The HYSYS simulation of the compressor shows adiabatic efficiency and polytropic efficiency greater than 100%.
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Recently, while using HYSYS to simulate a steam compressor, I found that the polytropic efficiency and adiabatic efficiency of the compressor reached 400%. This is clearly unreasonable, so the same operating conditions were simulated again using ASPEN PLUS. The results of the PLUS simulation are completely different from those of HYSYS; the polytropic efficiency and adiabatic efficiency are less than 100%, while the shaft power is roughly in line with the actual values. The simulated operating conditions are as follows: Medium: water vapor; Inlet pressure: 85 Kpa (absolute pressure); Temperature: 95℃ ； Exit pressure: 149 Kpa (gauge pressure); Temperature: 111.2°C. Variable efficiency: 416.76%, adiabatic efficiency: 437.24%. May I ask everyone, how does HYSYS address the above situation?
This situation may be due to incorrect HYSYS settings or parameters, or calculation errors that occurred during the simulation. It is recommended to check whether the settings and parameters in HYSYS are correct, and to confirm that the simulation conditions are accurate. If the conditions are correct, corrections or adjustments may be necessary to obtain a reasonable result. Additionally, other software can be tried for simulation purposes in order to compare and determine the source of the problem and the solution. .
In a situation like this, which parameters are prone to problems? Please give me some guidance. I’ll try to adjust it, thank you
Regarding the parameters used for compressor simulation, the main issues that can arise are as follows: 1. Whether the parameters of the compressor model are set correctly: During the simulation, it is necessary to set various parameters of the compressor model correctly, such as inlet and outlet flow rates, pressure, temperature, etc. If it is not set correctly, it will lead to incorrect results. 2. Accuracy of physical property parameters: During the simulation, accurate physical property parameters of the medium are required to calculate various parameters, such as density, specific heat, viscosity, etc. If the physical property parameters used are inaccurate, it will also lead to incorrect results. 3. Are the process conditions accurate? During simulation, it is necessary to set various parameters of the process accurately, such as fluid flow rate, temperature, pressure, etc., and it is also required to determine the phase and state of the substances. If the process conditions are not accurate, it will also lead to incorrect results. 4. Calculation errors: During the simulation process, errors may occur due to factors such as different calculation methods and limitations in calculation precision. Therefore, when conducting simulations, it is necessary to pay attention to the impact of errors and take measures to minimize them as much as possible. It is recommended that you check the above issues one by one; if the problems remain unresolved, you can turn to HYSYS’ technical support for assistance. .
Remove the outlet vaporization fraction and simply set the outlet pressure.
What is set now are the pressure and temperature directly, with no vaporization fraction set. It still doesn’t work
Exit pressure: 149 Kpa (absolute pressure). Temperature: 111.2°C. Under these conditions, it is no longer steam – it has already condensed; therefore, the calculation is incorrect
Error: 1. Water is in a liquid state at 95°C and 85 KPa； 2. The saturation temperature of water at 85 KPa should be 95.463°C; even when compressed to 0.149 KPa with an isentropic efficiency of 100%, the temperature will still reach 163°C.
Based on the data you provided, the simulations yield correct results. Both the isentropic efficiency and the polytropic efficiency are around 70%, which is an acceptable value. I got a similar result when using ASPEN for simulations as well. I just can’t figure out what’s wrong with HYSYS.
By setting the outlet pressure and outlet temperature directly, the data became acceptable. But if HYSYS cannot simulate the exit temperature and pressure under isentropic conditions, how can the pressure and temperature conditions at the compressor outlet be determined?