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Natural convection during melting in vertical finned tube latent thermal energy storage systems

Vogel, Julian and Johnson, Maike (2019) Natural convection during melting in vertical finned tube latent thermal energy storage systems. Applied Energy, 246, pp. 38-52. Elsevier. DOI: 10.1016/j.apenergy.2019.04.011 ISSN 0306-2619

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Official URL: https://doi.org/10.1016/j.apenergy.2019.04.011

Abstract

Natural convection can have a major impact on the melting process during charging in a latent heat storage system. Heat transfer enhancement by natural convection depends strongly on the dimensions, material properties and boundary conditions of the storage system. In complex geometries, such as shell-and-tube storage systems with extended fins, a good approximation of the impact of natural convection on the melting process is very difficult. There are no correlations for such geometries, and simulations of these storage systems require extensive computational effort. In the present work, we analyzed the impact of natural convection in four vertical shell-and-tube extended fin systems with a common tube height. To investigate the influence of the tube height, one of the fins was additionally modeled with two further tube heights. We scaled the resulting liquid fraction evolutions into a dimensionless form and used a convective enhancement factor to assess the strength of natural convection. A linear fit function for the mean convective enhancement factor was derived to estimate the melting process considering natural convection. With it, natural convection may be incorporated into the design process of storage systems to optimize the charging time. The results indicate a negligible impact of natural convection in fins with a small tube spacing and a high fin fraction. There is a considerable impact from natural convection in fins designed with a large tube spacing and a low fin fraction. However, large fin heights lead to decreased heat transfer enhancement by natural convection.

Item URL in elib:https://elib.dlr.de/127168/
Document Type:Article
Title:Natural convection during melting in vertical finned tube latent thermal energy storage systems
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Vogel, Julianjulian.vogel (at) dlr.dehttps://orcid.org/0000-0001-9792-2332
Johnson, MaikeMaike.Johnson (at) dlr.deUNSPECIFIED
Date:2019
Journal or Publication Title:Applied Energy
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:246
DOI :10.1016/j.apenergy.2019.04.011
Page Range:pp. 38-52
Publisher:Elsevier
ISSN:0306-2619
Status:Published
Keywords:Heat transfer; Phase change material (PCM); Finned tube heat exchanger; Computational fluid dynamics (CFD); Convective enhancement factor
HGF - Research field:Energy
HGF - Program:Storage and Cross-linked Infrastructures
HGF - Program Themes:Thermal Energy Storage
DLR - Research area:Energy
DLR - Program:E SP - Energy Storage
DLR - Research theme (Project):E - Thermochemical Processes (Storage)
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Thermal Process Technology
Deposited By: Johnson, Maike
Deposited On:03 May 2019 13:47
Last Modified:06 Sep 2019 15:21

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