The Wolfram Language provides seamless access to the curated and continuously updated Wolfram Knowledgebase, which includes a wide range of types of engineering data. Free-form linguistics provide a convenient mechanism for accessing all available data; more common categories also have specific associated Wolfram Language functions.
EntityValue — general access to values of properties for all types of entities
Quantity — representation of a quantity with over 10,000 possible units
FormulaData — computable access to named engineering formulas
ThermodynamicData — steam tables and other thermodynamic data for common fluids
PsychrometricPropertyData — thermodynamic properties of moist air