I have a question: can pressure drop in steam pipes cause a temperature drop?
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I’ve completely forgotten fluid mechanics. Help: What impact does the pressure drop caused by frictional resistance during the transmission of saturated steam in pipes have on the temperature of the steam pipes? If the temperature remains constant, will it change from saturated dry steam to superheated steam?
That's how it is. I don’t have any theoretical foundation; it’s based on practical experience. As the transmission distance increases, the pressure decreases, the moisture content increases, and the temperature drops.
Local losses in the pipes, frictional losses along the pipeline, as well as the heat lost due to external temperature differences all cause a decrease in the enthalpy of the steam. The moisture is then discharged through the drain valves along the pipeline; naturally, it is impossible for the steam to become superheated when the pressure in the pipeline remains constant. Personal opinion, for reference only
Just look at the Morrell curve to see
Logically, the pressure drop in steam pipes during transportation is very small... So the idea that steam will overheat due to pressure drop as it flows is basically not valid. Moreover, when public utilities generate steam, they take into account the possibility of temperature drops, and therefore operate with a slight degree of superheating...
It will not turn into superheated steam; to become superheated steam, it needs to be heated further. Since the flow velocity in steam pipes is relatively high, typically around 10 m/s or more, the flow rate is also very large. The heat generated by warming the pipes and the drain water resulting from normal operation can be ignored; in such cases, the steam pipe can be treated as an adiabatic flow system. The steam parameters at the entrance to the pipe, minus the losses due to pipe friction, give the steam parameters at the end of the pipe. Personal opinion
Isn’t the dry steam mentioned by the original poster nothing but supercritical steam?
Yes, it will. As the vapor pressure drops, the temperature will drop as well. The split-type temperature and pressure reducer works the same way. The distance from the outlet after pressure reduction to the inlet after temperature reduction needs to be calculated.
Look at the temperature-entropy diagram, of course, on the condition that the pipeline is properly insulated