Comparison of pressure loss between Verabar flowmeter and orifice flowmeter

The PowerBar and Orifice Flowmeters are differential pressure flowmeters and are throttle devices. Their measurement principle is that the fluid filled with the pipe flows through the throttling device in the pipe, causing local contraction near the throttle, the flow rate increases, and a static pressure difference is generated at both upstream and downstream sides. For a certain shape and size of the throttle, a certain pressure measurement position and straight forward and backward pipe sections, and certain fluid parameters, the relationship between differential pressure ΔP and flow Q before and after the throttling element conforms to the Bernoulli equation. This type of flowmeter inevitably creates a permanent pressure loss in the pipeline. Taking an orifice flowmeter as an example, the main cause of the fluid pressure loss is the formation of eddy currents in front and behind the orifice plate and the friction along the fluid. It makes part of the total mechanical energy of the fluid irreversibly turned into heat energy and disappears into the fluid. . People used nozzles, venturis and other throttling devices to minimize the eddy current area before and after the throttling, in order to reduce the pressure loss of the fluid. The Verabar flowmeter uses a revolutionary design of the warhead shape, which not only maintains high accuracy, high strength, and large-scale ratio in flow measurement, but also greatly reduces pipeline pressure loss. Comparison of the pressure loss of the power bar and the orifice plate: Empirical formula of orifice pressure loss: When β=0.6, PPLo=0.6×△P When β=0.7, PPLo=0.5×△P Where: β----- - Aperture ratio of orifices ΔP------ Differential pressure produced by orifices PPLo ----- Pressure loss produced by orifices Standard nozzle pressure loss is approximately: PPLn = 0.28 × △P ~ 0.33 × △ P It can be concluded from experiments that the pressure loss of Verabar is approximately: PPLv = 0.03 × ΔP Since the differential pressure ΔP of Verabar is an order of magnitude lower than the differential pressure ΔP of the orifice plate, the pressure loss ratio is smaller. In order of magnitude, the pressure drop of Verabar is minimal compared to the pressure loss of the orifice plate. Here we write the pressure loss expression: Power loss caused by the pressure loss of the throttling element, and its calculation expression is: Hp'=Q×PPL Where: Q------fluid volume flow PPL--- - Pressure loss due to the throttle Assuming that in order to compensate for the unrecoverable pressure loss caused by the throttle, we will add a pressure pump afterwards, the efficiency of which is assumed to be η. Then: Hp=Q×PPL÷η where: Q---------fluid volume flow rate AM3/S PPL------pressure loss produced by throttle device KPa η------motor Efficiency dimensionless constant Hp--------power loss KW For example: Take a steam measurement as an example to assume a measurement point, the measured medium is superheated steam, the pipe diameter is Φ325×13mm, the pressure is 3900KPaG, the temperature is 450°C At this temperature and pressure, the vapor density is 12.511Kg/M3. When the medium flow is 50T/H, the differential pressure generated by the power bar is 5.600KPa. Pressure loss produced by Verabar: PPLv=0.03×ΔP=0.03×5.600=0.168KPa According to the above formula, power loss: Hp=Q×PPL÷η The density of superheated steam under operating conditions is 12.511Kg/M3, so The volume flow rate of the medium (3900KPaG, 450°C) under the working conditions is: Volume flow rate = mass flow rate/media density Q=50×1000÷12.511≈3996.5M3/H=1.110M3/S (3900KPaG,450°C) Assuming motor efficiency η= 0.8: The power of the power loss is Hp=1.110×0.168÷0.8=0.233(KW) Assuming that it runs for 365 days a year and operates for 24 hours a day, the electricity cost per kilowatt is 0.8 yuan. Conversion to electricity: ¥/year = 365 × 24 × 0.233 × 0.8 ≈ 1633 ¥/year Assume that the same measurement point is measured using an orifice plate. Under the same conditions, the pressure difference of the orifice plate is 30 Kpa, and the orifice plate is β = 0.7. The resulting pressure loss: PPLo=0.5×30=15.0KPa The percentage reduction of the permanent pressure loss of the Veripar flowmeter to the orifice plate is: (15.0-0.168)÷15.0×100%=98.88 Combining the pressures of the two throttling devices above After the loss is obvious, the Verabar flowmeter is an efficient, energy-saving, equal-speed flow probe.

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