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:

Angle

radian, rad

degree, deg

Concentration

mass_percent

ppm

ppb

molality (mol / kg)

molarity (mol / liter)

mol / m3

If not, no worries. Others:

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?

Can we add emissivity, ε under dimensionless?

Can we add a thermal resistance category: kelvin_per_watts, K/W

Can we add a thermal resistance per unit area category: square_meter_degree_kelvin_per_watt, m²K/W

Can we add a specific volume category: would have all same units as density, just inverse

I see mol in the docs, but could we add it to the database file under substance amount category?

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)

Stephen FrankWed 5 May

I would support adding these units.

Note that for concentration, units of like type should be convertible. I think ppm and ppb would be convertible with each other, but not to (say) mol/kg. So you would need more than one category of units for concentration.

## Cory Mosiman 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:

## Angle

## Concentration

If not, no worries. Others:

`specific heat capacity`

which has the same units as`specific entropy`

. If so, could we add that as a category?`emissivity, ε`

under dimensionless?`thermal resistance`

category:`kelvin_per_watts, K/W`

`thermal resistance per unit area`

category:`square_meter_degree_kelvin_per_watt, m²K/W`

`specific volume`

category: would have all same units as density, just inverse`substance amount`

category?`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)`

## Stephen Frank Wed 5 May

I would support adding these units.

Note that for concentration, units of like type should be convertible. I think ppm and ppb would be convertible with each other, but not to (say) mol/kg. So you would need more than one category of units for concentration.