Heat ExchangersA heat exchanger, in

Heat ExchangersA heat exchanger, in a narrow sense, is a vessel in which an outgoing, processed hot liquid transfers some of its heat to an incoming cold liquid about to be processed. The amount of heat so transferred is not lost to the process, but is used over again, its equivalent need not be supplied by new fuel; it may be considered as cycle heat. The heat exchanger is the “valve” that prevents it from leaving. Hot gases and vapors similarly can pass part of their heat to the incoming cold liquid. As is known to all, heat transfer may also be conducted in the opposite direction in the heat exchanger, in which an outgoing cold gas takes up the heat of the incoming warmer gas, as in a liquid-air plant. In a side sense, a heat exchanger is a device which makes it possible to transfer heat from one fluid to another through a wall.Now let us consider the heat exchanger where an outgoing hot liquid transfers its heat to an incoming cold one. The typical example is the shell-and-tube heat exchanger, which is widely used because of its compactness. This type of heat exchanger consists of tubes. Another type is the concentric tube heat exchanger, there each inner tube with its outer tube forms a separate unite, and all these units are combined.There are still many other types of heat exchangers, whose constructions will be described later on.