Dear All,
I have a question regrarding the valve minor loss coefficient.
1) For PRV, seems like the minor loss coefficient is not working even I set the initial status as "Inactive";
2) For valves generally, I tried and found that the head loss seems only related to the initial loss coefficient. No matter how high I set the minor loss coefficient (local) value as, the head loss is the same number along with a steady initial loss coefficient. So I just wonder why so and how to settle up the coefficient to best present the minor head loss through the valves.
Best,
Meng
Hello Meng,
The minor loss only applies when the valve is fully open, which is when the calculated status is "Inactive." Please check the calculated status for the PRV to make sure this is not set to Closed. If the calculated status is Closed, this is likely related to conditions in your model. This link has information on how PRVs operate in WaterGEMS and WaterCAD.
If the calculated status is Inactive, adjust the precision for the headloss results field for the PRV. Right-click on the Headloss property field and choose "Units and Formatting" and increase the value for precision. It is possible that if the flow is small through the PRV that the headloss is small as well.
If that doesn't help, we may need to see a copy of the model.
Regards,
Scott
Hi Scott,
Thanks for the reply. Yes I set the PRV status as inactive and the same shown in "statue(calculated)" field every time step. It is only a test model, I've attached below. I am running a WaterGEMS V8i version, which is old, not sure if it's a version problem.
Also I found the same happend for other valves: Like in the model, I set a TCV and the status as "active". The loss coefficient(local) is not affacting the actual head loss and only the initial loss coefficient matters, which is weird.
test model.rar
I checked your model and saw that there is no demand applied to the downstream junction J-12. Since WaterGEMS is a demand driven software, without assigning demands there is no flow in the network. Once you have some demand applied, you will see flows in pipes along with the headloss from the PRV being applied.
Please go through the article Scott shared in the earlier response. As the article mentions the headloss would be calculated as the difference between the the upstream and downstream hydraulic grades.
Let me know if this helps.
Yashodhan Joshi