Experimental investigation on combined sensible and latent heat storage in two different configurations of tank filled with PCM (original) (raw)
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Experimental study on melting/solidification characteristics of a paraffin as PCM
Energy Conversion and Management, 2007
An experimental study is conducted in order to investigate the melting and solidification processes of paraffin as a phase change material (PCM) in a tube in shell heat exchanger system. The motivation of this study is to design and construct a novel storage unit responding to the melting/solidification characteristics of the paraffin. The PCM is stored in the vertical annular space between an inner tube through which the heat transfer fluid (HTF), here water, is flowing and a concentrically placed outer shell. This study focuses on the possibility of the heat transfer enhancement in the heat storage geometry. Enhancement is achieved by tilting the outer surface of the storage container, i.e. the surface of the outer shell with a tilting angle of 5°. The paraffin (P1) is used as the PCM because of its low cost, high energy storage density and large scale availability. At first, the thermophysical properties of the paraffin used are determined through differential scanning calorimeter (DSC) analysis. A series of experiments are conducted to investigate the effect of increasing the inlet temperature and the mass flow rate of the HTF both on the charging and discharging processes (i.e. melting and solidification) of the PCM.
Latent Heat Storage with Phase Change Materials (PCMs
Journal of Technology Innovations in Renewable Energy, 2013
Latent heat thermal energy storage with phase change materials (PCMs) is attractive since providing a high energy density storage due to the phase change by solidification/melting at constant temperature. Relative to sensible heat energy storage systems, latent heat storage with PCMs requires a smaller weight and volume of material for a given amount of captured/stored energy, and has the capacity to store heat of fusion at a constant or nearly constant temperature, thus maintaining a high and constant temperature difference between the heat exchanging surface and the PCMs. The present review paper will summarize the required properties of PCMs, with their respective advantages and disadvantages; the current state of development and manufacturing; the development of PCM applications, including their incorporation into heat exchangers, insertion of a metal matrix into the PCM, the use of PCM dispersed with high conductivity particles. PCM uses will be illustrated through some case-studies.
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.
Review on latent thermal energy storage using phase change material
Journal of Thermal Engineering, 2023
One of the appealing technologies that contributes to raising the energy storage density is latent heat thermal energy storage. The heat of fusion is isothermally stored at a temperature representing the temperature at which a phase-change material transitions between phases. The current research provides a review of how phase transition materials are used in melting and solidification. Generally, the range of working temperature extends from-20 °C to 200 °C for solidification and melting applications. The first range (-20 to 5 °C) is employed for commercial and domestic refrigeration. The second range (5 to 40 °C) is utilized to lower the energy requirements for airconditioning applications. The applications includes in third range (40 to 82 °C) are solar collector and heating of water. Applications of absorption cooling, waste electricity generations, and heat recovery are operated at high temperature range (82 to180 °C). There are various types of PCMs for all the above temperature ranges. The present review paper will discuss the application fi eld, Ge ometry, PCM ty pe, he at transfer augmentation technique and their effects on the performance. The conclusions are mentioned to give more insight about the PCM behavior in various applications.
Experimental study of fusion and solidification of phase change material (pcm) in spherical geometry
2016
The objective of this work is to investigate the parameters affecting the time for complete solidification and fusion in spherical capsules and develop correlations between this time and the investigated parameters. These correlations will be used in the numerical simulations of latent heat storage systems of the fixed bed type having the phase change material, PCM encapsulated in spherical containers. Four spherical shells of 35, 76, 106 and 131 mm diameter were used at temperatures ranging from -20°C to -5°C for solidification process and temperature of 10°C, 18°C, 25°C for the melting process. Water and mixtures of water and polyethylene glycol in percentages ranging from 7.5% to 50% were used as PCM. Based on the experimental results correlations of the time for complete solidification and complete fusion were developed and compared with the experimental measurements showing good agreement and confirming the suitability of using these correlations to predict the complete phase c...
International Journal of Energy Research, 2012
The present paper describes the analysis of the melting process in a single vertical shell-and-tube LHTES unit and it is directed at understanding the thermal performance of the system. The study is realized using a computational fluid-dynamic (CFD) model that takes into account of the phase change phenomenon by means of the enthalpy method. Fluid flow is fully resolved in the liquid PCM in order to elucidate the role of natural convection. The unsteady evolution of the melting front and the velocity and temperature fields is detailed. Temperature profiles are analyzed and compared with experimental data available in the literature. Other relevant quantities are also monitored, including energy stored and heat flux exchanged between PCM and HTF. The results demonstrate that natural convection within PCM and inlet HTF temperature significantly affect the phase change process. Thermal enhancement through the dispersion of highly conductive nano-particles in the base PCM is considered in the second part of the paper. Thermal behavior of the LHTES unit charged with nano-enhanced PCM is numerically analyzed and compared with the original system configuration. Due to increase of thermal conductivity augmented thermal performance are observed: melting time is reduced of 15% when nano-enhanced PCM with particle volume fraction of 4% is adopted. Similar improvements of the heat transfer rate are also detected.
Study of phase change modeling for a rectangular PCM container exposed to constant heat flux
Latent heat storage is one way of storing thermal energy that is capable of storing much more amounts of energy than the sensible heat storage. It has also the advantage of storing energy in a nearly isothermal phase change process. There are many phase change materials known, changing phase in a wide range of temperatures, which makes them suitable for different applications. In this study, temperature behavior of paraffin as a phase change material has been studied with two different numerical methods. Further the results have been verified with experimental data.
Melting enhancement of PCM in a finned tube latent heat thermal energy storage
Scientific Reports, 2022
The current paper discusses the numerical simulation results of the NePCM melting process inside an annulus thermal storage system. The TES system consists of a wavy shell wall and a cylindrical tube equipped with three fins. The enthalpy-porosity method was utilized to address the transient behavior of the melting process, while the Galerkin FE technique was used to solve the system governing equations. The results were displayed for different inner tube positions (right-left-up and down), inner cylinder rotation angle (0 ≤ α ≤ 3π/2), and the nano-additives concentration (0 ≤ ϕ ≤ 0.04). The findings indicated that high values of nano-additives concentration (0.4), bigger values of tube rotation angle (3π/2), and location of the tube at the lower position accelerated the NePCM melting process.
REVIEW ON LATENT HEAT STORAGE AND PROBLEMS ASSOCIATED WITH PHASE CHANGE MATERIALS
Energy storage devices have important role in the energy system as they minimize the mismatch between the supply and demand. This leads to improvement of the performance and the reliability of the systems. In thermal energy storage systems the Latent heat type thermal energy storages (LHTES) are attractive since they have high energy storage density and nearly isothermal operation at the phase transition temperature of the material usedthat is commonly known as phase change material (PCM). In this paper PCMs with solid-solid and solid-liquid phase transition are discussed. Though PCMs with solid-solid phase transition seem attractive due to their less stringent containment requirements but they are not widely used because of their low latent heat. PCMs with solid-liquid phase transition are the most studied and used latent heat storage materials. Those are discussed in details with their selection criterion, classification and applications. The steps involved in development of the energy storage systems and problems associated with PCMs are discussed in the next part of the paper. This will give better understanding of the latent heat storage systems to the reader.
A Study on Latent Thermal Energy Storage (LTES) using Phase Change Materials (PCMs) 2020
2020
The significant increase in energy requirements across the world, provides several opportunities for innovative methods to be developed to facilitate the storage and utilization of energy. The major energy demand is in the form of electrical energy for domestic as well as industrial sectors, a large part of which are the heating and cooling requirements. Appropriate utilization of thermal energy storage can effectively aid in reducing the electrical demand by storage and release of this thermal energy during peak hours. Thermal Energy Storage using Phase Change Materials (PCMs) is an attractive method of energy storage, with a wide variety of potential applications. Several configurations have been tested by researchers to develop energy storage devices with PCMs. The cycling of melting and solidification of PCMs results in storage and release of heat at a relatively small temperature difference. Design and deployment of these storage systems have certain challenges and considerations associated to them for instance, when used in buildings, PCMs should be non-toxic, non-corrosive, and others. viii In this thesis, we aim to provide models for designing Latent Thermal Energy Storage (LTES) devices with PCMs, based on their operating conditions, thermophysical properties of materials, and geometric parameters. The models are developed considering fluid dynamics and heat transfer involved in melting and solidification of PCMs. Parameters like inlet temperature and velocity, and volume of storage container are varied to determine the time taken for melting or solidification. For sizing and predicting performance of the storage devices we aim at presenting an analytical correlation, with time taken for melting as the variable defining the 'charging/discharging time' of storage device. Along with this, a transient model is developed to predict amount of PCM melted/solidified, along with rate of latent energy storage in defined time period intervals. ix