Phase Change Material Temperature Research Articles

RETRACTED: Study of the effect of the aspect ratio of a cylindrical lithium-ion battery enclosure in an air-cooled thermal management system

Batteries are utilized to store electrical energy in various devices due to their industrial importance, So in this paper, airflow is simulated in a channel to cool a two-dimensional, transient lithium-ion battery cylindrical cell. There is a circular PCM chamber around the battery. Battery cooling is evaluated by changing the aspect ratio of the PCM chamber and air velocity in the range of 0.2 to 0.4 and 0.001 to 0.005 m/s. COMSOL software is used for the simulations. The values of Tbattery, PCM chamber, the volume fraction (VFR) of molten PCM, and ambient air temperature are examined during the PCM charging and discharging process when the battery is working. The results of this study demonstrated that an enhancement in the air velocity causes the battery temperature (Tbattery), i.e., the maximum temperature and average temperature of the battery and the average temperature of PCM inside the chamber, to decrease. Also, the VFR of molten PCM is reduced with the air velocity. Over time, the values of air outlet temperature, Tbattery, and VFR of molten PCM decrease. Enhancing the aspect ratio intensifies the amount of temperature at the outlet. The aspect ratio of 0.2 corresponds to the lowest average temperature of the PCM chamber and the minimum VFR of molten PCM, while the aspect ratio of 0.35 corresponds to the highest average temperature of the PCM chamber and the maximum VFR of molten PCM.

Phase Change Process inside Toroidal Tube Heat Exchanger with Internal Fins

Inadequate melting of phase change material (PCM) in concentric tube and shell and tube heat exchangers appeal motivations for innovative latent heat thermal energy storage (LHTES) systems. In the current research, a novel application of toroidal tubes inside the LHTES system for charging of PCM is presented. The proposed heat exchanger geometry is numerically investigated with the help of enthalpy – porosity approach. Toroidal tubes are assumed to be filled with PCM (i.e., coconut oil) and fabricated inside cylinder accommodating the heat transfer fluid (HTF). To establish and accelerate homogenous melting, flat thin fins are attached inside the toroidal tubes, and transient simulations are performed. The system performance is investigated for variations of (i) fin numbers (Nf), (ii) fin length (L0), and (iii) fin orientations (Fo) in terms of (i) melt fraction (MF), (ii) average PCM temperature, (iii) energy stored by PCM, and (iv) Nusselt number (Nu). Simulation results indicate that fin orientation stands out as the dominant factor for heat transfer enhancement compared to fin numbers and fin length. In the toroidal tube LHTES system, it is found that even though fin numbers and fin length are identical, correctly oriented fins (i.e., case 8) can provide 50.52% more rate of energy storage than a system with random fin orientation (i.e., case 5). Moreover, the optimum fin orientation (i.e., case 8) can (i) save 65.28% time for 100% melting and (ii) provide 168% more rate of energy storage than a system without fins. Based on the melting progression pattern, the current study encourages the use of multiple PCMs having dissimilar melting point temperatures with fins.

Low temperature phase change materials for thermal energy storage: Current status and computational perspectives

Latent heat based thermal energy storage technology is quite promising due to its reasonable cost and high energy storage capacity. This technology is partially developed. The accelerated transition from non-renewable to renewable energy sources have attracted researchers to shift their focus towards demonstrating thermal energy storage utilizing latent heat at commercial level. Phase change materials utilizing latent heat can store a huge amount of thermal energy within a small temperature range i.e., almost isothermal. In this review of low temperature phase change materials for thermal energy storage, important properties and applications of low temperature phase change materials have been discussed and analyzed. Thermal energy storage technologies are compared in terms of technology readiness levels. Various techniques to improve the heat transfer characteristics of thermal energy storage systems using low temperature phase change materials have also been discussed. Moreover, the use of computational techniques to assess, predict and optimize the performance of the latent energy storage system for different low temperature applications is also presented. In this article, researchers and domestic energy management sector will find comprehensive guidelines for the performance improvement and technology selection for energy management via thermal energy storage.

EFFECT ON PHOTOVOLTAIC PERFORMANCE OF SOLAR PANELS

Photovoltaic (PV) cells energy production limitation leads to make its important to operate those panels in the best operating conditions. In addition, sunlight is lower and cell temperature is higher, all of which are variables that adversely affect power generation. The potential reduction of cell temperature by one of the alternative thermal control techniques, phase change material (PCM) installation is discussed in this article. Three types of PCM (RT15, RT35, and SP25E2) are used together in the proposed system to overcome wide temperature range, in such method to reduce the PV panel temperature. The proposed scheme is simulated using MATLAB. Simulation results shows that the effect of high temperature PCM is the overall effect. If the temperature is smaller than the PCM melting point, the use of PCM is disadvantage. This disadvantage is that the temperature of the panel increases more than the ambient temperature.

A review of novel methods and current developments of phase change materials in the building walls for cooling applications

The prime concern of the scientific community nowadays is high energy consumption and related greenhouse gas (GHG) emission. One of the major energy consumers is building sector, where nearly 30% of total energy is disbursed, with high priority to space cooling and ventilation. In addition, the contribution of buildings for GHG emission is also high. Various researchers in the recent past have suggested and successfully implemented different cooling methods to address this crisis. This paper evaluates various models suggested by researchers for building cooling with phase change materials (PCMs). Since the exposed area of high-rise buildings is more, there is a great chance for energy savings. The PCM impregnated building wall and building brick models have the promising potential for energy saving, by providing thermal comfort and conceding the peak temperature. This article emphasises the wall and building brick applications of PCM for building cooling, that illuminate the associated difficulties and possible alternatives. From the study, it was found that the PCM walls can be constructed with different techniques like adding PCM as a separate layer or inserting PCM in brick holes. In some cases, the PCM is added as a constituent in the cement mortar for plastering or for making concrete. These techniques will help to reduce the building cooling load, peak heat flux, and shift the peak temperature to off working hours. In cooling applications, it is preferred to keep the PCM layer near the heat source for better performance. The performance of a PCM wall highly depends upon the type of PCM used, location of PCM in the wall, type of application, and on the phase transition temperature of PCM.

Impact of innovative fin combination of triangular and rectangular fins on melting process of phase change material in a cavity

The increase in the gap between energy supply and demand have led to human focus on energy storage. With this purpose, this study numerically investigates the melting process of phase change material (PCM) in a storage by inserting innovative fins, which are combination of rectangular and triangular fins. Left wall of storage is assumed to be at a constant temperature which is higher than the melting temperature of PCM. The impacts of various efficient parameters on melting process are evaluated, which are schematic of internal fins, height of triangular fins, hot wall temperature, and different types of PCM. Results showed that among various studied geometries of fin, the proposed one herein augments the melting rate by about 57.56%. As the number of fins increments, melting time decreases, which leads to higher energy charging rate. By arrangement of triangular fins with different heights (ascending or descending) the melting time can be further shortened. The temperature of hot wall is inversely related to melting time, i.e., the higher hot wall temperature is, the shorter melting time is. Among evaluated PCMs, paraffin wax 811 showed better thermal performance with lower melting time and higher stored energy in a certain period of time.

Experimental investigation for the thermal management of a coaxial electrical cable system using a form-stable low temperature phase change material

This novel study was addressed to estimate the affecting rate of phase change materials (PCMs) on the thermal management of co-axial electrical cables applied in various applications. Four independent variables were selected to fulfill the objective based on the previous research studies in the literature on thermal management properties of PCMs and co-axial electrical cable features. Polyvinyl chloride (PVC) density, mass fraction of stearic acid (SA), as the utilized PCM, mass fraction of form-stable phase change material (FSPCM), and cable jacket's thickness were the studied parameters to seek out the intended responses. A melt impregnation method was used to embed the SA into the kaolin, which is used as supporting material to fabricate the aimed FSPCM composites. Besides, to gain a satisfying and precise point of view about the effects of PCM application in electronic cables, it is vital to investigate any possible mechanical properties variation affected by the selected parameters. Accordingly, tensile strength (stress) and elongation were also considered and compared with the expected PVC results. The application of FSPCMs in co-axial electrical cables was led to control and drop of the surface temperature by over 28.47 °C and a 4.62% decrease in cable loss.

Experimental Comparison of Three Characterization Methods for Two Phase Change Materials Suitable for Domestic Hot Water Storage

This study presents an experimental comparison of three characterization methods for phase change materials (PCM). Two methods were carried out with a calorimeter, the first with direct scanning (DSC) and the second with step scanning (STEP). The third method is a fluxmetric (FM) characterization performed using a fluxmeter bench. For the three methods, paraffin RT58 and polymer PEG6000, two PCM suitable for domestic hot water (DHW) storage, were characterized. For each PCM, no significant difference was observed on the latent heat and the total energy exchanged between the three characterization methods. However, DSC and STEP methods did not enable the accurate characterization of the supercooling process observed with the FM method for polymer PEG6000. For PEG6000, the shape of the enthalpy curve of melting also differed between the experiments on the calorimeter—DSC and STEP—methods, and the FM method. Concerning the PCM comparison, RT58 and PEG6000 appeared to have an equivalent energy density but, as the mass density of PEG6000 is greater, more energy is stored inside the same volume for PEG6000. However, as PEG6000 experienced supercooling, the discharging temperature was lower than for RT58 and the material is therefore less adapted to DHW storage operating with partial phase change cycles where the PCM temperature does not decrease below 52 °C.

Thermal Properties of Shape-Stabilized Phase Change Materials Based on Porous Supports for Thermal Energy Storage

The use of phase change materials (PCM) for thermal energy storage (TES) is of great relevance, especially for the exploitation, in various ways, of the major ecological resource offered by solar energy. Unfortunately, the transition to the liquid state of PCM requires complex systems and limits their application. The goal of producing shape-stabilized phase change materials (SSPCM) is mainly pursued with the use of media capable of containing PCM during solid/liquid cycles. In this work, four cheap shape stabilizers were considered: sepiolite, diatomite, palygorskite and zeolite and two molten salts as PCM, for medium (MT) and high temperature (HT). The SSPCM, produced with an energy saving method, showed good stability and thermal storage performances. Diatomite reaches up to 400% wt. of encapsulated PCM, with a shape stabilization coefficient (SSc) of 97.7%. Zeolite exhibits a SSc of 87.3% with 348% wt. of HT-PCM. Sepiolite contains 330% wt. of MT-PCM with an SSc of 82.7. Therefore, these materials show characteristics such that they can be efficiently used in thermal energy storage systems, both individually and inserted in a suitable matrix (for example a cementitious matrix).

Experimental investigations of high-temperature shell and multi-tube latent heat storage system

High-temperature thermal energy storage (TES) systems improve the reliability and performance of solar-thermal utilization systems due to their ability to levelize the gap between the energy supply and demand. The present work focuses on conducting extensive experimental investigations to study the performance characteristics of a latent heat storage (LHS) system. A customized experimental facility was designed and developed with air as the heat transfer fluid operating at a maximum temperature of 400 °C. Sodium nitrate used as the phase change material (PCM) was filled in the shell side of a multi-tube heat exchanger and performance parameters such as charging/discharging time, energy stored/discharged, and output power were estimated by varying the flow rate and inlet temperature of air. The axial and radial temperature distributions reveal that the heat transfer occurs predominantly due to natural convection during the charging process, whereas, discharging takes place primarily due to conduction heat transfer in the axial direction. The energy storage of ~ 19.5 MJ was achieved with maximum PCM temperature reaching up to 365 °C. A comparison with cast steel and concrete based sensible heat storage (SHS) mediums operating at similar experimental conditions indicates that the LHS medium possesses high energy storage density and low storage cost, however, a combination of SHS and LHS mediums can meet the diverse load requirements in the end-user applications.

Characteristic study of modified nano CuO powder-based paraffin composite and its experimental investigation of melting/solidification behavior for mobilized cold thermal storage systems

The low thermal conductivity of Phase Change Materials (PCM) reduces its performance and remains a challenging issue. In the present study, modified nano copper oxide powder (CuO) with various weight percentages is dispersed into paraffin wax to form Nano-PCM composites (NPCM). Transmission Electron Microscopy analysis showed the uniform dispersion of modified CuO and spherical in structure. Diffraction Scanning Calorimeter analysis (DSC) showed a trivial difference in the melting point of PCM and NPCM. The peak melting temperature of PCM was 18.56°C and for NPCM with 1% concentration was 17.14°C. The thermal conductivity of NPCM in solid and liquid states was high when compared to that of pure PCM. The thermal conductivity of NPCM with a 1% concentration is enhanced by 52% in a solid state and 20% in a liquid state. Solidification/Melting experiments conducted at different bath temperatures such as 15°C, 17°C, and 19°C for PCM and NPCM revealed that the solidification period and melting period reduced with an increase in concentrations of modified Nano CuO due to augmented heat transfer rates. The solidification time for NPCM with 1% concentration is reduced by 18.33% for discharging temperature 25°C, and melting time are reduced by 16.6% for charging temperature.

Melting characteristics of a longitudinally finned-tube horizontal latent heat thermal energy storage system

This study aims to analyze the effect of fin geometry on the thermal performance of longitudinally finned-tube horizontal latent heat thermal energy storage (LHTES) systems. The longitudinal fins with different fin heights, thickness, and numbers were applied in the horizontal shell-and-tube LHTES system and the paraffin was packed in the annulus. The melting fronts, average temperature, and velocity profiles of Phase Change Material (PCM) were graphically illustrated and compared for charging processes. It was found that the incorporation of longitudinal fins in a small quantity (2.85% of total volume) could reduce the complete melting time by 34% in comparison to the bare-tube configuration. Melting characteristics were compared using average liquid fraction, average PCM temperature, and stored energy. It was recommended that the fin height should not exceed half of the annulus gap. The optimum fin volume was identified by comparing the enhancement ratio for examined configurations. Furthermore, for the same fin volume configurations, this study evaluated (i) whether a large number of short fins are beneficial or a smaller number of long fins and (ii) whether thick short fins are beneficial or thin long fins? Comparison results showed that a small number of long fins were more beneficial than that of more short fins and the melting characteristics of thin long fins were superior to that of the thick short fins. Finally, the optimum fin configuration was justified, and the priority sequence was suggested for the design of longitudinally finned-tube energy storage systems.

Thermal performance evaluation of a latent heat thermal energy storage unit with an embedded multi-tube finned copper heat exchanger

ABSTRACT The experimental thermal characterization during charging and discharging of a prototype compact latent heat thermal energy storage system (LHTESS) with an embedded horizontally oriented finned multi-tube copper heat exchanger is presented. The thermal store was filled with a commercial-grade, CrodaTherm™ 60, phase change material (PCM) with a nominal melting temperature of 60°C. The proposed heat exchanger (HX) configuration mitigates the effect of low PCM thermal conductivity and increases the rates of heat transfer to and from the store during the charging and discharging processes compared to multi-tube copper HX without fins. The experimental testing regime assessed the impact of heat transfer fluid (HTF) volume flow rate and inlet temperature on I) transient PCM temperature distribution, II) the total charging/discharging time and III) instantaneous/average power during the charging and discharging processes. The experimental results showed that the HTF volume flow rate and inlet temperature play a significant role in the thermal performance of the LHTESS during the charging/discharging process. During the charging process, the influence of increasing HTF inlet temperature is greater than that due to increasing HTF volume flow rate. Moreover, it is shown that during the first 30 minutes of the discharging process, the average power output was 4.3, 5.1 and 5.3 kW for HTF volume flow rate of 2.5 and 7.2 and 10.5 l/min, respectively.

Molecular dynamics simulation on thermal enhancement for carbon nano tubes (CNTs) based phase change materials (PCMs)

In the study, CNTs based nanocomposite phase change materials (NPCMs) is considered for breaking through the constraint of the low thermal conductivity of conventional PCMs for thermal energy storage. A molecular dynamics simulation method is newly established to predict the structural, diffusive and thermal properties of composite PCMs based on CNTs. It is found that the PCMs is preferentially distributed as either one or two ring-shaped layers that discretely separated from the CNTs wall with a distance of 3.8 Å and 8.0 Å, respectively. The mean square displacement (MSD) and the self diffusion coefficient are characterized for featuring the molecule mobility and predicting the melting temperature of the composite PCMs. Interestingly, the dense phase existing between the CNTs wall and the PCMs is proven to be the dominant factor that negates the phase change enthalpy of the composite system. In realistic experiments using the CNTs with a radius of 10∼15 Å, the thermal conductivity is highly potential to be improved to 5∼15 W/m·K, indicating an augmentation of the thermal conductivity by approximate 32∼100 times compared to pure PCMs. The formation of efficient heat conduction paths explains for the intrinsic mechanism of the tremendous improvement in the CNTs based NPCMs, which could be achieved in the premise of strong binding effect of materials and reduced contact thermal resistance among CNTs in macroscopic PCM modules.

A novel energy-effective and carbon-emission reducing mortars with bottom ash and phase change material: Physico-mechanical and thermal energy storage characteristics

Novel cement based mortars containing bottom ash (BA) and phase change material (PCM) as thermal energy storing material were developed for thermal controlling of buildings. Form-stable BA/Capric-Stearic (C-S) acid eutectic mixture composite was produced at an impregnation rate of 30 wt% C-S. Melting temperature and latent heat capacity of form-stable composite PCM were observed as 23.65 °C and 52 J/g, respectively while the mortar containing 30 wt.% composite PCM had a melting temperature of 21.42 °C and latent heat value of 13.62 J/g. Water demand, porosity and absorption was increased depending on the variation of BA/C-S composite PCM. The compressive strength and dry unit weight of the mortar decreased up to 35 MPa at 28th day and 1826 kg/m3. The highest indoor heat difference between reference mortar and BA/C-S composite included-mortar was found to be 2.80 °C for heating and 1.95 °C for cooling period. Analytical approaches revealed that composite PCM adapted buildings have promising annual energy saving and carbon-emission reducing potential for various fuels. It was concluded that usage of the developed composite PCM has high potential for creation novel kinds of energy saving panels, concretes, mortars, bricks etc. used for inside temperature regulation of buildings.

A novel analytical approach to study the charging characteristics of a shell and tube thermal energy storage system

AbstractThis study presents a novel analytical solution of the phase change problem in a shell and tube arrangement of latent heat thermal energy storage (LHTES) system. The transient melting behavior of phase change material (PCM) is captured using time‐dependent boundary conditions and moving interface energy equation. An approximate mathematical model is developed with the help of dimensionless number (η), exponential integral function, Lambert W function, and Swamee and Oijha approximation. The proposed analytical solution is used for investigating the thermal performance of low, medium, and high melting temperature PCM for building, solar absorption cooling, and concentrated solar power (CSP) applications, respectively. The results obtained from the analytical approach are compared with a numerical model based on the enthalpy method. It is found that the root mean square difference between the average PCM temperature obtained from analytical solution and detailed numerical analysis is 3.3°C, 1.2°C, and 0.1°C for the low, medium, and high‐temperature systems, respectively. The temporal variation of melt front position and the effect of inner tube temperature are further investigated using the analytical solution. The mathematical model could be proposed as an effective tool for the assessment of shell and tube LHTES systems.

Experimental investigation of the charging and discharging of latent heat in phase change material (PCM) based aluminium tube heat exchanger

Nowadays, given the increasing importance of energy sources, the possibility of energy storage in the heat exchangers through the Phase Change Materials (PCM) and releasing it when needed has been extremely essential. This study seeks to develop a model as that of the domestic water heating system in which the phase change material is used for storing that heat energy as latent heat and it can be discharged during cooling. The behaviour of a PCM material is studied and the performance is tried to improve by using aluminium as the inner tubes instead of copper. In this experimental study, the thermal characteristics of PCM is studied by passing hot fluid and cold fluid through the tubes. Further the heat-storing capacity and the temperature distribution of wax along the tube was studied at different fluid temperatures. Also, the type of flow created by the fluid for different temperatures and the corresponding behaviour of the PCM during that particular temperature is also studied. A commercial grade Paraffin wax as PCM material with specific heat capacity of 2 kJ/kg-K is used and arrived at effectiveness around 0.48 for 40-50 °C and 0.59 for 50-60 °C. Logarithmic average of the temperature difference between 40°C-50 °C hot cycle is 10.654°C and during the cold cycle it is: 2.495°C, In the same way for 50°C -60 °C, during Hot cycle 11.56°C and for cold cycle 3.77°C. Finally, it is observed that based on the experimental study on the charging and discharging of latent heat storage, due to the low thermal conductivity of Phase change material, the rate of heat transfer during discharging is very low and the time required for discharging of latent heat storage is longer compared to the time required for charging of latent heat storage due to low heat transfer rate between PCM and hot Temperature fluid (Water).

Simultaneous and consecutive charging and discharging of a PCM-based domestic air heater with metal foam

• Study simultaneous and consecutive charging and discharging of storage heater. • Study a composite phase change material/metal heat exchanger cooled by air. • Study different modes of system operation for the purpose of domestic space heating. • Lower output air temperature for a higher air flow with a higher discharging rate. • 6.5 h for charging 15.32 kg phase change material with 90% porosity aluminum foam. Numerical investigations of the melting/solidification in a metal foam saturated with phase change material (PCM) were performed for simultaneous and consecutive operational modes. The composite is embedded in a rectangular compound cooled by passing air in a middle channel which is then employed to heat the room as a space heater. The composite is heated by two-rod heating elements to store thermal energy for peak-shaving purposes. The study covered the evaluation of the system in different operational modes for charging and discharging rate, the impacts of the metal foam and the influence of coolant flow rate on the solidification performance. The presence of PCM on one hand due to having almost constant temperature during the phase change process and the use of metal foam on the other hand due to proving high heat transfer rate from the PCM to the coolant, help in providing a uniform output temperature from the system which is a key factor for highly efficient space heaters. Moreover, evaluation of the operational modes can help to understand the behavior of the system in real scenarios when there is a need to charge the storage system and heat the room (discharging) simultaneously. The results show that the melting process is fully achieved due to the faster-charging process rate in modes I (8-hour charging and 8-hour discharging separately) and III (2-hour charging and 14-hour simultaneous charging-discharging), compared with mode II (2-hour charging and 2-hour discharging separately, repeated for 16 h). The temperature distribution in Mode III was more constant, which produced uniform heat exchanged between the PCM and the cooling fluid. The porosity is inversely proportional to the liquid development rate. The PCM melts entirely within 6.5 h for 90% porosity while 78% of the PCM melts in 8 h for the 95% porosity case. The final mean PCM temperature changed from 69.9 °C to 66.4 °C, when the air flow rate increases from 0.01 kg/s to 0.03 kg/s.

Enhancement of the Thermal Energy Storage Using Heat-Pipe-Assisted Phase Change Material

Usage of phase change materials’ (PCMs) latent heat has been investigated as a promising method for thermal energy storage applications. However, one of the most common disadvantages of using latent heat thermal energy storage (LHTES) is the low thermal conductivity of PCMs. This issue affects the rate of energy storage (charging/discharging) in PCMs. Many researchers have proposed different methods to cope with this problem in thermal energy storage. In this paper, a tubular heat pipe as a super heat conductor to increase the charging/discharging rate was investigated. The temperature of PCM, liquid fraction observations, and charging and discharging rates are reported. Heat pipe effectiveness was defined and used to quantify the relative performance of heat pipe-assisted PCM storage systems. Both experimental and numerical investigations were performed to determine the efficiency of the system in thermal storage enhancement. The proposed system in the charging/discharging process significantly improved the energy transfer between a water bath and the PCM in the working temperature range of 50 °C to 70 °C.

Performance enhancement of photovoltaic cells using phase change material (PCM) in winter

The performance of photovoltaic (PV) modules worsens due to increasing their operating temperature. In the current study, a passive cooling technique comprising an aluminum metal foam (AMF) with PCM for thermal regulation of a PV system is performed. Outdoors experiments are conducted comprising two modules: PV without any modifications and PV with AMF embedded in PCM denoted as PV/PCM/AMF. The temperature distribution on the surface of the PV panels, PCM temperature, open-circuit voltage, and output power produced were recorded during the winter period. The results revealed that the PV surface temperature of the PV-PCM/AFM system was 4 %, 7.4 %, and 13.2 % lower than that of conventional PV, and the power produced from PV-PCM/AFM system was 1.85 %, 3.38 %, and 4.14 % higher than that of conventional PV in December, January, and February, respectively.