Melting Latent Heat Research Articles

Fast estimation of the enthalpy–temperature function of Phase Change Materials

This paper presents a method for fast estimation of the enthalpy–temperature function of Phase Change Materials (PCMs). The method combines a simple experimental setup with a non-iterative, reliable mathematical algorithm that allows retrieving the enthalpy–temperature function from measurements of heat flux and temperature at a single point. Distilled water was used as reference PCM for validation purposes because its enthalpy function is known with high accuracy. Moreover, water is characterized by sharp melting/solidification processes and very high enthalpy of melting, which is challenging for the estimation method proposed. The results achieved show quite good accuracy in the determination of melting point (±0.06°C), latent heat of melting (±1.5%) and specific heats (±5−8%). To prove that the estimation method also works with PCMs undergoing progressive instead of sharp melting, a composite material made of a graphite-foam enclosing a solid–solid PCM was also tested. Finally, the potential interest of the method for identifying and diagnosing PCM degradation in thermal cycling tests was shown by testing a PCM with leakage problems. Compared to Differential Scanning Calorimeter (DSC) in step-scan mode, which is the reference method for determining the enthalpy–temperature function of a PCM, our method shows comparable accuracy while providing significant advantages, such as short testing time (less than 2 h instead of days) and low-cost experimental equipment. The proposed method could hence be of great value to accelerate PCMs development and benchmark, as well as for databases building-up.

Improving the thermal performance of novel low-temperature phase change materials through the configuration of 1-dodecanol-tetradecane nanofluids/expanded graphite composites

To improve the thermal conductivity (λ) of organic phase change materials (PCMs) in air-conditioning systems, a series of novel organic PCMs were prepared via a two-step method, including high-speed emulsification and natural physical adsorption. The effect of the mass ratio of the 1-dodecanol-tetradecane nanofluids to the expanded graphite (EG) onmass loss percentage and thermal stability of 1-dodecanol-tetradecane/EG composite PCMs was investigated. Differential scanning calorimetry, Hot Disk thermal constants analyser, and thermogravimetric analysis, as well as scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction were employed to analyse the thermal performance, surface topography, surface functional groups, and crystal structure of 1-dodecanol-tetradecane nanofluids/EG composite PCMs. The molar ratio of the 1-dodecanol and tetradecane with in the nanofluids was determined to be 26.3:73.7, while the optimal EG additional amount was 7 wt%. The results show that the melting and solidification temperatures (Tm and Ts) of the nanofluids are 3.43 °C and 4.17 °C, respectively, whereas the corresponding latent heats of melting and solidification (Hm and Hs) are 212.96 J/g and 213.00 J/g, respectively. After the natural adsorption process, the Tm and Ts of the 1-dodecanol-tetradecane/EG composite PCM with an optimal mass ratio of 93:7 are 3.63 °C and 7.71 °C, respectively, while the corresponding Hm and Hs decrease to 197.95 J/g and 198.81 J/g, respectively. Notably, the λ values of the nanofluids and the 1-dodecanol-tetradecane/EG composite PCM are 0.2186 W/(m∙K) and 2.4070 W/(m∙K), respectively, thereby indicating a tenfold increase in λ. The present study confirms that the 1-dodecanol-tetradecane/EG composite PCM is a potential candidate for cold energy storage in air-conditioning system and cold chain logistics.

A comprehensive numerical model for kerf width prediction in hot wire cutting of expanded polystyrene

Improving accuracy in cutting of expanded polystyrene (EPS) foam using hot wire depends on understanding and controlling the kerf width, which in turn depends on temperature distribution in the foam during cutting. We present here a comprehensive temperature-validated numerical thermal model that incorporates important factors such as convective heat transfer between the wire and molten/ablated foam and the surroundings, thermal coupling between the wire and EPS, temperature dependent EPS foam and wire properties and the latent heat of melting and ablation of EPS, to predict the three-dimensional temperature distributions in the EPS foam in the region immediately around the hot wire and across the entire width of the EPS foam being cut. Based on isothermal temperature contour at the melting point of the foam, kerf width is predicted and compared with experimental measurements. Average kerf width and kerf width variation across the width of the work are seen to be predicted reasonably by the model. The barrelling of the cut profile due to the variation of wire temperature along its length is also quantified and compared with experiments. Selectively switching off various model parameters such as temperature dependent EPS and wire properties and the thermal coupling between wire and EPS shows significant contributions of these factors towards the error in kerf width predictions. Convective heat losses are found to be important when the width of EPS being cut is less such as in thin sheets. As confirmed by experimental data, kerf width is higher near the work edges and stays constant within the bulk region of the work. The model developed comprehensively captures the thermal effects and thus can be used to improve precision while cutting EPS shapes.

Novel green and sustainable shape-stabilized phase change materials for thermal energy storage

Poly (ethylene glycol) (PEG) blended with poly (L-lactic acid) (PLLA) as novel green and sustainable shape-stabilized phase change materials (PCMs) were prepared and characterized in this study. The miscibility and morphology of the blends played an important role in the properties of the PCMs. The partial miscibility between PEG and PLLA resulted in suitable latent heat and a low leakage percentage of PCMs. The typical spherulite structure with a Maltese cross was examined in neat PLLA, as observed using polarized optical microscopy. However, the addition of PEG to PLLA led to the formation of ring-banded spherulites due to the presence of PEG altering the aggregation and twisting the PLLA lamellae. These PLLA crystalline structures can capture liquid (including molten PEG), stabilize the shape, and prevent leakage. The thermal mechanical analysis results indicated that the thickness of the PEG/PLLA blends was not significantly changed during the phase change process. The PEG/PLLA 75/25 blends exhibited appropriate film forming properties and mechanical strength. Moreover, differential scanning calorimetry analysis demonstrated the largest latent heat of melting (130.26 J/g), which could have great potential for developing novel phase change materials for thermal energy storage.

Investigation on compatibility and thermal reliability of phase change materials for low-temperature thermal energy storage

Two of the important aspects for the successful utilization of phase change materials (PCMs) for thermal energy storage systems are compatibility with container materials and stability. Therefore, the present study is focused on testing the corrosion resistance and surface characteristics of metals in contact with PCMs and thermal behavior of PCMs with heating/cooling cycles. The PCM selection is made by targeting low temperature (<100 °C) heat storage applications. The PCMs considered are paraffin wax, sodium acetate tri-hydrate, lauric acid, myristic acid, palmitic acid, and stearic acid. The metal specimens tested are aluminum, copper, and stainless steel because of their wide usage in thermal equipment. The tests are performed by the method of immersion corrosion test, and ASTM G1 standards are followed. The experiments are carried out at 80 °C and room temperature (30 °C) for the duration of 10, 30, and 60 days. Pertaining to thermal stability 1500 melting/freezing cycles are performed. Investigation has been carried out in terms of corrosion rate, SEM analysis of metal specimens, appearance of PCMs, and variation of thermophysical properties at 0th, 1000th, and 1500th thermal cycles. The most affected area of corrosion, including the dimension of pits, is presented, and comparison is made. Based on the corrosion experiments, recommendations are made for the metal–PCM pairs. Pure sodium acetate trihydrate is observed to suffer from phase segregation and supercooling. After 1500 thermal cycles, the variation in melting and freezing point temperatures for rest of the five PCMs are in the range of − 1.63 to 1.57 °C and − 4.01 to 2.66 °C. Whereas, reduction in latent heat of melting and freezing are in the range of 17.6–28.95% and 15.2–26.78%.

Thermal properties of three-dimensional hierarchical porous graphene foam-carbon nanotube hybrid structure composites with phase change materials

Developing novel shape-stabilized phase change materials (ssPCMs) is of vital importance for efficient utilization of thermal energy. In addition, elucidation of the host–guest interaction mechanism is a prerequisite for the methodical design and synthesis of ssPCMs. Here, we prepared a new hierarchical structure, porous graphene foam-CNT hybrid structures (GCNTs), to serve as matrix materials. Micropores and mesoporous channels were introduced during the reassembly of graphene foam and carbon nanotubes (CNTs). PEG was filled into the GCNTs via the solution impregnation method to prepare composite PCMs, whose structural and phase change properties were evaluated via FTIR, XRD, BET, and DSC. A theory was proposed that large pores improve loading capacity, while small pores improve supporting-immobilization capacity. The radius of gyration as well as the melting and diffusion processes were analyzed using molecular dynamics (MD) simulation methods, which revealed that PEG resides in the composite its flexibility is enhanced and the PEG molecules favor the formation of an amorphous liquid layer near the pore walls, resulting in decreased melting point and latent heat. MD simulations also indicated that PEG molecules form a liquid layer near pore walls and crystallize at the pore center. The highest loading rate achieved in the composites was 80 wt%, although the corresponding surface area was far below that of graphene foam due to the hierarchical porous structure. This study will provide insights into the host-guest interaction mechanism in porous composite materials and the design of novel composite phase change materials with improved phase change properties according to the design of suitable hierarchical porous materials.

Crossed analysis by T-history and optical light scattering method for the performance evaluation of Glauber’s salt-based phase change materials

Glauber’s salt (sodium sulfate decahydrate) is a phase change material (PCM) with promising thermal and physical properties. Moreover, it is very interesting from an economic point of view because it is possible to recover it as a waste product after the disposal of lead batteries. Nevertheless, it is restricted in its applications because of supercooling and phase segregation which require suitable additives that decrease the melting temperature and latent heat of fusion. The obtained mixtures are dispersions of powders in liquids, complex energy storage systems with properties depending not only on composition but also on preparation method. This last aspect is poorly addressed in literature for PCMs. Moreover, these systems are thermodynamically unstable, therefore information about the destabilization kinetic is necessary. The thermal analysis was based on the T-history method, considered by many authors as a more suitable method than Differential Scanning Calorimeter (DSC) for heterogeneous materials, since it requires larger-size samples. Nevertheless, long-term destabilization phenomena were not sufficiently investigated in literature, but they are very relevant because they influence the dispersion stability, homogeneity and energy performances. For this same reason, an optical light scattering method, based on the use of an innovative instrument, the Turbiscan®, was proposed in this work to study the stability of such heterogeneous PCMs. Two different compositions of Glauber’s salt/borax/bentonite were prepared under controlled sonication conditions and analyzed, as a case study. Transmission and backscattering profiles were studied, explained and correlated with thermal properties and sample compositions and preparation.

3D Lamellar Structure of Biomass-Based Porous Carbon Derived from Towel Gourd toward Phase Change Composites with Thermal Management and Protection.

The practical application of shape-stable phase change composites (PCCs) is beneficial to thermal energy management and energy conservation due to their superior properties. A shape-stable PCC was fabricated by incorporating poly(ethylene glycol) (PEG) with biomass-based porous carbon that was produced via freeze-drying and carbonization using a low-cost and environmentally friendly fresh towel gourd. The towel gourd derived porous carbon with the characteristics of porosity, unique three-dimensional (3D) lamellar structure, and high specific surface area allowed a high encapsulation capacity (up to 94.5 wt %) for PEG. Structural morphologies, as well as the properties of latent heat storage, thermal reliability, thermal energy management, and thermal protection ability of the fabricated shape-stable PCC, were investigated. The micromorphologies revealed that PEG molecular chains were arranged in a 3D lamellar tissue structure. The shape-stable PCC demonstrated excellent thermal reliability and a high melting latent heat of ∼164.3 J/g. The analysis of infrared thermal images indicated that the shape-stable PCC exhibited remarkable strengths in thermal energy management. The result of the thermal insulation simulation experiment proved that the shape-stable PCC had superior thermal protection ability. This study provided an innovative strategy for the design and development of shape-stable PCCs for great potential in heat-insulating protective textiles, solar thermal energy storage, energy-saving buildings, and infrared stealth of military targets.

Study on preparation and thermophysical characteristics of molten salt nanocomposite by microwave method

Molten salts are widely applied as heat transfer and thermal storage medium for solar thermal power. In order to research the effect of preparation conditions and the types of nanoparticles on the thermophysical properties of molten salt nanocomposite, different molten salt nanocomposites were developed by mixing the nitrates (Ca (NO3)2·4H2O–KNO3–NaNO3–NaNO2) with 1.0 wt% of SiO2, MgO, TiO2 and CuO nanoparticles using a microwave method, which was a new preparation process of molten salt nanocomposite based on high temperature mixing without water. The effect of different microwave heating temperature (250, 350 and 450 °C) and heating time (30, 60, 90 and 120 min) were experimentally studied. The melting point, latent heat and specific heat of the samples were analyzed by differential scanning calorimeter (DSC). The morphology was observed by scanning electron microscope (SEM). The results showed that the nanoparticles induced a decrease of the melting point of 0.1–2.4% while the latent heat decreased by 3.3–7.9%. Compared with other molten salt nanocomposites, the molten salt with the addition of SiO2 nanoparticles had the biggest increase in specific heat, which increased by 7.7% in solid state and 21.0% in liquid state after heating for 90 min at 250 °C. The total heat storage density could reach to 783.0 J/g between 30 and 500 °C, which was 13.3% higher than the base salt. In addition, according to the morphology of the samples, network nanostructures were observed in the molten salt nanocomposite doped with SiO2.

Thermal and microstructural analysis of the low-melting Bi-In-Pb alloy

Low-melting alloys, based on bismuth and indium, have found commercial use in soldering, safety devices, coatings, and bonding applications. In this respect, the accurate knowledge of their thermal properties such as melting and solidification temperatures, latent heat of melting, supercooling tendency, etc. is of large importance. In the present research, low-melting alloy with nominal composition Bi40In40Pb20 (at. %) was investigated by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) and by differential scanning calorimetry (DSC). Microstructural and chemical (SEM-EDS) analysis has revealed the existence of two coexisting phases in the prepared alloy, which was identified as BiIn and (Pb). Melting and solidification temperatures and the related heat effects were measured by the DSC technique. The solidus temperature obtained from the DSC heating curves was 76.3 °C and the solidus temperature obtained from the corresponding DSC cooling runs was 61.2 °C. The experimentally obtained results were compared with the results of thermodynamic calculation according to CALPHAD (calculation of phase diagram) approach, and a close agreement was noticed.

Preparation and study on thermophysical properties of inorganic salt hydrate as energy storage materials

In this paper, the preparation methods of new inorganic salt hydrate mixtures and their experimentally tested thermophysical properties are presented. Two inorganic salt hydrates mixed together at different weight proportions to study their thermodynamic properties for energy storage applications. Three samples having weight proportions of salt mixtures as 70:30, 80:20 and 90:10 are prepared and Differential Scanning Calorimetry (DSC) is used as a thermal analyzer to find the thermal stability of the samples. The DSC results of the salt hydrate are observed for determining the melting temperatures, latent heats and specific heats during melting and freezing process. The melting point, heat of fusion, and heat capacity of the salt hydrate samples are observed as 46.6 °C , 133.81 J/g and 8.75 J/gK for 70:30, 47.28 °C, 169.91 J/g and 15.95 J/gK for 80:20 and 47.26 °C, 173.96 J/g and 14.20 J/gK for 90:10. The time requirements for the completion of melting and freezing process of the salt mixture results are compared. Thermal and heat transfer characteristics of the newly prepared salt mixtures are experimentally investigated for the purpose of recommending it to use as thermal energy storage medium. The inexpensive inorganic salt hydrate mixtures, with greater enthalpy, higher heat storage capacity and good thermal reliability, shows great potential for heat storage applications in the low temperature solar thermal applications like water heaters, building space heating applications, domestic solar cookers and dryers.

Experimental study on thermal performance of an integrated PCM Trombe wall

In order to improve the thermal performance of Trombe wall, the mixture of 55% decanoic acid and 45% lauric acid as a kind of PCM was chosen to integrate with Trombe wall. The article presents a test of properties of the PCM and an experimental study on a small-scale integrated PCM Trombe wall. Two periodic heat input modes simulate the periodically varying solar radiation absorbed by the absorber. Its melting temperature and latent heat are 21.33 °C and 133.4 kJ/kg, respectively and its volume expansion rate is 7.94%. The experimental results show that the integrated PCM Trombe wall can increase indoor air temperature by 0.82 °C–1.88 °C for low heat input mode and 1.75 °C–3.27 °C for high heat input mode. Besides, two-dimensional heat transfer along the height and thickness directions of PCM wall results in large temperature difference in these two directions even if the absorber surface is heated evenly. There exists the irregular-shape liquid/solid interface. The PCM above the liquid/solid interface can be completely melted while that below the liquid/solid interface is always in the solid state. Therefore, it is suggested that the PCM with the suitable melting temperature, a wide range of phase change temperature and high latent heat should be chosen.

Feasibility study on temperature control with phase change material in intensive heat-releasing space during emergency power failure: A case analysis of information system room

Phase change material (PCM) is widely used to control temperature because of its easy control, and independent work even without external power supply. However, few studies focus on temperature control via a PCM cooling system without auxiliary facilities, in an intensive heat-releasing space during emergency power failure. This study takes an information system room with an emergency power failure as the research object. A cooling system implementing PCM plates is proposed and its feasibility is analyzed. A mathematical heat transfer model, which considers the air, heat source, phase change cooling devices, and the enclosure structure of room, is established. The performance of the PCM and air temperature are analyzed, and the effects of the melting temperature, latent heat, thermal conductivity, and size of the PCM plates are systematically investigated. Analysis results indicate that: (i) Under the condition of parameter optimization, the air temperature is 32.10 °C at 9 h. Therefore, the cooling system utilizing the PCM plates can effectively maintain the air temperature of the information system room below 35 °C within 9 h. Until 16 h, the air temperature remains below 35 °C. (ii) Increasing the aspect ratio of PCM plates and decreasing PCM latent heat have the similar effect on the air temperature control. Additionally, the two parameters are related to the surface area of the PCM plates. (iii) The lower the melting temperature of the PCM, the better the air temperature can be controlled. For the conditions considered in this study, the appropriate melting temperature is approximately 25 °C. (iv) As thermal conductivity increases, air temperature reduces, and fluctuation of the PCM heat flow significantly decreases. However, as the thermal conductivity approaches 1 W/(m·K), further increases in the thermal conductivity have no marked impact on air temperature control.

Eutectic composition of selected phase change materials for thermal energy storage applications

Latent heat storage in salt mixture has drawn so much attention because of the salt mixture’s capability of storing large quantity of heat when compared to single salt thereby, making it more feasible for use as phase change material. However it is worthwhile to find out among various combination of salts forming eutectic mixtures, the one that has the best energy storage capability by evaluating and comparing their melting points and latent heat storage. So in this research work, four different types of eutectic mixture of salts were prepared and experimentally investigated for the best thermal energy storage capability. The first eutectic mixture consists of 2.6g of LiNO3, 6.4g of NH4NO3 and 1g of NaNO3. The second eutectic mixture consists of1.75g of LiNO3, 3.9g of NH4NO3 and 1.1g of KNO3. The third one consists of 5.2g of LiNO3, 13.7g of NH4NO3 and 1g of NH4Cl) and the fourth one consists of 1.77g of LiNO3, 2.94g of NH4NO3, 1g of NaNO3 and 1g of NaCl. The latent heat and the melting point of the respective salt and their eutectic mixture were determined using digital differential scanning Apparatus. The results obtained showed that the melting points and latent heats of the first, second, third and fourth eutectic mixture were 79.50C and 112kJ/kg, 80.50C and 114kJ/kg, 81.40C and 109kJ/kg, 84.40C and 119kJ/kg respectively. In view of this, the eutectic mixture of 1.77g of LiNO3, 2.94g of NH4NO3, 1g of NaNO3 and 1g of NaCl with melting point of 84.40C and latent heat of 119KJ/Kg was found to possess the best thermal energy storage capability compared to others..Keywords—Eutectic mixture, Salts, Phase change materials (PCM), Latent heat storage

Preparation and thermophysical properties of three-dimensional attapulgite based composite phase change materials

• Attapulgite based three-dimensional carriers were prepared via “grafting from” method. • Pore size of 3D network can be adjusted by chain length and functional groups of connecting molecule. • SA/TATP have excellent thermal property and thermal reliability. • Melting point and melting latent heat of SA/TATP decrease with the decrease of TATP pore size. • Higher grafting rate of the carrier results in the larger thermal energy storage capacity. Aiming to reveal the relationship between the thermophysical properties of shape-stabled phase change materials (PCMs) with the structure of its matrix, a series of stearic acid/three-dimensional attapulgite (SA/TATP) composite PCMs were fabricated by vacuum impregnation method using TATP as matrix, which prepared via “grafting from” method and employed attapulgite (ATP) as raw material, diphenylmethane diisocyanate (MDI) as modifying agent and amines as linking molecules. The structure of carriers, thermophysical properties of the composite PCMs were analyzed, and the relationship between the thermophysical properties of SA/TATP and characteristics of the carrier were also studied. The results indicated that the thermophysical properties of the composite PCMs were improved significantly due to the introduce of organic bonding agents and the formation of three-dimensional network in the matrix. The latent heat of SA/TATP can be up to 136.81 J/g without leakage, and the maximum thermal conductivity of SA/TATP is 0.4215 W/m•K. The melting temperature and melting latent heat of the composite PCMs degenerate with the decrease of the pore size of the carriers. The relationship between the melting phase transition temperature, melting latent heat of SA/TATP and pore size of TATP can be descripted by the Gibbs–Thomson equation. In addition, the melting enthalpy of SA/TATP is positively associated with the grafting rate of the carrier.

Microencapsulation of stearic acid with SiO2 shell as phase change material for potential energy storage

Stearic acid (SA) is being used as phase change material (PCM) in energy storage applications. In the present study, the microencapsulation of SA with SiO2 shell was carried out by sol–gel method. Different amounts of SA (5, 10, 15, 20, 30 and 50 g) were taken against 10 ml of tetraethyl orthosilicate (TEOS) for encapsulation. The synthesized microencapsulated PCM (MEPCM) were characterized by Fourier transform infrared spectroscope (FT-IR), X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The characterization results showed that SA was successfully encapsulated by SiO2. Thermogravimetric analysis (TGA) exhibited better thermal stability of the MEPCM than SA. The enthalpy values of MEPCM were found to be unchanged even after 30 heating–cooling cycles by differential scanning calorimetry (DSC). The latent heats of melting and solidification of 50 g SA containing MEPCM were found to be highest i.e. 182.53 J/g and 160.12 J/g, respectively among all microencapsulated samples. The encapsulation efficiency values were calculated using thermal data and the efficiency was found to be highest i.e. 86.68% in the same sample.

Experimental studies on photovoltaic module temperature reduction using eutectic cold phase change material

An increase in Photovoltaic (PV) module temperature (TPV) affects the photoconversion efficiency (PCE). Annual TPV loss accounts higher than other losses in the PV system for hot climatic conditions. The main objective of this work is to introduce a novel passive Cold-PCM (C-PCM) to reduce the TPV. Commercial PCM’s are more expensive than a eutectic PCM. In this work, Lauryl alcohol and Ethyl alcohol are mixed in a ratio of 75:25 to form a eutectic mixture. The prepared eutectic mixture is having a melting temperature and latent heat of fusion of 21.75 °C and 199 J/g, respectively. Furthermore, C-PCM containers with 3-cm and 5-cm thickness are attached at the back surface of the PV module. It is observed that the 5-cm container exhibits higher heat transfer, which subsequently resulted in TPV reduction at a maximum of 10.3 °C. This decrease in TPV, enhanced the average voltage profile by 2.85%, thereby the average output power is also boosted by 2.8%. Consequently, this eutectic PCM can improve the average performance ratio, electrical efficiency and capacity utilization factor of the PV module by 72.63%, 10.09% and 19.41%, respectively. Thus the experimental results revealed that C-PCM could be a potential replacement to H-PCM for cooling down the TPV.

Effect of radiation on the mechanical, morphological and thermal properties of HDPE/rPTFE blends

Blends of high-density polyethylene and recycled polytetrafluoroethylene micronized powder (HDPE/rPTFE), were prepared using a Brabender Plasticorder at 100/0, 90/10, 80/20, 70/30, and 60/40 blend ratio and subjected to electron beam irradiation at doses ranging from 50 to 200 kGy. The effect of rPTFE loading and irradiation on the mechanical, gel fraction, morphological and thermal properties of the HDPE/rPTFE blends were studied. It was found that the addition of the rPTFE micronized powder to the HDPE matrix resulted in a slight deterioration of its mechanical properties due to poor adherence of the rPTFE particles to the HDPE matrix. The addition of rPTFE improved the thermal stability of the blends. However, when these blends were irradiated, there was an 8–10% increase in the tensile strength depending on the blend ratio. SEM images showed that electron beam irradiation has improved the adhesion between rPTFE micronized powder and HDPE matrix. The crystallinity of the rPTFE micronized powder in the blend increased, but it did not affect the latent heat of melting and latent heat of solidifying. Moreover, there was an increase in the storage modulus, loss modulus at 200 kGy and a shift in glass transition temperature toward higher temperatures at 200 kGy.

Improved thermal properties of stearic acid/high density polyethylene/carbon fiber composite heat storage materials

Composite phase change materials (CPCM) with improved thermal properties were fabricated by encapsulating stearic acid (SA) into high-density polyethylene (HDPE) with carbon fiber (CF). The HDPE acted as the supporting materials to prevent SA leakage. CF was introduced to enhance the thermal conductivity of the CPCM. Some characterization measurements were carried out to investigate the CPCM thermal properties. The patterns of Fourier transformation infrared spectroscopy (FT–IR) and X-ray diffractometry (XRD) revealed that the SA, HDPE and CF were combined physically, and the crystal structure of the mixture remained constant. The results of scanning electronic microscopy (SEM) indicated that the microstructure of the CPCM was relatively stable. The results of differential scanning calorimetry (DSC) indicated that the melting point and latent heat of CPCM6 were 68.48 °C and 140.17 kJ/kg, and the solidifying point and latent heat were 66.95 °C and 141.09 kJ/kg. Thermal gravimetric analysis (TGA) verified that the CPCM had an improved thermal stability within the working temperature range. The thermal conductivity of CPCM6 was 0.4043 W/m⋅K, which is 2.22 times greater than for SA. The addition of CF effectively enhanced the thermal conductivity of the SA. Overall, CPCM6 possesses the potential for application in heat storage fields.

Thermal performance of cold panels with phase change materials in a refrigerated truck

Applying the Phase Change Materials (PCMs) in the refrigerated truck is a reliable method of cold storage because they have high latent heat of melting and can have very low melting points. The PCM absorbs the cooling load of the container during its melting and ensures a constant temperature. In this study, the temperature variations inside the box of a 6-ton refrigerated truck are presented for three types of PCMs. The tested materials were Sub-Zero Eutectic PCMs named by E-26, E-29, and E-32. The tests were conducted for a constant path of 466 km length. Each PCM was studied at different truck speeds of 80–110 km h −1 . The overall heat transfer coefficient was obtained from the measurement results in different situations. The results showed that the speed of the truck increases the overall heat transfer coefficient. The minimum and maximum overall heat transfer coefficients of 0.27 and 0.33 W m −2 K −1 were obtained for E-26 and E-29 PCMs at the truck speeds of 81 and 110 km h −1 , respectively. Among the studied PCMs, the type E-26 gave the maximum melting time of 17200s at the truck speed of 81 km h −1 . For a stationary truck, E-26 PCM had the maximum melting time of 18,400 s. The maximum traveling distance of 491 km was obtained when PCM E-26 was used at a truck speed of 110 km h −1 .