Regulators on Dec. 24, 2013, approved a price hike of 3 cents for a first-class stamp, bringing the charge to 49 cents a letter in an effort to help the Postal Service recover from severe mail decreases brought on after the 2008 economic downturn.
C-value â Thermal Conductance. Thermal conductance is the time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces, in W/m2âK. C-value, hence, is the reciprocal of the R-value and can be expressed as Equation (3).
Thermal Diffusivity. a physical parameter of a substance that characterizes the rate of change of its temperature in transient thermal processes. Thermal diffusivity is a measure of the thermal-inertia properties of a substance. It is numerically equal to the ratio of the substanceâs thermal conductivity and the product of its specific heat (at constant pressure) and density. Thermal diffusivity is expressed in m 2 /sec.