Questions about saturated vapor pressure?
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This post was last edited by touchskyyy on 2022-5-20 10:53. I would like to ask the experts: is the saturated vapor pressure found in reference books an absolute pressure or a gauge pressure? If I find that the saturated vapor pressure of a liquid at 60 degrees Celsius is 0.7 MPa, then in a real-world metal tank containing this liquid, where the outer surface of the metal reaches 60°C due to direct sunlight, the pressure gauge measuring the vapor pressure on the tank should indicate 0.6 MPa (gauge pressure). Am I understanding correctly? Another example: water is added to a vacuum chamber to a 50% level. Initially, the pressure gauge reads -0.1 MPa. If I continue to heat the chamber until the water reaches 100°C, the pressure gauge should then read 0 MPa (gauge pressure). Is my understanding correct?
The table showing the relationship between saturated steam temperature and pressure uses absolute pressure. Not necessarily; the outer wall is at 60 degrees, but the temperature inside the medium isn’t necessarily the same – it might be below zero there. If it is a closed container, the gauge pressure should be between 0 and 0.005.
Thank you for your response. I didn’t express myself clearly: the outer surface is at 60 degrees. Assuming it’s not an insulated tank without any thermal insulation layer, and assuming that the material inside the tank will also reach 60 degrees as a result of heat transfer, I merely proposed a model – please forgive the lack of precision in my description.
The vapor pressure is generally absolute pressure, with 100°C corresponding to 0 MPa
Gauge pressure is generally not very precise.