As you can see in the figures below, the online CBE Thermal Comfort Tool allow to display different type of charts:
Even if the last one it’s not properly a psychrometric chart, it’s possible to consider an option to display this three types of charts also in ladybug psychrometric chart?
It’s quite an effort to add these capabilities into the psychromteric chart now but I will definitely keep this in mind as I work on the new version of the component for the revised version of Ladybug. I’ll also mention that Abraham has a bioclimatic chart in WIP, which really should be a part of the main components. It’s essentially the last chart with the axes flipped (although it is not yet using the PMV model to generate the comfort polygon and using rules of thumb at the moment).
I have been thinking about how an operative temperature plot would work. I have to ask Tyler Hoyt how he deals with cases in the CBE tool where (because the air can be warmer than the MRT), you would get values that are above the saturation line. If you have an explanation for this, Francesco, please share.
I did not understand what you mean when you say:
(because the air can be warmer than the MRT), you would get values that are above the saturation line.
the Operative temperature (to) is given by this equation so if the air temperature (or the mrt) increases, also the to increases and in a (to, x) chart, it occurs a shift to the right…
I just checked how the CBE tool works when you plot operative temperature on the x-axis. The tool simply does not allow you to set separate air and radiant temperatures and I guess that I could do something similar on a psych chart component.
To illustrate what I meant, you could take a case like the one below:
If I increased the air temperature without increasing the radiant temperature, the red dot would fall off of the psych chart (it would essentially be above the saturation line). This is because the warm, 100% humid air can hold more water vapor than air than 100% humid air at the cooler operative temperature. Does that make snese?
If I increased the air temperature without increasing the radiant temperature, the red dot would fall off of the psych chart
In a (to, x) chart, if you increase both the air temperature (ta) and the radiant temperature (tr), the red dot it moves to right because the operative temperature is directly proportional to ta and tr;
This happens also if you increase only one of the two temperatures (ta or tr).
I thought about how an operative temperature plot can be implemented in ladybug.
Even if the CBE tool does not allow you to set separate air (ta) and radiant temperatures (tmr) (it considers only the operative temperature, to, as an input) you can consider ta, tmr and the air velocity (v).
If there are all the data (ta, tmr and v) you can consider this equation.
If there are not the v values you can approximate to with this equation.
In the psychrometric chart component you can modify the “mollierHX” input and transform it from a Boolean input value to a numerical input and name it, for example, “chart type”: you can set 0 for the classic chart, 1 for the mollier HX plot, 2 for a (to,x) chart and 3 for a (t, RH) plot.
In a (to,x) chart, if the ta or the tmr increases (or both), the to moves to right, so if there is a RH of 100% the red point moves as for the case 1. If ta or tmr (or both) decreases the red point moves to the left (case 2).
I like this idea of chartType and I will try to implement it at some point. Because it is such a big task, I might wait until I do a revision of the code for the new Ladybug. Still, I put an issue on the github so that we remember it: