Latent Heat Storage Applications Research Articles

Experimental and numerical study of cylindrical encapsulated phase change material in packed bed thermal energy storage with expansion and shrinkage effects

Packed bed latent heat thermal energy storage (PBTES) is a promising technology for storing thermal energy with a relatively compact size and smaller temperature variation during phase change. In this study, a lab-scale low-cost PBTES with cylindrical shape encapsulation of phase change material (PCM) is designed and fabricated for evaluating the charging-alone and discharging-alone thermal performance for medium-temperature range (200–350 °C) latent heat storage applications. Air is used as a heat transfer fluid (HTF), and solar salt is employed as a PCM. A new numerical model incorporating shrinkage and expansion of PCM during phase change is developed by considering the packed bed as the porous medium and the melt fraction-based density variation of PCM to model the transport and solid-liquid phase change phenomena in the PBTES. The numerical model is validated with the in-house experimental results. The maximum thermal charging efficiency is found to be 67.1 % for the mass flow rate of 4.3 g/s and a maximum charging inlet air temperature of 360.9 °C. The maximum discharging efficiency of 86.1 % is obtained for the mass flow rate of 4.3 g/s and discharging inlet air temperature of 35 °C. It is found that the expansion and shrinkage effects are prominent during the phase change of PCM during the charging and discharging operations of the PBTES.

Combined passive enhancement techniques improve the thermal performance of latent heat storage system: A design anomaly?

Poor heat transfer rate due to low thermal conductivity of phase change material limits the wide application of latent heat storage (LHS) systems. Thermal performance enhancement techniques can be potential methods to address this major limitation of LHS systems. In this context, the present numerical study examines the individual and cumulative impact of two passive heat transfer enhancement techniques (the orientation of the domain and position of the heat transfer fluid (HTF) tube) on the thermal performance of the latent heat storage (LHS) system consisting of high-temperature (HT) phase change medium (PCM). The individual effect of orientation decreases the charging duration of θ = 0° (horizontal configuration) by 10.5 %, 15 %, and 19.04 % than θ = 30°, θ = 60° and θ = 90° (vertical configuration), respectively. However, the discharging duration remains unchanged for all inclinations (11.5–12 h). The individual effect of eccentricity decreases the charging duration of horizontal (θ = 0⁰, ey = −5 mm,-10 mm,-20 mm) system by 6.25 %,12.8 %, and 18.75 % than concentric horizontal (θ = 0°, ex = ey = 0) system. Moreover, the combined effect of orientation and eccentricity (θ = 0⁰,ey = −5 mm,-10 mm,-20 mm) reduces charging duration by 28.75 %, 33.33 %, and 38.1 % than vertical concentric domain (θ = 90°, ex = ey = 0), respectively. However, eccentricity in vertically upward and downward directions increases the discharging duration compared to the concentric domain. Hence, the combined effect results in a design anomaly for HT-LHS system. The charging and discharging performances are observed to be predominantly sensitive to the Rayleigh number than the Reynolds number.

Synthesis, characterization and determination of thermal properties of shape stabilized n-pentadecane based composite phase change materials including graphitic carbon nitride/alumina fillers for latent heat storage applications

Recently, Phase Change Materials (PCMs) has attracted significant interest for thermal energy storage (TES), which is a rational and convenient energy storage method. In the present work, new composite PCMs were prepared by performing easy impregnation process in which n-pentadecane was selected as PCM. For this, emulsion templated porous polymer composites were synthesized and employed as the frameworks to obtain new composite PCMs. To improve the heat transfer characteristics, the support matrices were prepared by loading of 1 wt% thermal conduction enhancer fillers namely, graphitic carbon nitride (g-C3N4), graphitic carbon nitride/alumina (g-C3N4/Al2O3) and alumina (Al2O3). The chemical structure, thermal stability and specific surface area characteristics of the frameworks were examined by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG) and Brunauer–Emmet–Teller (BET) surface area analyses. Furthermore, the morphology and distribution of the fillers were explored with Scanning Electron Microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Additionally, improvements in the thermal conduction properties of the composite matrices were determined through the tests performed based on the T-history method. Moreover, the examinations on the thermal properties of the obtained composite PCMs were carried out using Differential Scanning Calorimetry (DSC). It was found that the reductions in supercooling temperatures (ΔT) were observed for the synthesized composite PCMs compared to degree of supercooling of pristine n-pentadecane. According to the obtained results, the synthesized composite PCMs can be employed in the cold thermal energy storage (TES) applications considering their appropriate properties and favorable TES capacities between 79.49 kJ/kg and 121.50 kJ/kg.

Recycling of aluminium scrap into phase change materials for high-temperature storage applications: Thermophysical properties and microstructural characterisation

Metal scrap is often generated during conventional production processes and at the end-of-life of metallic components finding use as a recycled metal source. However, the impurities introduced in the recycling process can deteriorate the mechanical properties of the final product leading to down-cycling from structural applications or requiring great effort to make the material viable again.Metallic phase change materials (mPCMs) are promising materials due to their high energy storage density and high thermal conductivity relative to common inorganic and organic thermal storage materials. Metals used for thermal applications, such as mPCMs do not have strict mechanical requirements, and could potentially be made from recycled sources unsuitable for structural significant applications. Thermal storage offers an alternative use for scrap sources, especially aluminium alloys which according to the International Energy Agency are among the metals with the highest recovery rates.AlSi cast alloys are widely used in different applications, especially the automotive industry. In this work, the eutectic composition Al-12.6 wt% Si has been proposed as thermal storage material due to the great potential and excellent storage properties in the temperature range 500–600 °C. Thermophysical properties including melting temperature, heat of fusion, heat capacity and thermal diffusivity were experimentally determined via Differential Scanning Calorimetry (DSC) and Light Flash Analysis (LFA) in order quantify the impact of impurities typically present in commercial aluminium alloys such the 2000 and 3000 series.Four different AlSi alloys with different impurity levels from scrap-equivalent compositions were investigated as candidate materials for latent heat storage applications and their potential contribution in the circular economy.

Experimental and numerical investigation of a rectangular finned-tube latent heat storage unit for Carnot battery

Latent heat storage technology has a great potential in Carnot battery systems, and its thermal performance directly affects the system performance. In this paper, a rectangular phase change heat storage unit with finned-tube structure is designed and manufactured, and polyethylene wax/expanded graphite is adopted as the composite phase change material. The thermophysical properties of the polyethylene wax are characterized by experiments first, and then the heat transfer performance of the unit is investigated through varying inlet mass flow rates and inlet temperature on the test rig. Meanwhile, the detailed evolution of the phase change process is visualized and obtained by corresponding numerical simulations. Furthermore, the effects and selection principle of fin number, thickness, and material on the melting process are clarified by numerical simulations. Results shows that the influence of the inlet temperature is more significant than the mass flow rate on the melting/solidification time, however, changing the inlet temperature and mass flow rate has little effect on melting/solidifying the last 10 % of PCM. Heat conduction dominated the heat transfer process due to the high viscosity of polyethylene wax, inducing little stratification of the temperature distribution in the regions bounded by fins. The regions close to the corners and sidewalls are the primary factors delaying melting/solidification rate. Increasing fin number and thickness can effectively decrease the melting/solidification time at the expense of the heat storage capacity. Compared to selecting only high thermal conductivity fin materials, adopting fins with high thermal conductivity, low density, and low specific heat is a better approach for achieving higher heat storage capacity and shorter melting time. The present study explores candidate materials for medium-low temperature latent heat storage and potential applications of traditional finned-tube heat exchangers in medium-low temperature latent heat storage.

Experimental investigation on thermal properties and fire performance of lauric acid/diphenyl phosphate/expanded perlite as a flame retardant phase change material for latent heat storage applications

The form-stable composite energy storage developed in this study was produced by integrating a novel flame retardant phase change material formed of 90 wt% lauric acid (LA) as a phase change material and 10 wt% resorcinol bis(diphenyl phosphate) (RDP) as a flame retardant into a supporting material of expanded perlite (EP) without leakage. A differential scanning calorimeter (DSC) test is employed to characterize the mass ratio of LA_RDP, and a filter paper is used to assess the leakage test of LA_RDP/EP. Results from scanning electron microscopy (SEM) show that the flame retardant phase change material of LA_RDP has been successfully embedded into EP’s porous structure. Moreover, chemical compatibility of composites is analyzed by fourier transform-infrared spectrometer (FT-IR). According to the DSC test, the flame retardant phase change material developed of LA_RDP/EP has an appropriate phase transition temperature of ∼ 40–45 °C and fusion latent heat range of ∼ 86.02–88.29 J/g for thermal control in buildings. After 50 thermal cycles, the thermal cycling test depicted that the composite PCM possess outstanding thermal reliability. By incorporating 5 wt% expanded graphite (EG), the thermal conductivity of the LA_RDP/EP composite is enhanced by about 41.6%. In accordance with the thermogravimetric analysis (TGA) test, the produced flame retardant and EP reduces the mass loss of LA. Cone calorimetry is also utilized to examine the flame retardant phase change material composite’s flammability characteristics. LA_RDP/EP demonstrates valued thermal properties while lowering the flammability of LA. The findings demonstrated that the formed LA_RDP/EP composite might be assessed as a suitable material in thermal applications for effective and sustainable energy use.

MOF-derived hierarchical carbon/ZnO hybrid synergistically boosts photothermal conversion and storage capability of phase change materials

The weak photon-capturing ability is a long-standing bottleneck for pristine metal–organic framework (MOF)-based phase change materials (PCMs) in photothermal conversion and latent heat storage applications. Herein, we designed MOF-5-derived hierarchical nanoporous carbon/ZnO nanoparticle hybrid as dual efficient photonic harvester and molecular heater for synergistically boosting photothermal conversion and storage capability of PCMs using an in-situ anchoring strategy. Compared with post-decorated ZnO strategy, ZnO photosensitizers derived in situ from MOF-5 are capable of guaranteeing high dispersibility and enhanced photon-capturing capability in the hierarchical carbon framework. Resultantly, high-performance photothermal composite PCMs are obtained due to the constructed intense and broadband absorption photonic nanoheaters after paraffin wax (PW) is encapsulated inside MOF-5-derived hierarchical nanoporous carbon/ZnO (MOF-5-PC/ZnO). Benefiting from the synergistic effect of dual high-efficiency photonic harvester and molecular heater (MOF-5-derived ZnO nanoparticles and hierarchical nanoporous carbon), PW@MOF-5-PC/ZnO-700 °C composite PCMs obtain the optimal photothermal conversion and storage capacity. Meanwhile, PW@MOF-5-PC/ZnO composite PCMs exhibit superior shape stability, thermal stability, and durable reliability. Importantly, our proposed development strategy of high-efficiency photothermal composite PCMs is universal due to high customization and universality of PCMs and Zn-MOFs.

Evaluation of carbon based-supporting materials for developing form-stable organic phase change materials for thermal energy storage: A review

This paper thoroughly reviews the development and characterization of carbon-based form stable organic phase change materials (FS-OPCMs) for latent heat storage applications. The O-PCMs such as paraffin, fatty acids, polyethylene glycols (PEGs), etc., suffer from poor thermal conductivity and flow ability in their molten state, which restricts their many applications. Carbon-based materials are seen as a promising and viable way to overcome these challenges. They have a very high thermal conductivity and can hold liquid phase change materials (PCMs) in their pores. This review provides comprehensive coverage of the carbon structures and their classifications, including carbon nanotubes (CNT), carbon nanofiber (CNF), expanded graphite (EG), graphene, graphene oxide (GO), carbonized industrial solid wastes, and other carbon-based materials that can be used as supporting porous materials in developing FS-OPCMs for thermal energy storage (TES) applications. In addition, the thermal and chemical performance of carbon-based FS-OPCMs is extensively investigated and given. The applications of such composites are also discussed and summarized. Finally, the potential of these materials for thermal energy storage is presented. This review provides an in-depth insight into the potential of carbon-based materials for latent heat thermal energy storage (LHTES).

Shape-stabilized n-heptadecane/polymeric foams with modified iron oxide nanoparticles for thermal energy storage

This study based on design, preparation and characterization of polymerized high internal phase emulsion (poliHIPE) foams as support materials containing iron oxide (Fe3O4) nanoparticles for impregnation of n-heptadecane as phase change material (PCM). The Fe3O4 nanoparticles were synthesized mechanically assisted co-precipitation method and modified for harmonization with the emulsion system. Fe3O4 nanoparticles doped support materials were prepared via emulsion-templated strategy, and the produced polymeric foams used for preparation of shape-stabilized n-heptadecane based composite PCMs. The total latent heat was determined as 99.6 J/g by differential scanning calorimetry (DSC) analysis, while the impregnation ratio of n-heptadecane was found to be 67%. The performances of composites were also investigated via leakage test and heat storage rate measurement. Based on the analysis result, it was determined that shape-stabilized n-heptadecane based composite PCMs are promising energy materials for low temperature latent heat storage applications.

Use of Low Melting Point Metals and Alloys (Tm < 420 °C) as Phase Change Materials: A Review

Phase Change Materials (PCMs) are materials that release or absorb sufficient latent heat at a constant temperature or a relatively narrow temperature range during their solid/liquid transformation to be used for heating or cooling purposes. Although the use of PCMs has increased significantly in recent years, their major applications are limited to Latent Heat Storage (LHS) applications, especially in solar energy systems and buildings. PCMs can be classified according to their composition, working temperature and application. Metallic PCMs appear to be the best alternative to salts and organic materials due to their high conductivity, high latent heat storage capacity and wide-ranging phase change temperature, i.e., melting temperature and chemical compatibility with their containers. This paper reviews the latest achievements in the field of low-melting point metallic PCMs (LMPM-PCMs), i.e., those with melting temperatures of less than 420 °C, based on Zn, Ga, Bi, In and Sn. Pure LMPM-PCMs, alloy LMPM-PCMs and Miscibility Gap Alloy (MGA) LMPM-PCMs are considered. Criteria for the selection of PCMs and their containers are evaluated. The physical properties and chemical stability of metallic PCMs, as well as their applications, are listed, and new application potentials are presented or suggested. In particular, the novel application of metallic PCMs in casting design is demonstrated and suggested.

Microfluidic Production of Monodisperse Biopolymer Microcapsules for Latent Heat Storage.

Microencapsulation of phase change materials in a polymer shell is a promising technology to prevent them from leakage and to use them as a handleable powder state. However, the microencapsulation process is a time-consuming process because the typical shell-forming step requires polymerization or evaporation of the solvent. In this study, we report a simple and rapid flow process to prepare monodisperse biocompatible cellulose acetate (CA) microcapsules encapsulating n-hexadecane (HD) for latent heat storage applications. The microcapsules were prepared by combining microfluidic droplet formation and subsequent rapid solvent removal from the droplets by solvent diffusion. The diameter and shell thickness of the microcapsules could be controlled by adjusting the flow rate and the HD-to-CA weight ratio in the dispersed phase. We found that 1-hexadecanol added to the microcapsules played the role of a nucleation agent and mitigated the supercooling phenomenon during crystallization. Furthermore, cross-linking of the CA shell with poly(propylene glycol), tolylene 2,4-diisocyanate terminated, resulted in the formation of a thin and dense shell. The microcapsules exhibited a 66 wt % encapsulation efficiency and a 176 J g-1 latent heat storage capacity, with negligible supercooling. We believe that this microflow process can contribute to the preparation of environmentally friendly microcapsules for heat storage applications.

Phase change material mixed with chloride salt graphite foam infiltration for latent heat storage applications at higher temperatures and pressures

Phase change material mixed with chloride salt graphite foam infiltration for latent heat storage applications at higher temperatures and pressures

Thermal conductivity evolution of a compressed expanded natural graphite – Phase change material composite after thermal cycling

Compressed Expanded Natural Graphite (CENG) impregnated with Phase Change Material (PCM) is an interesting material for latent heat storage application requiring a high heat transfer rate. This composite material, that has orthotropic properties, undergoes expansion while the PCM changes phase that might affect its thermal properties and its mechanical integrity. In order to assess this possible evolution, the CENG-PCM thermal conductivities in the two principal directions have been measured before and after a 1500 thermal cycling test. The thermal characterisation was performed using two methods: a classic hot guarded plate method and a more originally inverse method. The results show no significant change of the thermal conductivity values after ageing cycles in spite of the appearance of cracks in the planar direction of the composite. We can conclude that the delamination of the CENG was not sufficient to affect the thermal conductivities. In addition, a DSC analysis shows that the latent heat is also almost unchanged after the thermal cycling.

Innovative Development of Programmable Phase Change Materials and Their Exemplary Application

The research project Fraunhofer Cluster of Excellence “Programmable Materials” aims to develop new materials that can change their properties according to defined boundaries. This article describes the development and use of a novel programmable phase change material (PCM) for latent heat storage applications. At the moment, these PCMs have a programmable trigger mechanism incorporated that activates the crystallization of the material as a reaction to a defined stimulus so that the stored heat is released. In future development stages, programmability is to be integrated on the material level. The latent heat storage that is based on PCMs can be recharged by using the energy of the sun. As an example, for a possible application of such a material, the use of a novel programmable PCM in greenhouses to support heating energy reduction or to reduce the risk of frost is explained. Using the hygrothermal simulation tool WUFI® Plus, the effects in greenhouse constructions without and with commercially available or novel programmable PCMs are calculated and presented in the present article. The calculations are based on the material data of calcium chloride hexahydrate (CaCl2-6H2O), as this material serves as a basic material for the development of programmable PCM compositions. The results of the simulations show a positive impact on the indoor temperatures in greenhouses in view of the risk of frost and the reduction of heating energy. Thus, the vegetation period can be extended in combination with a lower energy load. By an eligible actuation mechanism, an inherent material system for temperature control can be created.

Charging and discharging enhancement of a vertical latent heat storage unit by fractal tree-shaped fins

The popular application of latent heat storage (LHS) units using phase change materials is limited in converting and utilizing renewable energy due to their poor thermal efficiency. To address this deficiency, a tree-shaped fin inspired by nature is employed for the thermal enhancement of vertical LHS units. A three-dimensional mathematical model using the enthalpy-porosity method is developed to comprehensively evaluate the heat charging/discharging process of the new and traditional LHS units, focusing on the role of heat transfer fluid (HTF) direction. The results indicate that tree-shaped fins improve the temperature uniformity and facilitate the melting/solidification rate, which exhibits a preferable advantage that the full melting/solidification duration shortens by 34.5% and 49.2%, and the time-averaged heat storage/release rate augments by 49.4% and 96.4%. Interestingly, natural convection significantly improves the heat charging performance, while the role of natural convection can be considered negligible during discharging processes. Moreover, the HTF temperature seriously affects the performance of LHS units, while the role of HTF flow rate is less prominent. It is found that the upward flow of HTF is beneficial to the heat charging improvement while a downward flow mode facilitates the discharging performance, providing useful advice for practical applications of vertical LHS units.

A Review of Composite Phase Change Materials Based on Porous Silica Nanomaterials for Latent Heat Storage Applications.

Phase change materials (PCMs) can store thermal energy as latent heat through phase transitions. PCMs using the solid-liquid phase transition offer high 100–300 J g−1 enthalpy at constant temperature. However, pure compounds suffer from leakage, incongruent melting and crystallization, phase separation, and supercooling, which limit their heat storage capacity and reliability during multiple heating-cooling cycles. An appropriate approach to mitigating these drawbacks is the construction of composites as shape-stabilized phase change materials which retain their macroscopic solid shape even at temperatures above the melting point of the active heat storage compound. Shape-stabilized materials can be obtained by PCMs impregnation into porous matrices. Porous silica nanomaterials are promising matrices due to their high porosity and adsorption capacity, chemical and thermal stability and possibility of changing their structure through chemical synthesis. This review offers a first in-depth look at the various methods for obtaining composite PCMs using porous silica nanomaterials, their properties, and applications. The synthesis and properties of porous silica composites are presented based on the main classes of compounds which can act as heat storage materials (paraffins, fatty acids, polymers, small organic molecules, hydrated salts, molten salts and metals). The physico-chemical phenomena arising from the nanoconfinement of phase change materials into the silica pores are discussed from both theoretical and practical standpoints. The lessons learned so far in designing efficient composite PCMs using porous silica matrices are presented, as well as the future perspectives on improving the heat storage materials.

Experimental research on latent heat characteristics of binary mixed molten salt

At present, thermal storage is considered as one of the key technologies to alleviate the problem of instability and intermittence for renewable energy. Due to relatively high latent heat, latent heat storage by molten salt is considered to a potential technology. Because of the restriction of different thermophysical parameters, the application of latent heat storage by molten salt has many technical obstacles. So, it is an urgent work to find a better mixed molten salt formula with comprehensive thermophysical properties. In this paper, we selected halogen salts (NaCl, NaF) and alkali (NaOH) to prepare binary mixed molten salts. From the results, for the mixed molten salt of NaCl-NaOH, NaCl:NaOH=1:9 has a maximum latent heat value of 301.2J/g. The initial melting temperature is about 200°C. With the increase of the mass ratio of NaCl, the termination melting temperature increases firstly then decreases. For mixed molten salt of NaF-NaOH, NaF:NaOH=1:9 has a maximum latent heat value of 199.5J/g, the initial and termination melting temperatures are about 265°C and 380°C, repectively. The latent heat value of NaCl-NaOH and NaF-NaOH mixed molten salts decreased with the increase of the mass ratio of halogen salts.

Buoyancy-driven melting and solidification heat transfer analysis in encapsulated phase change materials

Controlled melting and solidification in encapsulated phase change materials (PCMs) is of practical interest, for example, in latent heat storage applications. The choice of PCMs and the dynamic heat transfer characteristics during phase change - affecting the transient charging/discharging rates - are decisive for the energy and power density of the heat storage option. For example, highly conductive, high melting point (above 700 K) metal alloys have a potential advantage as a high energy and power density latent heat storage, compared to the widely used low conducting molten salt and paraffin wax. This advantage depends on the relative dominance of heat transfer modes that vary depending on the thermal properties of the PCM, shape of the encapsulation, and the load conditions, and must be quantified to warrant a fair comparison. We developed a 2D transient phase change model of encapsulated PCMs, accounting for phase change over a temperature range, volumetric expansion and contraction, and multi-mode heat transfer within the encapsulated PCM. The enthalpy-porosity method was used to model the phase change in a fixed grid. Validation was performed with literature data of low and high-conductivity PCM experiments (RT27 and lead). Two types of PCMs were subsequently investigated in detail: a high-conducting binary-eutectic alloy Al-12.6Si and a low-conducting commercially available RT27 paraffin wax (Rubitherm GmbH). The model was used to compare the phase change process and the strength of the various modes of heat transfer in the PCM filled cylindrical stainless-steel encapsulations in horizontal and vertical orientation with constant temperature walls. A full parameter study and non-dimensional analysis are presented for different PCMs. The results quantified the influence of boundary conditions, thermophysical properties and geometrical parameters on the phase change process and the contribution of the natural convection within the encapsulation. The non-dimensional analysis linked the melt fraction and heat transfer rates to a combination of the Fourier, Stefan, Rayleigh and Nusselt numbers. Fitting of the exponents of non-dimensional number groups to the heat transfer calculations allowed to provide general correlations for melting time, melt fraction, heat transfer rates, and characteristics of melting. Such correlations provide general understanding of the transient heat transfer in phase change media and provide engineering tools for designing, for example, a latent heat storage unit.

Graphite foam infiltration with mixed chloride salts as PCM for high-temperature latent heat storage applications

An improved hybrid vacuum and pressure-assisted infiltration technique was developed for the infiltration of phase change materials (PCM) into the graphite foam matrix. A single chamber with no moving part infiltration setup was designed and fabricated. Pelletized PCM was introduced to provide enough porosity for air removal using vacuum pumps with no need for transfer PCM after melting and infiltration. Simple design, the use of stainless steel, and the corrosion resistance feature of PCM provides a very cost-effective design and easily controllable process. Mixed alkali and alkaline chloride salts as PCM were infiltrated into the high porosity graphite foam to enhance the thermal conductivity of latent heat storage medium. Chloride based PCM with proven corrosion-resistant features, high energy storage density that enables storage and release of energy at nearly constant temperatures close to the melting temperature of 355 °C are used in this study, as an example. The composites of infiltrated graphite foam and chloride salt PCMs were studied using SEM, EDS microstructural analyses to determine the effectiveness of the infiltration process. An infiltration efficiency greater than 90% of the available porosity was achieved. The thermal conductivity of the infiltrated samples was analyzed using a laser Nano-flash thermal conductivity device. The thermal conductivity of the foam/PCM composite was shown to be larger by a factor greater than 40 times of pure chloride PCM (1–2 W/m-K). Low-cost infiltration with proven efficacy and repeatability of infiltrated PCM could be a breakthrough for 3rd generation of CSP plant applications with supercritical CO2 power cycles.

Combined Effects of Eccentricity and Internal Fins on the Shell and Tube Latent Heat Storage Systems

A numerical simulation study was performed on shell and tube configuration for latent heat storage applications where a Phase Change Material “PCM” - N-eicosane -was used to fill the shell side. The effects of smooth tube eccentricity from the shell center were investigated first, two values of eccentricity (ε=0.267, ε=0.533) were compared to the concentric case (ε=0). It was found out that increasing the eccentricity reduces the melting time by 5% and 10% for ε=0.267 and 0.533 respectively. Then the combined effects of eccentricity and attaching fins to the tube within the shell side were investigated for two fin types: straight rectangular fins and flipped triangular fins. The fin addition to the concentric tube reduced the melting time by about 36%, whereas combining the fins - of either type - to the tube of eccentricities of 0.267 and 0.533 reduced the melting by almost 41 % and 48% respectively, when compared to the smooth concentric tube case.