- #1
fourthindiana
- 162
- 25
I attend a trade school, majoring in HVAC (Heating, Ventilation, and Air-Conditioning). My instructor has given me information that seemingly contradicts what my textbooks tell me about Charles' Law. My instructor is not a scientist. I asked my instructor to reconcile the two seemingly contradictory facts, and I did not understand his answer. I was hoping you people could explain this to me. Furthermore, I learn better by reading information than by hearing a person speak information.
My instructor said that superheated refrigerant vapor (vapor is the same as gas) in an air-conditioner does not follow a pressure/temperature relationship. Normally, if you know the temperature of a given gas, you can use a pressure/temperature chart to know the pressure of the gas at that temperature. My understanding of my instructor's statement that "superheated vapors don't follow a pressure/temperature relationship" is that if a refrigerant gas is superheated, you cannot use a pressure/temperature chart to know the pressure of a superheated gas is if you know the temperature of the superheated gas, and you cannot use a pressure/temperature chart to know the temperature of a superheated gas if you know the pressure of the superheated gas.
However, the statement that superheated refrigerant vapor in an air-conditioner does not follow a pressure/temperature relationship seems to violate Gay-Lussac's Gas Law. Gay-Lussac's Gas Law states that "the pressure of a gas of fixed mass and fixed volume is directly proportional to the gas's absolute temperature". Isn't the refrigerant in an air-conditioner in a fixed mass and at a fixed volume? Therefore, Gay-Lussac's Gas Law seems to imply that as the refrigerant is heated, the pressure of the refrigerant gas would always increase directly proportionately to an increase in temperature of the refrigerant, but my instructor says that superheated refrigerant gas does not follow a pressure/temperature relationship.
My idea that the Gay-Lussac's Gas Law contradicts my instructor's statement that superheated gases do not follow a pressure temperature relationship relies on my supposition that the refrigerant in an air-conditioner is at a fixed mass at a fixed volume. Is this where there is a flaw in my reasoning? If refrigerant gas in an air-conditioner is not at a fixed mass and a fixed volume, why does my textbook have a chart that shows the pressure/temperature relationship of refrigerant gases? I mean, if refrigerant gas in an air-conditioner is not at a fixed mass and a fixed volume, why do the refrigerant gases follow a pressure/temperature relationship when the refrigerant gases are not superheated?
My instructor's statement also seems to contradict the Combined Gas Law.
Since Gay-Lussac's Gas Law implies that as the refrigerant is heated, the pressure of the refrigerant gas would always increase directly proportionately to an increase in temperature of the refrigerant gas, how can superheated refrigerant gases not follow a pressure/temperature relationship?
My instructor said that superheated refrigerant vapor (vapor is the same as gas) in an air-conditioner does not follow a pressure/temperature relationship. Normally, if you know the temperature of a given gas, you can use a pressure/temperature chart to know the pressure of the gas at that temperature. My understanding of my instructor's statement that "superheated vapors don't follow a pressure/temperature relationship" is that if a refrigerant gas is superheated, you cannot use a pressure/temperature chart to know the pressure of a superheated gas is if you know the temperature of the superheated gas, and you cannot use a pressure/temperature chart to know the temperature of a superheated gas if you know the pressure of the superheated gas.
However, the statement that superheated refrigerant vapor in an air-conditioner does not follow a pressure/temperature relationship seems to violate Gay-Lussac's Gas Law. Gay-Lussac's Gas Law states that "the pressure of a gas of fixed mass and fixed volume is directly proportional to the gas's absolute temperature". Isn't the refrigerant in an air-conditioner in a fixed mass and at a fixed volume? Therefore, Gay-Lussac's Gas Law seems to imply that as the refrigerant is heated, the pressure of the refrigerant gas would always increase directly proportionately to an increase in temperature of the refrigerant, but my instructor says that superheated refrigerant gas does not follow a pressure/temperature relationship.
My idea that the Gay-Lussac's Gas Law contradicts my instructor's statement that superheated gases do not follow a pressure temperature relationship relies on my supposition that the refrigerant in an air-conditioner is at a fixed mass at a fixed volume. Is this where there is a flaw in my reasoning? If refrigerant gas in an air-conditioner is not at a fixed mass and a fixed volume, why does my textbook have a chart that shows the pressure/temperature relationship of refrigerant gases? I mean, if refrigerant gas in an air-conditioner is not at a fixed mass and a fixed volume, why do the refrigerant gases follow a pressure/temperature relationship when the refrigerant gases are not superheated?
My instructor's statement also seems to contradict the Combined Gas Law.
Since Gay-Lussac's Gas Law implies that as the refrigerant is heated, the pressure of the refrigerant gas would always increase directly proportionately to an increase in temperature of the refrigerant gas, how can superheated refrigerant gases not follow a pressure/temperature relationship?