SI Units | U.S. Customary Units and Algor Simulation | |
Primary | Mass | Force |
Primary | Length | Length |
Primary | Time | Time |
Derived | Force | Mass |
Tip | The discussion on this page is most relevant to the Model Units where the above units must be consistent. The Display Units do not need to be dimensionally consistent. By choosing the right Display Units, the confusion with converting the mass density (and instructions on this page) can be avoided! (See the page 'Selecting a Units System' for details.) |
weight = mass*g
mass = weight/g
mass density = weight density/g
mass density = | 0.284 lbf/in3 | = 7.35E-4 (lbf*sec2/in)/in3 |
386.4 in/sec2 |
0.22 BTU/(lbm*F) = 0.22 BTU/(lbf*F)
= 0.22 | BTU | x | 386.4 in | = 85 | BTU |
---|---|---|---|---|---|
lbf*F | sec2 | (lbf*sec2/in)*F |
where again the term lbf*sec2/in represents the mass. 85 is entered as the specific heat in the material properties. You should be able to confirm, dimensionally at least, that specific heat times mass will result in the correct value:
Note: The above calculations make use of the fact that one lbf equals one lbm at standard gravity. Thus, lbm is not recognized as a mass unit for Model Units. The Display Units do include the unit lbm, so the input can be simplified in many cases by creating a Display Unit that uses lbm.
Similar conversions are required with metric units when the Model Units are changed from the base of Newton, meter, second, kilogram. For example, the specific heat of water is about 4180 J/(kg*C). If the units of length in the model are millimeters, the Model Units of mass are derived based on Newton, millimeter, and second. Thus, the mass in kilograms first needs to be converted to a weight, and then converted to consistent mass units.
Autocad Properties Panel Missing
Convert provided mass to weight units (remember, the model is using Newtons):
4180 | J | x | 1 | = 426 | J |
kg*C | 9.81 m/sec2 | N*C |
4.18E6 is entered as the specific heat in the material properties.