What is the limit of negative pressure (vacuum)?
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What is the limit of negative pressure (vacuum)? Is it 0 Pa? Can negative values occur?
Gauge pressure: -0.1, absolute pressure: 0 Mpa. The absolute pressure will not be negative. This is a matter of definition, hehe.
Zero negative pressure is a theoretical limit, similar to the concept of limits in mathematics. In practical applications, even in conditions of extremely high vacuum, the pressure is only as close to zero as possible; it is impossible to actually reach zero.
Won’t it be -500 Pa? Why :)
Negative values are absolutely impossible; there is no air in a vacuum, so no pressure can be generated.
Reply to #4: Cautiously speaking, since the value of atmospheric pressure is 100 kPa, when the inside of the container is under vacuum, the maximum pressure exerted on the outside of the container is equal to the atmospheric pressure~~~ Therefore, the maximum degree of vacuum is -100 kPa~~~
See 3rd floor, 6th floor. But it is necessary to distinguish between absolute pressure, gauge pressure, and vacuum level. For example, with a negative pressure of 0.01 MPa, the absolute pressure remains positive at 0.09 MPa; the gauge pressure is the difference from atmospheric pressure, which is –0.01 MPa. The degree of vacuum is the absolute value of this difference from atmospheric pressure, namely 0.01 MPa. Therefore, the limit of vacuum is atmospheric pressure.
This post was last edited by Jing Xiaoshenwei sh on 2011-2-1 at 20:45. For example, if the negative pressure is 0.01 MPa, the absolute pressure remains positive, specifically 0.09 MPa. The gauge pressure is a deviation of -0.01 MPa from atmospheric pressure; the vacuum level is the absolute value of 0.01 MPa relative to atmospheric pressure. Is there a missing period? Therefore, the limit of vacuum is atmospheric pressure. Didn’t get it? Do you mean that when the vacuum is approximately 0, it means it’s roughly equal to atmospheric pressure, and thus it’s considered to be atmospheric pressure? But in our daily work, we always refer to it as “ultimate vacuum”, which means it’s approximately 0 Pa, right? Seeking advice!
The so-called negative pressure refers to a pressure lower than atmospheric pressure. Absolute pressure is the actual pressure; gauge pressure is the absolute pressure minus atmospheric pressure. Vacuum degree is defined as atmospheric pressure minus absolute pressure. Therefore, negative pressure is generally expressed in terms of vacuum level; in a state of negative pressure, the vacuum level is greater than 0. The maximum value for the vacuum level is 1 atmosphere, which is equivalent to 101.325 kPa. In a vacuum state, the pressure is 0, and the vacuum level equals 1 atmosphere. If the concept is clear, it’s easy to explain.
Reply to #8: Regarding the gauge pressure mentioned by “谨小慎微sh” in post #7, what you’re referring to is absolute pressure. However, in production, gauge pressure is still more commonly used.