How do I calculate this? I’m seeking help from experts
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The inlet pressure of the vacuum pump is 50 kPa (absolute pressure), the inlet temperature is 19 degrees Celsius, and the pumping capacity of the vacuum pump is 1000 L/S. The gas being pumped is a mixture of ethanol vapor and water vapor. I would appreciate it if someone could help me figure out how to determine the mass concentration of ethanol vapor. Thank you everyone! It was found that the saturated vapor pressure of ethanol at 19 degrees is 5.33 KPA
This post was last edited by Qingchengjun on 2020-6-4 at 14:19. The saturated vapor pressure of water at 19℃ is 2.2 kPa. If calculations are to be done using Raoult’s law, it is also necessary to know the percentage concentration a of ethanol in the solution: 5.33a/(5.33a + 2.2(1-a)); this represents the molar ratio
Calculate the partial volume based on the partial pressure, convert it to standard conditions, and then multiply by the molar amount
You also need to know the saturated vapor pressure of the solution
There were already so many conditions before; another person calculated the quantity, and I didn’t see the process
Hello, the person ahead of me used these parameters to do the calculation, but I didn’t see the algorithm used
Hello, I’m sorry to bother you, but could you provide a specific algorithm? I would be extremely grateful
Who said that? Ask them yourself. Is it really important to you? You can’t understand it, let alone use it for anything valuable
Since it is not a pure component, you need to know the concentration or composition of the ethanol-water solution. By then consulting the phase equilibrium curves for ethanol and water, you can determine the composition of the gas phase. The partial pressure of ethanol can be used to calculate the amount of ethanol present in the gas entering the vacuum pump, and thus the value can be determined. Currently, the parameters you have provided are insufficient; only when the solution is a pure component does this approach work. Alternatively, if you know the composition of the liquid, you can use simulation software to carry out the calculations. For example, in the case of a 50% ethanol solution, according to the phase diagram, ethanol makes up 66% of the gas phase. Therefore, 5.33 * 66% gives the partial pressure of ethanol in the gas. I hope I have explained this clearly
This post was last edited by henglinkou on 2020-6-4 at 15:17; it is considered to be a gas-liquid equilibrium situation – the liquid phase composition, temperature, and pressure need to be known in order to calculate the gas phase composition. It can be found in the data sheet or determined through software simulation.
Given your conditions, the components entering the vacuum pump are certainly not just water vapor and ethanol vapor; what are the other components? Air or syngas? You know that at this temperature, the saturated vapor pressure of ethanol vapor is 5.33 KPA. If this gas is not separated through subcooling, the volume fraction of ethanol will be 5.33/50 = 10.66%. Using this value, it is possible to calculate the volumetric flow rate of ethanol vapor per hour; this value can then be converted to a volume at standard conditions, and from there the amount of substance can be determined, allowing for the calculation of the mass of ethanol.