A heat exchanger is a device built for efficient heat transfer from one fluid to another, whether the fluids are separated by a solid wall so that they never mix, or the fluids are directly contacted. They are widely used in refrigeration, air conditioning, space heating, electricity generation, and chemical processing. One common example of a heat exchanger is the radiator in a car, in which a hot engine-cooling fluid, like antifreeze, transfers heat to air flowing through the radiator.

A tube bundle is one of the most common heat transfer surfaces, especially in shell-and-tube heat exchangers. It usually consists of a small number of rows of tubes housed in a rectangular frame, which may be mounted vertically, horizontally, or in an inclined position. The two most common tube arrangements are staggered and in-line. In-line tubes form rectangular with centers of their cross sections, where staggered tubes form isosceles triangles. This is characterized by the cylinder diameter.

Heat Flux Sensors measure the rate of energy transferred through a given surface. The sensors are several thermocouples whose measurements are averaged, a thermopile or a thermopile with a film heater. Heat-flux sensors are used in thermal and heat-transfer engineering applications. This device is used to measure the rate of heat transfer in watts/sq-m/sec. They are designed to measure radiant heat flux, convective heat flux, conductive heat flux and total heat flux.

Heat gun is a device which is used to emit a stream of hot air. These are often found in physics, materials science, chemistry, engineering, and other types of laboratory or shop settings. Heat guns can be used to dry and strip paint, apply heat shrink tubing, dry out damp wood, bend and weld plastic, soften adhesives, and thaw frozen pipes. Heat guns can have nozzles which deflect their air for various purposes, such as concentrating the heat on one area, or thawing a pipe without heating up the wall behind.