Calcium Chloride Hexahydrate Research Articles

Mutability of Nucleation Particles in Reactive Salt Hydrate Phase Change Materials.

Nucleation particles, solid phases dispersed throughout a medium to decrease the energy barrier for solidification or other reversible phase transitions, are generally selected on the basis of structural or interfacial energy considerations between the host phase and the solid phase that is crystallizing. However, the existence of chemical reactions between the nucleation particles and the host phase can obscure these underlying relationships, thereby complicating the process of selection of active nucleation particle phases. Here, we reveal the origin of nucleation activity of barium-based nucleation particles in the salt hydrate calcium chloride hexahydrate (CCH), a candidate for near room temperature thermal energy storage. We demonstrate that these compounds undergo a series of cation exchange and secondary precipitation reactions, resulting in an assemblage of solid precipitates with some degree of limited solid solution, which collectively dramatically reduce undercooling in CCH, but which obscure the identification of a single crystalline phase primarily responsible for the nucleation of crystalline CCH from the liquid. Importantly, this result illustrates a pathway to harness in situ chemical reactions to generate stable active nucleation particles in reactive phase change materials, which may not be readily synthesized by alternative methods, or which may not be active or remain stable when added in isolation.

Experimental investigation of distilled water production performance of conventional solar stills using CaCl2·6H2O phase change material reinforced with SrCl2·6H2O and graphene-based nanoparticles

This study aims to enhance the performance of conventional single-slope basin-type solar stills by integrating phase change materials (PCMs) and nanoparticles. Calcium chloride hexahydrate, known for its high heat storage capacity, was selected as the primary PCM. Strontium chloride hexahydrate was added as a nucleating agent to address the supercooling tendency. Additionally, graphene oxide (GO) and graphene nanoplatelets (GNP), which have not been previously used in solar stills or compared for their performance, were incorporated into the PCM to utilize their photothermal properties and enhance solar energy absorption. The integration of GO and GNP with the PCM-nucleating agent combination resulted in daily total distilled water productions of 5424ml/m2 and 5032 ml/m2, respectively. The integration of GO with the PCM-nucleating agent combination provided the most significant improvement in efficiency, with a 54.44 % increase compared to the standard still, a 15.4 % increase compared to the still using only the nucleating agent, and an 8 % increase compared to the still incorporating GNP.

Manufacturing of Continuous Core–Shell Hydrated Salt Fibers for Room Temperature Thermal Energy Storage

The encapsulation ofsalt hydrate phase change materials (PCMs) in uniform microscale bodies has yetbeen reported in research due in part to the delicate relationship betweenthermal performance and water‐to‐salt ratios which are easily altered duringmanufacturing. Herein, core–shell composite fibers comprised of a salt hydratePCM core and a poly(acrylonitrile) (PAN) shell are wet spun in a continuousprocess using a syringe pump and coaxial die. The PCM phase comprises calciumchloride hexahydrate (CaCl2·6H2O) with strontium chloride hexahydrate(SrCl2·6H2O) (3 wt%) and fumed silica(SiO2) (2 wt%) as additive, acomposition that is prepared from homogenous melt at 40 °C. 15 wt% PAN indimethylsulfoxide solvent is used to prepare the shell‐forming polymer gel. PCM and polymer gel injectionrates of 10–40 mL h−1 are used tospin coaxial fibers through a coagulation bath, yielding continuousmicrotubules with diameters in the range of 850–1500 μm. Cyclic testing showsthat after 1000 cycles, melting enthalpies incurred only a 3.5% decline from 131.46 to 126.9 J g−1. Success hereovercomes several coincidental drawbacks of PCM fiber performance andmanufacturing and delivers the first example of scalable roll‐to‐roll PCM fiber produced by wet spinning forbuilding material applications.

Computational and experimental analysis of PCM-infused brick for sustainable heat regulation

Examining the thermodynamics of phase change materials (PCMs) when merged into construction materials is a significant subject within the realm of building science and environmental responsibility. When infused to construction materials like bricks, PCMs have the capacity to elevate a building’s temperature regulation by minimizing the energy required for thermal contentment. This research is dedicated to learn about the thermal conduct and the consequences of the fusion of calcium chloride hexahydrate mineral (CCHPCM) within the pores of a masonry unit. To achieve this, we implemented a practical testing specifically designed to scrutinize how CCHPCMs alter the thermal performance of studied compounds. Multiple configurations were designed by adjusting the arrangement of CCHPCM within the bricks, resulting in three distinct setups. The first set involved filling one row of the bricks, the second set entailed filling two rows, and the final configuration entailed filling all the pores with PCM. Additionally, a computational modeling was executed to survey the thermic behavior of bricks infused with CCHPCM, operating with COMSOL Multiphysics application program. The elaborated work concluded to having an enhancement of the brick’s thermal storage capacity, for Set-3, in which all rows of bricks are filled with PCM, a delay of 2 h is observed compared to Set-0 the brick without CCHPCM. This simulation also encompassed comparative findings regarding the thermal performance of CCHPCM when incorporated into the masonry unit. Overall, this study supplied the valorization of CCHPCMs infused in masonry units and their usage in distinct layouts on upgrading its candidature to achieving environmental responsibility.

X-ray computed tomography analysis of calcium chloride hexahydrate solidification

Latent Thermal Energy Storages (LTESs) are receiving increasing interest, since they offer many advantages to the field of Thermal Energy Storages (TESs), such as a nearly isothermal solid–liquid phase transition and a high energy storage density. To boost the transition towards a climate-neutral future, a lot of work is surely needed on Phase Change Materials (PCMs) which are used inside LTESs. Salt hydrates, a particular class of PCMs, are very attractive in terms of cost and volumetric latent enthalpy but present drawbacks that still limit their effective deployment in real applications, such as supercooling and phase separation (or segregation). The current work assesses the suitability of X-ray Computed Tomography (XCT) as a novel technique in the field of LTESs to study the solidification of phase-change materials. In this study, calcium chloride hexahydrate (CaCl2·6H2O) is chosen as a representative PCM and the results derived are shown to be repeatable. For the first time, the direct measurement of the volumetric liquid fraction is correlated to temperature measurements allowing for the visualisation of supercooling and the validation of an enthalpy-porosity numerical model, which could be useful in the design of LTES. XCT methodology offers unmatchable features as compared to the other method to measure the volumetric liquid fraction. Given its accuracy and the rigorous protocol, it can be considered as a benchmark for new liquid fraction measurement technologies but it also permits to study how the different PCMs melt and solidify, giving new insights on the mechanisms at the basis of the most crucial challenges, among those: subcooling, segregation, and metastable phase change.

Preparation and investigation of a prefabricated salt hydrate phase change material partition for passive solar buildings

The incorporation of phase change material (PCM) into building structures offers a pathway for passive energy storage, enabling adaptable indoor temperature control and alleviating energy consumption. Despite these advantages, the widespread adoption of PCM in building structures faces challenges due to extended payback periods. In this study, a novel and cost-effective salt hydrate PCM composite, comprised of calcium chloride hexahydrate–potassium chloride (CCH–KCl), was developed. Melamine foam (MF) and strontium chloride hexahydrate (SCH) were synergistically utilized to address phase separation and supercooling issues. Numerical simulations were conducted to assess the performance of the developed salt hydrate PCM composite in building partition walls. Specifically, incorporating a 20 mm-thick composite resulted in peak temperature reductions of 0.72 °C during normal operation and 1.01 °C during power outages compared to structures without PCM, accompanied by a substantial reduction in energy consumption by 5376.68 kWh/year. Moreover, the cost of the developed salt hydrate PCM is 89.33 % lower than industrial paraffin, and it reduces CO2 emissions by 1.40 kg/year/m2 compared to paraffin's 1.11 kg/year/m2. In summary, the developed salt hydrate PCM composite exhibits commendable thermal regulation and economic advantages in building applications, serving as a pivotal contributor to emission reduction efforts.

Analysis of melting behavior of layered different phase change materials for a cylinder insert into a channel

Phase change materials (PCMs) have diverse fields of application due to higher thermal inertia. The present study explores the melting behavior in dual-layered different PCMs in a cylindrical lithium-ion battery module placed in a long channel under the hot air stream. The main cylinder is packed with paraffin wax and covered PCM is chosen as calcium chloridehexahydrate (CaCl2-6H2O). The material between two PCMs is considered highly conductive and impermeable. The involved mathematical equations in two-dimensional forms are numerically simulated the applying the finite volume technique. The primary important parameters of melting behavior are the difference in temperature and inlet air velocity. The analysis is carried out for the effective parameters such as the inlet air temperature (Thot = 100 °C and 120 °C) and air velocity (սair = 2.5 and 5.0 m/s). The results revealed that an increase in air velocity reduces the highest and average temperature of the PCM. The changes in melting time of PCMs decline with time. Higher inlet air temperature also causes fast melting of the PCMs over time. The analysis revealed that the application of PCMs is undue when there is no phase change process. The analysis also revealed that an increment in the inlet air velocity causes a decrease in the average temperature. For the same air inlet temperature (Thot) higher air velocity leads to a slower rate of the melting process Therefore, melting time is less by ∼ 30 % (for the inner layer) and 32 % (for the outer layer) with decreasing air velocity. The findings of this study will help the designer to improve the battery thermal management system by modulating the temperature.

X-ray computed tomography tracking of the calcium chloride hexahydrate crystallisation process

The research conducted on phase change materials (PCMs) for latent thermal energy storages (LTESs) is continuously growing in terms of publications, highlighting the importance of this topic. In fact, PCMs present many advantages that could help the energy transition and reduce CO2 emissions, by enhancing the performance of existing systems and better exploiting renewable energy. Therefore, it is of crucial interest to develop new and reliable methods to control LTES. Differently from sensible thermal energy storages, in LTESs the stored thermal energy is not proportional to the temperature. To really have an insight into the level of charge of these storages, it is important to know the liquid fraction, i.e., the amount of the liquid phase with respect to the whole amount of PCM. X-ray computed tomography (XCT) is a technology that allows to non-intrusively “look inside” the materials. In the current study, it was used to analyse the calcium chloride hexahydrate crystallization. This transient process of calcium chloride hexahydrate was tracked with a sequence of XCT scans, one every 6 minutes, resulting in 3D image stacks that were processed to obtain the volumetric liquid fraction evolution over time. Repeatability tests were run to evaluate the reliability of the XCT technique and the volumetric liquid fraction data was used to validate a numerical model developed within ANSYS Fluent framework. XCT offers great opportunities to study the heat and mass transfer mechanisms underlying the main issues of phase change materials, like, for example, supercooling and salt hydrate segregation.

Multifunctional applications of passive solar stills in water treatment: an eco-friendly approach

Conventional raw water treatment methods are expensive and require a sufficient energy supply for their operations. In remote and rural areas, these conventional methods are feasible due to a poor economy and interrupted power supply. This study provides a sustainable approach to treating raw water using solar energy and phase change material (PCM). Passive solar stills (SS) are sufficient to treat water in the presence of solar radiation, and we can increase the yield and quality of distillate water by using calcium chloride hexahydrate as a phase change material. Moreover, PCM-based solar still is also advanced by adding activated charcoal (AC) for the removal of fluoride from the raw water. The efficiency of the solar still was assessed for the eight parameters: yield (Y), fluoride (F), total dissolved solids (TDS), electrical conductivity (EC), pH, total alkalinity (TA), total hardness (TH), chloride (Cl). Through the number of water quality assessments, it was found that SS with PCM can reduce (%) the TDS (85%–100%), EC (90%–100%), pH (0%–15%), TH (90%–95%), TA (75%–90%), and Cl (80%–100%) and can increase the yield by 10%–15%. SS with PCM and AC also showed good removal of F from raw water. In addition to that, a statistical analysis was also carried out to understand the effect of different climatic factors on the performance of solar stills.

Preparation, characterisation and property modification of a calcium chloride hexahydrate phase change material slurry with additives for thermal energy transportation

Efficient thermal energy distribution and rational energy management are effective solutions to address the significant and fast-ascending energy consumption in building heating, ventilation, and air conditioning (HVAC). Phase change material (PCM) slurries with excellent thermal energy transportation and storage characteristics have been recognised as promising secondary refrigerants to simultaneously facilitate efficient heat/cold transport and effective thermal energy storage in air conditioning systems. Among various PCM slurries, salt hydrate PCM slurries have attracted increasing attention in recent years due to their many inherent advantages. This paper presented the preparation, characterisation, and property modification of a CaCl2·6H2O slurry based on a methodology proposed for optimal salt hydrate PCM slurry development. Theoretical modelling was first carried out to assess the availability of salt hydrate PCM slurries based on the phase diagram and solid fraction, followed by a series of property measurements to reveal the mechanisms and address the problems behind the phase transition, crystal particle morphology, stability and rheologic characteristics, using nucleating agents, surfactants and stabilisers. It was found that the salt hydrate PCM slurry developed provides a unit volume enthalpy twice that of water over the phase change temperature range of 5°C, together with acceptable fluidity. The results also showed that the PCM particle size can be well controlled, and the slurry can be stabilised, with the assistance of surfactants and stabilisers. Compared to other types of PCM slurries, the proposed salt hydrate PCM slurry has the advantages of being cost-effectiveness, easy preparation, adjustable phase change temperature, etc., which is promising to facilitate energy saving and rationalisation in building HVAC.

Calcium chloride hexahydrate based supercooling phase change material for a long-term recovery of low-grade thermal energy

The low-grade waste thermal energy massively exists in industrial processes and is difficult to be recovered in a long-term manner due to severe heat loss. This study presents a group of calcium chloride hexahydrate (CCH)-based phase change materials (PCMs) with a large degree of supercooling and high latent heat. The large degree of supercooling of the proposed PCMs could harness the low-grade thermal energy, store the latent heat in a long-term manner and release the heat by a trigger when required. A group of composite phase change material (CPCM) is proposed based on CCH as the core salt hydrate, calcium chloride as the solute, and polyethylene glycol (PEG 200) as the additive. This CPCM has a large supercooling capacity and high thermal storage density. The optimal ratio of CPCM components is found to be 88.9 wt% CCH with 2.22 wt% PEG 200, and 8.88 wt% CaCl2 with a phase transition temperature of 29.8 °C and a latent heat value of 193.74 kJ/kg. This represents a 35.6 % increase in latent heat compared to the pure CCH with a latent heat of 142.85 kJ/kg. Additionally, the reason for the addition of PEG 200 to improve CCH supercooling has been explored. This article creatively proposed the use of solubilizer PEG 200 to significantly increase the latent heat value and supercooling degree of hydrated salt PCMs, providing a promising direction for the preparation of large-scale supercooled high latent heat CPCMs to recover ultra-low-grade waste heat energy.

Exploring mushy zone constant in enthalpy-porosity methodology for accurate modeling convection-diffusion solid-liquid phase change of calcium chloride hexahydrate

Mushy zone constant (Am) is a crucial parameter in the momentum source term of enthalpy-porosity technique for modeling convection-diffusion solid-liquid phase change. Literature survey on the computations of Am found that the oriented customizable approaches have not revealed it in detail. Although the literature conducted an attempt on Am relationship by investigating the unconstrained melting of Calcium Chloride Hexahydrate (CaCl2·6H2O), they failed to directly establish the correlation between Am and ΔT; where ΔT is the driving temperature difference, which denotes an excess temperature of the hot wall above melting point of the CaCl2·6H2O. In view of the shortcoming in the literature, the relationship between Am and ΔT is here explored by the dimensionless analysis of the CaCl2·6H2O melting. The analysis finds a perfect correlation of dimensionless mushy zone constant (A) in terms of Grashof number (Gr) and Stefan number (Ste), i.e., A=Gr0.639Ste−2.947. Hence, a quick calculating method concerning Am values is established successfully. Then, the numerical verifications and validations for Am values implemented in enthalpy-porosity model are carefully taken into account. In addition, the theoretical reasonability is confirmed for the extrapolated Am values, and two interesting solid shapes of “Cap” and “Umbrella” are presented. Considering all of the applicable conditions herein, a generalized expression for melting fraction vs. dimensionless time is finally proposed.

A Eutectic Mixture of Calcium Chloride Hexahydrate and Bischofite with Promising Performance for Thermochemical Energy Storage

Thermochemical energy storage using salt hydrates is a promising method for the efficient use of energy. In this study, three host matrices, expanded vermiculite, expanded clay, and expanded natural graphite were impregnated with a eutectic mixture of CaCl2·6H2O and bischofite (MgCl2·6H2O). These composites were subjected to various humidity conditions (30–70% relative humidity) at 20 °C over an extended hydration period to investigate their cyclability. It was shown that only expanded natural graphite could contain the deliquescent salt at high humidity over 50 cycles. Hence, the expanded natural graphite composites containing either CaCl2·6H2O or CaCl2·6H2O/bischofite eutectic mixture were placed in a lab-scale open packed bed reactor, providing energy densities of 150 and 120 kWh/m3 over 20 h, respectively. The eutectic composite showed slightly lower temperature lift, water uptake rate, and power output but at reduced cost. Using the eutectic mixture also decreased the composite’s dehydration temperature at which the maximum mass loss rate occurred around 16.2 °C to 62.3 °C, allowing recharge using less energy-intensive heating methods. The cost of storing 1 kWh of energy with expanded natural graphite composites is only USD 0.08 due to its stability. This research leveraging cost-effective composites with enhanced stability, reaction kinetics, and high thermal energy storage capabilities benefits renewable energy, power generation, and the building construction research communities and industries by providing a competitive alternative to sensible heat storage technologies.

Numerical investigation on thermal performance of a solar greenhouse with synergetic energy release of short- and long-term PCM storage

To address the problem of low greenhouse temperature at late night in north China, a new strategy of synergetic release of short- and long-term PCM heat storage is proposed in this paper, i.e. supercooled salt hydrate units are activated to release seasonally stored latent heat after the organic PCM north wallboard with daily storage cannot provide the required indoor temperature. To achieve this strategy, a microclimate model considering multiple greenhouse elements, including solar radiation, crops, indoor air, water vapor, soil and PCMs, is developed and 3D computational fluid dynamic (CFD) simulations are employed to examine the thermal performances of this strategy under Beijing climate conditions. The results demonstrated that the new strategy promotes the greenhouse temperature suitable for tomato growth (15 °C) throughout the whole night in winter. The organic PCM (Tm = 25 °C) wallboard can reduce the daytime indoor temperature by 0.5–1.5 °C and increase the nighttime indoor temperature by 4–5.5 °C than without PCM wallboard on January 1st. But the greenhouse temperature with this single daily storage is still lower than the required 15 °C after 4:00 a.m. With consideration of the unit numbers and heating effects, triggering two supercooled sodium thiosulfate pentahydrate (STP) units at one time (rather than sodium acetate trihydrate (SAT) and calcium chloride hexahydrate (CCH)) is the reasonable choice for greenhouse heating under present conditions. The system can achieve synergetic energy release across seasons, days and nights, regulate the thermal environment in the greenhouse, and promote the quantity and quality of crop output.

Experimental study of single-phase change material thermal diode based on calcium chloride hexahydrate

Phase change material thermal diodes designed on the basis of different heat transfer forms and coefficients caused by different phase transition degrees in opposite heat transfer directions are considered as potential thermal management devices. However, the use of a variety of materials or only relying on numerical simulation research makes its structure complex or idealized, which reduces the possibility of practical application. Therefore, in this work, a simple thermal diode structure containing only CaCl<sub>2</sub>·6H<sub>2</sub>O single-phase variable material is proposed in combination with changes in heat transfer form and heat transfer coefficient in solid-liquid phase change and natural convection process. The corresponding device is prepared, and a steady-state heat flux test system is set up for experimental study, the measured results are close to those recorded in the literature with good accuracy. The influence of the temperature difference between hot end and cold end and the direction of positive heat transfer and negative heat transfer on the thermal rectification effect of the thermal diode are studied experimentally. The results show that the heat flux of the thermal diode decreases with the decrease of the difference in temperature between the cold source and hot source, and the thermal rectification ratio reaches to 1.58 when the forward and reverse along the antigravity direction and gravity direction, respectively. The optimal cold source temperature range is 20–25 ℃, which is close to room temperature. The proposed phase change material thermal diode structure has a certain application potential in energy saving and thermal management of building.

Evaluation of Phase Change Materials for Pre-Cooling of Supply Air into Air Conditioning Systems in Extremely Hot Climates

This research investigates the use of phase change materials (PCMs) in thermal energy storage (TES) unit-based cooling systems to increase the efficiency of air conditioners (ACs) by reducing the air inlet temperature. This study aims to evaluate different configurations of PCM enclosures, and different PCMs (paraffin and salt hydrate), by changing the speed of inlet air to achieve heat reduction of inlet air. The study includes experimental and simulation investigations. Every configuration simulates the hot-season atmospheric conditions of the UAE. A duct containing enclosures of paraffin RT-31 and salt hydrate (calcium chloride hexahydrate) was used for the simulation study using ANSYS/Fluent. A conjugate heat transfer model employing an enthalpy-based formulation is developed to predict the optimized PCM number of series and optimum airflow rate. Four designs of the AC duct were modelled and evaluated that contained one to four series of PCM containers subjected to different levels of supplied air velocities ranging from 1 m/s–4 m/s. The simulation study revealed that employing four series (Design 4) of PCM enclosures at a low air velocity of 1 m/s enhanced the pre-cooling performance and reduced the outlet air temperature to 33 °C, yielding a temperature drop up to 13 °C. The performance of salt hydrate (calcium chloride hexahydrate) was observed to be better than paraffin (RT-31) in terms of the cooling effect. Characterization of paraffin wax (RT-31) and salt hydrate was performed to establish the thermophysical properties. The experimental setup based on a duct with integrated PCM enclosures was studied. The experiment was repeated for three days as the repeatability test incorporating RT-31 as the PCM and a 3 °C maximum temperature drop was observed. The drop in the outlet air temperature of the duct system quantifies the cooling effect. Net heat reduction was around 16%.

Hybrid Polymer Salogels for Reversible Entrapment of Salt-Hydrate-Based Thermal Energy Storage Materials.

One of the challenges preventing wide use of inorganic salt hydrate phase change materials (PCMs) is their low viscosity above their melting point, leading to leakage, phase segregation, and separation from heat exchanger surfaces in thermal management applications. The development of a broad strategy for using polymers that provide tunable, temperature-reversible shape stabilization of a variety of salt hydrates by using the lowest possible polymer concentrations is hindered by differences in solubility and gelation behavior of polymers with change in the type of ion. This work addressed the challenge of creating robust, temperature-responsive shape-stabilizing polymer gels (i.e., salogels) using a low cost PCM, calcium chloride hexahydrate (CaCl2·6H2O, CCH). Due to the extremely high (9 M) concentration of chloride ions and the tendency to salting-out polymer chains, the previous strategy of using single-polymer salogels was not successful. Thus, this work introduced a strategy of using two polymers, poly(vinyl alcohol) and ultrahigh molecular weight polyacrylamide (PVA and PAAm, respectively), along with borax as a cross-linker to achieve temperature-reversible, shape-stable salogels. This system resulted in robust salogels whose gel-to-sol transition temperature (Tgel) was tunable within an application-relevant range of gelation temperature (30-80 °C). This behavior was enabled by a synergistic combination of dynamic covalent cross-links between PVA units and entanglements of PAAm chains which were combined into a single hybrid network. The hybrid salogels had <5 wt % polymer content, maintaining ∼95% of the heat of fusion of the pure PCM. Importantly, the noncovalent nature of gelation supported thermo-reversibility of gelation, shape stability, and retention of thermal properties over 50 melting/crystallization cycles.

Enhanced thermal reliability and performance of calcium chloride hexahydrate phase change material using cellulose nanofibril and graphene nanoplatelet

In recent years, thermal energy storage (TES) has gained attention for its role in enhancing renewable energy solutions and sustainable energy consumption. The usage of strontium chloride hexahydrate (SCH), graphene nanoplatelet (GNP), and cellulose nanofibril (CNF) additives were investigated to enhance the performance of calcium chloride hexahydrate (CCH) based on the melting/solidification behavior for TES applications. In this work, we develop a promising phase-change-material (PCM) formulation by introducing these additives that reduce supercooling, improve the thermal conductivity and stabilizing the energy storage capacity of CCH. Rheological characterizations demonstrated that the addition of 1 wt% of CNF into CCH produced the required improvement in viscosity and boosted solid-like rheological behavior. Structural characterizations show a physical mixing of the materials within the PCM composites. Our observations show that the amphiphilicity of CNF enables the surface attachment to GNP via hydrophobic interactions providing effective dispersion of GNP throughout the PCM composite. The addition of a nucleating agent, SCH decreased the degree of supercooling of ∼20 g of CCH from >20 °C to 3 °C at a cooling rate of 5 °C/min. Thermal characterization showed the resulting PCM composite has a latent heat of melting of 186 Jg−1, phase change temperature of 32 °C, and stable thermal properties after being subjected to 70 melt-freeze cycles. Adding CNF and GNP to pure CCH increased its thermal conductivity by 76 %. The high thermal conductivity of GNP and its effective dispersion by CNF is responsible for this enhancement. The study highlights the use of biodegradable nanocellulose for the preparation of sustainable PCM composites with improved performance. These PCM composites are scalable, they have potential to increase energy efficiency and revolutionalize the heating/cooling applications in buildings and other TES systems.

A phase change material (PCM) based novel retrofitting approach in the air conditioning system to reduce building energy demand

Improvement in air quality and reduction of airborne diseases can be effectively achieved by inducing fresh air into the building. However, this challenges the building’s energy consumption. As a proposed solution, the present study dwells into the use of phase change materials (PCM), a heat-based exchanger, as a retrofit with a Heating Ventilation and Air-conditioning system (HVAC), to extract thermal energy from fresh air and consequentially diminish the energy demand. Calcium chloride hexahydrate (CaCl2·6H2O) is used as PCM, selected by TOPSIS method based on entropy weights. The energy saved in the augmented PCM thickness (from 20 mm to 100 mm) and added longitudinal fins (5 mm in width and 50 mm in length) is assessed in comparison to the standard HVAC systems utilizing R134a. For summers in composite climate, the HVAC system retrofitted with a heat exchanger with 100 mm PCM thickness 48 fin configuration achieved peak and average energy savings of 12 % and 9 %, respectively, when the system operated for 6 h. For PCM thicknesses of 75 mm, 50 mm, and 20 mm, the maximum energy savings were 6.64 % with 48 fins, 5.22 % with 24 fins, and 3.22 % with 12 fins, respectively. The study provides policymakers with energy-efficient and sustainable solutions for HVAC systems, which can reduce energy demand and help combat climate change.

Optimizing supercooling and phase stability by additives in calcium chloride hexahydrate for cyclical latent heat storage

Calcium chloride hexahydrate (CaCl2·6H2O) based phase change material (PCM) is promising for latent heat storage due to its favorable thermal properties, but supercooling and thermal cyclic instability limits its wider application. We examine the role of nucleation agents, in particular strontium chloride hexahydrate (SrCl2·6H2O), as an additive to the PCM, on the degree of supercooling and the latent heat. Utilizing a water bath and a cooling chamber, we systematically evaluate the degree of supercooling in various PCM samples, while X-Ray diffraction and microscopic analysis are employed to characterize the role of the additive. The results suggest that particle shapes of the additives and their crystallographic phase contribute significantly to supercooling suppression. Optimizing a tradeoff between supercooling and latent heat reduction for long-term nucleation performance, we identify designer PCM composition with an optimal 3 wt% of SrCl2·6H2O for an automated thermal cycling system by differential scanning as well as drop calorimetry. Incorporating 2 wt% potassium chloride (KCl) shifts the composition at the peritectic point away from the unfavorable CaCl2·4H2O phase, enhancing the freeze-thaw cycle stability of CaCl2·6H2O. Notably, the latent heat variation is ∼0.08% over 1000 freeze-thaw cycles.