Calculating Flow Rates & Conversion Factors for Flow Meters and Valves

February 15, 2022 Johan van't Leven

FLUIDAT: the online flow rate calculator

Fluidat is Bronkhorst’s online calculation software to calculate flow rates and conversion factors for both flow meters and valves. Besides making calculations, you have access to over 1800 different fluid properties and corresponding data.

Working with fluids and ever-changing process conditions, you can face many challenges. Especially when you try to understand the fluid behaviour depending on actual pressure and temperature conditions in the process. How does the fluid (gas or liquid) behave in your application? What are the requirements for your process? This will influence the choice of your flow meter. So, a correct selection of your flow meter is crucial and understanding how your process works even more.

Online flow rate calculator/ software: FLUIDAT

This is where Fluidat can assist you. Fluidat helps you understand the instruments capability. When pressure or temperature conditions change or even when the medium changes, flows must be converted to the new situation. Fluidat can help you decide if your flow meter is capable to do so. Sometimes we must accept that returning the instrument for recalibration is the only option.

​Calculating flow rates

Traditionally, fluid data have been stored in technical handbooks and manuals with graphs and tables of data mentioning fluid properties along with their coefficients. However, this is very inflexible and does not allow immediate access to changing fluid behaviour (due to external factors). 

Knowing this can be very complex for users, Bronkhorst developed on online flow rate calculator; Fluidat. With this tool you can calculate flow rates and conversion factors for your flow meter and valves.

Example of a gas conversion made in FLUIDAT
Example of a gas conversion made in FLUIDAT

Gas Conversion Factor

Thermal mass flow meters and flow controllers are very reliable devices, but the accuracy depends on the temperature, pressure and medium. In the ‘gas conversion’ part of Fluidat, the user has to choose a gas to find the conversion factor. This gas should be different than the one the instrument was calibrated for. This gas can be a pure gas, or you can create a gas mixture. 
With this tool you simply choose the ‘Fluid from’ and ‘Fluid to’, to find the conversion factor. You can also select your exact model to improve the accuracy of the conversion. The conversion factor can then be applied to the output measurement of the flow controller to know the actual flow of the new gas.

Orifice Calculation

Flow controllers and pressure controllers are equipped with control valves. The size of the control valve is based on the customer wishes. Inlet pressure, Outlet pressure, Flow, Temperature and Medium (gas or liquid) are the most important parameters here. The values of these parameters can be recalculated with the Orifice Calculation tool provided by Fluidat.

When a gas is used with a higher density than the original gas, you can recalculate the flow rate or inlet pressure to reach the maximum flow of the instrument again. When you use a thermal mass flow controller, you should also use the Gas conversion tool  in Fluidat.

Vapour generation calculation tool for Controlled Evaporation Mixing in FLUIDAT
Example of a CEM calculation in FLUIDAT

Vapour generation calculation tool

Creating a vapour by using a liquid flow, a carrier gas and a heater, is something what Bronkhorst is doing for years now with the CEM (Controlled Evaporation Mixing) systems. 
Our CEM calculation tool makes this very easy. You can calculate whether a liquid can be evaporated at the carrier gas flow rate, pressure, and temperature you have in mind. It is not only pure physics that is applied here, but you can also select the right Bronkhorst CEM model for this evaporation.

Example of a Pressure Drop Calculation for flow meters in FLUIDAT
Example of a Pressure Difference Calculation in FLUIDAT

Pressure difference calculator

With the Pressure difference calculator you can calculate and size your ES-FLOW ultrasonic flow meter and (mini) CORI FLOW mass flow instruments.

By selecting the instrument and actuator, the program calculates the pressure drop over the instrument and - if you have selected an actuator - the Kv value.
After the calculation, you will get an overview with the selected instrument and the calculation of the total error over the complete range of the instrument. This is expressed in a trompet-curve.

FLUIDAT; your flow calculation tool

Fluidat is a very useful tool if you use Bronkhorst instruments, or if you are interested in the physics of flow measurement and control. In this blog I showed some examples of Fluidat. However, with Fluidat you can also generate all kinds of gas and liquid properties. Generating vapour and pressure lines is also possible to see whether a medium is in the gas or liquid state at a certain pressure and/or temperature.

Register at to take full advantage of this free online flow rate calculator.

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