#2829 Unit Additions / Clarifications

como Tue 4 May

I saw in the docs that certain types of units (i.e. angles, concentration) need to be modeled as dimensionless. I'm wondering if we could consider changing this? Specifically, I would be looking for:


  • radian, rad
  • degree, deg


  • mass_percent
  • ppm
  • ppb
  • molality (mol / kg)
  • molarity (mol / liter)
  • mol / m3

If not, no worries. Others:

  1. Are there ever times where you will define two categories that have the same units? Example, I wanted to define specific heat capacity which has the same units as specific entropy. If so, could we add that as a category?
  2. Can we add emissivity, ε under dimensionless?
  3. Can we add a thermal resistance category: kelvin_per_watts, K/W
  4. Can we add a thermal resistance per unit area category: square_meter_degree_kelvin_per_watt, m²K/W
  5. Can we add a specific volume category: would have all same units as density, just inverse
  6. I see mol in the docs, but could we add it to the database file under substance amount category?
  7. Can we move watts_per_square_meter_degree_kelvin, W/m²K under a new category: thermal transmittance and also add btu_per_hour_square_foot_degrees_fahrenheit, Btu/(h⋅ft2⋅°F)

SlimerDude Tue 4 May

Hi como,

This is probably more of a question for the Project Haystack forum given that Fantom uses Project Haystack units as its reference (or vice versa) - but I'm sure Brian or someone can help you out here.

brian Tue 4 May

Agree, I think at this point that database is owned by the project haystack community. The master version should probably eventually move to the Haystack's GitHub repo actually.

But in the meantime, I would suggest reposting this there.

como Tue 4 May

Gotcha - will do. Brian is this somewhere in one of the project haystack repos?

Also, I noticed that the units.txt file in Fantom implemented dimensional analysis and also has conversion to base units (which is awesome!). Could we also get this added to the Project Haystack database file?

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