Analysis of Nusselt Number Distribution in Case of a Strongly Heated, Horizontal Rod 后印本

摘要: The presented research was focused on a comparison between different means of obtaining a Nusselt number distribution, in a situation where neither temperature nor heat flux density is constant. Two fundamentally different measurement techniques have been utilized, alongside a CFD simulation, in order to designate temperature distributions in a horizontal rod. Dry air under normal pressure, regarded as a perfect gas, was chosen as the working fluid, whereas the rod's cross-section was restricted to a ring. In this scenario heat exchange between the rod and the fluid is driven predominantly by natural convection, with a slight impact of thermal radiation, particularly at temperatures approaching the top end of the available range. Temperature margins achieved at the heated end of the rod ranged from 60K up to 150K, resulting in local Rayleigh numbers falling in-between 6.0x10(3) and 2.6x10(4). Reconstruction of Nusselt numbers from a discrete temperature distribution was possible thanks to a dedicated method implemented using a Scilab script. A segregated, steady-state solver based on the SIMPLE scheme was utilized for the purpose of numerical simulations on the fluid side, whereas a heat conduction equation was solved over solid domain in the considered conjugated heat transfer problem. A corresponding set of empirical data has been obtained, using both resistance temperature detectors and a thermal imaging camera, both for the sake of numerical model validation and comparison of individual methods. The Nusselt numbers resulting from each approach were compared against values computed using available correlations valid for horizontal configuration.