Data Points!!!

Which data points should we use? The entropy from 1 to 2 should be the same, but when you measure the different entropies, there are different. Which should we use? Is it better to go from one point (i.e. start of the compressor) and just follow the assumptions of same pressure, temperature, entropy, or enthalpy etc?

Professor Oldham is going to cover a lot of these issues in lecture on Monday, but there are definitely some simplifying assumptions you can make when you are drawing your cycle diagrams.

First off though, while the compression process from 1 to 2 ideally is isentropic, you have enough data to show the real process which is certainly not isentropic. Where it is sufficient to make some simplifying assumptions is from 2 to 3 and 4 to 1 under the vapor dome, where you can assume the process (during the phase change) to occur at constant pressure and temperature.

So just to make sure im doing it right, do we just use the entropy values from the excel file you gave us and interpolate using the temperature we recorded to get the entropy for the T-s plot?

The only thing that is in that file is the T-S data to be able to draw the vapor dome. You'll need a full set of the thermodynamic tables in the back of 'Fundamentals of Thermodynamics' in order to draw your T-S cycle diagrams at each compressor speed (and fan speed after you take the data from this week's lab).