Investigation of Thermal Behavior of Paraffins, Fatty Acids, Salt Hydrates and Renewable Based Oils as PCM (original) (raw)
Related papers
2021
Latent heat thermal energy storage (LHTES) using phase change materials (PCM) is a renewable energy solution that is applicable for implementation in space cooling due to its high energy storage density. A novel thermal energy storage which will encapsulate a PCM layer to absorb the rejected heat from the building during occupied hours and release it to the ambient air during night-time is going to be developed. On the grounds of this development, a selection of seven PCMs are examined. The selected materials comprise the basic classes of PCM, namely: paraffins, fatty acids, and salt hydrates. The objective of this study is to identify experimentally the thermal properties of commercial PCM, renewable based oils, PCM in water emulsions, and PCM polymer blends. The supporting materials used in the polymerization of the PCM are polyethylene glycol diacrylate (PEGDA) and polyvinylpyrrolidone (PVP). The characterization of the thermophysical properties of the PCM is achieved by using differential scanning calorimetry (DSC) in dynamic operation mode. The values of the thermophysical properties for the commercial PCM and the renewable based oils provided by the manufacturers are compared with the experimental results. The long term stability of the thermophysical properties of PCM after 50, 100, 150, and 200 thermal cycles equivalent to a 6-month duty cycle in a real-life application is presented. The cases of the PCM emulsions and the PCM polymer blends are analyzed. The obtained results demonstrate the stability of the PCM under thermal cycling and the supercooling effect during the liquid-solid phase change.
Materials, 2020
Thermal-Energy Storage (TES) properties of organic phase change materials have been experimentally investigated and reported in this paper. Three paraffin-based Phase Change Materials (PCMs) and one bio-based PCM are considered with melting temperatures of 24 °C, 25 °C and 26 °C. Sensible heat storage capacities, melting characteristics and latent heat enthalpies of the studied PCMs are investigated through Differential Scanning Calorimetry (DSC) measurements. Two alternative methods, namely the classical dynamic DSC and a stepwise approach, are performed and compared with the aim to eliminate and/or overcome possible measurement errors. In particular, for DSC measurements this could be related to the size of the samples and its representativity, heating rate effects and low thermal conductivity of the PCMs, which may affect the results and possibly cause a loss of objectivity of the measurements. Based on results achieved from this study, clear information can be figured out on how...
Analysis of PCM Material in Thermal Energy Storage System
ijesd.org
A phase-change material (PCM) is a substance with a high latent heat storage capacity which on melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Various PCM like Paraffin wax, sodium acetate tri-hydrate and phenolphthalein are considered which are used to absorb heat from the coolant water from the engine. The conduction and convection criterion of heat transfer enable the PCM to store this heat as latent heat. The amount of convection and temperature change brought about due to the heat flux has been simulated and studied in detail using GAMBIT and FLUENT .
Storage Capacity in Dependency of Supercooling and Cycle Stability of Different PCM Emulsions
2021
Phase-change materials (PCM) play off their advantages over conventional heat storage media when used within narrow temperature ranges. Many cooling and temperature buffering applications, such as cold storage and battery cooling, are operated within small temperature differences, and therefore, they are well-suited for the application of these promising materials. In this study, the storage capacities of different phase-change material emulsions are analysed under consideration of the phase transition behaviour and supercooling effect, which are caused by the submicron size scale of the PCM particles in the emulsion. For comparison reasons, the same formulation for the emulsions was used to emulsify 35 wt.% of different paraffins with different purities and melting temperatures between 16 and 40 °C. Enthalpy curves based on differential scanning calorimeter (DSC) measurements are used to calculate the storage capacities within the characteristic and defined temperatures. The enthal...
IOP conference series, 2019
Phase Change Materials (PCMs) provide a greater density of energy storage with a smaller temperature difference between storing and releasing heat compared to sensible heat storage methods. This paper reports results of study on bio-PCM made of vegetable oil ester and water mixtures. T-history thermal analysis method was implemented in determining thermal properties of the bio-PCM candidates. Comparison analysis was also performed in order to evaluate how favorable the investigated bio-PCM compared with conventional salt based PCM and propylene glycol. The study results showed that with right amount vegetable oil ester, the bio-PCMs can reduce freezing point and reduce or even eliminate super-cooling of water. On the other hand, salt based PCMs and propylene glycol showed high super-cooling and lower latent heat storage. This study has shown that the investigated water based bio-PCMs are strong PCM candidates for sub-zero energy storage applications.
Preliminary investigation of thermal behaviour of PCM based latent heat thermal energy storage
E3S Web of Conferences
Solid-liquid phase change is used to accumulate and release cold in latent heat thermal energy storage (LHTES) in order to reduce energy consumption of air cooling system in buildings. The storing capacity of the LHTES depends greatly on the exterior air temperatures during the summer nights. One approach in intensifying heat transfer is by increasing the air’s velocity. A LHTES was designed to be integrated in the air cooling system of a building located in Bucharest, during the month of July. This study presents a numerical investigation concerning the impact of air inlet temperatures and air velocity on the formation of solid PCM, on the cold storing capacity and energy consumption of the LHTES. The peak amount of accumulated cold is reached at different air velocities depending on air inlet temperature. For inlet temperatures of 14°C and 15°C, an increase of air velocity above 50% will not lead to higher amounts of cold being stored. For Bucharest during the hottest night of the...
Review on phase change materials (PCMs) for cold thermal energy storage applications
Applied Energy, 2012
Thermal energy storage (TES) is a technology with a high potential for different thermal applications. It is well known that TES could be the most appropriate way and method to correct the gap between the demand and supply of energy and therefore it has become a very attractive technology. In this paper, a review of TES for cold storage applications using solid-liquid phase change materials has been carried out. The scope of the work was focussed on different aspects: phase change materials (PCM), encapsulation, heat transfer enhancement, and the effect of storage on food quality. Materials used by researchers as potential PCM at low temperatures (less than 20 ºC) are summarized and some of their thermophysical properties are reported. Over 88 materials that can be used as PCM, and about 40 commercially available PCM have been listed. Problems in long term stability of the materials, such as corrosion, phase segregation, stability under extended cycling or subcooling are discussed. Heat transfer is considered both from theoretical and experimental point of view and the different methods of PCM encapsulation are reviewed. Many applications of PCM at low temperature can be found, such as, ice storage, conservation and transport of temperature sensitive materials and in air conditioning, cold stores, and refrigerated trucks.
Melting of PCM inside a novel encapsulation design for thermal energy storage system
2021
Phase Change Materials (PCMs) encapsulated inside different shape and size enclosures have been playing an important role in designing thermal energy storage (TES) systems for a wide range of applications. In the present work, transient heat transfer and the melting process of n-octadecane PCM encapsulated in a novel Pear-Shaped Thermal Energy Storage (PS-TES) system with and without constraint are numerically investigated and verified with experimental visualizations. An adiabatic cylindrical rod, placed at the axis of symmetry of the pear-shaped enclosure, is used to create the constraint. A mathematical model is developed and numerically solved to study energy transport processes inside the proposed PS-TES systems. The heat transfer characteristics such as melt fraction, Nusselt number, and energy stored in the system and their temporal variation during the melting process are determined. The melting process is visualized numerically to track the solid-liquid interface during the melting process as well. Comparison of results from the unconstrained and constrained cases reveals that the existence of the adiabatic constraint inside the system decreases the melting rate, as the total time required to complete the melting process in the constrained melting (~178 min) is almost twice that of unconstrained melting (~97 min). The effect of the Rayleigh number on the melt fraction, Nusselt number, and the stored energy is studied and discussed as well. Furthermore, a comparison between the melt fraction results for pearshaped system and a convectional cylindrical container with the same height and same volume shows that the complete melting time for the PS-TES system (~97 min) is less compared to the one for the cylindrical case (~108 min). A comprehensive experimental setup is also developed using a constant temperature bath and thermal regulator to visualize melting images and track the melting front during the phase change process. Numerical images of heat transfer field and solid-liquid interface, as well as the temporal variation of melt fraction in both test cases, are compared with experimental visualizations, and an excellent agreement is reported.
Applied Thermal Engineering, 2019
For an efficient use of latent heat storage, it is necessary to know the phenomena that occur during the phase change from solid to liquid. This makes it possible to optimize the conditions that serve to reduce the charging and discharging time. The objective of this work is to study experimentally the process of heat transfer during the PCM (Phase Change Material) fusion. Two storage tanks of the same volume with a different filling positions of PCM are used in the setup. In the first tank, the paraffin is integrated directly in its lateral part, and in the second, the content of PCM is centered on the axis. It was observed that the total PCM melting in the first configuration lasts almost twice as long as in the second. Furthermore, the analysis of the thermal behavior of the storage has shown that the phase change during melting takes place on layers that are far from the exchange surface.
Investigation of heat transfer in a polymeric phase change material for low level heat storage
Energy Conversion and Management, 1997
A new material for low level heat storage has been elaborated. It is a stable mixture of water with a water soluble polymerised and cross-linked monomer such as polyacrylamid. Quantitative results regarding the thermophysical properties of the material are presented. These parameters are used in a theoretical approach describing the progression of a phase change front in a slab of finite thickness, and the computed results are found to be in good agreement with the experimental data for the considered duration of freezing and thawing in samples. 0 1997 Elsevier Science Ltd. All rights reserved Phase change material (PCM) Energy storage Latent heat Simulation Coolness storage NOMENCLATURE A, B, C, D = Dimensionless numbers C, = Thermal capacity (kJ kg-' K-l) E, e = Thickness (m) k = Thermal conductivity (Wm-' K-r) L = Latent heat (kJ kg-') n = Integer Q, 4 = Heat quantity (kJ) r, s = Exponents 7' = Temperature (K) t, u = Time (s) x = Spatial coordinate