1 / 14

Welcome to systec Controls

Welcome to systec Controls. Principles of dp-Operation. Principles of dp-Measurement. How do dp-Mesurements work? Equations of the EN-ISO 5167 Types of standard dp elements Acvantages and disadvantages of various dp-elemets calculation of dp-elements. Energieerhaltungsprinzip.

lolita
Download Presentation

Welcome to systec Controls

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Welcome to systec Controls Principles of dp-Operation

  2. Principles of dp-Measurement • How do dp-Mesurements work? • Equations of the EN-ISO 5167 • Types of standard dp elements • Acvantages and disadvantages of various dp-elemets • calculation of dp-elements

  3. Energieerhaltungsprinzip • cinetic + potential Energy is constant • Dp-measurement means conversion of potential Energy (pressure) into cinetic energy (velocity)

  4. Principle of constant Energy • Orifice: In the neck, velocity increases (cinetic E increases) and pressure decreases (potential E decreases)

  5. Principle of constant Energy • Integrating pitot tube: At the impact point of the probe, the velocity is zero (cinetic E decreases) an the pressure raises (potential E increases)

  6. Flow Equation of EN ISO 5167-1 Flow Equation of deltaflow

  7. Flow equation • C Flow factor, depending on dimensions and Reynolds • ß Diameter ratio d/D •  blockage factor •  expansion factor (takes densitiy variations in account) • dp differential pressure •  denistiy at working conditions

  8. Flow equation for liquids • When measuring liquids, the equation is less complicated: • =1 • , C and  are almost constant • ß, d and  are constant

  9. The effect of C and The term is similar to the deltaflow term These are factors, which have been developed by experiments The blockage factor  is from Re=8000 constant C is a function of Reynolds (Re) and does depend on flow exampel: orifice; DN 200; ß=0,5 Re=100.000, C=0,6056 Re=1.000.000, C=0,6032 Error in C= 0,4% deltaflow, DN200 Re=100.000, =2,4093 Re=1.000.000, =2,4093 Error in  =0,0% For big flow spans, the Re-impact on C must be compensated!

  10. The effect of  Due to the pressure loss at the primary element, density of compressible fluids change. Thais has an influence on the flowmeasurement which is compensated by . For incompressible fluids: =1 Exampel: Air, 20°C, 1bar Orifice; DN200; ß=0,6 deltaflow 200 Nm³/h =0,9999 =1,0000 2000 Nm³/h =0,9844 =0,9984 Änderung 1,55% 0,16% For big flow spans, the impact of  must be compensated!

  11. Pressure loss of primary devices (see VDI/VDE 2040-1) High pressure steam example ID 250, 185bar, 540°C, 550 t/h deltaflow Venturi-nozzle orifice beta 0,74 0,8 dp 2011 mbar 1998 mbar 3367 mbar Pressure loss 169 mbar 299 mbar 1111 mbar cost (6Pf/kWh) 24.154 DM/a 42.733 DM/a 158.789 DM/a

  12. Uncertaincies of primary devices (see VDI/VDE 2040) Uncertaincies of standard primary devices: 0,6-2% Uncertaincies of deltaflow: <0,6%

  13. Mechanical construction Orifice Nozzels Venturi

  14. Advantages and disadvatages

More Related