Understanding refrigerants is difficult enough without having to look at charts like these

It’s not that these charts are inherently bad, they are extremely useful once you know what you are looking at. But getting to that point is quite challenging. So that got me thinking, could I just project the temperature (red lines on the plot above) onto a 3rd axis – the z-axis in my case.

The answer was yes, it took a bit of faffing and I don’t have many of the extra contours that the graph above does, but I think the 3D plot shows something that 2D plots don’t. They can give a more concrete feeling of what the above graph is showing.

R32 Pressure Enthalpy Temperature Graph

You can scroll your mouse over it and see the pressure at any point or the enthalpy. You can also spin the chart around. One enlightening way to rotate it is so that you rotate it so they Pressure axis is at the bottom of the screen and the Temperature is on the left.

From that angle you can clearly see that the two-phase section is flat as enthalpy increases. Which means that it is gaining internal energy, but not gaining temperature.

Quality is a thermodynamics name which essentially means the proportion of the fluid that is a gas vs a liquid. A quality of 100% is fully liquid, while 50% is mixed gas and liquid.

R290 Pressure Enthalpy Temperature Graph

It is possible to compare the two graphs, spin them to similar directions and see how they differ. In the case of the above two, you can see that R290 (propane) can reach a much higher temperature in the liquid, two-phase and gas zones, than R32. This is advantageous as the only way a refrigerant can heat another fluid (like water) is by being hotter than it. Which is why R290 heat pumps can heat hot water to a higher temperature than R32 heat pumps.

You could easily discover this from a traditional pressure enthalpy chart, but there is something about seeing it in 3D that I like.