Questions about the specific heat capacities of water and water vapor
Thread Content
The first three figures are three tables from a handbook on chemical properties. Question 1: At 200 degrees Celsius, why are there three different values for specific heat under constant pressure? Question 2: Can water vapor reach saturation at 200 degrees Celsius under constant pressure? If it can reach saturation, what is the difference in its heat value compared to superheated vapor?
Could some expert give an explanation? I don’t want to read professional books anymore :L
It can’t be explained in just one or two sentences; to understand this chart, you need to thoroughly study the meaning of these three parameters: PVT
Saturated, superheated, unsaturated – is the extra energy in these different states used to do work?
1. The first one should be problematic; the difference in the second one is that it is overheated. 2. Saturation can be achieved, and the corresponding pressure is the saturation pressure. As for the calorific value you mentioned, it seems you don’t understand what it is
This post was last edited by wiseboy on 2020-1-7 at 15:30. Final answer: 1. Saturated water vapor – the statement is correct, and the data are also correct； 2. Dry saturated water vapor is a highly unscientific term; strictly speaking, it is incorrect. In fact, it is superheated steam, but the data is correct as well. I guess this book is outdated, and its author is also old and frail.
This post was last edited by test_FEYN on 2020-1-8 at 12:03. The temperature of saturated water vapor at standard pressure is 100°C; therefore, my understanding of the values given here is that the 200°C mentioned refers not to standard pressure, but rather to the specific heat capacity at a pressure of 1550 kPa, right?
Yes, under the corresponding pressure. Also, if you have high precision requirements, it’s better not to use this book; the values in it can still be inaccurate. It’s better to use software for such checks, like Aspen or similar