Questions regarding the calculation of water vapor enthalpy
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Hello everyone. Recently, I encountered a problem while calculating the enthalpy of water vapor in flue gases: using the formula from the chemical process design manual (see attached diagram), at 1 standard atmosphere and 200°C, the enthalpy of water is 210.86 Kcal/kg, while at 0°C it is 120.24 Kcal/kg. Taking 0°C as the reference point, the enthalpy of water at 200°C is 210.86 – 120.24 = 90.62 Kcal/kg. Using the specific heat values, the specific heat of water is 1 Kcal/(kg*°C), while that of water vapor is approximately 0.45 Kcal/(kg*°C). Without taking into account the heat of vaporization, the enthalpy of water at 200 degrees Celsius is 100*1 + 0.45*(200-100) = 145 Kcal/kg. I would like to ask the experienced experts here: why is there such a large difference between these two calculation methods? What is the reason for this? Thank you!
It must be due to the heat of vaporization
Can it reach 200 degrees Celsius at standard atmospheric pressure?
It does change, but at standard atmospheric pressure, the variation within a certain temperature range is very small, so it should have little impact on calculations
According to Table 1, I recalculated it: the enthalpy of water at 200°C is 400.5349875 KJ/kg, and at 0°C it is 28.19448606 KJ/kg. The difference from your calculation results is quite large
This post was last edited by xgjxgj1985 on 2018-11-30 at 14:10. The understanding was incorrect, so it was edited out