# Approach for the determination of heat transfer coefficients for filling process of pressure vessels with compressed gaseous media

 dc.contributor.author Na Ranong, C. dc.contributor.author Maus, S. dc.contributor.author Hapke, J. dc.date.accessioned 2014-12-15T08:32:59Z dc.date.available 2014-12-15T08:32:59Z dc.date.issued 2008 dc.description.abstract Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008. en_ZA dc.description.abstract For fast and effective simulation of filling processes of en_ZA pressure vessels with compressed gaseous media the governing equations are derived from a mass balance equation for the gas and from energy balance equations for the gas and the wall of the vessel. For simplicity the gas is considered as a perfectly mixed phase and two heat transfer coefficients are introduced. The first one is the mean heat transfer coefficient between the gas and the inner surface of the pressure vessel and the second one is the heat transfer coefficient between outer surface of the vessel and the surroundings. Although the process is transient, steady-state heat transfer coefficients for free convection are used between outer surface of the vessel and the surroundings. The use of available correlations for steady-state heat transfer coefficients to describe transient processes is common practice, e.g. in the modelling of the transient behaviour of heat exchangers [1]. But no correlations – neither steady-state nor transient – are available for the heat transfer coefficient between inflowing gas and inner surface of the vessel. To solve this problem a CFD tool is used to determine the gas velocities at the vicinity of the inner surface of the vessel for a number of discrete surface elements. The results of a large amount of numerical experiments show that there exists a unique relationship between the tangential fluid velocities at the vicinity of the inner surface of the vessel and the gas velocity at the inlet. Once this unique relationship is known the complete velocity distribution at the vicinity of the inner surface can be easily calculated from the inlet velocity of the gas. The nearwall velocities at the outer limit of the boundary layer are substituted into the heat transfer correlation for external flow over flat plates. The final heat transfer coefficient is the areaweighted mean of all local heat transfer coefficients. The method is applied to the special case of filling a 70 MPa composite vessel for fuel cell vehicles with hydrogen. Because of the heat capacity of the composite wall consisting of an inner aluminium liner wrapped with carbon fibre, heat transfer from the compressed gas to the vessel wall strongly influences the temperature field of the gas which is predicted by the model and confirmed by experiments. dc.description.librarian vk2014 en_ZA dc.format.extent 5 pages en_ZA dc.format.medium PDF en_ZA dc.identifier.citation Na Ranong, Ch, Maus, S & Hapke J 2008, Approach for the determination of heat transfer coefficients for filling process of pressure vessels with compressed gaseous media, Paper presented to the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July 2008. en_ZA dc.identifier.isbn 9781868546916 dc.identifier.uri http://hdl.handle.net/2263/43058 dc.language.iso en en_ZA dc.publisher International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics en_ZA dc.relation.ispartof HEFAT 2008 en_US dc.rights University of Pretoria en_ZA dc.subject Heat transfer coefficient en_ZA dc.subject Filling process en_ZA dc.subject Pressure vessels en_ZA dc.subject Compressed gaseous media en_ZA dc.subject Transient process en_ZA dc.subject CFD en_ZA dc.subject Velocity distribution en_ZA dc.subject Fuel cell vehicles with hydrogen en_ZA dc.subject Steady-state heat transfer coefficients en_ZA dc.title Approach for the determination of heat transfer coefficients for filling process of pressure vessels with compressed gaseous media en_ZA dc.type Presentation en_ZA
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