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Materials used for heat accumulation are substances with the phase change at temperatures below 80 °C. In such substances, a high amount of energy can be stored due the phase change. Because of possible corrosion of the heat container components, it is necessary to know their resistance in the given medium. In this work, the corrosion of aluminum, copper and carbon steel was studied in two liquid media: zinc nitrate hexahydrate and calcium chloride hexahydrate. Corrosion tests have shown that steel is the least resistant to corrosion in both media. Aluminum has been proved as the most durable material in zinc nitrate hexahydrate media. On the other hand, pitting corrosion on aluminum occurred in the calcium chloride hexahydrate making it unsuitable for the use in this media. From the comparison of two studied PCMs follows that zinc nitrate hexahydrate is a more aggressive medium in comparison with calcium chloride hexahydrate. From the point of view of corrosion, zinc nitrate hexahydrate is not suitable for heat accumulation when using the studied metals. When using the calcium chloride hexahydrate as PCM, copper is suitable as a construction material; aluminum and carbon steel show pitting corrosion.

CaCl2·6H2O is selected as the original substrate for research, and a new composite phase change material (CPCM) suitable for air-conditioning was developed through experiments. The new modified CaCl2·6H2O CPCM uses glycerol as a temperature regulator and barium hydroxide octahydrate as a nucleating agent. The experimental results show that when the mass ratio of CaCl2·6H2O to glycerol is 85:15, the melting temperature of the CPCM is 11.8 °C and the enthalpy of phase change is 112.86 J/g. The chemical composition of the CPCM was characterized by Fourier transform infrared spectroscopy, which confirmed that the material was successfully developed. When the amount of barium hydroxide octahydrate nucleating agent was 1.0 wt.%, the supercooling of the CPCM decreased to 1.22 °C. CPCM still show good stability after 50 thermal cycles and can be used in practical production.

The solid-liquid phase change material named as PCM-Ca with 49.1% in mass water, 49.7% calcium chloride, and 1.2% strontium chloride was discovered and outlined in this paper. Differential scanning calorimetry, simultaneous thermal analyzer, thermal conductivity analyzer, temperature recorder, and digital vibrating-tube densimeter were used to characterize the thermal properties of PCM-Ca. The results indicated that PCM-Ca has the phase change temperature at 28.7°C, the latent heats in the process of fusing and crystallizing are 193.4 and 193.0 kJ/kg, the thermal conductivity is 1.2801 W/mK at the melting point, and the density is 1.48 ⋅103 kg/m3 at room temperature. Thirty times repeated thermal cycling tests show excellent thermal stability in terms of latent heat and nucleation temperature, and the maximum deviations of the latent heat and the phase change temperature of PCM-Ca are 0.2% and 2.7%, respectively.

4th International Conference on Solar Heating and Cooling for Buildings and Industry (SHC) -- DEC 02-04, 2015 -- Istanbul, TURKEY WOS:000387506400117 Inorganic salt hydrates are promising candidates as latent heat storage materials entailing, for example, a high thermal energy storage density and cheap price [1,2] in spite that they have many handicaps. For almost all applications, Phase change materials (PCMs) have to be encapsulated, that is, they have to be hermetically sealed within barrier containments, preferably within small microcapsules. Encapsulation improves heat transfer, cycling stability, and material compatibility with the environment. However, no attempt has been completely successful to microencapsulate salt hydrates so far due to the high surface polarities of these substances, edge alignment effects, their tendency to alter their water content [3]. This work is aimed to encapsulate some commonly used salt hydrates; sodium sulphate decahydrate (Na2SO4 center dot 10H(2)O) and calcium chloride hexahydrate (CaCl2 center dot 6H(2)O) in a hydrophilic polymer; polyvinyl alcohol (PVA) stably for passive thermal energy storage systems. So that an economically beneficial application mean will be validated. (C) 2016 The Authors. Published by Elsevier Ltd.

Salt hydrates have issues of supercooling when they are utilized as phase change materials (PCMs). In this research, a new method was adopted to prepare a salt hydrate PCM (based on a mixture of calcium chloride dihydrate and calcium chloride anhydrous) as a novel PCM system to reduce the supercooling phenomenon existing in CaCl2·6H2O. Six samples with different compositions of CaCl2 were prepared. The relationship between the performance and the proportion of calcium chloride dihydrate (CaCl2·2H2O) and calcium chloride anhydrous (CaCl2) was also investigated. The supercooling degree of the final PCM reduced with the increase in volume of CaCl2·2H2O during its preparation. The PCM obtained with 66.21 wt % CaCl2·2H2O reduced the supercooling degree by about 96.8%. All six samples, whose ratio of CaCl2·2H2O to (CaCl2 plus CaCl2·2H2O) was 0%, 34.03%, 53.82%, 76.56%, 90.74%, and 100% respectively, showed relatively higher enthalpy (greater than 155.29 J/g), and have the possibility to be applied in buildings for thermal energy storage purposes. Hence, CaCl2·2H2O plays an important role in reducing supercooling and it can be helpful in adjusting the solidification enthalpy. Thereafter, the influence of adding different percentages of Nano-SiO2 (0.1 wt %, 0.3 wt %, 0.5 wt %) in reducing the supercooling degree of some PCM samples was investigated. The test results showed that the supercooling of the salt hydrate PCM in Samples 6 and 5 reduced to 0.2 °C and 0.4 °C respectively. Finally, the effect of the different cooling conditions, including frozen storage (−20 °C) and cold storage (5 °C), that were used to prepare the salt hydrate PCM was considered. It was found that both cooling conditions are effective in reducing the supercooling degree of the salt hydrate PCM. With the synergistic action of the two materials, the performance and properties of the newly developed PCM systems were better especially in terms of reducing the supercooling degree of the PCM. The novel composite PCMs are promising candidates for thermal energy storage applications.

An experimental study is conducted to evaluate a latent storage energy unit inside a tunnel greenhouse. This unit maintains the air temperature inside the greenhouse lower than the diurnal setpoint, during the hot day and higher than the nocturnal temperature, during the cold night. This latent storage unit is constituted of a LPHE (Latent Polypropylene Heat Exchanger) that is filled with a PCM (Phase Change Material). As a result, the diurnal temperature reach inferior to 40 °C, for an air flow rate equal to 280 m3/h and the nocturnal temperature reach superior to 25 °C, for 220 m3/h. An economic evaluation of the LPHE and a comparison with a SPHE (Sensible Polypropylene Heat Exchanger).

CaCl2·6H2O is a salt hydrate that is attractive as phase change material (PCM). However, in literature, different values are indicated for its melting enthalpy. Here, two possible influence factors on the maximum storage capacity of CaCl2·6H2O are investigated via differential scanning calorimetry (DSC): deviations of the water content from the stoichiometrically correct concentration and different basic raw materials used in the preparation process. While both influence factors are found to have a considerable impact on the maximum storage capacity of CaCl2·6H2O, the influence of deviations of the water content is more important than that of the basic raw materials.

This communication presents the comparative study of two different types of thermal management systems for room’s heating applications using calcium chloride hexahydrate as the thermal energy storage material encapsulated in panels and balls. During the daytime, TMS was outside the test room to store the solar heat in TMS. The solar heat made available to charge the PCM from solid to liquid and to warm the test room throughout the observation period during night time. As the room temperature drops significantly during the night time, so as the level of comfort. Both the thermal management systems have been used to heat the test room during night time and the temperature of the test room has been maintained at thermal comfort level without any conventional source of energy, i.e. using passive system. Also the experimental values were compared with those of the theoretical values and are found in good agreement with each other. Thus, it can be concluded that the experimental study carried out for both the thermal management systems have been validated by theoretical approach or vice versa and hence found to be satisfactory towards the successful operation of these systems.

Thermal energy storage performance of a new type of PCM heat exchange tube was researched, in which its main body was based on the traditional structure of a double-tube exchanger and was full of PCM (calcium chloride hexahydrate) in the annular area between the inner tube and the outer tube. The hot air at the temperature of 40°C was chosen as a fluid medium, and the temperature measurements of the test points were made at the inlet and the outlet of this new type of PCM heat exchange tube. The experimental results showed that, this new type of PCM heat exchange tube could store thermal energy from the hot air by means of PCM (calcium chloride hexahydrate) in the annular area, whose performance laid good foundations for its engineering applications for recovery and utilizations of greenhouses, air conditioning and industrial afterheat or waste heat etc.

This communication presents the experimental study of PCM based thermal management systems for space heating and cooling applications using energy and exergy analysis. Two different types of based thermal management system (TMS-I and TMS-II) using calcium chloride hexahydrate as the heat carrier has been designed, fabricated and studied for space heating and cooling applications at a typical climatic zone in India. In the first experimental arrangement the charging of PCM has been carried out with air conditioning system while discharging has been carried out using electric heater for both the thermal management systems. While in the second arrangement the charging of PCM has been carried out by solar energy and the discharging has been carried out by circulating the cooler ambient air during the night time. In the first experiment, TMS-I is found to be more effective than that of TMS-II while it was found to be reverse in the case of second experiment for both the charging and discharging processes not only for energetic but also for the exergetic performances.

Phase change temperature adjustment of calcium chloride hexahydrate added small quantity of barium hydroxide and strontium chloride hexahydrate was researched. The experimental results demonstrated that, its phase change temperature adjustment could be achieved by means of adding excess water, and its suitable adjustment range of phase change temperature was 21.76°C-26.16°C as the proportion of the added excess water was 0-10% by weight. According to the calculation equation gained by the theoretical regression of the experimental results, its phase change temperature with different proportions of excess water may be forecasted during the suitable adjustment range of phase change temperature. This characteristic is of important application value for temperature control in greenhouse or air conditioning etc.

In this study, experiments are conducted to investigate melting and solidification characteristics of calcium chloride hexahydrate (CaCl2.6H2O) as a phase change material (PCM). In the present study, some parameters that affect the melting and the solidification time of PCM used to store low temperature energy have been observed experimentally. These parameters are inlet temperature and mass flow rate of water used as a heat transfer fluid (m = 2.51, 3.75, and 4.95 kg min−1), fin numbers inside the PCM. For this purpose, PCM has been stored constantly between the coaxial pipes and water adjusted to 45°C for the melting process and to 5°C for the solidification process, and was circulated by a pump through the inner pipe at the experimental setup. During the experiments, when the water mass flow rate is increased to 49 and 97% with respect to the starting mass flow rate (m = 2.51 kg min−1), a rate of 5 and 15% decrease at the melting time is obtained, respectively. As a result, it has been observe...

This paper thermo-physically characterizes salt hydrate, paraffin wax and milk fat as phase change materials (PCMs). The three PCMs are compared in terms of improving heat sink (HS) performance for cooling electronic packaging. An experimental study is carried out on commercially available finned HS with and without PCM under natural ventilation (NV) and forced ventilation (FV) at different heat loads (4 W to 10 W). The results indicate that integration of all of the PCMs into the HS improves its cooling performance; however, milk fat lags behind the other two PCMs in terms of cooling produced. A three-dimensional pressure-based conjugate heat transfer model has been developed and validated with experimental results. The model predicts the parametric influence of PCM melting range, thermal conductivity and density on HS thermal management performance. The HS cooling performance improves with increased density and conductivity while it deteriorates with the wider melting range of the PCMs.

Etude de la stabilite au cyclage thermique de l'hexahydrate de chlorure de calcium additionne de differents chlorures. Mesure de la chaleur latente de fusion de ce sel

This paper reports on research into storing energy at ambient temperatures by use of phase change materials mainly based upon CaCl2, 6H2O. This process has a highly reversible solid-liquid equilibria that will not degrade for thousands of cycles. Different compositions, from pure stabilized calcium chloride hexahydrate (phase transition Θ ≃ 28.2°C, ΔH = 190–200 J/g) to multicomponent solutions with KCl and NH4Cl (existence of two eutectic valleys, 22.5-25°C temperature range, and ΔH ≃ 190–200 J/g), have been studied and characterized by differential scanning calorimetry. Solutions containing nitrate ion and showing the existence of an anion exchange reaction lead to the formation of an eutectic compound (phase transition Θ ≃ 19.7°C and ΔH ≃ 170–180 J/g). From a rough analysis of the Cp signals, which are very sensitive to slight composition changes, the influence of several parameters on the behavior of these solutions was studied.

The way in which strontium chloride hexahydrate prevents the supercooling of latent heat storage systems based on calcium chloride hexahydrate was investigated. It can be established from the ternary equilibrium system CaCl2SrCl2H2O and proved also experimentally that crystals of strontium chloride hexahydrate separated from one another are unsuitable for the prevention of the supercooling of calcium chloride hexahydrate melts, because of the dehydrating properties of the melt. Cohering agglomerates (of 2–3 cm) of microcrystals, containing adhering water, preserve for a much longer time their nucleating property, because concentration conditions established in the interior of the aggregation differ from the composition needed for the melt. The life of the nucleating agent depends on the length of time for which this concentration gradient is equalized by diffusion processes.

Experimental results of DSC analyses of binary mixtures of calcium chloride hexahydrate and ammonium chloride are presented and analysed. Evidence for the formation of a mixed compound CaCl 2 · 2NH 4 Cl · 2H 2 O is given.

Mixtures of CaCl2·6H2O with some nitrate hydrates [Ca(NO3)2·4H2O and Mg(NO3)2·6H2O] or anhydrous nitrates NH4NO3 and KNO3) were studied as latent heat storage materials for greenhouse purposes. The melting points and the heats of fusion of these mixtures showed no deterioration after thermal heat cycles (30°-10°C, 1000 times). Temperature data of solidification both for vertical and horizontal sample tube settings were given.

An improved method for measuring the enthalpy of melting of salt hydrates in large nonstirred samples is presented. Results for calcium chloride hexahydrate are around 200 J/g. The decline of this value with consecutive cycles of cooling and heating is due to stratification followed by degradation to the tetrahydrate. The application to heat storage is discussed. A procedure for an accelerated stability test is proposed.

Samples of calcium chloride hexahydrate containing varying amounts of KCl in combination with SrCl2, BaSO4 and NaCl have been prepared and studied by thermogravimetric and differential scanning calorimetric methods. The additives improve the stability of the intermediate hydrate and change the stoichiometry of the dehydration process.

The stability of calcium chloride hexahydrate with an admixture of nucleating agent was tested during 1000 cooling—heating cycles and was found satisfactory. The experimental set-up based on computer monitored heating and natural cooling in a cold room is described. Addition of lithium chloride decreases phase transition temperature, but affects the stability.

Etude calorimetrique de l'influence d'additions de chlorure de potassium ou de bromure de calcium hexahydrate sur le comportement a la fusion du chlorure de calcium hexohydrate

A new mineral, calcium chloride hexahydrate, was discovered in the Don Juan Pond in Victoria Land, Antarctica. The optical properties, chemical analysis, and powder patterns obtained by x-ray diffraction agree with those of artificial calcium chloride hexahydrate. The name Antarcticite is proposed for the new mineral.

Low-cost, impure grades of calcium chloride hexahydrate appear technically promising and economically attractive as low temperature energy storage media. Results to date of continuing, long-term durability studies show stable performance and suggest that incongruent melting and supercooling tendencies of this salt have been overcome. Passive and active methods of recovering stored heat from the salt medium are discussed.

The results from the experimental testing of a latent heat storage unit containing calcium chloride hexahydrate are presented. Thermal performance data are evaluated from the experimental results by the aid of a quasi-stationary heat transport model and the procedure employed seems well suited both for the rating and for the optimization of latent heat storage units.