Can I model a Vapor Quality value of 0 or 1?

Can I model a Vapor Quality value of 0 or 1?


When we set the Fluid Type to Two Phase, we are required to enter a value for Quality (Vapor Quality). Vapor Quality has a range of 0 to 1 where 0 represents 0 % vapor and 1 represents 100 % vapor. So, if we entered  a quality of 0.2604, this would represent 26.04 % vapor and 73.96 % liquid in the two-phase flow stream.

Note, by defining Quality, the software automatically calculates the fluid temperature which is then visible from the results for the nodes.

So, if the inlet Quality for a model is set to zero, this represents 100% liquid. In that case, we would usually model the system as a liquid flow system and set the pressure and temperature of the liquid. If you wish to model as two-phase flow stream, you can increase the quality at the inlet ever so slightly to a value such as say, 0.05 to instigate two-phase flow conditions at the inlet.

Likewise, if you modeled a system with an inlet quality of 1, it would essentially be 100% gas and we would tend to model a gas flow system by setting the pressure and temperature at the inlet as opposed to vapor quality. If you wish to model as two-phase condition at or near saturated conditions, you can decrease the quality value at the inlet of the model ever so slightly to a value such as say, 0.95 (depending on inlet pressure conditions) to instigate two-phase flow conditions at the inlet.


    • Related Articles

    • Static pressure below fluid vapor pressure or negative

      This message is often indicative of a data-entry issue and every step should be taken to correct this issue in order to obtain more accurate results. This warning can occur for a number of reasons as follows: 1. When a data-entry error/omission has ...

    • K Value (Input K Value vs Calculated K Value)

      Why is the calculated K Value different to the K Value I have defined for the K Node? The difference arises from the change in density of the flowing fluid. Lets look at the example in the image below. The top model is a liquid flow system based on ...

    • Resolution of Model when exported to Excel

      To ensure a good level of resolution when you export your model to Excel, set the zoom level for the Flowsheet to a minimum level of around 80% in FluidFlow. Select: File | Excel | Write to Excel. Providing you have Excel installed on your PC, the ...

    • How do I model a submersible pump?

      When modelling a submersible pump which of course has no suction piping, it is necessary to insert a short section of pipework between the model inlet boundary and the pump suction connection. This is necessary to complete the model connectivity. The ...

    • How do I model a closed-loop system

      When modeling closed loop systems, we need to include a reservoir node (simply to assign a fluid, pressure and temperature) to the system. The reservoir node is modeled "in-line" and upstream of the pump node. The image below gives an example of this ...