Computational Studies on Metal Foam and Heat Pipe Enhanced Latent Thermal Energy Storage

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
K. Nithyanandam ◽  
R. Pitchumani
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Metal Foam ◽  
Heat Pipes ◽  
High Energy ◽  
Heat Transfer Fluid ◽  
Design Parameters

Thermal energy storage is a distinguishing component of a concentrating solar power (CSP) system, which enables uninterrupted operation of plant during periods of cloudy or intermittent solar availability. Latent thermal energy storage (LTES) which utilizes phase change material (PCM) as a heat storage medium is attractive due to its high energy storage density and low capital cost. However, the low thermal conductivity of the PCM restricts its solidification rate, leading to inefficient heat transfer between the PCM and the heat transfer fluid which carries thermal energy to the power block. To address this limitation, LTES embedded with heat pipes and PCM's stored within the framework of porous metal foam that have one to two orders of magnitude higher thermal conductivity than the PCM are considered in the present study. A transient, computational analysis of the metal foam enhanced LTES system with embedded heat pipes is performed to investigate the enhancement in the thermal performance of the system for different arrangements of heat pipes and design parameters of metal foam, during both charging and discharging operation.

Design and Analysis of Metal Foam Enhanced Latent Thermal Energy Storage With Embedded Heat Pipes for Concentrating Solar Power Plants

2013 ◽  
Author(s):  
K. Nithyanandam ◽  
R. Pitchumani
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Power ◽  
Metal Foam ◽  
Heat Pipes ◽  
High Energy ◽  
Metal Foams ◽  
Concentrating Solar Power

Thermal energy Storage is a critical component of Concentrating Solar Power (CSP) plant, enabling uninterrupted operation of plant during periods of cloudy or intermittent solar weather. Investigations of Latent Thermal Energy Storage (LTES) which utilizes Phase Change Material (PCM) as a heat storage medium is considered due to its high energy storage density and low capital cost. However, the low thermal conductivity of the PCM restricts the solidification rate of the PCM leading to inefficient heat transfer between the PCM and the HTF which carries thermal energy to the power block. To address this, LTES embedded with heat pipes and PCM’s stored within the framework of porous metal foams possessing one to two orders of magnitude higher thermal conductivity than the PCM are considered in the present study. A transient, computational analysis of the metal foam (MF) enhanced LTES system with embedded heat pipes is performed to investigate the enhancement in the thermal performance of the system for different arrangement of heat pipes and design parameter of metal foams, during both charging and discharging operation.

Computational Modeling of Latent Thermal Energy Storage System With Embedded Heat Pipes

2010 ◽  
Author(s):  
Karthik Nithyanandam ◽  
Ranga Pitchumani
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Heat Pipes ◽  
Energy Storage System ◽  
High Energy ◽  
Thermal Energy Storage System

Due to the intermittent nature of solar energy availability, storing sun’s energy in the form of latent thermal energy of a phase change material (PCM) is an effective technique that is widely used in energy storage and load management applications. In a Latent Thermal Energy Storage System (LTES), a heat transfer fluid (HTF) exchanges energy with a PCM. The advantages of an LTES include its isothermal operation and high energy storage density. However, the low thermal conductivity of PCM poses a significant disadvantage due to reduction in the rate at which the PCM can be melted (charging) or solidified (discharging). This paper explores an approach to reducing the thermal resistance of PCM in a LTES through embedded heat pipes. A heat pipe is a passive heat transfer device that efficiently transfers large amount of energy between the PCM and HTF thus indirectly amplifying the effective thermal conductivity of PCM. A transient computational analysis of a shell and tube LTES embedded with heat pipes is performed for charging to determine the position of melt front and energy stored as a function of time. The influence of the number and orientation of heat pipes and design configuration of the system is analyzed to identify configurations that lead to improved effectiveness.

Heat Transfer Analysis of a Low-Temperature Heat Pipe-Assisted Latent Heat Thermal Energy Storage System With Nano-Enhanced PCM

2018 ◽  
Author(s):  
Mahboobe Mahdavi ◽  
Saeed Tiari ◽  
Vivek Pawar
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Low Temperature ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Heat Pipes ◽  
Energy Storage System ◽  
Heat Transfer Fluid ◽  
Thermal Energy Storage System

In the current study, the thermal characteristics of a low-temperature latent heat thermal energy storage system are studied numerically. A cylinder container encloses a paraffin-based PCM, which is heated via a heat transfer fluid passing through a tube at the center. Heat pipes are incorporated into the PCM to enhance the heat transfer rate between the heat transfer fluid and the PCM. In addition, high thermal conductive nanoparticles are dispersed into the PCM to increase its thermal conductivity. A transient model is developed using ANSYS-FLUENT to simulate the charging process and study the impact of heat pipes and nanoparticles on the performance of the system. The effects of different parameters, such as the quantities of heat pipes as well as the nanoparticles types and volume fraction, are investigated.

scholarly journals Thermal Performance of a PCM-Based Thermal Energy Storage with Metal Foam Enhancement

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3275 ◽  
Author(s):  
Xue Chen ◽  
Xiaolei Li ◽  
Xinlin Xia ◽  
Chuang Sun ◽  
Rongqiang Liu
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Metal Foam ◽  
Storage System ◽  
Fluid Phase ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Release Process

The energy transport inside a phase change material (PCM) based thermal energy storage system using metal foam as an enhancement technique is investigated numerically. The paraffin is used as the PCM and water as the heat transfer fluid (HTF). The transient heat transfer during the charging and discharging processes is solved, based on the volume averaged conservation equations. The flow in PCM/foam and HTF/foam composites is modelled by the Forchheimer-extended Darcy equation, while the two-temperature model is employed to account for the local thermal non-equilibrium effect between the foam matrix and fluid phase. The results show that the overall performance is greatly improved by inserting metal foam in both HTF and PCM sides. A nearly 84.9% decrease in the time needed for the total process is found compared with the case of pure PCM, and 40% compared with the case of metal foam insert only in the PCM side. Foam porosity and HTF inlet temperature greatly affect the dynamic heat storage/release process.

Numerical Analysis of Latent Thermal Energy Storage System With Embedded Thermosyphons

2012 ◽  
Author(s):  
Karthik Nithyanandam ◽  
Ranga Pitchumani
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Power ◽  
Storage System ◽  
High Energy ◽  
Concentrating Solar Power ◽  
Discharge Performance ◽  
Low Thermal Conductivity

Latent thermal energy storage (LTES) system offers high energy storage density and nearly isothermal operation for concentrating solar power generation. However, the low thermal conductivity possessed by the phase change material (PCM) used in LTES system limits the heat transfer rates. Utilizing thermosyphons to charge or discharge a LTES system offers a promising engineering solution to compensate for the low thermal conductivity of the PCM. The present work numerically investigates the enhancement in the thermal performance of charging and discharging process of LTES system by embedding thermosyphons. A transient, computational analysis of the LTES system with embedded thermosyphons is performed for both charging and discharging cycles. The influence of the design configuration of the system and the arrangement of the thermosyphons on the charge and discharge performance of the LTES installed in a concentrating solar power plant (CSP) is analyzed to identify configurations that lead to improved effectiveness.

Effect of High Temperatures and Heating Rates on High Strength Concrete for Use as Thermal Energy Storage

2010 ◽  
Author(s):  
Emerson E. John ◽  
W. Micah Hale ◽  
R. Panneer Selvam
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Molten Salt ◽  
High Temperatures ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Heating Rates ◽  
Storage Media ◽  
Concrete Mixtures

In recent years due to rising energy costs as well as an increased interest in the reduction of greenhouse gas emissions, there is great interest in developing alternative sources of energy. One of the most viable alternative energy resources is solar energy. Concentrating solar power (CSP) technologies have been identified as an option for meeting utility needs in the U.S. Southwest. Areas where CSP technologies can be improved are improved heat transfer fluid (HTF) and improved methods of thermal energy storage (TES). One viable option for TES storage media is concrete. The material costs of concrete can be very inexpensive and the costs/ kWhthermal, which is based on the operating temperature, are reported to be approximately $1. Researchers using concrete as a TES storage media have achieved maximum operating temperatures of 400°C. However, there are concerns for using concrete as the TES medium, and these concerns center on the effects and the limitations that the high temperatures may have on the concrete. As the concrete temperature increases, decomposition of the calcium hydroxide (CH) occurs at 500°C, and there is significant strength loss due to degeneration of the calcium silicate hydrates (C-S-H). Additionally concrete exposed to high temperatures has a propensity to spall explosively. This proposed paper examines the effect of heating rates on high performance concrete mixtures. Concrete mixtures with water to cementitious material ratios (w/cm) of 0.15 to 0.30 and compressive strengths of up to 180 MPa (26 ksi) were cast and subjected to heating rates of 3, 5, 7, and 9° C/min. These concrete mixtures are to be used in tests modules where molten salt is used as the heat transfer fluid. Molten salt becomes liquid at temperatures exceeding 220°C and therefore the concrete will be exposed to high initial temperatures and subsequently at controlled heating rates up to desired operating temperatures. Preliminary results consistently show that concrete mixtures without polypropylene fibres (PP) cannot resist temperatures beyond 500° C, regardless of the heating rate employed. These mixtures spall at higher temperatures when heated at a faster rate (7° C/min). Additionally, mixtures which incorporate PP fibres can withstand temperatures up to 600° C without spalling irrespective of the heating rate.

Solid/Liquid Phase Change Heat Transfer in Latent Heat Thermal Energy Storage

2009 ◽  
Author(s):  
D. Zhou ◽  
C. Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Calcium Chloride ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Metal Foams ◽  
Chloride Hexahydrate

Phase change materials (PCMs) have been widely used for thermal energy storage systems due to their capability of storing and releasing large amounts of energy with a small volume and a moderate temperature variation. Most PCMs suffer the common problem of low thermal conductivity, being around 0.2 and 0.5 for paraffin and inorganic salts, respectively, which prolongs the charging and discharging period. In an attempt to improve the thermal conductivity of phase change materials, the graphite or metallic matrix is often embedded within PCMs to enhance the heat transfer. This paper presents an experimental study on heat transfer characteristics of PCMs embedded with open-celled metal foams. In this study both paraffin wax and calcium chloride hexahydrate are employed as the heat storage media. The transient heat transfer behavior is measured. Compared to the results of pure PCMs samples, the investigation shows that the additions of metal foams can double the overall heat transfer rate during the melting process. The results of calcium chloride hexahydrate are also compared with those of paraffin wax.

Thermal Analysis of Elemental Sulfur in a Shell-and-Tube Configuration for Thermal Energy Storage Applications

2016 ◽  
Author(s):  
Mitchell Shinn ◽  
Karthik Nithyanandam ◽  
Amey Barde ◽  
Richard Wirz
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Energy Storage ◽  
Numerical Model ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Elemental Sulfur ◽  
Low Cost ◽  
High Energy ◽  
Shell And Tube

Currently, concentrated solar power (CSP) plants utilize thermal energy storage (TES) in order to store excess energy so that it can later be dispatched during periods of intermittency or during times of high energy demand. Elemental sulfur is a promising candidate storage fluid for high temperature TES systems due to its high thermal mass, moderate vapor pressure, high thermal stability, and low cost. The objective of this paper is to investigate the behavior of encapsulated sulfur in a shell and tube configuration. An experimentally validated, transient, two-dimensional numerical model of the shell and tube TES system is presented. Initial results from both experimental and numerical analysis show high heat transfer performance of sulfur. The numerical model is then used to analyze the dynamic response of the elemental sulfur based TES system for multiple charging and discharging cycles. A sensitivity analysis is performed to analyze the effect of geometry (system length), cutoff temperature, and heat transfer fluid on the overall utilization of energy stored within this system. Overall, this paper demonstrates a systematic parametric study of a novel low cost, high performance TES system based on elemental sulfur as the storage fluid that can be utilized for different high temperature applications.

scholarly journals Performance Evaluation of a Small-Scale Latent Heat Thermal Energy Storage Unit for Heating Applications Based on a Nanocomposite Organic PCM

2019 ◽  
Vol 3 (4) ◽  
pp. 88 ◽  
Author(s):  
Maria K. Koukou ◽  
George Dogkas ◽  
Michail Gr. Vrachopoulos ◽  
John Konstantaras ◽  
Christos Pagkalos ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Behavior ◽  
Latent Heat ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Solidification Processes

A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to the PCM, and a water pump to circulate water as a heat transfer fluid (HTF). The performance of the unit using the commercial organic paraffin A44 was studied in order to understand the thermal behavior of the system and the main parameters that influence heat transfer during the PCM melting and solidification processes. The latter will assist the design of a large-scale unit. The effect of flow rate was studied given that it significantly affects charging (melting) and discharging (solidification) processes. In addition, as organic PCMs have low thermal conductivity, the possible improvement of the PCM’s thermal behavior by means of nanoparticle addition was investigated. The obtained results were promising and showed that the use of graphite-based nanoplatelets improves the PCM thermal behavior. Charging was clearly faster and more efficient, while with the appropriate tuning of the HTF flow rate, an efficient discharging was accomplished.

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