Interpretation of the expander performance curve
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I would like to ask the experts: what do the horizontal axis U/Co on one of the two performance curves of the expander, and the isentropic head on the other curve represent? What is their relationship with the inlet and outlet pressures, temperatures, and speed of the machine? How can these values be converted?
I don’t know which company made this machine? Isentropic head, also known as isentropic pressure head or isentropic efficiency. The curve shows the relationship between entropy efficiency, head, and power at different rotational speeds.
This is from Croystar. I would like to ask how to calculate the isentropic head – is it based on temperature, pressure, and flow rate?
Very professional knowledge. It is recommended that you refer to textbooks on chemical engineering related to university courses, as they provide detailed explanations of isentropy and isenthalpy. If you are involved in drill design or technical management, it is recommended that you refer to the above textbooks. If you are part of the plant operation team, there is no need to study this. For expanders, they serve as energy-saving devices in ethylene plants. In my experience, serious problems or accidents caused by expanders are quite rare; even maintenance tasks related to them are infrequent. It is basically a very stable device. The above is for reference only.
The current situation is as follows: one of our units’ expanders is set to operate at such low flow rates and high speeds in order to achieve the maximum amount of cooling with minimal energy consumption. As a result, the temperature of the bearings has risen by 10 degrees, and vibration levels are also higher than before. I suspect that this mode of operation isn’t very reasonable, and I hope to compare it using these theoretical data.
Where is the optimal operating point set for your expander? From the curve, different rotational speeds correspond to different efficiencies; referring to the data table, operating at the speed corresponding to the optimal design efficiency should be reasonable. Therefore, it is recommended to refer to the curve to control the actual operating conditions. That seems reasonable, right?
I have the same problem as you – I can’t understand this curve. Then, strangely enough, those in production usually tell you that there’s no need to study this. I think maybe it’s just that they don’t want to study it or don’t understand it. In fact, understanding this should be helpful for adjusting things according to different production conditions
Heroes see things alike – without understanding this, it’s impossible to accurately determine whether the machine is operating properly, and judgments regarding various abnormalities will also be inaccurate.