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  • 1
    Online Resource
    Online Resource
    Thermal Charging Optimization of a Wavy-Shaped Nano-Enhanced Thermal Storage Unit
    MDPI AG ; 2021
    In:  Molecules Vol. 26, No. 5 ( 2021-03-09), p. 1496-
    Details
    In: Molecules, MDPI AG, Vol. 26, No. 5 ( 2021-03-09), p. 1496-
    Abstract: A wavy shape was used to enhance the thermal heat transfer in a shell-tube latent heat thermal energy storage (LHTES) unit. The thermal storage unit was filled with CuO–coconut oil nano-enhanced phase change material (NePCM). The enthalpy-porosity approach was employed to model the phase change heat transfer in the presence of natural convection effects in the molten NePCM. The finite element method was applied to integrate the governing equations for fluid motion and phase change heat transfer. The impact of wave amplitude and wave number of the heated tube, as well as the volume concertation of nanoparticles on the full-charging time of the LHTES unit, was addressed. The Taguchi optimization method was used to find an optimum design of the LHTES unit. The results showed that an increase in the volume fraction of nanoparticles reduces the charging time. Moreover, the waviness of the tube resists the natural convection flow circulation in the phase change domain and could increase the charging time.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules26051496
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2008644-1
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  • 2
    Online Resource
    Online Resource
    Evaluation of the Melting Performance in a Conical Latent Heat Thermal Unit Having Variable Length Fins
    MDPI AG ; 2021
    In:  Sustainability Vol. 13, No. 5 ( 2021-03-02), p. 2667-
    Details
    In: Sustainability, MDPI AG, Vol. 13, No. 5 ( 2021-03-02), p. 2667-
    Abstract: A conical shell-tube design with non-uniform fins was addressed for phase change latent heat thermal energy storage (LHTES). The shell was filled with nano-enhanced phase change material (NePCM). The cone aspect ratio of the shell and the fins aspect ratio were adopted as the geometrical design parameters. The type and volume fraction of the nanoparticles were other design parameters. The investigated nanoparticles were alumina, graphite oxide, silver, and copper. The finite element method was employed to solve the natural convection flow and phase change thermal energy equations in the LHTES unit. The Taguchi optimization method was utilized to maximize the melting rate in the unit. Two cases of ascending and descending conical shells were investigated. The outcomes showed that the shell-aspect ratio and fin aspect ratio were the most important design parameters, followed by the type and concentration of nanoparticles. Both ascending and descending designs could lead to the same melting rate at their optimum design. The optimum design of LHTES could improve the melting rate by up to 18.5%. The optimum design for ascending (descending) design was a plain tube (a cone aspect ratio of 1.17) filled by 4.5% alumina-Bio-PCM (1.5% copper-Bio-PCM).
    Type of Medium: Online Resource
    ISSN: 2071-1050
    URL: Article
    DOI: 10.3390/su13052667
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2518383-7
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  • 3
    Online Resource
    Online Resource
    The Thermal Charging Performance of Finned Conical Thermal Storage System Filled with Nano-Enhanced Phase Change Material
    MDPI AG ; 2021
    In:  Molecules Vol. 26, No. 6 ( 2021-03-14), p. 1605-
    Details
    In: Molecules, MDPI AG, Vol. 26, No. 6 ( 2021-03-14), p. 1605-
    Abstract: A latent heat thermal energy storage (LHTES) unit can store a notable amount of heat in a compact volume. However, the charging time could be tediously long due to weak heat transfer. Thus, an improvement of heat transfer and a reduction in charging time is an essential task. The present research aims to improve the thermal charging of a conical shell-tube LHTES unit by optimizing the shell-shape and fin-inclination angle in the presence of nanoadditives. The governing equations for the natural convection heat transfer and phase change heat transfer are written as partial differential equations. The finite element method is applied to solve the equations numerically. The Taguchi optimization approach is then invoked to optimize the fin-inclination angle, shell aspect ratio, and the type and volume fraction of nanoparticles. The results showed that the shell-aspect ratio and fin inclination angle are the most important design parameters influencing the charging time. The charging time could be changed by 40% by variation of design parameters. Interestingly a conical shell with a small radius at the bottom and a large radius at the top (small aspect ratio) is the best shell design. However, a too-small aspect ratio could entrap the liquid-PCM between fins and increase the charging time. An optimum volume fraction of 4% is found for nanoparticle concentration.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules26061605
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2008644-1
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  • 4
    Online Resource
    Online Resource
    Simulation of a Fast-Charging Porous Thermal Energy Storage System Saturated with a Nano-Enhanced Phase Change Material
    MDPI AG ; 2021
    In:  Energies Vol. 14, No. 6 ( 2021-03-12), p. 1575-
    Details
    In: Energies, MDPI AG, Vol. 14, No. 6 ( 2021-03-12), p. 1575-
    Abstract: The melting of a coconut oil–CuO phase change material (PCM) embedded in an engineered nonuniform copper foam was theoretically analyzed to reduce the charging time of a thermal energy storage unit. A nonuniform metal foam could improve the effective thermal conductivity of a porous medium at regions with dominant conduction heat transfer by increasing local porosity. Moreover, the increase in porosity contributes to flow circulation in the natural convection-dominant regimes and adds a positive impact to the heat transfer rate, but it reduces the conduction heat transfer and overall heat transfer. The Taguchi optimization method was used to minimize the charging time of a shell-and-tube thermal energy storage (TES) unit by optimizing the porosity gradient, volume fractions of nanoparticles, average porosity, and porous pore sizes. The results showed that porosity is the most significant factor and lower porosity has a faster charging rate. A nonuniform porosity reduces the charging time of TES. The size of porous pores induces a negligible impact on the charging time. Lastly, the increase in volume fractions of nanoparticles reduces the charging time, but it has a minimal impact on the TES unit’s charging power.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    URL: Article
    DOI: 10.3390/en14061575
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2437446-5
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