【Daily Question】Theoretical Foundation 2020.11.07
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Multiple-choice question: The question is as shown in the figure ( ). Answer: C. Hint: Extra rewards will be given to those who can explain the solution process; the answer can be viewed upon response
B, the vacuum level is gauge pressure. I understand, right?
C 【Explanation】 The true pressure P of a system is known as absolute pressure. The pressure measured by a vacuum gauge is the degree of vacuum P1, which indicates that the actual pressure is lower than atmospheric pressure. The relationship between P1, atmospheric pressure B, and absolute pressure P is: P = B – P1； The pressure gauge measures gauge pressure Pe, which indicates that the actual pressure is greater than atmospheric pressure. The relationship between Pc, atmospheric pressure B, and absolute pressure P is: P = B + Pe.
Excuse me, doesn’t the vacuum gauge show a negative value?
C. Regarding the definition of vacuum level: vacuum level = atmospheric pressure – actual pressure. When the vacuum level is negative, it indicates that the actual pressure is greater than the atmospheric pressure. Additionally, gauge pressure = true pressure – atmospheric pressure. Source: \"Principles of Chemical Engineering\" (Yao Yuying) (Revised Edition)