DESIGN ANALYSIS FOR A ROTAMETER USING CFD

Rotameter is a variable area type of flow meter used to measure the flow rate of liquids and gases .In the present study design and analysis of Rotameter performance is done using ANSYS FLUENT 14 software. Validation of CFD methodology is done by using flow through pipe in a turbulent flow. K-ω-SST model was found to be best suited for this class of flows. In the design of Rotameter assuming CD as 2.4 and maximum flow rate of 100 lpm, preliminary design of a Rotameter has been done for the flow of water. After simulation using CFD flow rate obtained from CFD is not same as that from the preliminary designed values .Hence it is concluded that coefficient of drag is also dependent on diameter ratio. Improved design methodology of Rotameter is presented by considering effect d/D on coefficient of drag, by using a correlation derived on the basis of CFD computations. The effect of upstream disturbance (like valves) at various locations on the performance of Rotameter is analyzed using validated CFD methodology. It is concluded that has as long as the locations of disturbance is more than 5Din upstream of the inlet , the error in the measurement will be less than 2% . The validated CFD methodology is used to analyse the effect of density and viscosity of fluid on the accuracy of metering by a Rotameter .A need for the development of correlation for viscosity correction factors are highlighted. The analysis also demonstrated that a Rotameter designed and calibrated for water flow can be used for measurement of air flow at different pressures as long as correction factor are applied. The maximum error of in such cases will be order of 5%. The study has demonstrated that a validated CFD methodology can be used to accurately predict the performance of Rotameter even under non -standard conditions