Physical properties of a fluid

The properties shown will generally vary with the temperature (inter alia) but these variations are negligible for what concerns us and we will assume that these properties are constant :

• the thermal conductivity k ( in W/(m K) )
• the specific heat c ( in J/(kg K) ), which expresses the fact that one kg of air contains less quantity of heat than one kg of water when both are at the same temperature
• the density r ( pronounce "ro", in kg/m ³ ), which expresses the fact that one cubic meter of air is less heavy than one cubic meter of water
• the viscosity m ( pronounce "mu", in kg/(m s) ), it expresses the fact that it is harder to move water than air

A small table to recapitulate these values, taken at ambient temperature and pressure :