Heat Transfer Fluid Inlet Research Articles

Numerical and experimental investigation on a latent heat thermal storage device featuring flat micro heat pipe arrays with offset strip fins

In this paper, a latent heat thermal storage device is designed and manufactured. The device uses flat micro heat pipe arrays as the core heat transfer element, multichannel flat pipes as the heat transfer fluid channel to provide and remove heat, and offset strip fins to strengthen the heat exchange of the phase change material side. The performance of the device under different operating conditions was explored, and a 3D computational fluid dynamic model of the device is established. The model is simplified by using the method of equivalent thermal conductivity and equivalent specific heat capacity. The performance of a latent heat storage unit under small temperature difference is also studied. Results show that the inlet temperature of fluid has a great influence on the performance of the device. During charging process, when the fluid temperature changes from 63 °C to 73 °C, the charging power increases from 921.1 W to 1302.1 W (41.3%). During discharging process, when the fluid temperature decreases from 18 °C to 8 °C, the discharging power increases from 831.1 W to 1210.5 W (48.9%). Regarding the flow rate, when the fluid flow rate increases from 2 L/min to 3 L/min (50%), the average charging power increases from 1,069.2 W to 1,199.3 W (12.2%), and the average discharging power increases from 895.1 W to 1,068.3 W (19.3%). Simulation results show that the phase change material in the thermal storage unit can melt completely when the temperature difference is 4 °C, but the melting time is longer when the heat transfer temperature difference is less than 6 °C. Heat transfer temperature difference refers to the variance between the heat transfer fluid inlet temperature and the phase change material phase transition temperature. The main thermal resistance is concentrated in the part where multichannel flat pipes transfer heat to the flat micro heat pipe arrays and the phase change material side.

Numerical study of a positive latent cold storage system for industrial applications: Discharge mode

In this work, a comprehensive numerical study on a latent heat storage system is presented. The adopted storage system consists of a tank with a fixed bed of phase-change materials (PCMs). A numerical model simulating the dynamic and thermal behaviour of this system during the discharge period has been developed and validated using experimental data from the literature. During the discharge mode, when the inlet heat transfer fluid (HTF) is maintained at a temperature near the melting temperature of the PCM, a quasi-stabilization of the outlet HTF temperature is observed. The duration of the discharged energy is increased when the flowrate of the fluid is decreased. A detailed study was also carried out to better understand the behaviour of latent storage system using multiple PCMs. The obtained results for a multi-PCM configurations reveal that the latent energy released during the discharge period depends on the placement order of the PCMs inside the tank, the flow rate of the HTF and the level temperature of the HTF at the inlet to the tank. This numerical study could a be a key solution in industrial cold applications such as air conditioning and thermal comfort, the medical and food sectors.

Numerical simulations and experimental verification of the thermal performance of phase change materials in a tube-bundle latent heat thermal energy storage system

• Thermal performance of tube-bundle LHTS studied numerically and experimentally. • Charging and discharging are studied using lauric acid and water as PCM and HTF. • Three HTF initial temperatures and flow rates are examined. • PCM charging and discharging results were superior in comparison with double pipe LHTS. • Charging and discharging time was shortened by 85.3% and 82.5% respectively. Theoretical simulation and experimental validation of a new design tube-bundle latent-heat thermal storage (LHTS) working under solar-thermal application conditions was performed. A laboratory-scale experimental test rig was designed and tested for charging and discharging processes by using lauric acid and water as a phase-change material (PCM) and heat-transfer fluid (HTF), respectively. Six equal size tubes with 2 cm diameter and 45 cm length were clamped together with a central diameter tube for carrying the HTF. The temperature of the PCM during charging and discharging in the tubes in the bundle was measured radially. A 3D numerical model using ANSYS FLUENT was developed to simulate the time-dependent liquid fraction, temperature, and stored power of the PCM. The simulation was conducted after the successful validation with the experimental results at different HTF inlet temperatures (70 °C, 75 °C, and 80 °C) and (10 °C, 15 °C, and 20 °C) for charging and discharging processes, respectively, as well as with different Reynolds numbers (750, 1250, and 1750) for both processes. Although the design of the proposed LHTS was very simple, the results revealed that it has a superior thermal performance and fast charging and discharging period when compared to a double-pipe LHTS. Accordingly, the time was shortened by about 85.3% and 82.5% for charging and discharging processes, respectively.

Experimental thermal study of a new PCM-concrete thermal storage block (PCM-CTSB)

Phase change material concrete as a new building envelope has been widely used in passive building energy conservation, but less research has been done for it as a heat storage block in an active low-temperature thermal storage system. To enhance the heat storage capacity of PCM-concrete, overcome the PCM leakage problem and reduce the cost of heat storage, clastic light shale ceramsite (CLSC) was used to absorb paraffin to prepare PCM-CLSC aggregate and PCM-concrete thermal storage blocks with different PCM weight percentage (0, 2 wt%, 4 wt% and 6 wt%). The absorption, compatibility, thermal and mechanical properties of PCM-CLSC aggregate and PCM-concrete thermal storage blocks have been tested. To improve the charging and discharge rate, the active thermal storage and release system has been designed. Besides, the study presents the effects of PCM weight percentage and the characteristics of heat transfer fluid (HTF) on the performance of an active thermal storage system. The experimental results show that PCM-CLSC aggregate has good absorption and compatibility. The thermal conductivity and compressive strength of PCM-concrete thermal storage blocks decreased with the increase of PCM weight percentage, and the average specific heat capacity increased by 12.54% (2 wt% PCM), 31.60 (4 wt% PCM) and 41.23% (6 wt% PCM), respectively. Also, by increasing the PCM weight percentage, HTF flow rate and inlet temperature, it is possible to improve the heat storage and release capacity while effectively increasing the heat transfer rate and reducing the thermal resistance.

Thermal performance analysis of compact thermal energy storage unit-An experimental study

In this study, an experimental setup is developed to assess the thermal performance of a compact Latent Heat Thermal Energy Storage System (LHTESS) prototype during the charging/discharging stages. The LHTESS consists of a shell and horizontally oriented multi-tube heat exchanger and a commercially available paraffin wax RT44HC, which has a phase change temperature between 41°C and 43 °C as the energy storage medium. The testing campaign evaluated the influence of several operating conditions including the heat transfer fluid (HTF) volume flow rate and inlet temperature on the LHTESS power input and output, melting and solidification time and the energy stored and released. From the experimental results, it was observed that increasing the HTF inlet temperature has a significant effect on charging time compared to changing the HTF volume flow rate. When the LHTESS was charged using a fixed HTF inlet temperature of 60 °C, the charging process period took 296.3 min, 233.5 min, 204.8 min and 197.8 min when the HTF volume flow rate is 3.0, 4.5, 6.0 and 7.5 L/min. However, when the LHTESS was charged at HTF volume flow rate of 4.5 L/min, the results show that the charging completion time for HTF inlet temperatures of 55°C, 60 °C and 65°C are 316.6, 233.5 and 209.67 min, respectively. The results from the experimental analysis showed that the discharge time was significantly longer than the charging time due to an ever-growing layer of solid PCM around the external surface of heat exchanger throughout the discharging process which reduces the heat transfer coefficient between the PCM and HTF. This did not change substantially with the changing HTF volume flow rate.

Experimental analysis of Thermal Efficiency of functionalized Graphene (COOH) reinforced PCM for thermal energy storage system

In this work, the emphasis is on the thermal conductivity of paraffin wax and nano material which is functionalized graphene (COOH). Firstly COOH graphene is combined in various concentrations with paraffin wax to achieve higher thermal conductivity and then it is analysed for thermal conductivity having flow rate of heat transfer fluid(HTF) as 50ml at 8 second. When COOH functionalized graphene is used in this experiment, the thermal conductivity of paraffin wax increases. This study included experiments on varying concentrations of functionalized graphene (COOH) and inlet HTF temperatures for thermal properties, density, specific heat and nanofluid properties. The graphene is combined by stirring it with the paraffin wax. Graphene concentrations are 0.25 volume%, 0.5 volume% and 0.75 volume% for the flow rate of 50 ml in 8 second. Thermal conductivity increases with increase in the concentration of graphene. In the winter season, where environmental losses are higher than the summer season and the air temperature is 18°C, while it is above 29°C in the summer season, it also reduces PCM charging time around 30 to 50 percent with the use of functionalized graphene. In all concentrations, HTF temperature varies from 80°C to 90°C, with observed input energy, environmental losses, charging time, charging rate and performance. All values are noted after a 10 minute interval, till the cylinder is fully charged.

Thermal energy storage performance of PCM/graphite matrix composite in a tube-in-shell geometry

Melting heat transfer performance and measuring energy storage efficiency via total melting time of PCM/graphite matrix in a tube-in-shell for solar thermal energy storage and recovering waste heat applications is studied experimentally. The phase change material (PCM)-organic/paraffin (P56-58), is impregnated into the graphite matrix, with the bulk density of 50 g/L. The effect of inlet temperature (Tinlet = 75 °C and 85 °C) of heat transfer fluid (HTF) on total melting time is obtained. The time-history of temperature measurements, thermal camera imaging, and liquid fraction are obtained to reveal the thermal performance of PCM/graphite matrix in a tube-in-shell latent heat thermal energy storage (LHTES) system in detail. The results show that the PCM/graphite matrix has a remarkable effect on the phase change heat transfer and total melting time. The thermal performance of the PCM/graphite matrix is presented comparatively with the conventional tube-in-shell storage unit. Effective thermal conductivity which enhances the heat transfer rate is shown to increase 35 times compared to that of pure paraffin. The total melting time decreases by about 92% compared to the conventional tube-in-shell unit. Uniform melting behaviour is observed based on highly conductive abundant thermal paths for PCM/graphite matrix. Heat transfer takes place by dominant conduction for the PCM/graphite matrix. Leakage issue is prevented using graphite matrix encapsulation. Total melting time is decreased by about 31% with the increase in HTF inlet temperature for the PCM/graphite matrix.

Evaluating the performance of liquid immersing preheating system for Lithium-ion battery pack

Abstract Preheating batteries is crucial to improve the performance and lifetime when using lithium-ion batteries in cold weather conditions. Even though the immersing preheating system (IPS) has demonstrated attracting advantages, there is still lack of systematical evaluation about its performance and factors affecting the performance. To bridge the knowledge gap, this work considered the following key performance indicators: the rate of temperature rise, the temperature uniformity of the cell and the pack and the energy storage density; and the influences of the inlet flow rate and inlet temperature of heat transfer fluid (HTF), the gap between the batteries, the number of the batteries and the location of the HTF inlet and outlet on the preheating performance were investigated. A 3D CFD model was developed, which has been validated against experiments. Based on simulations, it was found that the IPS can achieve a high rate of temperature rise, which is up to 4.18 °C/min, and a small temperature difference in the battery pack, which is less than 4 °C. The number of batteries has been identified to have the biggest impact on the rate of temperature rise and the uniformity of the battery pack. Allocating the inlet on the left/right faces of IPS can effectively reduce both maximum temperature difference of the cell and the pack.

Design and investigation of single tank phase change thermal storage domestic hot water system

Thermal energy storage (TES) is extensively applied in production and daily life. As a basic work, we designed a single tank phase change TES domestic hot water system using night valley power. Based on the single tank TES experimental platform, a 2D numerical model of the system was established. To optimize the performance of a single tank TES system, the effect of heat transfer fluid (HTF) inlet velocity and temperature on the heat release of the storage tank was analyzed based on simulation. The enhanced heat transfer effect of the radial cascade system and axial cascade system was also compared. The results showed that 0.8 m/s is the optimal HTF inlet velocity in the calculation range. The rule of the heat release about the HTF inlet temperature just meets the different hot water requirements in winter and summer. The heat release capacity of the radial cascade system and axial cascade system is higher than that of the conventional single-stage system, and the proportion of latent heat release in radial cascade is larger. This study will provide theoretical guidance for the optimal design of the single tank TES domestic hot water system in the future.

Compound charging and discharging enhancement in multi-PCM system using non-uniform fin distribution

In the present study, a numerical model of a vertical shell and tube latent heat storage system validated with the experimental data is presented. The developed model comprises of three blocks of phase change materials (PCMs) having melting point temperatures (Tm) 360 °C, 335.8 °C and 305.4 °C, respectively. A non-uniform distribution of fins in three PCM blocks is initially employed to study the performance of the single PCM system (Tm=335.8 °C). The effect of inlet heat transfer fluid temperature on the charging and discharging performances of the single PCM and multiple PCM (m-PCM) systems is analysed by varying a Stefan number (Steref) parameter, calculated based on the single PCM system. The charging and discharging times for the m-PCM system are either similar or lesser than the single PCM system for Steref≥1, however, there is an improvement of 21–25% in the specific power charged and discharged by the m-PCM system for all the Sterefvalues (0.5, 1, 1.5 and 2) considered. By employing a compound enhancement technique which is a combination of non-uniform fin-distribution and PCM blocks length ratio optimization for the m-PCM system, 30% and 9% reduction in the charging and discharging time, respectively, over the single PCM system is achieved.

Exploration of a plate heat exchanger utilising a phase change material: an experimental and computational study

In this article, the heat transfer mechanism of a phase change material (PCM) chamber during charging and discharging processes was studied both numerically and experimentally. A flat plate thermal storage system with dimensions of 500 × 100 × 12 mm, and a PCM thickness of 12 mm was thus investigated. The thermal storage material selected was commercial paraffin wax with a melting temperature of about 60 °C. A diffusion-advection numerical model was used to study heat transfer in this system, as it was observed that the experimental results were in good agreement with this model. In this way, natural convection was found to be the dominant phenomenon in the model. The effects of heat transfer fluid (HTF) temperature and volume flow rate on the melting and solidification time were also assessed, producing the finding that, by elevating the inlet HTF temperature from Th = 343 K to 348 K and then 353 K, the charging time can be reduced by up to 35%.

A technical, financial and CO2 emission analysis of the implementation of metal foam in a thermal battery for cold chain transport

Latent thermal energy storage (LTES) can be a valuable component in a wide range of energy systems. The low thermal conductivity of most phase change materials (PCMs) has resulted in the development of several PCM enhancement methods. However, most of the comparisons of enhancement techniques implemented in LTES heat exchangers are based on a single operating point which limits the findings to the tested heat transfer fluid inlet temperature and mass flow rate. Furthermore, an analysis of the financial impact of an enhancement method is not available. In this article, the validity of implementing metal foam as a thermal conductivity enhancer is assessed in a cold chain application. A modular LTES design is constructed with and without metal foam. The charging time of both thermal batteries is experimentally correlated as a function of the heat transfer fluid inlet temperature and mass flow rate. The metal foam reduces the charging time of the battery between 24 % and 40 % depending on the heat transfer fluid inlet condition. Discounted savings for the implementation of metal foam of up to 10 times the investment cost are possible but depend on the number of cycles per year and the rate of return.

Performance analysis of an air rock thermocline TES tank for concentrated solar power plants using the coupled DEM–CFD approach

One of the most common solutions currently available to meet future energy needs in the world is concentrated solar power (CSP) plants combined with thermocline thermal energy storage (TES) tank subsystems. The air rock thermocline TES tank asserts to be an effective and inexpensive TES subsystem for CSP plants. In this study, a discrete element method (DEM) combined with a numerical model of computational fluid dynamics (CFD) was adopted to investigate the thermal performance of a scale model of an air rock thermocline TES tank. The study is carried out to optimize TES thermocline tank's thermal behavior by changing the heat transfer fluid (HTF) inlet velocity. The DEM–CFD coupled model is validated against analytical and experimental data. The results show that the use of the distributor reduced the influence of the wall effect by distributing the HTF in a regular way as the fluid passes through it, especially at high inlet velocity. Moreover, the results show that each TES tank subsystem has a critical velocity at which the tank operates most efficiently. Furthermore, the results demonstrated that the maximum value of the overall cycle efficiency was equal to 70.15% at 10 m/s, while the minimum value was equal to 42.5% at 2 m/s. The highest capacity and utilization ratio are 81.31 and 72.81% at 16 m/s, while the lowest capacity and utilization ratio are 52.01 and 44.75% at 2 m/s. The pumping energy needed to overwhelm the pressure drop rises when the HTF inlet velocity increases. This study can provide an effective reference for the efficient operation regulation and optimal design of the thermocline tank.

Experimental investigation on thermal behavior of paraffin in a vertical shell and spiral fin tube latent heat thermal energy storage unit

Aided by the phase change material (PCM) with high thermal storage density, latent heat thermal energy storage (LHTES) technology may provide a solution to the energy supply-demand dilemma, e.g. LHTES in solar energy utilization and waste heat recovery. This paper presents an experimental investigation on the thermal performance of a LHTES unit equipped with vertical multitube shell and spiral-finned tube. Using paraffin as PCM and water as heat transfer fluid (HTF), the thermal charging and discharging characteristics of the LHTES unit can be evaluated. The thermophysical properties of latent heat and phase change temperature of PCM were characterized by the differential scanning calorimeter (DSC). Tests were conducted under different inlet temperatures and flow rates of HTF, during which the temperature variation of PCM, heat stored/released, mean charging/discharging power, total charging/discharging time and instantaneous effectiveness were acquired. Experimental results indicate that the natural convection of melted paraffin impacts substantially on the phase-change rate of paraffin. Once melt completes, the natural convection intensity surges temporarily. Moreover, the increase of inlet HTF temperature and flow rate during charging can dramatically improve the heat transfer between HTF and PCM, which in turn shortens the total charging time. The HTF flow rate was found to play little role on the heat transfer during discharging since the thermal resistance of the solidified PCM increases considerably.

Performance analysis of a waste heat recovery solar chimney for nocturnal use

Solar chimney is one of the best ways to produce artificial wind to drive wind turbines. But the main problem associated with is that it’s dependence on solar energy and hence can’t be used during night times. The objective of the present work is to modify the existing model; so that it can be used for the generation of power even in nocturnal and cloudy conditions. There are many ways to recover waste heat from different industries, but solar chimney can give one of the leading possible ways to recover it. Waste heat can be used to heat the base or absorber of the solar chimney’s collector; or it can be used to heat the air flowing inside the chimney. Ansys 2019 R1 has been used for the Computational Fluid Dynamics (CFD) validation and analysis of the solar chimney with heat recovery heat exchanger. A heat exchanger (HE) plate of aluminium alloy has been used with syltherm-800 as heat transfer fluid (HTF), and exchanging heat with the air inside the chimney near its base. Effect of different parameters like HTF inlet temperature, mass flow rate of HTF, ambient temperature of air, and diameter of heat exchanger plate on the performance of solar collector of chimney has been analysed. Also, the maximum conversion efficiency of about 5% is achieved, which is more in comparison to solar chimney operating at normal day conditions. Limitation of the present work is related to the storage of heat during day time or there should be continuous supply of waste heat during chimney operations. In this paper, authors have proposed a CFD method for the modification and improvement of solar chimney in Manzanares (Spain) with a waste heat recovery heat exchanger for nocturnal use.

Effect of Inlet and Geometrical Parameters on the Melting of PCM Capsules of Elliptical Cross Section.

This paper focuses on the melting of phase change material capsulated in the elliptical cross-section horizontal cylinder under convective boundary conditions. Different parameters are discussed, namely, the HTF inlet temperature and velocity and the axes ratio of the capsule cross-section. The effect of HTF inlet temperature, inlet velocity, and the capsule axes ratio was studied using the CFD software FLUENT 6.3.26. A comparison between the numerical and experimental results was made for the system. The experimental results matched well with the heat transfer model. It is shown that the inlet temperature of the heat transfer fluid (HTF) has a great effect on the process of paraffin wax melting. The increase of HTF inlet temperature increases the Phase change material( PCM) liquid fraction at constant charging time and decreases at the same time the total time of the capsulated paraffin wax melting. The geometry of the capsule cross-section represented by its axes ratio has a sensible effect on the process of paraffin wax melting. Increasing the axes ratio of the capsule, i.e. elongated the capsule in the perpendicular direction of flow increasing the PCM liquid fraction at constant charging time and decreases the total time of the capsulated paraffin wax melting. The increase of HTF inlet velocity has a weak effect on the process of paraffin wax melting in the inlet velocity range 0.003-0.012 m/s.

Experimental study on the charging and discharging behaviour of capric–lauric acid/oleic acid mixture in a cold thermal energy storage system for cold storage applications

In this study a capric–lauric acid/oleic acid mixture was synthesized to form a low temperature PCM for cold storage applications. An experimental investigation was carried out in a double helical coil cold thermal energy storage unit (CTESU) to study the charging and discharging behaviour of capric–lauric acid/oleic acid mixture. The inlet temperature and flow rate of the heat transfer fluid (HTF) were selected as experimental parameters to analyse the cold thermal energy storage performance of PCM. The analysis includes charging and discharging behaviour, energy dissipation rate, energy storage rate, energy charging efficiency, energy discharging efficiency and influence of HTF inlet temperature and flow rate under varied experimental parameters. With the increased contact area, the developed double helical coil considerably improves the heat transfer performance of the cold thermal energy storage unit. The discharging rate was 18% faster than the charging process due to predominance of natural convection. The PCM solidification during charging process is controlled by conduction. With increasing HTF flow rate during the discharging process, the melting rate was 16% higher than lower flow rates. In contrast, as flow rates increased, the charging rate did not change significantly. The role of natural convection and stratification which leads to unnecessary mixing of PCM consequently lowering the cooling energy stored. Also results suggest that capric–lauric acid/oleic acid can be utilized as a potential PCM for low temperature storage applications.

Experimental analysis of a latent heat storage unit with multichannel flat tube and copper foam

The poor performance of phase change materials (PCMs) in thermal conductivity constrains the widespread application of latent heat storage units (LHSUs) in engineering while the low bulk density and large specificity of copper foam make it an ideal choice to solve this problem. This study proposes a new LHSU which is based on multichannel flat tube and copper foam. With water as the heat transfer fluid (HTF), copper foam is applied to enhance the heat performance of PCM (paraffin). The ratio of the heat exchange area to the PCM volume of this unit is 576.3 1/m, and the compactness factor is 71.8%. In order to evaluate the performance of this unit, a study is conducted on different HTF injection modes, the distribution of PCM temperature at different inlet temperatures and HTF flow rates, charge/discharge power, and the effectiveness of LHSU. According to the results, bottom injection is the optimal HTF injection method in the charge and discharge processes. The average effectiveness during the charge and discharge processes reaches up to 0.383 and 0.409, respectively. Compared with the traditional coil type LHSU, the unit proposed in this research performs better in heat transfer performance.

Thermodynamic Analysis of a High-Temperature Latent Heat Thermal Energy Storage System

Thermal energy storage (TES) technologies are becoming vitally important due to intermittency of renewable energy sources in solar applications. Since high energy density is an important parameter in TES systems, latent heat thermal energy storage (LHTES) system is a common way to store thermal energy. Though there are a great number of experimental studies in the field of LHTES systems, utilizing computational codes can yield relatively quick analyses with relatively small expense. In this study, a numerical investigation of a LHTES system has been studied using ANSYS FLUENT. Results are validated with experiments, using hydroquinone as a phase-change material (PCM), which is external to Therminol VP-1 as a heat transfer fluid (HTF) contained in pipes. Energy efficiency and entropy generation are investigated for different tube/pipe geometries with a constant PCM volume. HTF inlet temperature and flow rate impacts on the thermodynamic efficiencies are examined including viscous dissipation effects. Highest efficiency and lowest entropy generation cases exist when when flow rates are lowest due to low viscous heating effects. A positive relation is found between energy efficiency and volume ratio while it differs for entropy generation for higher and lower velocities. Both efficiency and entropy generation decreased with decreasing HTF inlet temperature. The novelty of this study is the analysis of the effect of volume ratio on system performance and PCM melting time which ultimately proved to be the most dominant factor among those considered herein. However, as PCM solidification and melting time is of primary importance to system designers, simply minimizing entropy generation by decreasing volume ratio in this case does not lead to a practically optimal system, merely to decrease heat transfer entropy generation. Therefore, caution should be taken when applying entropy analyses to any LHTES storage system as entropy minimization methods may not be appropriate for practicality purposes.

Thermal Performance Analysis of the Charging/Discharging Process of a Shell and Horizontally Oriented Multi-Tube Latent Heat Storage System

In this study, the thermal performance of latent heat thermal energy storage system (LHTESS) prototype to be used in a range of thermal systems (e.g., solar water heating systems, space heating/domestic hot water applications) is designed, fabricated, and experimentally investigated. The thermal store comprised a novel horizontally oriented multitube heat exchanger in a rectangular tank (forming the shell) filled with 37.8 kg of phase change material (PCM) RT62HC with water as the working fluid. The assessment of thermal performance during charging (melting) and discharging (solidification) was conducted under controlled several operational conditions comprising the heat transfer fluid (HTF) volume flow rates and inlet temperatures. The experimental investigations reported are focused on evaluating the transient PCM average temperature distribution at different heights within the storage unit, charging/discharging time, instantaneous transient charging/discharging power, and the total cumulative thermal energy stored/released. From the experimental results, it is noticed that both melting/solidification time significantly decreased with increase HTF volume flow rate and that changing the HTF inlet temperature shows large impacts on charging time compared to changing the HTF volume flow rate. During the discharging process, the maximum power output was initially 4.48 kW for HTF volume flow rate of 1.7 L/min, decreasing to 1.0 kW after 52.3 min with 2.67 kWh of heat delivered. Based on application heat demand characteristics, required power levels and heat demand can be fulfilled by employing several stores in parallel or series.