Commercial Phase Change Materials Research Articles

A novel approach for the active‐mode indirect drying of food grains with high temperature thermal energy storage system

AbstractThis article introduces a novel approach for the active‐mode indirect drying of food grains using an independent high‐temperature thermal energy storage (TES) system. It uses commercial software to conduct numerical analysis of a solar drying unit fused with indirect TES. Employing commercial grade phase change material X‐180, solar drying unit incorporates scheffler dishes, receiver, TES, thermic fluid pump, air blower, and dryer fitted with a radiator. Heat transfer fluid Thermenol‐66 has been used to facilitate the heat transfer from receiver to TES and dryer. Two distinct TES designs, one without fins (case A) and the other with fins (case B), have been used to encapsulate phase change material and facilitate the flow of heat transfer fluid. The dynamic performance of independent solar drying unit components was examined at various mass flow rates during charging and discharging process. The results demonstrate that adding 42 fins, i.e. (case B), reduces the charging and discharging time to 22% and 24%, respectively. Due to high charging and discharging power, the rate of temperature change in case B is 19% higher compared to case A. To maintain drying quality, the dryer should have a continual flow of hot air at a constant temperature. Therefore, utilization of the TES, case A, provides a significantly higher uniformity index and a more extended drying period during the discharge process.

Thermo-Chemical Characterization of Organic Phase Change Materials (PCMs) Obtained from Lost Wax Casting Industry

The high global energy demand drives the search for sustainable alternatives for energy production and storage. Among the most effective solutions are phase change materials (PCMs). In particular, organic PCMs offer a high capacity to store and release thermal energy in response to external thermal variations, even over a wide temperature range. They find profitable applications in various sectors, from construction to electronics, offering flexibility and considerable energy storage according to need. In the search for new and effective PCMs, reusing by-products from different industries would offer both economic and environmental benefits. With this goal in mind, several organic PCMs with different characteristics and origins were analyzed in the present study. Two of them were by-products of the lost wax casting industry. In fact, we wanted to verify whether this waste could be employed as an effective, low-cost PCM. For comparison purposes, two commercial PCMs were selected, namely a paraffin and a microencapsulated PCM. Finally, a PCM blend was produced by mixing a commercial PCM and a waxy by-product. The five selected or developed PCMs were subjected to different tests to investigate their chemical composition, thermal characteristics, and thermal stability before and after repeated (i.e., 100) cycles of melting and crystallization processes. The results demonstrated that the durability of the non-commercial PCMs with regard to thermal loads was not inferior, and was in some cases even superior, to commercial PCMs. This study therefore proposes an innovative path to reuse the by-products of different production processes to support the environment.

Development and Investigation of Nitrate Phase Change Filler Material for Solar Process Heating Applications

Thermocline thermal energy storage system is an imperial system for solar process heating applications. The thermal energy storage system comprises filler material and heat transfer fluid. In the present study, the commercial phase change material (PCM) (filler material) solar salt (60%NaNO3+40%KNO3) is synthesized, and it is encapsulated with a 1mm thickness of stainless steel 316L encapsulation with the macro-size of 60mm; the encapsulated PCMs is considered as a single particle in the thermocline thermal energy storage system. The performance of the single encapsulated PCM is studied with a constant heat transfer fluid (Therminol-VP1) flow rate of 0.00015 kg/s during the charging process. The specific heat of the solar salt is measured in Differential Scanning Calorimeter (DSC) in the solid phase is found as 1.381 J/gK, and liquid phase is identified as 1.551 J/g-K, the enthalpy during the phase change process is found as 116.72 J/g. As well, the thermal conductivity of the solar salt is measured in Transient Heat Conduction method, and the thermal conductivity follows the linear relationship of -0.0025(T)+0.4023 (45ºC<T<100ºC) in the sensible region. The temperature variations and the phase change phenomena for the solar salt is identified and the contours are provided. The charging time for the encapsulated solar salt is identified as ~138 minutes. The energy storage cost for the single filler material (Solar Salt + SS316L encapsulation) is identified as Rs.5.93/- (USD 0.071) for the period of charging duration.

CFD simulation of solid/liquid phase change in commercial PCMs using the slPCMlib library

Modelling the solidification and melting behavior of phase change materials (PCMs) can present several challenges, including non-isothermal phase change, multi-step transitions, complex enthalpy-temperature relations and convective heat transfer. To tackle these challenges, this study proposes a novel numerical method based on real experimental data for modelling complex phase change behavior of commercial PCMs in Ansys Fluent CFD software. The phase transition of PCMs is simulated with the apparent heat capacity (AHC) method, which is implemented as a User-Defined Function (UDF). Heat convection is simulated with the Boussinesq approximation. The method is validated by comparing to the Ansys Fluent built-in Solidification and Melting (S&M) model for the case of piecewise constant heat capacity. The results show that AHC method provides excellent agreement with S&M model for a piecewise constant heat capacity model. In addition, the AHC method solves convergence problems even for narrow phase change temperature ranges when a smooth heat capacity function is assumed. Finally, the AHC model is also tested on a set of commercial PCMs exhibiting complex phase change behavior. Temperature dependent specific heat capacities are determined from heat capacity data provided by PCM manufacturing companies and are imported as cubic Hermite spline functions from the solid-liquid phase change material library slPCMlib available at https://slpcmlib.ait.ac.at/. From the presented case study and tested PCMs it can be concluded that the AHC method is numerically robust when used with sufficiently smooth heat capacity functions, and it can be recommended for the analysis of heat transfer with PCMs showing a complex phase change behavior.

Effect of steam flow parameters on the partial load behaviour of a PCM storage

To estimate the achievable thermal power in passive latent heat thermal energy storage (LH-TES) systems and the corresponding charging/discharging times for customised storage design and operation, relevant influencing parameters and their impact must be sufficiently known and understood. These parameters include not only the well-researched parameters on the phase change material (PCM) side, but also the parameters on the heat transfer fluid (HTF) side, such as the inlet temperature, the mass flow rate and the resulting heat transfer coefficient (HTC) between the HTF flow and the tube wall. For heat exchangers, these influences have been studied well, however for highly transient LH-TES studies are scarce. This article presents the influence of relevant parameters focusing on the ones related to the HTF side, using analytical and numerical parameter studies in Matlab®. The effect of different HTCs for varying flow conditions of the HTF in different zones of the tube is utilised to introduce the dominant heat transfer surface between the storage and the HTF (DHTS) as an indirect operating parameter. It corresponds to the area where the HTF phase change occurs and where most of the total energy is transferred. The numerical study indicates that the size of the dominant heat transfer area and thus the DHTS can be adapted by the HTF mass flow rate and the temperature difference between the HTF inlet temperature and the PCM phase change temperature. Based on this knowledge, new conjugate design and operating strategies for a test rig with a nominal thermal power of 1 kW using the commercial PCM PLUSICE A133 as storage material are proposed. They lead to a peak shaving behaviour of the storage with defined charging and discharging times.

Selection and thermophysical assessment of phase change materials (PCMs) for space cooling applications in buildings

Phase change materials are gaining more attention in building comfort applications because of their latent heat thermal energy storage (TES) capacity. Identifying the best PCM candidate is a pivotal factor that significantly impacts the thermal performance of a building. This study delves into assessing prospective PCM candidates for potential utilization in cooling systems within buildings in hot subtropical climates. Extending the application of multicriteria decision-making (MCDM) methodologies, this research scrutinizes various commercial PCMs by conducting an exhaustive analysis of pertinent literature in the context of this specific application objective. Thermophysical properties are integrated into the MCDM framework to identify the most fitting candidates with optimal properties and attributes. The properties and attributes of PCMs are subjected to scoring and weighting through the AHP based on their significance in the given application context. TOPSIS and VIKOR techniques select the suitable PCM from the identified PCMs. The results showed that latent heat receives the highest weightage, amounting to 50.2%, due to its paramount importance. Furthermore, OM37 emerged as a promising choice for building space cooling, considering the prescreened temperature range of 30 °C–40 °C and for the specific location under consideration. Following PCM selection, thorough characterization was performed to evaluate the suitability of the chosen PCM for integration within building envelopes. The thermal conductivity of OM37 was determined to be 0.20 W/mK, while the morphology by a Field Emission Scanning Electron Microscope (Fe-SEM) intricate porous structure. Furthermore, a differential scanning calorimeter (DSC) suggests melting and solidification temperatures of 40 °C and 34 °C with a total enthalpy of 197.04 j/g, and a Thermogravimetry Differential Thermal Analysis (TG/DTA) showed a substantial weight loss of approximately 98.9% at around 247.3 °C. The presented experimental test results agree with the literature data and other researchers’ results.

Innovative Integration of Phase Change Materials and Conceptional Design of Test Cases – New Products for the Building Envelope

The building sector contributes to a great part of energy consumption and has a major impact on climate in Europe. Development of climate-friendly and energy-efficient products is required to reach low and net-zero energy buildings and to facilitate the energy transition. The building envelope is critical in defining the demand for space heating and cooling as well as ensuring thermal comfort and indoor environmental quality through proper ventilation. This paper presents the conceptual test cases integrating phase change materials (PCMs) in the building envelope. PCM absorbs, stores, and releases the heat energy in a controlled manner taking advantage of the temperature difference between night and day. Hence PCM can support the thermal management of the building by minimizing unwanted heat gains and losses while integrated into walls or support the energy efficiency of ventilation while supplying fresh air. Smart ventilated heat harvesting windows and multifunctional sandwich panels are developed within the EU-funded iclimabuilt project. Additionally, commercial air-guided PCM storages are presented as ready-to-install products for decentralized ventilation and heat recovery systems.

Mild hybrid energy dual-slope solar stills: Design and performance

The critical increase in the lack of available freshwater worldwide owing to different anthropogenic and natural causes has led mankind to seek serious solutions, such as the use of solar stills. This study shows the design and performance of a dual-slope solar still powered by a mild hybrid power supply system. Different power supply configurations were created for the solar still, and commercial phase change materials were incorporated into the prototype. The highest freshwater production rate in the active solar still (6.76 l/m2d) was obtained when power was supplied from the portable photovoltaic plant at the beginning of the test, with an associated cost per liter of produced water of 0.2218 USD. It was shown that phase change materials increased the heat retention time and optimized the energy supply in the solar still. However, their use did not result in lower freshwater production costs.

Microencapsulation study of bioderived phase change material beeswax with ethyl cellulose shell for thermal energy storage applications

ABSTRACT The commercial shape-stabilized phase change material (PCM) products are obtained from synthetic raw materials. These materials are produced from carbon-intensive petroleum-refining processes. The carbon footprint can be minimized by using biobased products. Beeswax is a naturally available PCM with high phase transition enthalpy comparable to synthetic PCMs. In the previous literature studies, beeswax was shape-stabilized with synthetic materials. In the present study, beeswax was shape-stabilized with biopolymer ethyl cellulose by emulsion solvent evaporation method. The study aims to determine optimum microencapsulation process parameter levels for synthesizing microcapsules with high thermal energy storage (TES) capacity. The optimized process parameters for formulating microcapsules were 60:40 core/shell ratio, 2% PVA concentration, ethyl acetate solvent, and 40°C evaporation temperature. The microcapsules prepared with optimized process parameters were characterized using differential scanning calorimeter (DSC), T-history analysis, Fourier transform infrared (FTIR) spectroscope, and scanning electron microscope (SEM). FTIR and SEM analysis confirmed ethyl cellulose shell formation over the beeswax core. The optimized MPCM formulation possesses 115.8 J/g melting enthalpy with peak phase transition temperature of 58.2°C and thermal conductivity of 0.219 W/mK. The porous structure of the shell reduced melting enthalpy of optimized MPCM formulation to 84.6 J/g after 50 thermal cycles. The synthesized microcapsules comprise sustainable materials and have high TES capacity. The fabricated microcapsules can be used as TES additive in composite and coating formulations in food packaging.

Experimental and numerical investigation of PCMS on ceilings for thermal management

In this study, experimental investigation of phase change materials (PCM) integrated into building on ceilings was assessed for thermal management capabilities by comparing two building test models with and without PCM based on fluctuation in PCM temperatures owing to ambient temperature variations. Commercial organic PCM (OM-30) with a peak melting point of 31.10 C was used as PCM with high-density polyethylene (HDPE) as the encapsulation. Differential scanning calorimeter (DSC) was used to examine the thermophysical characteristics of PCM such as phase transition temperature, latent heat, and specific heat capacity. The various PCM temperature ranges included for the study are (i) Above phase change melting temperature range ii) within Phase Change melting temperature range iii) Proximity to PCM onset melting temperature range iv) proximity to PCM end melting temperature range. Under free-floating ambient Condition, the indoor air temperature was dropped in PCM installed room up to 1.69 °C, 5.79 °C, 2.26 °C, & − 2.87 °C compared to without PCM room for a PCM Melting temperature difference of 8.77 °C,1.55 °C, 1 °C & 0.44 °C respectively. Also, it was divulged that the PCM utilized 3.2%, 31.4%, 6.9%, & 12.27% of the total latent heat energy deployed in order to produce a temperature difference of 1.69 °C, 5.79 °C, 2.26 °C, & − 2.87 °C compared to without PCM room.

Investigation of the impact of phase change materials at different building envelope placements in a semi-arid climate

Researchers in the building industry are becoming increasingly interested in phase change materials (PCM). Due to the potential for passive temperature management offered by these PCMs, HVAC (Heating, Ventilation, and Air-Conditioning) equipment will use less energy. Still, to prevent leakage during phase change, an enclosure is needed when installing PCMs in buildings. So, to determine this passive indoor temperature regulation cost, payback period, and energy savings, it is crucial to assess the PCM energy savings in various building envelope placements. So, this is done by using the EnergyPlus simulation engine for the case of the commercial PCM RT 28HC, this article will assess and compare 8 potential building envelope positions in a semi-arid region. These eight different building configurations have one case without PCM and the other cases have PCM placed in the interior surface of the following specific placements, a PCM placed in walls envelope only, in floors envelope, in ceilings and roofs envelope only, in walls, ceilings, and roofs envelope, in walls and floors envelope only, in floors, ceilings and roofs envelope and all envelopes for a 10 m square-shaped building. This study's primary goal is to evaluate the reduction of indoor air temperature fluctuations, PCM energy savings, PCM activation, and payback period for these various building layouts. The findings show excellent temperature indoor stabilization in summer, for the case with PCM installed on all interior envelope surfaces showing a maximum indoor temperature fluctuation decrease of 110.2 °C for August. In addition, the case with the PCM placed only in the walls, roof, and ceilings has shown the highest yearly energy savings, nevertheless, the case with PCM placed only in the walls has the lowest payback period of nearly 22 years and a half.

PMMA nano-encapsulated phase change material colloids for heat management applications

Phase Change Materials (PCM) emulsions or micro-nano-encapsulated into organic and inorganic shells have attracted scientific interest for their potential to enhance the thermal capacity and the efficiency of heat transfer liquids. In this work, RT21HC, a commercial PCM with transition temperature at 21 °C, has been successfully nano-encapsulated into Poly(methyl-methacrylate) (PMMA) shells by an emulsion polymerization process after the selection of proper surfactant and synthesis parameters, in order to obtain complete encapsulation and stable colloidal dispersions. Water-based colloidal dispersions containing 10 wt% PCM were obtained and characterized from point of view of microstructure, colloidal stability, rheological properties, apparent heat capacity and thermal diffusivity, in order to show the potential of these colloidal dispersions as advanced heat management fluids. With the aim to mitigate the phenomenon of PCM crystallization supercooling that is caused by nano-confinement and is cause of apparent thermal capacity loss, the effect of incorporation into the nano-capsules of two fatty esters, two fatty alcohols and a fatty acid as nucleating agents, has also been studied.

Phase-Change-Material-Impregnated Wood for Potential Energy-Saving Building Materials

PCMs (phase change materials) are ideal for thermal management solutions in buildings. This is because they release and store thermal energy during melting and freezing. When this material freezes, it releases a lot of energy in the form of latent heat of fusion or crystallization energy. Conversely, when the material melts, it absorbs the same amount of energy from its surroundings as it changes from a solid to a liquid state. In this study, Oriental spruce (Picea orientalis L.) sapwood was impregnated with three different commercial PCMs. The biological properties and the hygroscopic and thermal performance of the PCM-impregnated wood were studied. The morphology of PCM-impregnated wood was characterized through the use of scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). PCM-impregnated wood demonstrated low performance in terms of storing and releasing heat during phase change processes, as confirmed by DSC. The results show that PCMs possess excellent thermal stability at working temperatures, and the most satisfying sample is PCM1W, with a phase change enthalpy of 40.34 J/g and a phase change temperature of 21.49 °C. This study revealed that PCMs are resistant to wood-destroying fungi. After the 96 h water absorption test, the water absorption of the wood samples decreased by 28%, and the tangential swelling decreased by 75%. In addition, it has been proven on a laboratory scale that the PCM material used is highly resistant to biological attacks. However, large-scale pilot studies are still needed.

Numerical investigation of a latent cold storage system using shell-and-tube unit

The use of cold thermal storage systems in low-temperature industrial applications is considered one of the most promising ways of improving energy efficiency and reducing the use of power during peak periods. In this study, the thermal performance of a shell-and-tube cold storage system under realistic operating conditions is investigated numerically. The proposed model is developed based on energy balances and then validated using existing experimental data from the literature. Glycol/water is used as the heat transfer fluid (HTF) and the phase transition phenomena in the phase change material (PCM) is simulated using the enthalpy–porosity approach. The influence of several design and operating parameters, including the HTF mass flow rate, HTF temperature, PCM type, and volume, on the cold storage performance during the crystallization process is presented and analyzed. The numerical results show that increasing the HTF mass flow rate accelerates the PCM crystallization process. However, the delivery periods of constant thermal power and constant HTF outlet temperature are reduced. The HTF inlet temperature has a significant effect on the cold storage performance, and the complete charging period is reduced by approximately 37% when the HTF inlet temperature is reduced from −4 °C to −7 °C. Increasing the number of tubes in the cold storage unit is concluded to significantly improve the thermal performance of the system, and using water/ice as a cold storage medium is more suitable than using the commercial PCMs RT2-HC and RT4-HC. Finally, the proposed numerical model for cold storage systems can be successfully used to design and simulate their realistic operation under different conditions.

Liquid flow spinning mass-manufactured paraffin cored yarn for thermal management and ultra-high protection

Thermal management and ultra-high protection textiles are critical for polar scientists, astronauts and firefighters. Phase change materials (PCMs) effectively retard huge thermal changes, and thermal damage by absorbing or releasing heat during phase transition. However, due to the materials and engineering challenges inherent in PCMs based textiles, commercial PCMs usually suffer with high rigidity, no-breath-ability, easy leakage and abrasion, limiting their potential applications. Herein, we proposed a mass-producible liquid flow spinning (LFS) method, in which molten paraffin is poured into continuous hollow silicon tubes and then wrapped by staple fibers to form paraffin-coated yarns (PCYs) on a friction spinning frame. The obtained PCYs showed enhanced mechanical properties (break strength of 7.80 N, wear resistance of 2000 cycles) due to the novel core-sheath yarn structure. Besides, thanks to the high melting enthalpy (60.967 J/g) of PCYs, the yarns showed the excellent temperature regulating effect. A double-sided joint PCYs fabric (PCYF) is fabricated to study the PCYs performance further, results show that the PCYF can withstand 10,000 cycles of abrasion without breakage and PCMs leakage. Furthermore, owing to the much gaps provided by the stretch fibers and interweaving points, the fabric exhibits good breathability. In particular, compared with commercial PCMs based textiles, our PCYF is superior in thermal protection performance (9 °C lower). The fireproof performance is also excellent as our PCYF can withstand flame temperatures higher than 1142 °C. The PCYs production method provided here could pave the way for human thermal protection textiles.

Development and Experimental Characterization of an Innovative Tank-in-Tank Hybrid Sensible–Latent Thermal Energy Storage System

This study focuses on the development and testing under lab-controlled conditions of a hybrid sensible–latent thermal energy storage (TES) system for domestic hot water (DHW) provision in residential buildings. The TES system’s design is based, for the first time in the literature, on a commercial tank-in-tank architecture integrating a macro-encapsulated commercial phase change material (PCM) inside the external tank to guarantee the safe provision of DHW and increase overall energy storage density at a reasonable cost. The PCM is a salt hydrate with a nominal melting temperature of 58 °C. The overall tank-in-tank TES volume is about 540 dm3. Almost one tenth of this volume is occupied by the PCM macro-capsules. The developed TES system was comparatively tested against the same configuration operated as a sensible TES. The obtained results showed the ability of the PCM to increase the thermal inertia inside the external tank, thus guaranteeing the quite stable provision of heat to the integral DHW tank during the stand-by periods. This effect was confirmed by the PCM’s ability to achieve an energy storage capacity up to 16% higher than the reference sensible TES system.

Thermal management in vacuum pressure swing adsorption processes using phase change materials

Vacuum pressure swing adsorption (VPSA) is a mature separation process; however, given the current energy situation, further improvements in terms of process operations are required. To this end, the use of a thermal energy storage system during VPSA cycles appears promising, as the exothermic heat and endothermic heat generated by adsorption and desorption are known to reduce the working capacity. In this study, we investigated thermal management by using a commercial phase change material (PCM) composed of phenolic resin and microencapsulated paraffin wax in the VPSA process to purify an equimolar CH4/CO2 gas mixture using zeolite 13X. Here, VPSA processes were simulated using our one-dimensional nonisothermal column model considering the melting and solidification of the PCM. The influence of the PCM mixing ratios was evaluated based on the specifications of CO2 products and the column length, wherein the VPSA processes were designed, such that the purity and recovery of CH4 products met the prescribed criteria to achieve a reasonable comparison. The temperature variation (270–351 K) in the cyclic steady state owing to the exothermic and endothermic heat produced during the adsorption and blowdown steps, respectively, was suppressed to 276–344 K by the latent heat of the PCM, resulting in low CH4 co-adsorption and improved purity of the CO2 product. Finally, we proposed a method involving the intensive installation of a PCM in the central part of the column and demonstrated that the advantages of improved adsorbent performance realized by mixing the PCM outweighed the disadvantages of increased PCM volume, resulting in a shorter column length than that in the case without the PCM. These results demonstrate the superiority of PCM-installed VPSA systems.

Lightweight aggregates as carriers for phase change materials

This paper initially reports on development of lightweight aggregates impregnated with phase change material (LWA-PCM), for application in mortars, plasters and other building materials. This is followed by a study into the development and characterisation of prototype cement mortars using the LWA-PCMs. The work has developed methodologies for efficiently impregnating and hosting phase change materials (PCMs) into lightweight aggregates (LWAs), including aerated concrete particles (ACG) and perlite. PCMs can store and release energy within a given temperature range, moderating thermal fluctuations, resulting in the reduction of energy lost in buildings and increasing thermal comfort. Three commercial PCMs, with melting points between 18 °C and 25 °C, were used in this study. Methods, including vacuum impregnation and immersion, and conditions for optimal absorption of the PCMs into ACG, were developed and evaluated experimentally. Different coating materials, to limit leakage of PCMs from the aggregates, were also trialled as part of this study. Compared to immersion, vacuum impregnation resulted in an increased absorption by up to 15.6 % depending on the type and viscosity of the PCMs.The impregnated aggregates were incorporated into cement mortar mixes, at replacement rates between 10% and 50% (by volume). The effects of PCM impregnated particles on both the mechanical and thermal properties of the cement mortars have been evaluated. Increasing the amount of PCM loaded particles decreased both the flexural and compressive strengths of the cement mortars, by up to 38% and 49% respectively. However, the volumetric heat capacity of the materials increased by nearly 60%. This paper presents a new approach for the design of PCM-loaded aggregate particles, with the potential to be incorporated into different construction materials to improve the energy efficiency and resilience of buildings.

Simultaneous effect of biochar-additive and lightweight heat exchanger on phase change material for low-grade thermal energy storage

In this paper, we report the experimental performance of a low to medium temperature (20–50 °C) latent heat heat storage (LHS) system. The power and temperature ranges of the LHS have relevance to various applications such as heat sink and storage for high-power electronics devices and low-temperature district heating (LTDH). This new LHS includes a lightweight heat exchanger (LHE) with a complex heat transfer area for organic phase change materials (PCMs). The model PCMs provide a medium-low phase transition temperature range, namely decanoic acid (DA) and a commercial PCM. To facilitate the storage performance of the system, biochar (BC) additive is further investigated to simultaneously enhance the thermal properties of the PCM within the LHE. The PCMs are characterized using common material characterization methods such differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The system investigation focuses on the effect of the heat exchanger, the PCM type and the additive concentration on the duration and power of charging-discharging cycle as well as the storage capacity. Two weight percentages (1 % and 2 %) of BC were studied, while the addition of 1 % BC to DA resulted in the most effective storage performance in both the system (444 kJ storage capacity) and characterization (170.5 kJ/kg melting enthalpy) experiments. The lightweight structure of the grid enabled loading of a large PCM amount (1.84 kg) as well as swift charging (430 W during 25 min). The system indicated a cooperative enhancement with BC additive as the charging power increased by 32 % (570 W) and charging time decreased by 33 % (17 min). A conceptual modular design of the investigated system is proposed to heat up the floor or the bench of a smart city bus stop. The modular unit of ten integrated LHEs filled with BC enhanced DA is estimated to provide 1.2 kWh storage capacity sufficient for heating the bus floor for 6 h or the bus bench for 15 h. This is a potential solution for reclaiming the excess heat from LTDH substations, while buffering their undesired temperature variations.

Experimental measurement of thermophysical properties of some commercial phase change materials (PCM) for air conditioning applications

This paper presents the measurement of liquid phase density, thermal diffusivity, thermal conductivity, and dynamic viscosity of five commercial PCM (RT2HC, RT5HC, OM05-P, OM08, CrodaTherm9.5) in the temperature range 2 − 30 °C. The density of RT2HC, RT5HC, OM05-P is 23-24% lower than water, that of OM08 is 6% higher than water and that of CrodaTherm9.5 is 14% lower than water. The thermal diffusivity of RT2HC, RT5HC, OM05-P is 22-24% lower than water, that of OM08 is around a half of water and that of CrodaTherm9.5 is 38-40% lower than water. The thermal conductivity of the five PCM is 72-74% lower than water. The dynamic viscosity of RT2HC, RT5HC, OM05-P and OM08 is 2 − 3 times higher than water, and that of CrodaTherm9.5 is from 7.4 to 8.3 times higher than water. The five PCM are expected to provide convective heat transfer performance significantly lower than water .