Inorganic Phase Change Materials Research Articles

The effectiveness of organic PCM based on lauric acid from coconut oil and inorganic PCM based on salt hydrate CaCl2.6H2o as latent heat energy storage system in Indonesia

A latent heat energy storage system utilizing phase change materials (PCM) is an alternative strategy to reduce the use of Air Conditioning (AC) system in big cities in Indonesia in order for energy conservation in the future. In this research we used two kinds of materials, namely organic PCM based on lauric acid from coconut oil (CO) and inorganic PCM based on salt hydrate CaCl2.6H2O, because they have thermophysical parameters suitable for human's thermal comfort application in the building. The CO which contained more than 50% lauric acid has the melting temperature (Tm) of about 26 °C and heat entalphy (ΔH) around 103 kJ/kg, while CaCl2.6H2O has the melting point of 29 °C and heat entalphy of 190 kJ/kg. In this paper we report the effectiveness of those two kinds of PCM in reducing the air temperature as one of some criteria for human's thermal comfort. The experiments were performed in a close and adiabatic room and the time-temperature measurements were done automatically using Arduino microcontroller and LM35 temperature sensor connected to the PC.

Preparation and Characterization of Inorganic PCM Microcapsules by Fluidized Bed Method.

The literature shows that inorganic phase change materials (PCM) have been very seldom microencapsulated, so this study aims to contribute to filling this research gap. Bischofite, a by-product from the non-metallic industry identified as having good potential to be used as inorganic PCM, was microencapsulated by means of a fluidized bed method with acrylic as polymer and chloroform as solvent, after compatibility studies of both several solvents and several polymers. The formation of bischofite and pure MgCl2·6H2O microcapsules was investigated and analyzed. Results showed an efficiency in microencapsulation of 95% could be achieved when using 2 min of fluidization time and 2 kg/h of atomization flow. The final microcapsules had excellent melting temperatures and enthalpy compared to the original PCM, 104.6 °C and 95 J/g for bischofite, and 95.3 and 118.3 for MgCl2·6H2O.

Preparation of organic based ternary eutectic fatty acid mixture as phase change material (PCM), optimizing their thermal properties by enriched solar treated exfoliated graphite for energy storage

Rapid economic and social development has led to increase the demand on energy gradually. In thermal system, the energy can be stored for reusing or recycling purpose. The latent heat storage (LHS) is the most effective method for storing the thermal energy and it mainlydependson organic and inorganic Phase change material (PCM).This study is based on preparation of organic based ternary eutectic fatty acid mixture based on capric-myristic-palmitic acid (CA-MA-PA) as PCM in the mass ratio and optimizing their thermal behaviour by using solar enriched treated graphite and then exfoliated by microwave in the ratio 99.83:0.17.The structure morphology was analysed by using scanning electron microscope (SEM),itsfunctional group were proven by Fourier transform infrared spectroscopy (FT-IR) then phase change temperature composite PCM were obtained by using Differential Scanning Calorimetric (DSC).The thermal conductivity viewed by KD2pro were increased from 0.149W/mK to 0.190W/mK. Overall resultexamined that CA-MA-PA/Exfoliated graphite nanoplatelets (xGnP) can be used for low temperature LHS.

The Effect of Additives on the Crystallization PCM CaCl<sub>2</sub>.6H<sub>2</sub>O for Stabilizing the Air Temperature for Energy Conservation

Phase Change Material (PCM) is a material that uses the phase transition properties as latent heat storage for certain application. Salt hydrate CaCl2.6H2O (melting temperature, Tm = 29°C, and melting entalphy, DH = 190 kJ/kg) is a common inorganic PCM that can be used for regulating the air temperature of the room, in order to reduce the electrical energy consumption for energy conservation. General problems of inorganic PCM, in particular during the crystallization or latent heat release, are the subcooling and phase separation effects. It is worth mentioning that understanding the crystallization of PCM is important to keep its performance for application. In this research we choose two types additive materials as nucleator to CaCl2.6H2O to overcome those two negative effects, namely Ba2CO3 and K2CO3. We also study the amount of additives needed for effective reduction of subcooling and its phase stability by performing the cycling process. The average temperature and maximum temperature of the subcooling will be determined from temperature vs time recording.

Sonocrystallization Technique to Optimizing the Crystallization Process of PCM CaCl<sub>2</sub>.6H<sub>2</sub>O

Salt hydrate CaCl2.6H2O is one of inorganic Phase Change Material (PCM) that have melting temperature (Tm) of about 29 °C and latent heat of fusion (DH) of around 190 kJ/kg that can be used for latent thermal energy storage. This material can be used for conditioning the air-temperature of the room, in order to reduce the electrical energy consumption for air conditioning (AC) system. In order to reduce the subcooling and phase separation effects of CaCl2.6H2O to maintain its performance, we adopt sonocrystallization technique that uses ultrasound radiation for crystallization of CaCl2.6H2O. The data are taken qualitatively for the crystal growth observation and quantitatively based on real-time temperature recording. The results show that sonocrystallization can slightly reduce the phase separation effect and improving the quality of the crystal. Hence, the resulted crystals have large and long size, uniform distribution and dense arrangement.

Experimental Investigation of the Concentration Dependent Maximum Storage Capacity of two Inorganic Phase Change Materials

Abstract In large latent heat storages with the phase change material (PCM) being a salt hydrate, it is difficult to assure the stoichiometrically correct hydrate concentration of the salt hydrate. In this study, the influence of the composition of CaBr 2 + H 2 O around the congruent melting CaBr 2 ·6H 2 O and CaCl 2 + H 2 O around the semi-congruent melting CaCl 2 ·6H 2 O on the maximum storage capacity is investigated via differential scanning calorimetry (DSC). For a CaBr 2 concentration around 0.8 wt% lower than the concentration of CaBr 2 ·6H 2 O, a decrease of over 17% is found for the maximum storage capacity. For a CaCl 2 concentration around 0.7 wt% lower than the concentration of CaCl 2 ·6H 2 O, a decrease of over 11% is found for the maximum storage capacity. While reproducible results for the maximum storage capacity for samples of the same concentration of CaBr 2 + H 2 O are obtained via DSC, this is not the case for the CaCl 2 + H 2 O samples. Thus, the difficulty to measure representative enthalpy curves of non-congruent melting salt hydrates via DSC is shown.

Thermal characteristics of room temperature inorganic phase change system containing calcium chloride

A novel inorganic calcium-based phase change material(PCM-Ca) consisted of 47.1%(mass fraction) water, 47.7% calcium chloride, 2% potassium nitrate, 2% potassium bromide and 1.2% strontium chloride with a solid-liquid phase change temperature of 21.4 °C was investigated systematically. Among the components of PCM-Ca, calcium chloride and water act as the latent heat storage materials, and potassium nitrate, potassium bromide and strontium chloride work as the modifier, thickener and nucleating agent, respectively. Thermochemical properties including melting point, latent heat, density and thermal conductivity of the PCM-Ca were measured experimentally. The experimental results indicate that the melting latent heat, thermal conductivity at the melting point and density at room temperature for the PCM-Ca are 203.3 kJ/kg, 1.3637 W·m–1·K–1 and 1.55×103 kg/m3, respectively. Moreover, a thirty-run-cycling test showed that the PCM-Ca has a good thermal characteristic with no phase segregation or supercooling, and the maximum deviations of latent heat and phase change temperature are only 0.2% and 1.6%, respectively.

Determination of thermo-physical properties and stability testing of high-temperature phase-change materials for CSP applications

This paper presents the thermo-physical properties and stability testing results of six high-temperature phase-change candidate materials for potential use as a cascaded storage system for concentrating solar power applications. This type of storage is a promising technology because it offers a higher utilization of the possible phase change and a more uniform heat-transfer fluid outlet temperature, compared with the single phase-change material (PCM) storage system. The tested materials were inorganic eutectic PCMs with reported phase-change temperatures between 300°C and 600°C. Four PCMs were made from carbonate salts (Na2CO3, K2CO3, and Li2CO3) and two from chloride salts (NaCl, MgCl2, and KCl). The phase-change temperature, phase-change enthalpy, and specific heat of these PCMs were measured using a differential scanning calorimeter. Large material samples were tested in an oven subjected to multiple melt–freeze cycles. The results showed that the carbonate PCMs have a very high degree of sub-cooling in the initial cycles, which decreased in subsequent cycles. The chloride PCMs have a negligible degree of sub-cooling. There is some disagreement between the measured and reported thermo-physical property values of the tested materials, which demonstrates the uncertainty associated with published property values. One carbonate PCM and one chloride PCM were recommended as promising latent heat storage materials.

Determination of the eutectic concentration between Mn(NO3)2·6H2O and NaNO3 using the DSC peak sharpness method

While inorganic eutectic phase change materials (PCM) present the advantage of a high volumetric melting enthalpy and a high thermal stability under repeated heating/cooling cycles, there is a lack of known materials in the temperature range of 20–24 °C, interesting for building applications. The DSC peak sharpness method is employed to determine the eutectic concentration between Mn(NO3)2·6H2O and NaNO3, which is 96.5 mass% Mn(NO3)2·6H2O and 3.5 mass% NaNO3. Thereby, the DSC peak sharpness method is demonstrated to yield the same result independently of the two chosen heating/cooling rates of 0.5 and 2 K min−1. The eutectic PCM has an onset temperature of 22.1 °C and a melting enthalpy of (126 ± 6) J g−1. Even though the same eutectic concentration is obtained for both heating/cooling rates, the heating/cooling rate of 0.5 K min−1 reveals that the melting peak of Mn(NO3)2·6H2O is composed of two overlapping melting peaks. The second melting peak supposedly corresponds to the eutectic between Mn(NO3)2·6H2O and Mn(NO3)2·4H2O, which melts at a slightly lower temperature than Mn(NO3)2·6H2O (difference of −0.6 °C). This assumption is in accordance with the water content of the purchased Mn(NO3)2·6H2O measured via Karl Fischer titration being (0.66 ± 0.2) mass% too low.

Numerical and Experimental Analysis on Inorganic Phase Change Material Usage in Construction

This work demonstrates the significance of Phase Change Material (PCM) in the construction of working sheds and product storage magazines in fireworks industries to maintain less temperature variation by passive cooling. The inorganic PCM, namely Calcium Chloride Hexahydrate (CCH) is selected in this study. First, the performance of two models with inbuilt CCH was analysed, using computational fluid dynamics. A significant change in the variation of inner wall temperature was observed, particularly during the working hours. This is mainly due to passive cooling, where the heat transfer from the surroundings to the room is partially used for the phase change from solid to liquid. The experiment was carried out by constructing two models, one with PCM packed in hollow brick walls and roof, and the other one as a conventional construction. The experimental results show that the temperature of the room got significantly reduced up to 7 °C. The experimental analysis results had good agreement with the numerical analysis results, and this reveals the advantage of the PCM in the fireworks industry construction.

A new method of application of hydrated salts on textiles to achieve thermoregulating properties

Abstract Recently there has been a lot of attention to fibers and fabrics with thermoregulatory effects. We can acquire this quality using Phase Change Materials (PCM). In this investigation a simple method was used to keep Na 2 SO 4 ·10H 2 O as an inorganic PCM on textile structure. By this method it is not necessary for PCMs to be microencapsulated. Thermophysical properties and thermal stability effects of treated fabric was checked out by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). Fourier transform infrared spectroscopy (FT-IR) and X-ray diffractometry (XRD) analysis were used to study the chemical structure of the fabric with PCMs. The air transfer, water permeability, and some physical properties of treated fabric were also investigated. The results showed that, silicone rubber polymer could be applied on textile structure to hold PCM without microencapsulating, and treated textile can be served as an appropriate smart thermal insulator.

Performance evaluation of a thermoelectric energy harvesting device using various phase change materials

This paper compares the performance of a group of organic and inorganic phase change materials for a heat storage thermoelectric energy harvesting device. The device consists of thermoelectric generators and a closed container filled with a phase change material. One side of the generators is mounted on the aircraft fuselage and the other to the thermal mass. The group of inorganic and organic phase change materials was tested across two temperature ranges. These ranges are defined as "positive" and "negative", with the former being a sweep from +35°C to −5°C and the latter being a sweep from +5°C to −35°C. The performance in terms of electrical energy output and power produced is examined in detail for each group of materials.

Simulation of the transient behaviour of encapsulated organic and inorganic phase change materials for low-temperature energy storage

In this paper, a detailed mathematical model was presented for the transient behaviour of rectangular macro-encapsulated phase change material (PCM) in both melting and freezing phases and was validated using published experimental data. A second order fully implicit finite difference scheme was employed to solve for the storage material solid–liquid moving boundary problem. Two PCMs of melting temperature in the range of 30 °C, calcium chloride hexahydrate and paraffin wax C18 have been studied and investigated under various operational parameters to compare their thermal performance and storage characteristics. Simulations have been carried out to assess the effect of working fluid temperature, convective heat transfer coefficient and storage material thickness employed on the transient variation of the PCM temperature, the thermal energy storage capacity and the material melting time. It was shown that a paraffin C18 storage mass needs double the container volume, about 3 times the melting time and has 1.2 times the thermal storage capacity of a similar mass of inorganic CaCl2.6H2O salt hydrate. However, CaCl2.6H2O PCM has higher volumetric storage capacity providing an opportunity to design compact energy storage systems. In addition, a relationship between the PCM storage mass and the corresponding melting time and storage capacity has been established.

Improved measurement technique for the characterization of organic and inorganic phase change materials using the T-history method

In the past decade, the interest in phase change materials (PCMs) has grown significantly due to their ability to store large amounts of thermal energy in relatively small temperature intervals. Accurate knowledge of thermo-physical properties is a prerequisite for any reliable utilization of these materials. The T-history method is widely used for the investigation of PCM. This paper presents an improved measurement technique for the characterization of PCM using the T-history method. The suggested improvements include the arrangements made in three different prospects: the experimental setup, data processing and data representation. T-history measurements of organic RT21 and inorganic SP22 A17 (RUBITHERM® GmbH) PCM were performed. The applied arrangements resulted in the temperature accuracy of ±0.3°C and the reduction of uncertainty associated with heat stored/released between the cooling and heating measurements. The obtained results showed some important aspects of the T-history PCM investigation and could provide more effective design and development process of the thermal energy storage systems based on the investigated materials.

Research on Thermal Character of Inorganic High Temperature Phase Change Materials

Recently advances in testing methods and study of the inorganic salt establish the high temperature phase change energy storage materials as a promising candidate for solar thermal power generation, industrial process heat use and waste heat recovery. In this paper, a phase change model related to the warming-cooling method was established to test the phase change temperature and the heat of LiCl-NaCl(1.08-1) and Ca(NO3)2-NaNO3(4-7). The result tested by the warming-cooling method is mainly in line with the one tested by other method. The data allows a promising development of the energy storage.

Study on differential scanning calorimetry analysis with two operation modes and organic and inorganic phase change material (PCM)

Phase Change Materials (PCM) allow storing thermal energy as latent heat when phase change occurs. In order to characterize these materials the phase change enthalpy and temperature should be perfectly known. Differential Scanning Calorimetry (DSC) is the most used technique to determine PCM's thermophysical properties. There are mainly two DSC operation modes: dynamic and step mode. A selection of the two most common PCM materials (paraffin and salts hydrates) was performed to conduct measures with the two DSC operation modes. The main objective of this paper is to determine the most appropriate operation mode for each type of PCM. A slow dynamic mode is recommended when analyzing salt hydrates with DSC. No significant differences between the two DSC modes were observed for paraffin.

Testing method of phase change temperature and heat of inorganic high temperature phase change materials

An analytical temperature model and an enthalpy difference function, based on lumped parameter method and assumption of rectangular effective specific heat, are presented in this study, which can measure the enthalpy change of inorganic salt high temperature. It is easy to carry out in practicable test, because an automated test equipment is designed to measure and record the T-history curves of the PCMs and “Valley, Bottom, and peak” and “Peak, Top, and Valley” criteria are proposed to select the starting temperature of phase-changing process (TS), the ending temperature of phase-changing process (TE) and the melting point (Tm) of the PCMs. The binary eutectic LiNO3–NaNO3 (5.5:4.5, mass ratio), LiCl–NaCl (7:3, mass ratio) and Li2CO3–Na2CO3 (4:6, mass ratio) are tested, whose melting point and heat of fusion are (198.9°C, 255kJ/kg), (559°C, 460kJ/kg) and (499°C, 374kJ/kg). The maximum deviation between measurements and the values from DSC and references is less than 8%. It can be seen that with this method it is possible to obtain both melting point and heat of fusion in a simple way which will be of great help in selecting heat storage material in solar-energy and industrial waste heat utilization and in the subsequent design of a thermal energy storage system.

Investigation and Development on Phase Transition Temperature Control and Adjustment of Inorganic Salt Hydrates

Whereas inorganic salt hydrates are typical inorganic phase change materials suitable for the temperature range of 0-150°C, their investigation and applications on thermal energy storage have received more and more during the recent years. A review on investigation progress and applications of their phase transition temperature control and adjustment was made in this paper, which is of important reference and practical value for understanding and predominating the investigation and engineering applications on their phase transition temperature control and adjustment.

Microencapsulation of Alkaline Salt Hydrate Melts for Phase Change Applications by Surface Thiol‐Michael Addition Polymerization

AbstractThe microencapsulation of alkaline salt hydrates suitable as inorganic phase change materials (PCMs) via surface Michael‐type addition polymerization of thiols and acrylates is reported. The encapsulation performance depending on the resins' acrylate‐to‐thiol ratio and monomer functionality is investigated, and the best encapsulation performance is found for resin compositions with considerable acrylate excess ratios. The step‐growth nature of the reaction can be substantiated via comparative bulk polymerizations. A multistage encapsulation mechanism is proposed in order to explain the different dependencies on the acrylate to thiol ratio observed in PCM encapsulations in comparison to bulk polymerizations.magnified image

Conductivity particles dispersed organic and inorganic phase change materials for solar energy storage–an exergy based comparative evaluation

The performance enhancement of a shell and tube latent heat thermal storage (LHTS) system due to dispersion of conductivity nano-particles is investigated. Two phase change materials (PCM) are considered, one is organic PCM (paraffin wax) and the other is inorganic (hydrated salt). The numerical study involves both charging and discharging modes. The performance enhancements of the two PCMs are compared in terms of exergy stored/recovered and exergy efficiency.