Hello forum,
I'm having doubt (due to client "inquiries"), therefore I'm addressing this question to you all.
I'm using sealed, gas-law model, hydropneumatic tank element, to model the surge vessel. Total volume is 200m3 and initial gas volume is 20m3. Approx. 160s into the simulation time, the gas volume goes to ~120m3, after which the gas volume starts to decrease. After analyzing the "Water inflow" chart, I calculated that approx 100m3 of water flows out of the tank until 160th second, after which, water starts flowing back in.
Simple logic: at the beginning of simulation, vessel contains X kg of air which occupies 20m3 of volume, at starting pressure and temperature. At 160th second, we still have X kg of air, occupying ~120m3 of volume at minimum pressure and whatever temperature according to pv=krt. Therefore, at 160th second of simulation, the vessel still contains about 80m3 of water.
Is this logic right or not?
The client finds it essential to retain some water within the vessel, during the transient event.
Thanks in advance.
Velibor Kosanovic said:Simple logic: at the beginning of simulation, vessel contains X kg of air which occupies 20m3 of volume, at starting pressure and temperature. At 160th second, we still have X kg of air, occupying ~120m3 of volume at minimum pressure and whatever temperature according to pv=krt. Therefore, at 160th second of simulation, the vessel still contains about 80m3 of water. Is this logic right or not?
Yes, if I understand you correctly, this statement seems right to me. The temperature and mass of air is assumed to be constant, so HAMMER uses PV = K for the gas law calculation. This is explained in more detail in the section "Transient Simulation Behavior" in the following article from our Wiki: Modeling Reference - Hydropneumatic Tanks
If the initial gas volume is 20 m^3 with a total tank volume of 200 m^3 and the reports show the the gas volume is 120 m^3 at a certain time, then the gas has expanded by 100 m^3 and there is 80 m^3 of water left in the tank.
Regards,
Jesse DringoliTechnical Support Manager, OpenFlowsBentley Communities Site AdministratorBentley Systems, Inc.
Answer Verified By: Velibor Kosanovic