What is a Heat Exchanger?
A heat exchanger is a device designed to efficiently transfer or "exchange" heat from one matter to another. When a fluid is used to transfer heat, the fluid could be a liquid, such as water or oil, or could be moving air. The most well known type of heat exchanger is a car radiator. In a radiator, a solution of water and ethylene glycol, also known as antifreeze, transfers heat from the engine to the radiator and then from the radiator to the ambient air flowing through it. This process helps to keep a car's engine from overheating. Similarly, Aavid’s heat exchangers are designed to remove excess heat from aircraft engines, optics, x-ray tubes, lasers, power supplies, military equipment, and many other types of equipment that require cooling beyond what air-cooled heat sinks can provide.
There are various types of heat exchangers. Aavid’s heat exchangers provide air-to-liquid cooling, liquid-to-air cooling, liquid-to-liquid cooling, or air-to-air cooling. With air-to-liquid cooling, heat is transferred from the air to a liquid. One example of air-to-liquid cooling is cabinet cooling. With liquid-to-air cooling, the heat is transferred from the liquid to the air. This type of cooling is generally used to cool process fluids. Liquid-to-liquid cooling is also used to cool process fluids, but the heat is removed by another liquid instead of by air. Lastly, with air-to-air cooling, heat is transferred from one air or gas stream to another.
Aavid has been manufacturing one of the most widely used heat exchanger technologies, tube and fin heat exchangers, for decades. Tube and fin heat exchangers provide air-to-liquid cooling or liquid-to-air cooling. They consist of fin, hairpin tubes, return bends to connect the hairpins, a tube sheet to support and properly align the tubes, a header with inlets and outlets, side plates for structural support, and usually a fan plate. The tubes provide the path for liquid coolant, and the fin adds surface area for more heat convection. Copper is often selected for tube and fin material due to its excellent thermal conductivity and compatibility with water and ethylene glycol solutions. However, stainless steel is used for tube and fin when it's necessary for the coolant to be deionized water or other corrosive fluids.
Aavid’s oil cooler flat tube heat exchangers also have tubes and fin; however, the tubes are flat instead of round. This helps to minimize pressure drop when oil or ethylene glycol is used as the coolant. The surface area of the flat tubes is also much greater than the surface area of the tubes in a tube and fin heat exchanger. The additional surface area of the tubes in an oil cooler flat tube heat exchanger maximizes heat transfer when poor heat transfer fluids like oil or ethylene glycol are used. These oil cooler heat exchangers consist of fin, flat tubes, a welded header with inlets and outlets, and plates, including an optional fan plate.
Another type of heat exchanger is a plate-fin heat exchanger, which can provide air-to-air, air-to-liquid, liquid-to-air, or liquid-to-liquid cooling. Plate-fin heat exchangers consist of finned chambers separated by flat plates and are circuited in alternating hot and cold fluid passages. Heat is transferred via fins in the passageways, through the separator plate, into the cold fluid via the separator plate, and into the cold fluid via fin once again. The heat exchanger also has manifold ducting, mounting brackets, and a frame.
Aavid’s liquid-to-liquid brazed plate heat exchangers also have plates, but with a herringbone pattern of grooves, stacked in alternating directions. This forms separate flow channels for two liquid streams so that the two fluids are never in direct contact. The heat exchanger plates are brazed together at the edges and at a matrix of contact points between sheets. The liquid-to-liquid heat exchanger can be compared to a shell and tube heat exchanger, which is used in similar applications.
The thermal performance of heat exchanger technologies can vary quite a bit, so when selecting a heat exchanger it's important to understand what performance is needed as well as what fluids are available for removal of heat. It's also important to evaluate the entire system when deciding on a heat exchanger, as there are multiple considerations including flow rate, pressure drop, materials compatibility, and more.