Why doesn’t the volume change while the pressure does after the gas is compressed by a pump?
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This post was last edited by sunjl1981 on 2013-1-6 at 23:42. Taking the compression of acetylene in a water ring pump as an example, the pressure is very low before it enters the pump; after entering the water ring pump and undergoing compression (it’s probably electricity that is converted into static pressure energy, right?) ) It still has the same large volume after coming out, but the pressure has changed. We know from the ideal gas law that PV = NRT; since the pressure has changed and the volume remains unchanged, the value on the left side increases, so the value on the right side must also increase. This means that either N or T must increase. As for acetylene, I think there must be some balance between consumption and production (with the gas tank acting as a buffer in case of fluctuations); the amount of substance N won’t change much. Therefore, it’s only the temperature T that can increase. I haven’t measured the temperature at the outlet of the water ring pump, but the temperature before it enters the vertical separation cooler isn’t very high. Yet even after cooling, the pipe remains thick – why is the pressure still so high? Seeking advice from experts! :I’m a bit stupid, I can’t even figure out such a simple question. # , , &
The volume of the gas before and after the compressor certainly changes; it’s just that in the case of acetylene, the pressure change before and after compression isn’t very significant
1. The volume change after gas compression refers to the situation where, for the same amount, the discussion by the original poster should be based on the premise of an equal amount； 2. What changes after compression is the temperature; therefore, a cooler is used for cooling after compression ； 3. The use of the gas equation of state is conditional; not all gas transformations conform to it ； 4. As for the case where the pressure remains unchanged after cooling, it should be the same as above, with changes in the gas and its quantity.
Thank you. I suddenly realized that I might have gotten the volume wrong – for the same pipe diameter, if 100 meters are compressed to 30 meters, the volume will be different, right?
Fourth grade already? It seems the landlord needs to pick up some knowledge of chemical engineering principles! 1. Generally, for pipes under pressure, a smaller diameter should be used (calculated based on an appropriate flow rate) ； 2. N is variable, just like when using a pump to inflate a balloon ； The size of the pipeline after the pump remains the same regardless of anything ； 3. Crude acetylene contains water; when pressurized, liquid water will condense, causing the temperature to rise ； Generally, a gas-water separator and a cooler are required ； 4. With what was mentioned above, it should be clearer now! ?
I wonder if the original poster understands the working principle of water ring pumps? The inlet gas volume of a water ring pump is large, while the outlet gas volume is small. Taking a certain fixed gas as an example, its volume decreases after passing through the water ring pump, which results in an increase in pressure. I don’t know how you came to the conclusion that the volume remains unchanged This post was last edited by clq20040107 on 2008-1-16 21:20.]
:'(You were able to tell that I don’t understand the principles of chemical engineering. 1. Actually, I also think that the pipes should be smaller under pressure, which is why I had such a question. However, the pipes at the inlet and outlet of the water ring pump in our company are of the same diameter, which is why I was confused. Are the pipe diameters at the inlet and outlet of your company’s water ring pumps different?) I would like to ask that, secondly, I am considering the overall situation with n remaining constant; after all, if 2 moles of acetylene pass through before the pump, it can’t be that only 1 mole or 3 moles remain after the pump, right? 3. Thank you for letting us know; we also have water removal equipment. 4. Thank you for your help, but I don’t have the permission to rate at the moment; I’ll do it later.