| Air cooled heat exchangers are used to transfer heat from a process fluid to ambient air. The process fluid is contained within heat conducting tubes. Atmospheric air, which serves as the coolant, is caused to flow perpendicularly across the tubes in order to remove heat. In a typical air-cooled heat exchanger, the ambient air is either forced or induced by a fan or fans to flow vertically across a horizontal section of tubes. For condensing applications, the bundle may be sloped or vertical. Similarly, for relatively small air-cooled heat exchanger, the air flow may be horizontal across vertical tube bundles. In order to improve the heat transfer characteristic of air-cooled exchanger, the tubes are provided with external fins. These fins can result in a substantial increase in heat transfer surface. Parameters such as bundle length, width and number of tubes rows vary with the particular application as well as the particular finned tube design. Atmospheric air (having temperature varying from 20 to 450C, depending on season) can be used as cooling medium if the process fluid is to be cooled up to 600C. If it is to be cooled below 600C, then atmospheric air cannot be used as a cooling medium, as minimum driving force required for heat transfer in air cooled heat exchanger is 100C. |
