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Comparison of Thermal Performance between annular fins and Longitudinal fins in Latent Heat Storage Unit

Journal of Thermal Science 2023年第3期32卷 1227-1238页

作者： ZHU Yuxi QIU Yan School of Energy and Power Engineering Shandong UniversityJi'nan 250061China

As a simple and effective method of heat transfer enhancement,fins are widely used in latent heat storage ***,the choice of annular fins and longitudinal fins has always been *** this paper,the melting process of phase change material(PCM)in annular fins and longitudinal fins latent heat storage units with the same volume is numerically *** ensure the same thermal penetration,three-dimensional spaces occupied with fins are specially controlled to be the *** with finned structures,the effects of natural convection(NC),placement mode and heat transfer fluid(HTF)inlet direction on the melting process are *** results show that the melting time in annular finned structure is always 10%less than that in longitudinal finned structure,which demonstrates the superior of the annular fins in the latent heat storage *** melting time is the shortest in vertical unit with annular fins and HTF inlet at the ***,the correlation formulas of the liquid fraction are proposed in the vertical unit with HTF inlet at the bottom.

关键词： latent heat storage annular fins longitudinal fins natural convection

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Thermal performance of a metal hydride reactor for hydrogen storage with cooling/heating by natural convection

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Energy Storage and Saving 2023年第4期2卷 597-607页

作者： Konstantin Borisovich Minko Maksim Nashchekin Department of Engineering Thermophysics Moscow Power Engineering Institute(MPEI)National Research UniversityMoscow111250Russia

Metal hydride(MH)systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ***,the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling *** convection of air may be used to passively remove/add heat as required for proper operation of a MH *** these conditions,the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of *** operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet,a tubular MH reactor based on this principle is examined in this ***-thirds of the internal volume ofø25.4×1 mm tube is occupied by a composition of LaNi5 and aluminium foam(one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2).annular fins are used to increase heat transfer to *** and simplified mathematical models of the systems of this class are proposed and *** is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining *** from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30℃ takes 15 min.A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30-300 W fuel cells.

关键词： Metal hydride Hydrogen storage Natural convection annular fins CFD Numerical simulation Optimization

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Magnetohydrodynamic Effect on Free Convection of Three Dimensional Laminar Flow in Porous Annulus

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Journal of Energy and Power Engineering 2013年第9期7卷 1691-1704页

作者： Manal H. AL-Hafidh Muna S. Kassim Department of Mechanical Engineering Faculty of Engineering Baghdad University Baghdad 10071 Iraq Department of Mechanical Engineering Faculty of Engineering Al-Mustansiriya University Baghdad 10052 lraq

A numerical study has been carried out to investigate heat transfer by free convection under the effect of MHD （magnetohydrodynamic） for steady state three-dimensional laminar flow in horizontal and vertical cylindrical annulus filled with saturated porous media （sand silica） with fins attached to the inner cylinder. A single electric coil placed around the inner cylinder to generate a magnetic field. The governing equations which used are continuity, momentum （using Darcy＇s law） and energy equations which are transformed to dimensionless equations. The finite difference approach is used to obtain all the computational results using Fortran 90 program. The parameters affected on the system are Rayleigh number ranging within （102 ~ Ra＊〈 104）, and MHD （Mn）（0 〈_ Mn 〈_ 100） and radius ratio Rr （0.225, 0.338 and 0.435）. The results obtained are presented graphically in the form of streamline and isotherm contour plots and the results show that heat transfer decrease with the increase of magnetohydrodynamic. It was found that the average Nusselt number increase with Ra＊ and decrease with H~ Mn and Rr. A correlation for the average Nusselt number in terms of Ra＊ and Mn, has been developed for the inner cylinder.

关键词： Free convection magnetohydrodynamic horizontal and vertical annulus laminar flow porous media annular fins numerical solution.

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