ABSTRACT
Heat exchangers are devices that facilitate exchange of heat between two fluids that are at different temperatures, without making them mix with each other. Heat exchangers are widely used in numerous devices, such as automobile radiators, inter-coolers of high-pressure compressors, air-conditioning systems, large power plants, and so on. In a mixing chamber the fluids involved are allowed to mix, whereas in heat exchangers the fluids involved are not allowed to mix. For example, in a typical heat exchanger such as a car radiator, heat is transferred from the hot water flowing through the radiator tubes to the air flowing through the closely spaced thin plates attached to the tubes. Heat transfer in a heat exchanger usually involves convection in each fluid and conduction through the wall separating the two fluids. The temperature range, the phases of the fluids (liquid or gas), the quantity of thermal energy to be transferred, and the permissible pressure drops for the hot and cold fluids determine the heat exchanger configuration for a given application. In practice, the design and selection of heat exchangers often involve a trial-and-error procedure.
