Units

SI Units (but with kmol)

• m
• s
• kg
• kmol
• K

Convert units to these at the top of a problem, then do the math, then convert back to the desired units at the end.

• Avoid doing any unit conversions in the middle of a problem, as this can lead to mistakes and complicates the equation.
• Proper equations are dimensionally consistent, so if you convert all units to SI, the math will work out correctly.
  • Checking that the units are consistent in equations is something your boss will do to quickly check your work. (I do that all the time to spot errors quickly when talking to students.)
  • Additive terms always have the same units, so L + complex_expression implies complex_expression has units of L. If it doesn’t, then the equation is wrong.

Derived units

• energy: J = kg·m²/s²
• pressure: Pa = N/m²
• force: N = kg·m/s²
• power: W = J/s = kg·m²/s³
• density: kg/m³
• MW: kg/kmol
• dynamic viscosity $\mu$: Pa·s = N·s/m²
• kinematic viscosity $\nu=\mu/\rho$: m²/s
• thermal conductivity: W/(m·K)
• specific heat capacity: J/(kg·K)
• R: 8314.46 J/(kmol·K)
• g: 9.80665 m/s²

The following should all be intuitive and used whenever needed. They are convenient for making unit conversions.

• $F=ma$
• pressure: $P=F/A = \rho gh$
• energy (work): $W=F\cdot d$
• power $\dot{W} = W/t = Fv = P A v$
• mass flow rate: $\dot{m} = \rho Av$
• volume flow rate: $\dot{V} = Av$

Conversion Factors

• 3.2808 ft/m
• 2.2046 lb/kg
• 101325 Pa/atm
• 100³ cm³/m³
• 1000 L/m³
• 4.184 J/cal
• 1.8 °F/°C
• 273.15 K = °C
• 1 lbf = 32.174 lbm·ft/s²
  • 1 lbm creates 1 lbf of force at 32.174 ft/s²

Now, do all this for English units. Let AI help.