower than 4.5 × 10−4 K·m2·W−1. Finally, a closed thermal management device is fabricated and measured by using a graphite vessel to encapsulate the magnet and the PCMs such as paraffin and low-melting-point alloy. This device demonstrates good recyclability for repeated thermal charging/discharging. Our work provides a new method to develop the practical thermal management device based on pressure-enhanced close contact melting.

Analysis of the influence of asymmetric V-shaped fins on the melting of phase change materials in latent heat storage units

Improving the melting performance of latent heat storage devices is highly important for achieving efficient utilization of thermal energy. To achieve this goal, this paper proposes an innovative thermal storage unit with asymmetric V-shaped fins. The influence of structural parameters including eccentricity, fin angle, height and shape on the melting process of phase change materials is analysed. The results show that compared with concentric tubes without eccentricity, when the eccentricity is increased to the point where the bottom fins are in contact with the outer tube, the total melting time is shortened by 33.56%, and the average heat storage rate is increased by 32.95%. At the same time, increasing the angle and height of the top branch fins can strengthen the natural convection in the heat storage unit and shorten the total melting time by 13.54%. It is worth noting that changing the upper-side branch fin parameters has little effect on the melting process. In addition, when the shape of the branch fins constituting the V-shaped fin changes from rectangular to trapezoidal, the total melting time decreases by 3.11%. In summary, the use of asymmetric V-shaped fins can improve the melting performance and heat storage performance of eccentric heat storage units, and changing the fin shape can further shorten the total melting time and increase the average heat storage rate.

Parametric analysis of system performance and cost of heating systems with heat pump and latent thermal energy storage

This paper presents a parametric analysis examining the impact of phase change material (PCM) melting temperature, latent thermal energy storage (LTES) volume, and solar collectors’ surface area on the performance and costs of heating systems integrating a heat pump and LTES by using dynamic system simulations. The computational models, implemented in TRNSYS software, and the numerical procedure were validated by comparing the numerical results with experimental measurements. The computational models represent the entire heating systems and thus consider the mutual interaction of heat production, distribution and automatic regulation system as well as a building which represent the heat load, in transient boundary conditions. Two main system designs with different LTES roles were considered – a system in which the role of the LTES is to provide more favorable operating conditions and a system in which the LTES role is to store the heat on a sufficiently high temperature to be used directly for heating. System performance was analyzed in terms of the share of renewable energy in total delivered energy, power consumption, stored energy in LTES, seasonal performance factor, average solar collector efficiency and total annual costs. The results showed that, regarding the system in which LTES was used as a heat source for the heat pump, a better overall performance and lower costs were observed in systems with PCMs with melting temperatures in range between 19 and 29 °C, compared to systems with PCMs with melting temperatures outside this range. For system in which the heat from the LTES was used directly for heating, the highest values of system performance criteria and the lowest cost were achieved with the PCM of 54 °C melting temperature. Almost all of the considered system performance criteria and total costs were higher when the LTES volume and solar collector surface area were larger as well.

Predicting the PCM-incorporated building's performance using optimized linear kernel and tree-based machine learning methods

The devising of a precise machine learning-based energy consumption prediction model holds significant importance for taking effective decisions during the early stages of phase change material (PCM) incorporated building design to reduce energy consumption. Few researchers have developed prediction models for estimating the consumption of energy in PCM incorporated buildings. However, there is a need to develop the best-performing machine learning-based prediction model, which is less complex, involve a lower number of hyperparameters, and has a greater ability to generalize hidden patterns among the dependent and independent variables. To address the above shortcomings, the linear kernel and tree model-based prediction models were formulated for PCM-incorporated buildings located in eight cities of subtropical highland climate, considering the variations in their hyperparameters. The evaluation and validation of the formulated models for prediction were performed utilizing several statistical metrics. Test results substantiated that the ensemble-boosted tree-based prediction model (EBT20) exhibited superior efficacy in estimating the energy consumption for PCM-integrated building, having an average R2 > 0.93, NMBE <4 %, and CV-RMSE <8 %. The developed model showed less complexity and better generalization ability at the optimized values of ensemble boosted tree hyperparameters, which are as follows: minimum leaf size = 32, number of learners = 99, and learning rate = 0.1. From comprehensive evaluation conducted to evaluate the interpretability of the prediction model, it was found that the building orientation and PCMs melting temperature are the most influential parameters for achieving energy savings of up to 33 % in the selected climate zone.

Enhancing melting performance in multi-tube latent heat exchangers: Investigating the effect of inner tube number and arrangement

The latent heat energy storage system holds promising application prospects in the field of energy. However, the critical bottleneck remains the melting speed of phase change materials (PCMs). In this study, the melting dynamics of PCM within a triplex-tube heat exchange system are investigated, focusing on the effects of varying the number and arrangement of inner tubes. The system performance with four, five, six, and seven inner tubes is compared, revealing a decrease in melting time with an increasing number of inner tubes. However, excessive numbers do not yield more significant enhancement. A novel arrangement scheme is proposed, recommending six inner tubes. Additionally, the effects of inner tube spacing, upper angle and lower angle are explored. Increasing these parameters initially decreases melting time but then exhibits a reverse trend. Specifically, appropriate spacing enhances coverage area, expediting rapid connectivity of melting areas and thereby augmenting natural convection. While an increase in the upper angle delays PCM melting in the upper half, optimal arrangement enhances lower half PCM melting. Balancing melting rates of three difficult-to-melt areas in the lower half with proper lower angle achieves optimal performance. Compared with the base case, the proposed arrangement with the tube spacing of 40 mm, upper angle of 92°, and lower angle of 62° reduces melting time by 44.8 %. These findings provide a theoretical and experimental foundation for enhancing PCM-based energy storage system performance, offering valuable insights for engineering applications.

Optimization of fin arrangement in solar thermal storage devices and convolutional neural network modeling

Solar energy, a renewable and eco-friendly source, faces challenges in aligning energy production with storage durations. Phase change materials (PCMs) effectively tackle this issue, yet their poor thermal conductivity limits solar thermal storage device performance. Conventional solutions involve adding fins, but limited volume compromises overall heat storage capacity. Our study enhances device performance by rearranging fins while maintaining the same area. The H/R = 0.5 fin arrangement with equal spacing significantly improves heat storage, reducing total melting time by 54.31% with a higher entropy value. Further, arranging five fins, predominantly in the lower part, shortens PCM melting time without compromising upper material melting, enhancing device temperature uniformity. Utilizing computed data, we trained a Convolutional Neural Network (CNN) model, maintaining a maximum error within 5%, with an actual maximum error of only 1.56%. The efficacy of CNN in addressing prediction challenges is noteworthy, showcasing improved solar thermal storage device performance.

Numerical study of PCM melting performance in a rectangular container with various longitudinal fin structures

This paper uses the enthalpy-porosity technique to conduct a three-dimensional numerical investigation on the effect of adding longitudinal fins in energy storage units to enhance the melting process, with a specific focus on natural convection. By reducing the extension length of the upper part of the fins and increasing the extension length at the bottom, the work aims to enhance heat transfer while reducing obstruction to convection. The effects of rectangular, trapezoidal, and triangular longitudinal fins with thicknesses of 0.2, 0.25, and 0.3 mm on the melting characteristics were compared while maintaining a constant filling volume of RT42 phase change material (PCM) within the rectangular container. The results indicate that the enhanced heat transfer capacity of fins with different structures increases as the fin length increases. Triangular fins exhibit the most significant heat transfer enhancement effect, with the least hindrance to convection. When the fin thickness is 0.2 mm, the triangular fin decreases the melting completion time by 15.7 %, increases the heat storage rate by 18.7 % compared to the rectangular fin, and exhibits optimal natural convection intensity and temperature distribution in the energy storage unit. Additionally, the maximum flow velocity and average Nusselt number can be increased by 21.2 % and 18.5 %, respectively. It was also found that triangular fins are more suitable for high-temperature working conditions.

Thermodynamics analysis of fins integration in sono-PCM reactor: Sonic power influence

This research presents a novel approach of integrating fins into a sonochemical phase change material (PCM) reactor to tackle the challenge of low PCM thermal conductivity, with a focus on cooling the ultrasonic reactor. Through comprehensive numerical simulations using a Fluent-based CFD code, we analyze the thermal performance of the sono-PCM system with and without fins under varying power densities (45.5 and 85.6 kW/m3) and operating times (up to 1 h). Our results highlight the remarkable advantage of fins in accelerating the heat transfer and melting process, reducing the time for a 50% PCM melt by 28.1 and 45.2% for power densities of 45.5 and 85.6 kW/m3, respectively. Enthalpy analysis further confirms the efficiency of the fins, demonstrating a reduction of ∼19% in water enthalpy after 1 h for both power densities. Moreover, the presence of fins significantly enhances the heat recovery by the PCM, leading to 20.1 and 73.2% increase in PCM enthalpy for power densities of 45.5 and 85.6 kW/m3, respectively. These enhancements are attributed to the increased surface area of contact provided by fins, which facilitate efficient heat dissipation within the bulk PCM. This study not only provides crucial insights into PCM systems with fins but also opens up avenues for advanced thermal energy management strategies, revolutionizing heat storage and transfer processes across various engineering applications.

Exploring the impact of tube rotation on the melting performance of multi-tube latent heat storage systems: A numerical investigation

This study explores the impact of tube rotation on the melting performance of a multi-tube latent heat energy storage system through numerical analysis. The system involves a phase change material (PCM) contained within a tube, which absorbs heat from hot water flowing through a tube surrounding the PCM, as well as two tubes enveloped by the PCM. The investigation considers the angle between the line connecting the centers of the two inner tubes and the horizon (α = 0°, 45°, 90°, and 135°), along with the direction of rotation of inner tubes. Results are compared with data from scenarios involving only outer tube rotation and stationary systems. Temporal variations in temperature and liquid fraction contours, along with the temporal evolution of average temperature and average liquid fraction of PCM are presented. It was determined that for each α, the melting performance varied from best to worst across the system configurations as follows: the system with all three rotating tubes, the system with only the outer rotating tube, and the stationary system. The minimum time required to complete PCM melting for cases at α = 0°, 45°, 90°, and 135° is respectively 44.92 %, 42.11 %, 41.32 %, and 40.62 % less than that of the stationary system.

Performance assessment of single-sided operation in a high-temperature latent heat storage system under fault conditions during charging and discharging

As the high-temperature latent heat storage (LHS) market continues to expand, ensuring its safe and stable operation is paramount for facilitating its rapid development. In specific operational scenarios and instances of failures, large-scale integrated LHS systems may operate with either single or partial sets of heat exchange tubes. However, a notable research gap exists in the comprehensive exploration of the impact of partial operational conditions on the thermal performance of LHS systems. Consequently, this study conducted experiments involving both- and single-sided charging and discharging using a cylindrical high-temperature LHS system equipped with two sets of heat exchange tubes. To comprehend the ramifications of single-sided operation on temperature distribution across both active and inactive sides, as well as its influence on charging/discharging power and accumulated stored/released energy on the active side. The analysis of phase change material (PCM) temperature distribution revealed that single-sided charging significantly influenced the inactive side, while single-sided discharging exhibited a comparatively minor impact on the inactive side. As PCM melted during charging, temperature disparities diminished due to natural convection, while non-uniform temperature persisted in unmelted PCM. Examination of the PCM liquidus indicated that the metal heat exchange tube enhanced heat transfer on the inactive side, resulting in substantial PCM melting during charging. However, the heat transfer effect of metal heat exchange tubes during discharging was insignificant, leading to a considerable amount of liquid PCM on the inactive side after discharging. The total heat storage for both-sided charging was 1002.71 MJ, whereas, for single-sided charging using two tubes, it was 1074.42 MJ and 1000.60 MJ, respectively. Correspondingly, during discharging, the average powers were 682.74 MJ, 543.62 MJ, and 538.11 MJ, respectively. The cycle efficiency for the both-sided operation was 68.09 %, while those for single-sided operations of two tubes were 50.6 % and 53.78 %, respectively. The reduced cycle efficiencies of single-sided operations were attributed to prolonged charging and discharging durations and the presence of more liquid PCM on the inactive side after discharging.

Experimental assessment of the heat shielding performance by the integration of phase change material and liquid cooling plate

This research focuses on innovative stealth equipment by integrating a liquid cooling plate and phase change material (PCM), and the temperature rise on the cold surface and PCM melting rate is reported to illustrate the PCM thermal behavior in lifting the heat shielding performance. Results show that the integrated PCM system is effective in delaying the temperature rise within a certain time. A slower temperature rise on the cold surface is found at the first 1200 s, and a significant acceleration in the temperature rise is given within 1200 s ∼ 2000 s as the heat flood breaks through the PCM layer. The PCM melting rate increases rapidly and then rises slowly, and the complete melting time is shortened as increasing heat power. The heat shielding performance is significantly reduced with increasing the liquid flow rate, and the influence of the coolant temperature on the temperature rise becomes more and more prominent as the completion of the PCM melting process. A slower temperature rise is observed at the lower PCM phase transition temperature, and a further increase in the PCM covering layer has little influence on the temperature rise at the initial stage.

Thermodynamic modeling and performance analysis of photovoltaic-thermal collectors integrated with phase change materials: Comprehensive energy and exergy analysis

Phase change materials (PCMs) integrated with photovoltaic-thermal (PVT) collectors can simultaneously generate and store electrical and thermal energy. However, design optimization requires accurate modeling of the complex heat transfer processes in PCMs under varying operating conditions. This study introduces an efficient simulation approach with generalized Nusselt number correlations to enable precise and rapid analysis of PCM thermal performance. A numerical model is developed to quantify heat fluxes, node temperatures, energy and exergy outputs across PCM solid, melting, and liquid states. Extensive analysis is conducted to explore the impact of irradiation, ambient temperature, PCM thickness, tilt angle, and wind speed on PVT performance. Key findings include: (1) thermal energy yield exceeds electrical output by 2.8 times owing to PV's low efficiency, while electrical exergy dominates thermal exergy by 5.3 times highlighting electric output's primacy; (2) electrical output chiefly depends on irradiation, while thermal energy and exergy are highly sensitive to ambient temperature and wind speed; (3) thermal energy escalates 4.5 times faster than electrical energy with irradiation rise, but thermal exergy drops sharply from 10.1 to 0.34 W as ambient temperature increases from 0 to 35 °C due to quality factor degradation. The study provides new generalized correlations, validated model, and extensive performance assessment to advance PCM-based PVT collector design.

Selection of phase change material for latent heat thermal energy storage using a hair-pin heat exchanger: Numerical Study

Abstract Phase change materials (PCMs) are promising for storing thermal energy as latent heat, addressing power shortages. Growing demand for concentrated solar power systems has spurred the development of latent thermal energy storage, offering steady temperature release and compact heat exchanger designs. This study explores melting and solidification in a hairpin-type heat exchanger (HEX) using three PCMs (RT 50, RT 27, and RT 35). A 3D model of the hairpin type heat exchanger (HEX) is drawn using Ansys-workbench. High-temperature fluid/Low-temperature fluid (HTF/LTF) with Stefan numbers (0.44, 0.35, and 0.23) flows through the inner pipe to charge the outer pipe's PCM. The Enthalpy-porosity model is used to study the melting and solidification of various PCMs, and the results were compared. Also, individual thermophysical properties that affect the heat transfer during the melting and solidification process have been discussed. It is observed that low thermal conductivity material with high latent heat is preferred for cold climates. In this study, RT 27 excels in cold climates due to extended solidification time, while RT 50 is effective in tropical regions due to its high melting points and lower latent heat.

Bionic-response surface combination optimization method for latent heat storage performance improvement

Improving the melting and solidification rate of phase change material is crucial for enhancing the charging or discharging power of a latent heat storage system. This research proposed a novel two-tube heat exchanger latent heat storage unit with longitudinal fins of horsetail stem based on the bionic structure of horsetail stem cross-section. Numerical modeling of transient melting of phase change material in horsetail stem fins by natural convection was established. The model’s accuracy was verified and compared with horsetail stem fins and conventional straight fins. Moreover, we optimized and designed the new fin structure based on the response surface method with minimum melting time as the objective function. The optimization results show that the optimized ponytail fins have a more uniform temperature distribution of the phase change material, significantly eliminating the influence of the heat transfer hysteresis zone, and reaching the steady state more quickly under the heat storage condition. Compared to straight fins, optimized horsetail stem fins reduced the heat storage area by only 3.80% and shortened the phase change material melting time by 44.30%. The solidification time was also reduced by 54.59%. This study provides a new idea for the structural design of phase change heat storage fins.

Pore-scale study of melting characteristic of phase change material embedded with novel open-celled metal foam

Metallic porous structure is a prevailing heat transfer enhancer for the melting of phase change material (PCM), while the effect of the structure on the enhancement performance is yet to be understood. In this work, a pore-scale numerical study on PCM melting embedded in a truncated cuboctahedron porous structure, referred as TCD metal foam, was performed. The solid–liquid interface, temperature and the variation of liquid fraction were analyzed and compared with those with the tetrakaidecahedron porous structure, referred as TKD metal foam. The effects of natural convection, porosity, pore density and heating temperature are explored. It is found the natural convection shortens the PCM melting time by about 7 % with the considered porosity range and thus cannot be ignored. Results also show that the TCD metal foam better enhances PCM melting near the porous cell corners compared to the TKD metal foam. Further analysis shows the TCD metal foam can better enhance melting at the former stage due to the larger surface area, while the TKD metal foam can better enhance melting at the later stage due to the thicker metallic ligaments. With essentially the same melting time at ɛ = 0.941, the half-melting takes 17.2 % of the complete melting time for TCD metal foam and 20.3 % of the complete melting time for TKD metal foam. A critical porosity value exists when comparing the enhancement performance of these two metal foams, below which the better melting enhancement is shifted from the case with TCD metal foam to the case with TKD one. The critical porosities are 0.941, 0.923 and 0.899 at the pore densities of 10, 20 and 30 PPI respectively.

Melting of a phase change material in a rectangular cavity in the presence of metallic fins

The melting of the phase change material (PCM) octadecane, confined in a rectangular cavity heated from the bottom, is numerically studied. Simulations are performed through finite element software in order to analyze the impact of metal fins within the enclosure on the melting time. The results are analyzed in terms of the time-dependent position of the melting front, time-dependent average liquid fraction, and time needed for the PCM melting. The obtained outcomes highlight how, with a low number of metallic fins, the initial melting regime dominated by conduction at a certain time gives way to a convective melting regime characterized by Rayleigh–Bénard cells, in full agreement with the results of the theoretical analysis. On the contrary, with a high number of metallic fins, conduction is the only mechanism that governs heat transfer and the rapid melting slows down when the phase change front reaches the top of the fins. More specifically, the addition of the fins within the cavity yields a reduction in the time needed for the complete PCM melting up to 90% in the analyzed cases. The reported results provide new insights regarding the heat transfer mechanisms involved in PCMs melting within bottom-heated enclosures.

Oscillatory instability of magneto-convection during the melting of non-Newtonian ferromagnetic nano-enhanced phase change materials at low Rayleigh number

This work complements mechanism of the oscillatory instability of magneto-convection in the process of melting heat transfer controlled by magnetic field at low Rayleigh number (Ra), aiming to provide a theoretical basis for improving the stability of energy storage system and melting manufacturing process. A latent heat storage cavity unit exposed in uniform magnetic field is designed to reveal the magnetic-controlled heat transfer in solid–liquid phase change process. The volume average method is used to describe porous media composite nano-enhanced phase change materials in latent heat unit. Special attentions are paid to the key parameters of Magnetic number (Mn) and Ra, and coupling flow heat transfer mechanism of magnetic force and natural convection effect is numerically studied. The evolution stages of different flow patterns are divided according to the Kelvin force, vorticity, velocity, flow field and isotherm distributions of characteristic points. Main results show that the magnetic field-modulated phase change process at low Ra can be divided into three stages, of which the second stage is characterized by periodic oscillations. Increasing Mn at fixed Ra accelerates the second stage of oscillatory convection heat transfer coming earlier and promotes melting. When Mn increase to 5 × 106, the full melting time is reduced to the greatest extent, resulting in 11.6 % reduction in heat storage but 17.4 % increase in heat storage efficiency. Three mechanisms of magnetic forced convection coupled with natural convection are found during the increase of Ra: synergistic (Ra < 2 × 103), antagonistic (2 × 103≤ Ra < 1 × 104), and natural convection-dominated (Ra = 1 × 104). Finally, the mode distribution map of Ra-Mn regulation is obtained, in which the unstable transformation mechanism of steady-state, periodic oscillation and chaotic oscillation heat transfer in the melting process under the control of magnetic field is described.

Predicting the performance of a photovoltaic unit via machine learning methods in the existence of finned thermal storage unit

The process of cooling the photovoltaic (PV) cells is essential since increasing solar cell temperatures reduces electrical effectiveness. One suggested method to reduce cell temperature is employing PCM (phase change material) mixed with nanomaterial. Thermoelectric modules between the layers are also recommended to increase electrical efficiency. By taking advantage of machine learning predictive algorithms, the objective is to forecast the effectiveness of a PV unit equipped with finned thermal storage unit in existence of nanomaterials, while maintaining an appropriate accuracy based on two evaluation metrics throughout prediction. According to the data analytics of the simulation, the selected models used to achieve this goal are linear regression, polynomial regression, lasso regression, and an Auto-Regressive Integrated Moving Average (ARIMA) model. These models were then examined employing the root mean squared error (RMSE) and mean absolute percentage error (MAPE) across three cases, namely plain mode, mode with fins, and plain mode with the effect of gravity. The test RMSE and MAPE of these models across the above-mentioned cases were then calculated for comparison purposes, where the best-performing model for predicting both PCM temperature and melting fraction (MF) was ARIMA, with an average RMSE of 0.11, and an average MAPE of 0.0003 for predicting PCM temperature and an average RMSE of 0.003, and an average MAPE of 0.0034 for predicting MF across all cases. The ARIMA model was then used to predict the MF, PCM temperature, and PV temperature of the last case, namely mode with fins and the effect of gravity. Finally, this model was also used to predict the time at which the PCMs are completely melted in all modes, as well as to predict PV temperature. The total electrical efficiency of the mode with fins and the effect of gravity were calculated using the predicted PV temperature, yielding a result of 13.993 %.

Limitations of the enthalpy-porosity method for numerical simulation of close-contact melting on inclined surfaces

One of the main challenges for latent thermal energy storage (LTES) systems is low heat transfer rates due to the low thermal conductivity of most phase change materials (PCM). Close-contact melting (CCM) can accelerate melting times in LTES systems but the current numerical techniques for solid liquid phase change have difficulties with accurately predicting this process. In this study, close-contact melting of PCM on an inclined surface is simulated using the enthalpy-porosity method in ANSYS Fluent. All PCM properties, including density, are temperature-dependent. In this way, phenomena such as natural convection, volume change and buoyancy between the solid and liquid are taken into account. The volume change is compensated by a gaseous expansion volume. Both 2D and 3D simulations are used to show discrepancy between state-of-the-art enthalpy porosity modelling and experimentally observed phenomena in the case of CCM. The mushy zone constant, which is set to 105 to allow motion of the solid bulk, causes the solid phase to deform as a highly viscous fluid instead of moving as a rigid body. The velocity differences inside the solid are more than 50 % of its sinking velocity. As a result, the movement of the solid resembles creep behaviour and the obtained CCM patterns are not physically accurate. Furthermore, the density difference between the solid and liquid phases causes an avalanching effect in the mushy zone, which artificially strengthens convection. In conclusion, the enthalpy porosity method exhibits significant limitations in accurately capturing close-contact melting phenomena.