MEASUREMENTS WITH FLOW METERS（与流量计测量）.pdfVIP

UNIVERSITY OF MINNESOTA DULUTH DEPARTMENT OF CHEMICAL ENGINEERING ChE 3211-4211 MEASUREMENTS WITH FLOW METERS OBJECTIVE The purpose of this experiment is to calculate the coefficient of discharge from experimental data for a venturi meter and an orifice meter. Determine the relationship between volumetric flow rate, Q, and the pressure drop, ΔP, for each meter Is it linear? Determine the pressure recovery for each meter. Determine the relationship between Reynolds number and the coefficient of discharge and the pressure recovery for each meter. INTRODUCTION The chemical, paper, and minerals processing industries and pollution control facilities all have various fluid streams entering and leaving different processes. In order to control these processes and to calculate mass balances for these processes it is important to be able to accurately measure the flow rate of these fluids as they move through pipes, conduits, or channels. There are many different types of instruments used to measure the flow rates, but the most common flow measurement instruments are the variable head meters and the variable area meters. Variable head meters work on the principle that a variation of the flow rate through a constriction with a constant cross-sectional area causes a pressure drop suffered by the fluid as it flows through the constriction. The pressure drop is related to the flow rate, and hence variations of the pressure drop can be used to measure variations in the flow rate. The most common examples of variable head meters used in industry are the venturi meter and the orifice meter. The venturi meter A sketch of a typical venturi meter is shown in Figure 1. It is made up of an inlet section A, consisting of a short truncated cone with a recommended cone angle around 21 E, a throat section B one throat d