<P> A thermocouple is a temperature - measuring device and widely used type of temperature sensor for measurement and control, and can also be used to convert heat into electric power . </P> <P> A thermoelectric cooler is a solid state electronic device that pumps (transfers) heat from one side of the device to the other when electric current is passed through it . It is based on the Peltier effect . </P> <P> A thermal diode or thermal rectifier is a device that causes heat to flow preferentially in one direction . </P> <P> A heat exchanger is used for more efficient heat transfer or to dissipate heat . Heat exchangers are widely used in refrigeration, air conditioning, space heating, power generation, and chemical processing . One common example of a heat exchanger is a car's radiator, in which the hot coolant fluid is cooled by the flow of air over the radiator's surface . </P>

List and define the three mechanisms of heat transfer