A heat exchanger is a device which transfers (or exchanges) heat from one fluid to another. There are many different names for heat exchangers because of their varied applications. When considering what you want from a heat exchanger you should think about which medium you want to heat or cool and what you are using it for.
Finned Tube Heat Exchanger Or Air Cooled Heat Exchanger
Suitable for: air/gas to fluid
A finned tube heat exchanger, air cooled heat exchanger (ACHE), cooler or dryer works by flowing a liquid into a series of tubes, whilst pumping gas or air around or over the pipework to cool the fluid down.
Sometimes finned tube heat exchangers, ACHEs, coolers or dryers are enclosed in duct work, and sometimes they are fully exposed with air flowing over them. The efficiency of these units comes from the extended surface – the fins – that protrude into the air/gas flow and improve the heat transfer ability of the structure.
Finned tube heat exchangers are often used for heat recovery in processes that exhaust hot gasses. The heat in the gas is transferred into a liquid, usually water or a thermal oil. The heated liquid can be then used in an application where you would normally use even more energy to heat it up.
ACHEs are ideal for chemical applications, petrochemical cooling, steam cooling, in textiles processing, grain drying, concrete curing, paper manufacture and food processing. As air is the most used process fluid in the world, the application range for ACHEs is extremely varied.
Shell And Tube Heat Exchanger
Suitable for: fluid to fluid / fluid to gas
Shell and tube heat exchangers work by passing a hot or cold fluid or gas through a series of tubes (known as a tube bundle) enclosed in a large metal shell. The counter flowing hot or cold fluid or gas is pumped into the shell – where the heat transfer occurs.
Typically these designs are used for high pressure applications, but conversely also where a vacuum condition may require a structure that can cope with high stresses.
The containment aspect of a shell and tube is such that it may be more suitable for hot gasses than a finned tube bank, particularly where the gases maybe noxious or dangerous to health, or mandated to be kept away from release into the atmosphere. Common applications of the shell and tube heat exchanger are within oil, gas and chemical industries.
Plate Heat Exchanger Or Gasket Plate Heat Exchanger
Suitable for: fluid to fluid / fluid to vapour
Plate heat exchangers or gasket plate heat exchangers work by passing fluids through a series of plates that are compacted together side-by-side.
Plate heat exchangers are most often found in liquid to liquid applications, such as hot process water that contains chemicals/contaminants heating up cold mains water to provide clean hot water.
District heating systems can benefit from plate heat exchangers or gasket plate heat exchangers, allowing individual houses to use the correct amount of hot water from a centralised source. Plate heat exchangers can also be used to cool oils using water, where the two liquids can’t mix.