thermodynamic horsepower. The power that would be produced by a turboprop engine under standard-day sea-level conditions if the engine were run at a maximum turbine inlet temperature.
thermodynamics. The branch of physics that deals with mechanical actions caused or controlled by heat.
thermoelectricity. The flow of electrons caused by heat in a metal or in a junction of two metals. The current flowing in a thermocouple circuit is a form of thermoelectricity.
thermograph (meteorology). A continuously recording thermometer.
thermometer. An instrument used to measure temperature. Some thermometers measure the change in the volume of a liquid caused by its expansion or contraction with changes in its temperature. Others measure the change in pressure of a confined gas as its temperature changes.
Electrical thermometers measure the current produced in a thermocouple as the temperature difference between the thermocouple junctions changes, and resistance thermometers measure temperature by measuring the current forced by a constant voltage through a resistance that changes with the temperature.
thermonuclear action. The release of energy that takes place when the nucleus of one element is changed into the nucleus of another element by the action of heat.
thermopile. An assembly of thermocouples connected together. These thermocouples can be connected in series to get a higher voltage or in parallel to get a larger amount of current. Thermopiles are used to measure temperature or to change electromagnetic radiant energy into electrical power.
thermoplastic material. A type of plastic material that becomes soft when it is heated, and hardens when it is cooled. Thermoplastic materials can be softened and hardened many times without the strength or quality of the material being affected. Transparent acrylic plastic resin is an example of a thermoplastic material.
thermosetting material. A type of plastic material that, when once hardened by heat, cannot be softened by being heated again. Phenolic resin is an example of a thermosetting material.
thermostat. A temperature-sensitive electrical switch. A thermostat is used with a combustion heater to control the temperature of the air inside the cabin of an aircraft. The thermostat contains an electrical switch that closes when the temperature drops to a preset value.
Current flowing through the closed switch opens the heater fuel valve, allowing the heater to begin heating the air. When the cabin air temperature rises to the upper value for which the thermostat is set, the switch opens, and the fuel valve shuts off the flow of fuel to the heater.