scholarly journals Fundamental heat transfer processes related to phase change thermal storage media

1981 ◽  
Author(s):  
E. Sparrow ◽  
J. Ramsey
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Storage ◽  
Transfer Processes ◽  
Storage Media

scholarly journals Preparation of Stable Phase Change Material Emulsions for Thermal Energy Storage and Thermal Management Applications: A Review

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 121
Author(s):  
Liu Liu ◽  
Jianlei Niu ◽  
Jian-Yong Wu
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage Capacity ◽  
Heat Storage ◽  
Thermal Storage ◽  
Stable Phase ◽  
Storage Media

Thermal energy storage (TES) is an important means for the conservation and efficient utilization of excessive and renewable energy. With a much higher thermal storage capacity, latent heat storage (LHS) may be more efficient than sensible heat storage. Phase change materials (PCMs) are the essential storage media for LHS. PCM emulsions have been developed for LHS in flow systems, which act as both heat transfer and thermal storage media with enhanced heat transfer, low pumping power, and high thermal storage capacity. However, two major barriers to the application of PCM emulsions are their instability and high degree of supercooling. To overcome these, various strategies have been attempted, such as the reduction of emulsion droplet size, addition of nucleating agents, and optimization of the formulation. To the best of our knowledge, however, there is still a lack of review articles on fabrication methods for PCM emulsions or their latest applications. This review was to provide an up-to-date and comprehensive summary on the effective strategies and the underlying mechanisms for the preparation of stable PCM emulsions and reduction of supercooling, especially with the organic PCMs of paraffin. It was also to share our insightful perspectives on further development and potential applications of PCM emulsions for efficient energy storage.

scholarly journals Molten Salt Spectroscopy for Quantification of Radiative Absorption in Novel Metal Chloride-Enhanced Thermal Storage Media

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Philip D. Myers ◽  
D. Yogi Goswami ◽  
Elias Stefanakos
Keyword(s):  
Heat Transfer ◽  
Transition Metal ◽  
Melting Temperature ◽  
Latent Heat ◽  
Thermal Storage ◽  
Metal Chloride ◽  
Eutectic System ◽  
Metal Chlorides ◽  
Storage Media ◽  
Radiative Absorption

This study describes the development and characterization of novel high-temperature thermal storage media, based on inclusion of transition metal chlorides in the potassium–sodium chloride eutectic system, (K–Na)Cl (melting temperature of 657 °C, latent heat of 278 J/g). At the melting temperature of (K–Na)Cl, infrared (IR) radiation can play a major role in the overall heat transfer process—90% of spectral blackbody radiation falls in the range of 2–13 μm. The authors propose inclusion of small amounts (less than 0.2 wt.%) of IR-active transition metal chlorides to increase radiative absorption and thereby enhance heat transfer rates. A new IR-reflectance apparatus was developed to allow for determination of the spectral absorption coefficient of the newly formulated phase-change materials (PCMs) in the molten state. The apparatus consisted of an alumina crucible coated at the bottom with a reflective (platinum) or absorptive (graphite) surface, a heated ceramic crucible-holder, and a combination of zinc sulfide (ZnS) and zinc selenide (ZnSe) windows for containment of the salt and allowance of inert purge gas flow. Using this apparatus, IR spectra were obtained for various transition metal chloride additives in (K–Na)Cl and improved IR activity, and radiative transfer properties were quantified. Further, thermophysical properties relevant to thermal energy storage (i.e., melting temperature and latent heat) are measured for the pure and additive-enhanced thermal storage media.

Novel Ionic Liquid Thermal Storage for Solar Thermal Electric Power Systems

2001 ◽  
Author(s):  
Banqiu Wu ◽  
Ramana G. Reddy ◽  
Robin D. Rogers
Keyword(s):  
Heat Transfer ◽  
Ionic Liquids ◽  
Thermal Power ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Liquid Temperature ◽  
Storage Density ◽  
Heat Transfer Fluids ◽  
Solar Thermal Power ◽  
Storage Media

Abstract Feasibility of ionic liquids as liquid thermal storage media and heat transfer fluids in a solar thermal power plant was investigated. Many ionic liquids such as [C4min][PF6], [C8mim][PF6], [C4min][bistrifluromethane sulflonimide], [C4min][BF4], [C8mim][BF4], and [C4min][bistrifluromethane sulflonimide] were synthesized and characterized using thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), nuclear magnetic resonance (NMR), viscometry, and some other methods. Properties such as decomposition temperature, melting point, viscosity, density, heat capacity, and thermal expansion coefficient were measured. The calculated storage density for [C8mim][PF6] is 378 MJ/m3 when the inlet and outlet field temperatures are 210°C and 390°C. For a single ionic liquid, [C4mim][BF4], the liquid temperature range is from −75°C to 459°C. It is found that ionic liquids have advantages of high density, wide liquid temperature range, low viscosity, high chemical stability, non-volatility, high heat capacity, and high storage density. Based on our experimental results, it is concluded that ionic liquids could be excellent liquid thermal storage media and heat transfer fluids in solar thermal power plant.

The Heat Charge and Discharge Characteristics Simulation of Phase Change Thermal Storage Device

2011 ◽  
Vol 179-180 ◽  
pp. 239-242
Author(s):  
Hai Chuan Tian ◽  
Feng Xu ◽  
Guo Li Yang ◽  
Teng Fei Wu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Storage ◽  
Thermal Storage ◽  
Storage Device ◽  
Transfer Model ◽  
Two Dimensional ◽  
Unsteady Heat Transfer ◽  
Discharge Characteristics ◽  
Release Property

The two-dimensional unsteady heat transfer model is been established. Analyzing on heat storage-release property of phase change thermal storage device within the fluid parallel spiral pipes in various conditions, suggestions are put forward to strengthen thermal storage for the device.

Analysis of a Latent Heat Storage Device With Radial Fins

2013 ◽  
Author(s):  
Y. Kozak ◽  
T. Rozenfeld ◽  
G. Ziskind
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Latent Heat ◽  
Close Contact ◽  
Thermal Storage ◽  
Ambient Air ◽  
Contact Melting ◽  
Storage Device ◽  
Melting Time ◽  
Cfd Model

Phase-change materials (PCMs) can store large amounts of heat without significant change of their temperature during the phase-change process. This effect may be utilized in thermal energy storage, especially for solar-thermal power plants. In order to enhance the rate of heat transfer into PCMs, one of the most common methods is the use of fins which increase the heat transfer area that is in contact with the PCM. The present work deals with a latent heat thermal storage device that uses a finned tube with an array of radial fins. A heat transfer fluid (HTF) flows through the tube and heat is conducted from the tube to the radial fins that are in contact with the bulk of the PCM inside a cylindrical shell. The thermal storage charging/discharging process is driven by a hot/cold HTF inside the tube that causes the PCM to melt/solidify. The main objective of the present work is to demonstrate that close-contact melting (CCM) can affect the storage unit performance. Accordingly, two different types of experiments are conducted: with the shell exposed to ambient air and with the shell submerged into a heated water bath. The latter is done to separate the PCM from the shell by a thin molten layer, thus enabling the solid bulk to sink. The effect of the solid sinking and close-contact melting on the fins is explored. It is found that close-contact melting shortens the melting time drastically. Accordingly, two types of models are used to predict the melting rate: numerical CFD model and analytical/numerical close-contact melting model. The CFD model takes into account convection in the melt and the PCM property dependence on temperature and phase. The analytical/numerical CCM model is developed under several simplifying assumptions. Good agreement is found between the predictions and corresponding experimental results.

Effect of Inclination on Freezing in a Sealed Cylindrical Capsule

1984 ◽  
Vol 106 (2) ◽  
pp. 394-401 ◽  
Author(s):  
E. D. Larson ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Liquid Phase ◽  
Phase Change ◽  
Layer Thickness ◽  
Relative Importance ◽  
Fusion Temperature ◽  
Capsule Wall ◽  
Transfer Processes ◽  
Freezing Period

Experiments were performed to study the heat transfer processes that occur during freezing inside of a sealed cylindrical capsule when the inclination of the capsule is varied parametrically from vertical to horizontal. The phase-change medium was 99 percent pure n-eicosane paraffin. It was found that the amount of mass that solidified during a given freezing period was insensitive to the inclination of the capsule, as was the amount of energy extracted from the capsule. Only highly localized quantities such as the local frozen layer thickness reflected the inclination of the cylinder. Parametric variations were also performed for the degree of sub-cooling of the capsule wall below the fusion temperature and for the degree of superheating of the liquid phase at the onset of freezing. These variations facilitated the identification of the relative importance of the latent and sensible energies to the total extracted energy.

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