Thermal Conductivity Of Phase Change Materials Research Articles

Phase-change heterostructure with HfTe2 confinement sublayers for enhanced thermal efficiency and low-power operation through Joule heating localization

Although phase-change random-access memory (PCRAM) is a promising next-generation nonvolatile memory technology, challenges remain in terms of reducing energy consumption. This is primarily because the high thermal conductivities of phase-change materials (PCMs) promote Joule heating dissipation. Repeated phase transitions also induce long-range atomic diffusion, limiting the durability. To address these challenges, phase-change heterostructure (PCH) devices that incorporate confinement sublayers based on transition-metal dichalcogenide materials have been developed. In this study, we engineered a PCH device by integrating HfTe2, which has low thermal conductivity and excellent stability, into the PCM to realize PCRAM with enhanced thermal efficiency and structural stability. HEAT simulations were conducted to validate the superior heat confinement in the programming region of the HfTe2-based PCH device. Moreover, electrical measurements of the device demonstrated its outstanding performance, which was characterized by a low RESET current (∼1.6 mA), stable two-order ON/OFF ratio, and exceptional cycling endurance (∼2 × 107). The structural integrity of the HfTe2 confinement sublayer was confirmed using X-ray photoelectron spectroscopy and transmission electron microscopy. The material properties, including electrical conductivity, cohesive energy, and electronegativity, substantiated these findings. Collectively, these results revealed that the HfTe2-based PCH device can achieve significant improvements in performance and reliability compared with conventional PCRAM devices.

Synergistic impact of horizontal fin installation height and nanoparticle volume fraction to enhance charging performance of phase change materials (PCMs)

This study numerically analyses the synergistic influence of nanoparticle and orthogonal fin on heat transfer performance of phase change materials using enthalpy-porosity method. The natural convection heat transfer and heat conduction during the melting process are coordinated by varying nanoparticle volume fraction and installation height of fin. Results illustrate that the optimal installation height of horizontal fin and nanoparticle volume fraction is 8.9 mm and 1.0 vol%, respectively. The corresponding total melting time is 1024 s and average energy charging rate is 484.5 W. Compared with the optimum conditions without nanoparticle (φ = 0.0 vol% and d = 7.0 mm), total charging time is reduced by 29.8% and average charging rate is increased by 51.1%. The equivalent Nusselt number demonstrates that the addition of high volume fraction nanoparticle decreases the convective heat transfer intensity. The low volume fraction nanoparticle enhances PCM thermal conductivity and has an insignificant effect on natural convective heat transfer. The Prandtl number demonstrates that when the volume fraction is 1.0 vol%, the effect of increasing thermal conductivity on strengthening heat conduction is greater than the negative effect of decreasing natural convection heat transfer caused by viscosity. Effective design guidelines to improve thermal charging performance of PCM-based LHTES devices are finally provided.

Flame retardant composite phase change materials with MXene for lithium-ion battery thermal management systems

A high-quality thermal management system is crucial for addressing the thermal safety concerns of lithium ion batteries. Despite the utilization of phase change materials (PCMs) in battery thermal management, there is still a need to raise thermal conductivity, shape stability, and flame retardancy in order to effectively mitigate battery safety risks. This study investigates a flame-retardant PCM composed of polyethylene glycol, expanded graphite, MXene, APP (ammonium polyphosphate), and ZHS (Zinc hydroxy stannate). The properties of the PCM and its thermal management performance during the operation of batteries are explored and evaluated. The results demonstrate that the incorporation of MXene enhances both the enthalpy of phase transition and thermal conductivity of PCM. Furthermore, the synergistic flame retardancy of APP and ZHS increases the carbon residue content, enabling PCM to achieve a V0 flame retardant rating. PCM exhibits a noticeable cooling effect on the battery temperature, reducing the highest temperature of the battery module to 57.03 °C during 3C discharge while maintaining a temperature difference of within 5 °C. This research contributes valuable insights into the potential use of PCMs with MXene in thermal management systems for batteries, with the aim of improving lithium batteries safety during operation.

Effectiveness of phase change materials and their properties on the performance of geothermal and foundation-based energy systems: A review

As buildings contribute notably to emissions of greenhouse gases, it is important to move towards building heating and cooling systems with good sustainability attributes and efficiencies, such as ground-source heat pumps (GSHPs). In this review, an integrated picture of the effect of utilizing phase change material (PCMs) having various physical properties on the performance of GSHPs and foundation-based geothermal systems is presented. Two major questions are addressed in this paper: how effective is a PCM for enhancing the performance of both conventional GSHP systems and foundation-based geothermal energy systems? The results show that PCMs can be effective at enhancing performance for conventional GSHP and foundation-based geothermal energy systems by, on average, 17% and 36%, respectively. However, the degree of PCM effectiveness depends on some parameters such as its physical characteristics (thermal conductivity, latent heat, phase change temperature) and design considerations (ground loop configuration, depth, etc.) among other factors. The results also show that, in general, the greater the PCM thermal conductivity, the higher the effectiveness of the PCM. Furthermore, by adding composites such as expanded graphite to the PCM, the thermal conductivity of a PCM increases more than 250% which can potentially improve the performance of geothermal systems. More research is warranted to maximize the system performance improvements by enhancing the PCM.

Thermal Energy Storage Heat Exchanger Design: Overcoming Low Thermal Conductivity Limitations of Phase-Change Materials

Abstract Recently, there has been a renewed interest in solid-to-liquid phase-change materials (PCMs) for thermal energy storage (TES) solutions in response to ambitious decarbonization goals. While PCMs have very high thermal storage capacities, their typically low thermal conductivities impose limitations on energy charging and discharging rates. Extensive research efforts have focused on improving PCM thermal conductivity through the incorporation of additives. However, this approach presents challenges such as achieving uniform mixtures, maintaining high latent heat, and cost. Alternatively, it has been demonstrated that, in this study, reducing the length scale of the PCM-encasement thickness can eliminate the low thermal conductivity effect of PCMs. To illustrate this concept, a one-dimensional PCM slab was numerically simulated. The thickness of the slab was varied to represent dimensions found in flow passages of compact heat exchangers, and the heat transfer coefficient of the heating fluid was varied to represent lower and upper bounds while also including nominal values encountered in air-to-air heat exchangers. The thermal conductivity was parametrically varied from the natural value of the PCM to simulated enhanced values (potentially achieved through additives) of up to 400 times larger. Results show that reducing the PCM-encasement thickness yields substantially better performance than by improving the thermal conductivity, thereby demonstrating the potential for compact heat exchanger design to overcome the PCM thermal conductivity limitations.

Numerical modeling and optimization of tube flattening impacts on the cooling performance of the photovoltaic thermal system integrated with phase change material

In this research, a computational fluid dynamics-based numerical simulation is performed to evaluate the influence of tube flattening on the cooling performance of a photovoltaic thermal system integrated with phase change material. Such a study is executed to obtain the four evaluation parameters, including average photovoltaic panel temperature, phase change material melting percentage, tube pressure drops, and the difference between the highest and lowest temperature points on the photovoltaic panel. To obtain the optimum percentage of tube flattening to optimize the cooling performance of the systems, multi-objective optimization by utilizing response surface methodology is done by considering some design requirements, including minimizing average photovoltaic panel temperature, maximizing phase change material melting percentage, minimizing tube pressure drops, and minimizing the difference between the highest and lowest temperature points on the photovoltaic panel. Finally, a parametric analysis is done to explore how certain critical factors (solar radiation, fluid mass flow rate, phase change material thermal conductivity, phase change material enthalpy of fusion, and phase change material melting point) affect the efficiency of the systems. The findings indicate that as tube flattening rises from 0 % to 75 %, the average photovoltaic panel temperature and the difference between the highest and lowest temperature points on the photovoltaic panel decrease which is a positive effect. Conversely, increasing the tube flattening results in an increase in the tube pressure drops and a reduction in the phase change material melting percentage. These changes adversely affect the cooling performance. Considering these impacts and conducting an optimization process, the ideal tube flattening value is 54.78 %. In this optimized state, the average photovoltaic panel temperature reaches 55.21 ˚C, phase change material melting percentage comprises 42.54 %, tube pressure drops is 184.8 Pa, and the difference between the highest and lowest temperature points on the photovoltaic panel is 33.42 ˚C.

Thermal performance of phase change materials with anisotropic carbon fiber inserts

In thermal energy storage systems, phase change materials (PCMs) are widely used for thermal energy management. Most PCMs have low thermal conductivities, which limits the heat transfer rate within PCM and thus makes the phase-changing process very slow. However, thermal conductivities of PCMs can be altered by inserting targeted additives. We hypothesize that the size and shape of these additive inserts play a key role in thermal management efficiency. To this end, the impacts of carbon fiber (CF) inserts on the phase change behavior and consequent heat transfer efficiencies of inorganic and organic PCMs were investigated using experiments and simulations. Long, anisotropic CFs with high thermal conductivities formed continuous fast heat flux tunnels inside PCMs to enhance the heat transfer. Such CFs could extend the phase change fronts from the limited container-shaped interface to the larger surface of numerous CF inserts inside the PCM. These special CF inserts work with a new heat transfer mechanism, different from conventional small additives or long isotropic CF inserts. The thermal energy release rate increased by 2.5 times with 1 wt.% anisotropic CF inserts in inorganic PCM. However, CF inserts in liquid organic PCM hindered the natural convection and compromised the improved heat conduction. The lab-scale multiphysics simulations support these experimental observations and indicate that CF inserts have potential to enhance heat transfer in inorganic PCMs, but they are less effective in organic PCMs.

Study on performance of carbon nanotube composite phase change cold storage sphere with annular fins

Aiming at the poor phase change material thermal conductivity, high shell layer thermal resistance and low cold storage efficiency in encapsulated cold storage sphere systems, we adopt computational fluid dynamics to numerically investigate the cold storage process after adding carbon nanotubes to phase change paraffin cold storage spheres. The heat transfer model of a new type of annular-finned cold storage sphere and cold storage device is established, and the effects of sphere diameter, shell material, fins and refrigerating medium flow rate on the cold storage process are investigated. The results show that the optimum fin length of the sphere is 11 mm and the optimum fin spacing is 8 mm at a sphere diameter of 50 mm. The completion time of the carbon nanotube-added annular finned sphere is 48 min shorter than that of the traditional pure paraffin sphere without fins, and the cooling efficiency increases by 61.7 %, which is better than those of adding either fins or carbon nanotubes; carbon nanotube additions are better than fin additions to the single-variable factors to enhance the cooling effect. The convective heat transfer coefficients at 4 m/s and 5 m/s refrigerating medium flow rates increase by 20.1 % and 42.3 %, respectively, compared with those at 3 m/s. We provide a theoretical basis and reference value for the optimal design of an accumulator sphere and its devices.

Impact of different surfactants on graphene nanoplates enhanced paraffin-based phase change material

Phase change materials (PCMs) is a unique material that been widely explored for thermal energy storage (TES). PCM nature of low thermal conductivity limits the performance and heat transfer characteristics. Nano-filler been used widely to enhanced PCM thermal conductivity and improved the thermal physical properties. This research work study the nano-filler impact of graphene nano plate (GNP) enhanced paraffin-based PCM with different surfactant (cetryl trimethyl ammonium bromide; CTAB and SDBS) being added. Two step method being applied to fabricate the composites of RG (RT44HC with GNP), RGC (RG with CTAB) and RGS (RG with SDBS) in different weight percentage. The analysis on Fourier transform infrared spectrum shows stable results chemically and physically. The thermal stability shows an improvement as GNP prolong the weight degradation temperature of the composite. An improvement in thermal conductivity to 59.1% achieved as the SDBS surfactant added to RG composite. The addition of GNP and surfactant gives promising results and improvement in RG composite development for TES application in photovoltaic thermal (PVT) system.

Experimental study about the impact of open cell aluminium foam (OCAF) insertion in salt-based phase change material (PCM) for electronics thermal management

Thermal management of electronic components is a critical task in a harsh thermal environment. Spacecraft and satellites' electronics are susceptible to highly intermittent heating and cooling thermal conditions, which imposes challenges for robust thermal management system design. Phase change materials (PCM) are a promising solution for overcoming these challenges and enhancing thermal control performance. The lower PCM thermal conductivity and PCM supercooling limit PCM utilisation in electronic thermal control systems. The present study aims to provide solutions for enhancing the heat transfer within the PCM, boosting the PCM thermal conductivity, and diminishing the PCM supercooling. The open-cell aluminium foam (OCAF) was adopted for boosting the heat transfer within the PCM. A thermal management module (TMM) integrated with a salt-based PCM/OCAF composite was developed for electronics thermal management. The TMM was tested under intermittent thermal conditions of heating and cooling. An electric heater and Peltier cooler were affixed to the TMM for the heating and cooling process, respectively. Three levels of heat fluxes were adopted: 700, 1000, and 1400 W/m2. The heating process lasted one hour; then, the TMM was cooled by the Peltier element to the initial temperature. The research novelty covers the gap in understanding how OCAF affects salt-based PCM supercooling when subjected to varying heating loads during intermittent cycles. The outcomes reported a remarkable improvement in thermal management efficiency. The PCM-based TMM reduced the highest temperature by about 20.4 %, 21.6 %, and 23 % at the three heating levels. The OCAF diminished the PCM supercooling curiously. The reduction in PCM supercooling was 43.5 % compared to the 100 % PCM case obtained at the heat flux of 1400 W/m2.

Experimental and numerical investigations of an open-cell copper foam (OCCF)/phase change material (PCM) composite-based module for satellite avionics thermal management in a thermal vacuum chamber (TVC)

Small satellites' thermal control in the space environment is crucial. Phase change materials (PCM) are promising options for satellite thermal management in space thermal conditions. The current work provides an experimental and numerical investigation of a thermal control module (TCM) using an open-cell copper foam (OCCF)/PCM combination. The experimental tests were carried out in a thermal vacuum chamber (TVC), which simulated the vacuum space environment. The PCM thermal conductivity was boosted using OCCF and aluminium fins. The metallic parallel fins divided the heat sink into six cuboid cavities and were filled with PCM. Two samples with different pores per inch (PPI) of OCCF were adopted, one with 10 PPI and the other with 20 PPI. For the experimental work, the adopted PCM was SP 31. Two levels of heating loads were applied to the TCM: 10 W and 7 W. The numerical model was verified using the experimental work findings. The experimental work concluded that the PCM capsulation sealing is a dominant factor for successful capsule design under vacuum operation. The thermal conductivity enhancers (TCEs) remarkably improved the thermal management performance of the PCM. The case with PCM reported a reduction in the maximum temperature by about 43.67 % and 41.4 % at 7 W and 10 W, respectively, relative to the case without PCM. The PCM/fins combination could improve the PCM performance and mitigate the maximum temperature from 41.7 °C to 39.6 °C with a reduction percentage of 5 %. The OCCF reported better thermal performance than the metallic fins. The OCCF with 10 PPI decreased the PCM maximum temperature by 10.3 %. The OCCF with 20 PPI reported a reduction in the PCM maximum temperature by 13.8 % at 10 W heating power.

Numerical study on using multichannel tube and PCM for improving thermal and electrical performance of a photovoltaic module

The electrical efficiency of a crystalline silicon module drops with increasing cell temperature. Phase change material (PCM) was commonly used to perform the thermal management of a PV module, while its poor thermal conductivity may act as a barrier to wide application. In the current study, an innovation design that utilizes excellent heat storage capacity (HSC) of PCM and high thermal conductivity of multichannel tube is introduced into a PV module (MPCM-PV). Computational Fluid Dynamics (CFD) modeling of the MPCM-PV together with experimental validation was conducted. It was determined that the established model can predict the performance of the MPCM-PV at reasonable accuracy. The effect of the structural and physical parameters on the operating performance of the MPCM-PV module was analyzed. The electric energy production was increased by 4.75 % when the number of channels was increased from 1 to 5. Additionally, the rectangular-shape channel rather than triangular shape was more beneficial for the MPCM-PV temperature reduction. Further, it was found that the low melting point and large HSC of PCM lead to the higher electric energy production. The electrical energy increments of 1.71 % and 0.32 % were respectively achieved when the HSC was increased from 240 kJ/kg to 560 kJ/kg and the melting temperature was decreased from 44 °C to 38 °C. The sensitive analysis suggested that the channel shape and the HSC have the most significant impact on electric energy production. These findings provide insight into the design the MPCM-PV system and can guide the development of efficient PV system.

Experimental assessment on the thermal control performance of composite phase change material for fast charging power module

The broader introduction of electric vehicles requires an improvement of battery technology or a more extensive charging infrastructure setup. In order to solve the thermal control problem of high power fast charging piles, the novel thermal control method combining liquid cooling and a small amount of composite phase change materials covered on the upper surface of the charging power module is proposed. An experimental study on the temperature rise and temperature uniformity of the power module surface is compared with single liquid cooling. Results show that adding a small amount of composite phase change material can keep its maximum temperature in the allowable operating range and make temperature uniform around the power module surface compared to the reference solution. The addition of composite phase change materials with a filling thickness of 3 mm gives an overall temperature decrease of 15.531 °C. Compared to the single liquid cooling, increasing the liquid flow rate or decreasing the liquid initial temperature will weaken the further thermal control improvement on the power module. The addition of composite phase change material can effectively keep its maximum temperature in the operating range for the fast charging pile under the larger heat generation power. The phase transition temperature of 52 °C is recommended because of the minimal temperature peak of the power module is obtained. Increasing the composite phase change material thermal conductivity from 6.05 W·m−1·K−1 to 8.99 W·m−1·K−1 will reduce the maximum temperature of the power module by 5.88 %. However, the temperature rise process of the power module suggests that the heat dissipation is mainly determined by the liquid cooling, and very low heat dissipation through the conduction and radiation of composite phase change materials. A slower temperature rise in the latent heat absorption process is observed as increasing the composite phase change material filling thickness, but no significant reduction in the temperature rise is found in the operating time of 15 min. The benefit of using the composite phase change material is reduced by 7.71 % as the cycle times are given as 100. Developing the more effective and stable composite phase change material or replacing the composite phase change materials at regular intervals is needed to ensure its effectiveness for the thermal control performance of the fast charging power module. The present research works show very promising results on the limited researches on the cooling scheme of power devices in higher current fast charging piles.

Thermal Balance of a Water Thermal Accumulator Based on Phase Change Materials

The arrangement of a water thermal accumulator (WTA) containing phase change materials (PCM) is presented and analyzed. The hot or cool water is used as a working body. The accumulator contains two concentric cylindrical tubes. The inner tube is used for hot or cool water flowing, while the volume between the inner and outer tubes is filled with PCM. The thermal energy in the accumulator is stored as a result of flowing the hot water through the inner tube due to the phase transition in PCM. This accumulated energy can be extracted from PCM as a result of flowing the cool water through the inner tube. For the enhancement of the thermal conduction coefficient, the PCM is doped with the nanocarbon particles having a thermal conductivity coefficient exceeding that of PCM by 4–5 orders of magnitude. The thermal balance of the accumulator is calculated on the basis of the solution of the time-dependent heat conduction equation by taking into account the heat absorbed and released as a result of the phase transition as well as the convection thermal exchange in the melted PCM. The calculation results determine the interconnection between the thermal conductivity of PCM and the characteristic time of thermal exchange between PCM and the working body. The calculations indicate that the characteristic thermal exchange time decreases as the thermal conduction coefficient enhances, so that the dependence becomes close to saturation at the thermal conductivity coefficient of about 5 W/m K. Such a coefficient can be reached by doping the paraffin-based PCM with a reduced graphene oxide at a content of about 2% (weight).

Surface-Modified Compressed Expanded Graphite for Increased Salt Hydrate Phase Change Material Thermal Conductivity and Stability

Surface-Modified Compressed Expanded Graphite for Increased Salt Hydrate Phase Change Material Thermal Conductivity and Stability

Energy storage potential analysis of phase change material (PCM) energy storage units based on tunnel lining ground heat exchangers

Low geo-temperature geothermal energy in the surrounding rock can be extracted by tunnel lining ground heat exchangers (GHEs) and stored in phase change material (PCM) plates to realize the cold energy utilization. However, the research of the coupling heat transfer of tunnel lining GHEs and PCM plates has been rarely reported. In this study, a 3D coupling heat transfer model of tunnel lining GHEs and PCM plates was developed to investigate the cold energy storage performances of PCM plates under different PCM and tunnel parameters. The circulative iteration calculation is used to solve the coupling model. The results show that the cold energy storage of PCM plates utilizing tunnel lining GHEs for energy storage is feasible. The PCM melt fraction and solid phase PCM proportion within the PCM plates decrease and increase respectively with an increase in the PCM thermal conductivity and melting temperature and a reduction in the surrounding rock temperature. The cold energy storage efficiencies of PCM plates improve by 77.8% and 34.1% as the PCM thermal conductivity and melting temperature increase by 1 W/(m K) and 4 ℃. Moreover, the cold energy storage efficiency of PCM plate enhances by 68.5% as the surrounding rock temperature reduces from 10 to 1 ℃. A larger difference between the surrounding rock temperature and PCM melting temperature is efficient for the cold energy storage of PCM plates, and the cold energy storage time and temperature difference show a power function relationship. Finally, increasing the tunnel lining GHEs length is conducive to enhancing the cold energy storage efficiency of PCM plates, whereas this enhancement is limited. In actual applications, selecting a reasonable tunnel lining GHEs length is necessary.

A highly accurate model for prediction of thermal conductivity of carbon-based nano-enhanced PCMs using an artificial neural network

Nano-PCMs, which contain nanostructured materials, can enhance the low thermal conductivity of phase change materials (PCMs). It is crucial to predict the precise thermal conductivity of nano-PCM to assess the heat transfer during phase change procedures such as melting and solidification. In this study, artificial neural network (ANN) and response surface method (RSM) were used to develop a model for predicting the thermal conductivity of carbon-based nano-enhanced phase change materials (NEPCMs) using 482 experimental samples collected from various datasets. The carbon-based nano-particles were SWCNTs, MWCNTs, graphite, graphene, and (CNFs). Six input parameters were considered with varying temperature, mass fractions, sizes, thermal conductivities of PCMs and nano-particles, and the phase of PCM. The ANN was designed using a multi-layered feed-forward structure and Levenberg–Marquardt back-propagation algorithm with one hidden layer consisting of eight neurons. The transfer function was varied to achieve optimal performance. It was revealed that the predictive capacity of the ANN model is greater than that of the RSM model based on their corresponding the coefficient of determination (R2) and root mean square error (RMSE) values. The developed ANN achieved a R2 value of 0.99, while the RSM method model achieved an R2 value of 0.79.

Protic dialkylammonium-based ionic liquids as promising solid-solid phase change materials for thermal energy storage: Synthesis and thermo-physical characterization

The widespread deployment of renewable energies such as solar and wind implies the parallel development of energy storage systems to deal with their intermittency. Storing renewable energy as thermal energy is one of the alternatives under constant research. In this regard, phase change materials (PCMs) are able to store large amounts of energy at a nearly constant temperature in the form of latent heat. Nevertheless, most of these PCMs undergo solid-liquid transitions, which hamper their implementation due to leaking issues, forcing the need for containment and increasing the final cost of the TES system.Therefore, a class of PCMs possessing solid-solid transitions has emerged to avoid these problems, the so-called organic ionic plastic crystals (OIPCs). Currently, the scientific literature and the number of OIPCs available for TES are rather scarce. Herein, we present the synthesis, the structural, and the thermo-physical characterization of nine OIPCs based on the dioctylammonium cation combined with different organic and inorganic acids as the anions. Particular attention has been paid to the most characteristic thermal properties of PCMs (latent heat, transition temperature, subcooling, thermal conductivity, and energy storage density), evaluating their thermal stability and the reliability of the most promising materials over thermal cycling as well. Among the prepared OIPCs, 3 of them, [DOA][NO3], [DOA][Cl], and [DOA][FOR], exhibited promising properties with remarkable solid-solid transition enthalpies of 156.6 J/g (at 41.4 °C), 101.2 J/g (at 20.0 °C) and 58.4 J/g (at 29.7 °C), respectively. These 3 OIPCs showed high potential to be used and integrated as PCMs in TES systems at temperatures below 45 °C.

Design and thermal performance evaluation of a new solar air collector with comprehensive consideration of five factors of phase-change materials and copper foam combination

The low thermal conductivity of phase-change materials (PCMs) reduces the heat storage capacity, heat release efficiency, heat peak migration capacity, and heat collection efficiency of PCM-based solar air collectors (SACs) in building heating systems, thereby affecting the comprehensive heating requirements of building users. To solve this problem, in this study, a new SAC was designed with PCMs and copper foam (Type 2: PCMACFC-SAC model) by comprehensively considering five factors, namely thermal conductivity, heat storage capacity, heat release efficiency, heat peak migration capacity, and heat collection efficiency, based on a pure PCM-based SAC (Type 1: PCM-SAC model). Thereafter, the two models were compared. Comparative results of the thermal-performance evaluation index revealed that the thermal conductivity of the Type 2 test block was 2.2–2.3 times that of the Type 1 test block, indicating significantly improved thermal conductivity of the copper foam and PCM composite test block. Although the PCMACFC-SAC displayed better heat storage speed rate, time, and quantity, its nighttime heat release time was approximately 19.64% less than that of the PCMs-SAC; PCMACFC-SAC had a lower output temperature and smaller temperature fluctuation range over the solar day, which can increase indoor thermal comfort. The daily average heat collection efficiency of the PCMACFC-SAC decreased by 12.77%, indicating a stronger heat peak migration ability, which can transfer a greater amount of heat energy to be released at night.

Study on the temperature control performance of photovoltaic module by a novel phase change material/heat pipe coupled thermal management system

High photovoltaic (PV) module temperature leads to the degradation of electrical efficiency, and passive PV thermal management systems, such as phase change materials (PCMs) and heat pipes (HPs), have been widely adopted to address this challenge. Due to the low thermal conductivity of PCM and the limited heat exchange capacity in the HP condensation section, this paper proposes a novel configuration for a PV thermal management system utilizing a phase change material/heat pipe coupled module (PV-PCM/HP). The experimental results showed that the performance of the coupled PCM/HP system was superior to that of the single system. A numerical model was developed to simulate and analyze the temperature variation and coupled heat transfer characteristics of the PV-PCM/HP system. The main components of heat transfer gradually change from PCM (PCM-dominated) to HP (HP-dominated), and PCM even plays a negative role during the solidification stage, which means that the coupled thermal management depends on HP only. Four design parameters (the number of HPs, PCM thermal conductivity, PCM phase change temperature, and PCM thickness) of the PV-PCM/HP system are discussed to investigate the effects on the performance of the PV-PCM/HP thermal management system. This shows that the increase in the number of heat pipes and PCM thickness can effectively improve the performance, but they should be determined according to technical and economic analysis. When the PCM thermal conductivity is >2.7 W/(m·K), it has little effect on thermal management performance under the conditions described in this paper. The value of the PCM phase change temperature should be determined according to actual weather conditions, and the purpose is to make the PCM melting period coincide with the period of higher solar radiation and lower phase change temperatures.