Analisis Ketakpastian Pengukuran (Uncertainty Measurement) Pada Pengujian Karakteristik Aliran Fasa Tunggal Aliran Air Vertikal Ke Bawah Pada Penukar Kalor Saluran Annular Bercelah Sempit

Abstract

Abstract : The promising performance of narrow annulus channels has given rise to intensive research on pressure drop and heat transfer characteristics of flows at the small scale. To check the classical models and to validate new ones, experiments need to be conducted. Although more care has been devoted lately to the design of experiments in terms of control of the geometry and of the boundary conditions, the uncertainties which inevitably affect each measurement do not seem to have been given the proper consideration. Correctly calculating uncertainties not only allows a correct assessment of the experimental data obtained, but can also be used to decide which measurements need to have the highest precision to achieve a certain accuracy, thus saving money on the others. In this paper, a quantitative criterion is given to assess the accuracy achievable in the determination of the friction factor in the laminar and turbulent regime for the flow of water in a narrow gap annular channel heat exchanger. The influence of the five quantities (pressure drop, length, diameter, volume flow rate and temperature) measured to determine friction factor in the laminar and turbulent regime are studied separately and when combined. It is found that volume flow rate and pressure drop measurements are determinat for the final of uncertainty. Uncertainty measurement of volume flow rate is the dominant factor in uncertainty of Reynolds number. Uncertainty measurement of volume flow rate and pressure drop are the dominant factors in uncertainty of friction factor. Uncertainty calculation of actual friction factor is the dominant factor in uncertainty analysis of Poiseuille number. At low Reynolds number, uncertainty calculation of Poiseuille number very high and become decrease along with increasing of Reynolds number.

Keywords : Narrow annulus, Uncertainty measurement, Reynolds number, Friction factor, Poiseuille number