superheat (refrigeration system). Heat energy added to a refrigerant after it changes from its liquid state into a vapor. The thermal expansion valve in a refrigeration system meters just enough liquid refrigerant into the evaporator for all of it to be changed from droplets of liquid into a vapor by the time it reaches the end of the evaporator coils. If all of the refrigerant vaporizes before it reaches the end of the coils, any additional heat raises its temperature. This additional heat is called superheat.
superheated water. Water that has been heated to a temperature above that at which it normally changes its state from liquid into steam. Water may be superheated by holding it under pressure. More heat energy must be added to it before its molecules move fast enough to leave the surface of the liquid and become steam.
superheterodyne radio receiver circuit. The type of circuit used in most modern radio receivers. A radio-frequency signal is received, amplified, and mixed with a signal produced inside the radio by a local oscillator. The frequency of the oscillator signal is always a fixed amount different from the radio-frequency signals being received.
When the two signals are mixed, two more signals are produced. The frequency of one is the sum of the other two, and the frequency of the other is the difference between them. The signal whose frequency is the difference is called an intermediate frequency, an IF. The IF is amplified and changed into an audio-frequency voltage that duplicates the AF used to modulate the radio-frequency signal in the transmitter.
superhigh frequency (radio frequencies). Electromagnetic radiation whose frequency is between 3.0 and
30.0 gigahertz. At this frequency, the wavelengths are between 100 and 10 millimeters.
superrefraction (radar technology). More than normal bending of a radar beam resulting from abnormal vertical gradients of temperature and/or water vapor.
supersaturated solution. A solution in which a solid is dissolved in a liquid until the liquid will hold no more. A supersaturated solution of salt and water has some salt crystals in the liquid. The amount of crystals depends upon the temperature of the solution. As the temperature decreases, more crystals precipitate out of the solution.
supersede. To replace, or take the place of, something. When a manufacturer issues a revision to an instruction manual, the revised manual supersedes the original one. If there is a difference in the instructions in the two manuals, the instructions in the latest (the superseding) manual, are to be followed.
supersonic aerodynamics. The branch of aerodynamics that deals with flight at a speed greater than the speed of sound.
supersonic flight. Flight at an airspeed in which all air flowing over the aircraft is moving at a speed greater than the speed of sound.
superstructure. The framework of formers and stringers attached to the main truss of a truss-type aircraft fuselage. The superstructure gives the fuselage its shape, but it is not a main strength-carrying part of the fuselage.