What is the difference between the measured flow rates of saturated steam and superheated steam under the same conditions?
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With the pressure (0.6 MPa) remaining constant, in the same pipeline using the same flow meter (vortex flow meter or orifice plate), when the steam temperature rises from 165°C to 350°C and becomes superheated steam, does the reading of this flow meter increase? Has this really changed, or is it the density affecting the flow meter’s display?
The density shouldn’t increase, right? Could it be that the water carried by the steam has vaporized, causing the volume to increase a little?
For saturated steam at 0.6 MPa, the specific volume is 0.2727 m3/kg. For superheated steam at 0.6 MPa and 350°C, the specific volume is 0.4057 m3/kg. Therefore, as the temperature of saturated steam increases, its specific volume increases while its density decreases. With a constant mass flow rate, a flow meter that measures volume should show an increased reading.
Thank you for your answer. Our customers use saturated steam to heat the bottom of the tower; if the steam supplier suddenly changes this saturated steam to superheated steam, does that mean an increase in the customers’ costs? To maintain the previous heating effect, will the mass flow rate increase?
It is said that, for the same heating effect, superheated steam is more expensive than saturated steam; so where does the heat that is not utilized go? Energy must be conserved
When saturated steam is used for heating, the gas liquefies and releases latent heat, which is the primary heat source utilized. If it is superheated steam, it remains steam even after leaving the vessel, as the latent heat has not been released; therefore, the heating effect should be worse. I don’t know much about steam applications, and I’m not aware of any successful cases of using superheated steam for heating
Makes sense. According to the ideal gas law, after superheating, the density should decrease at the same pressure
The heat exchange efficiency of superheated steam is low; one can refer to Spysack’s documents
As mentioned on floor 7, using superheated steam for heat retention can be understood, on a macro level, as heat exchange occurring in two stages. The first stage involves cooling the superheated steam to saturated steam; during this stage the temperature of the steam drops significantly, but the actual amount of heat released is relatively small due to the low specific heat capacity of gases. The second stage involves cooling saturated steam to saturated water; during this stage, the temperature of the steam does not drop, but a large amount of heat is released. Because during the heat exchange with saturated steam, the steam temperature does not drop, and as a result the temperature at the hot side also does not decrease; this leads to a larger logarithmic temperature difference for heat exchange, thereby enabling better heat exchange efficiency. At the same time, since phase change releases latent heat, more heat is released as well; therefore, in conventional steam heating, saturated steam is used to achieve higher efficiency. If saturated steam is replaced with superheated steam, while the heat exchange equipment remains unchanged, the actual heat exchange efficiency is likely to decrease; in other words, more superheated steam will be required to achieve the same effect as saturated steam. Because although the quality of the heat source as superheated steam enters the heat exchanger increases, the amount of heat carried out of the heat exchanger also increases.