Vacuum

A given space filled with gas at pressures below atmospheric pressure.

Various approximate ranges are:

low vacuum, 101325 to 3000 Pa

medium vacuum, 3000 to 0. 133 Pa

high vacuum, 0.133 to 1.333x10^-4 Pa

very high vacuum, 1.333x10^-4 to 1.333224x10^-7 Pa

ultrahigh vacuum, 1.333224x10^-7 Pa and below

Heat Transfer

In a vacuum heat transfer is by radiation only.

See also: Absolute Vacuum, Pressure.