Numerical Investigation of the Freezing of a Phase Change Material in a Thermal Storage Device With an Embedded Evaporator

2016 ◽  
Author(s):  
H. Ezzat Khalifa ◽  
Mustafa Koz
Keyword(s):  
Natural Convection ◽  
Numerical Models ◽  
Thermal Storage ◽  
Time Dependent ◽  
Storage Device ◽  
Freezing Process ◽  
Vapor Compression ◽  
Local Cooling ◽  
Storage Devices ◽  
Freezing Cycle

Two time-dependent mathematical and numerical models with different levels of complexity and fidelity were developed to investigate the freezing of a PCM configured as a slab with an embedded serpentine microchannel evaporator of a vapor compression refrigeration system. The time-dependent PCM freezing process was first analyzed using finite-element modeling (FEM) of a representative 2-D domain. This model incorporates 2-D conduction and natural convection within the molten PCM. The FEM revealed that natural convection is negligible and that the freezing front advances in essentially 1-D fashion. However, the long execution time of FEM makes it unsuitable for repetitive design optimization of thermal storage devices. Consequently, a fast-executing quasi 2-D reduced-order model (ROM) was developed. The ROM is then utilized to study the freezing process in a multi-slab thermal storage device that is designed to store ∼500 W-h of “cooling” during ∼8 h of freezing operation at night, to be subsequently released for local cooling of room air during the day. The results show that (1) freezing rate is strongly affected by the frozen PCM thermal conductivity; (2) freezing almost ceases once the refrigerant is fully evaporated; (3) refrigerant exit quality drops precipitously toward the end of the freezing cycle.

scholarly journals Experimental and Numerical Study of an Electrical Thermal Storage Device for Space Heating

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2180 ◽  
Author(s):  
Guizhi Xu ◽  
Xiao Hu ◽  
Zhirong Liao ◽  
Chao Xu ◽  
Cenyu Yang ◽  
...  
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Three Dimensional ◽  
Thermal Storage ◽  
Flow Channel ◽  
Electrical Heating ◽  
Space Heating ◽  
Storage Device ◽  
Three Dimensional Model ◽  
Transient Thermal

An electrical thermal storage (ETS) device for space heating is designed in this study. The proposed device is charged by the off-peak electricity and releases its thermal energy to warm the space all day long. The natural convection occurring in the flow channel drives the flowing of air to be heated up and warm the space. The dynamic process of a fully charging/discharging cycle of the device is tested. Meanwhile, a three-dimensional model is developed to simulate the transient thermal behavior. It is found that the experimental and numerical results agree with each other which indicates the validation of the proposed numerical model. The results show that the temperatures of the bricks and the outlet air can be as high as 1002 K and 835 K, respectively. The natural convection occurring in the flow channel transfers 40.4% of the total electrical heating energy to the space for the charging process and 26.9% for the discharging process. Heat losses to the space through the adiabatic material shares 13.3% of the total heating energy for the charging process and 7.2% for the discharging process. Based on those findings, three methods are recommended to improve the device in the successive research.

Numerical Investigation of the Melting of a Phase Change Material in a Thermal Storage Device With Embedded Air Flow Channels

2016 ◽  
Author(s):  
Mustafa Koz ◽  
Hamza S. Erden ◽  
H. Ezzat Khalifa
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Air Flow ◽  
Melting Process ◽  
Thermal Storage ◽  
Time Dependent ◽  
Storage Device ◽  
Aluminum Tubes ◽  
Change Material

Two time-dependent mathematical and numerical models with different levels of complexity and fidelity were developed to investigate the melting of a phase change material (PCM) configured as a number of aluminum-encased, PCM-filled slabs with embedded micro-channel aluminum tubes, and with parallel air-flow passages interposed between the slabs. Melting was first analyzed with the COMSOL Multiphysics® finite-element model (FEM) in a 2-D domain representing a full-size slab. The melting process is simulated via the apparent heat capacity method. The model captures the effect of natural convection in the PCM melt as well as the conjugate heat transfer through the aluminum tubes. A fast-executing quasi 2-D reduced-order model (ROM) was developed for repetitive design optimization studies. The ROM relies on a time-dependent 1-D closed-form solution of the heat conduction equation in a melting PCM, coupled with variations of the air temperature and heat transfer coefficient. Consequently, the FEM results were employed to develop corrections to the ROM. The corrected ROM was then utilized to study the melting process in a multi-slab thermal storage device that is designed to freeze the PCM at night and release 500 W-h of cooling over a span of ∼10 h during the day.

Thermoeconomic Optimization of CSP Hybrid Power Plants With Thermal Storage

2014 ◽  
Author(s):  
Stefano Barberis ◽  
Massimo Rivarolo ◽  
Alberto Traverso
Keyword(s):  
Power Plants ◽  
Thermal Storage ◽  
Time Dependent ◽  
Storage Devices ◽  
Load Demand ◽  
Point Analysis ◽  
Combined Cycles ◽  
Variable Power ◽  
The Impact ◽  
Proper Account

This paper investigates the integration of Concentrating Solar Power technology in Combined Cycles for power production. Starting from a state of the art of CSP plants, the paper investigates alternative plant configurations, assessed and compared with a through-life thermoeconomic analysis. Plant layouts include thermal storage to manage the load demand of the plant throughout the day, considering both variable solar input and variable power demand. Focus is on the impact of thermal storage devices on optimal layouts. The hybrid combined CSP plants are analyzed using original software tools, WTEMP for the design point analysis and WECoMP for the time-dependent thermoeconomic optimization, to take into proper account the time-dependent nature of both the electrical load demand and the hour-by-hour irradiation during the year. The analysis shows that combining CSP technology with existing combined cycles a significant reduction of fuel consumption and greenhouse gas emissions is obtained, with an optimal solar share factor of about 20%, providing the grid with fully dispatchable power generation.

scholarly journals Ionic Liquid Electrolytes for Electrochemical Energy Storage Devices

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4000
Author(s):  
Eunhwan Kim ◽  
Juyeon Han ◽  
Seokgyu Ryu ◽  
Youngkyu Choi ◽  
Jeeyoung Yoo
Keyword(s):  
Ionic Liquid ◽  
Energy Storage ◽  
Lithium Ion ◽  
Electrochemical Energy Storage ◽  
Storage Device ◽  
Energy Storage Device ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Storage Ability ◽  
Electrochemical Energy

For decades, improvements in electrolytes and electrodes have driven the development of electrochemical energy storage devices. Generally, electrodes and electrolytes should not be developed separately due to the importance of the interaction at their interface. The energy storage ability and safety of energy storage devices are in fact determined by the arrangement of ions and electrons between the electrode and the electrolyte. In this paper, the physicochemical and electrochemical properties of lithium-ion batteries and supercapacitors using ionic liquids (ILs) as an electrolyte are reviewed. Additionally, the energy storage device ILs developed over the last decade are introduced.

scholarly journals Implications of NVM Based Storage on Memory Subsystem Management

2020 ◽  
Vol 10 (3) ◽  
pp. 999
Author(s):  
Hyokyung Bahn ◽  
Kyungwoon Cho
Keyword(s):  
Random Access ◽  
Disk Drive ◽  
Main Memory ◽  
Memory Storage ◽  
Storage Device ◽  
Storage Devices ◽  
Large Memory ◽  
Memory Subsystems ◽  
Non Volatile Memory ◽  
Management Techniques

Recently, non-volatile memory (NVM) has advanced as a fast storage medium, and legacy memory subsystems optimized for DRAM (dynamic random access memory) and HDD (hard disk drive) hierarchies need to be revisited. In this article, we explore the memory subsystems that use NVM as an underlying storage device and discuss the challenges and implications of such systems. As storage performance becomes close to DRAM performance, existing memory configurations and I/O (input/output) mechanisms should be reassessed. This article explores the performance of systems with NVM based storage emulated by the RAMDisk under various configurations. Through our measurement study, we make the following findings. (1) We can decrease the main memory size without performance penalties when NVM storage is adopted instead of HDD. (2) For buffer caching to be effective, judicious management techniques like admission control are necessary. (3) Prefetching is not effective in NVM storage. (4) The effect of synchronous I/O and direct I/O in NVM storage is less significant than that in HDD storage. (5) Performance degradation due to the contention of multi-threads is less severe in NVM based storage than in HDD. Based on these observations, we discuss a new PC configuration consisting of small memory and fast storage in comparison with a traditional PC consisting of large memory and slow storage. We show that this new memory-storage configuration can be an alternative solution for ever-growing memory demands and the limited density of DRAM memory. We anticipate that our results will provide directions in system software development in the presence of ever-faster storage devices.

scholarly journals Layered double hydroxide membrane with high hydroxide conductivity and ion selectivity for energy storage device

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jing Hu ◽  
Xiaomin Tang ◽  
Qing Dai ◽  
Zhiqiang Liu ◽  
Huamin Zhang ◽  
...  
Keyword(s):  
Energy Storage ◽  
High Performance ◽  
Ion Selectivity ◽  
Storage Device ◽  
Hydroxyl Groups ◽  
Flow Battery ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Ions Transport ◽  
Double Hydroxides

AbstractMembranes with fast and selective ions transport are highly demanded for energy storage devices. Layered double hydroxides (LDHs), bearing uniform interlayer galleries and abundant hydroxyl groups covalently bonded within two-dimensional (2D) host layers, make them superb candidates for high-performance membranes. However, related research on LDHs for ions separation is quite rare, especially the deep-going study on ions transport behavior in LDHs. Here, we report a LDHs-based composite membrane with fast and selective ions transport for flow battery application. The hydroxide ions transport through LDHs via vehicular (standard diffusion) & Grotthuss (proton hopping) mechanisms is uncovered. The LDHs-based membrane enables an alkaline zinc-based flow battery to operate at 200 mA cm−2, along with an energy efficiency of 82.36% for 400 cycles. This study offers an in-depth understanding of ions transport in LDHs and further inspires their applications in other energy-related devices.

Exergy Analysis of Thermal Energy Storage With Specific Remarks on the Variation of the Environmental Temperature

1996 ◽  
Vol 118 (2) ◽  
pp. 81-88 ◽  
Author(s):  
G. Bisio
Keyword(s):  
Energy Storage ◽  
Constant Temperature ◽  
Exergy Analysis ◽  
Environmental Temperature ◽  
Variable Temperature ◽  
Thermal Storage ◽  
Exergy Efficiency ◽  
Basic Question ◽  
Storage Devices ◽  
Temperature Environment

Energy storage is a key technology for many purposes and in particular for air conditioning plants and a successful exploitation of solar energy. Thermal storage devices are usually classified as either variable temperature (“sensible heat”) or constant temperature (“latent heat”) devices. For both models a basic question is to determine the efficiency suitably: Only exergy efficiency appears a proper way. The aim of this paper is to examine exergy efficiency in both variable and constant temperature systems. From a general statement of exergy efficiency by the present author, two types of actual definitions are proposed, depending on the fact that the exergy of the fluid leaving the thermal storage during the charge phase can be either totally lost or utilized elsewhere. In addition, specific remarks are made about the exergy of a system in a periodically varying temperature environment.

Comparative study of the transient natural convection in an underground water pit thermal storage

2017 ◽  
Vol 208 ◽  
pp. 1162-1173 ◽  
Author(s):  
Chun Chang ◽  
Zhiyong Wu ◽  
Helena Navarro ◽  
Chuan Li ◽  
Guanghui Leng ◽  
...  
Keyword(s):  
Natural Convection ◽  
Comparative Study ◽  
Thermal Storage ◽  
Underground Water ◽  
Transient Natural Convection

scholarly journals Layered double hydroxide membrane with high hydroxide conductivity and ion selectivity for energy storage device

2020 ◽  
Author(s):  
Jing Hu ◽  
Xiaomin Tang ◽  
Qing Dai ◽  
Zhiqiang Liu ◽  
Huamin Zhang ◽  
...  
Keyword(s):  
Energy Storage ◽  
High Performance ◽  
Ion Selectivity ◽  
Storage Device ◽  
Hydroxyl Groups ◽  
Flow Battery ◽  
Energy Storage Devices ◽  
Storage Devices ◽  
Ions Transport ◽  
Double Hydroxides

Abstract Membranes with fast and selective ions transport are highly demanded for energy storage devices. Layered double hydroxides (LDHs), bearing uniform interlayer galleries and abundant hydroxyl groups covalently bonded within two-dimensional (2D) host layers, make them superb candidates for high-performance membranes. However, related research on LDHs for ions separation is quite rare, especially the deep-going study on ions transport behavior in LDHs. Here, we report a LDHs-based composite membrane with fast and selective ions transport for flow battery application. The hydroxide ions transport through LDHs via vehicular (standard diffusion) & Grotthuss (proton hopping) mechanisms is uncovered. The LDHs-based membrane enables an alkaline zinc-based flow battery to operate at 200 mA cm− 2, along with an energy efficiency of 82.36% for 400 cycles, which is among the highest efficiencies for zinc-based flow batteries. This study offers an in-depth understanding of ions transport in LDHs and further inspires their applications in other energy-related devices.

Sign in / Sign up

Export Citation Format

Share Document