ABSTRACT
Heat transfer represents one of the most important steps in industrial processing, encompassing many widely differing industries and disciplines. The subject in its broadest sense can be divided into two categories. The first is transfer of heat at temperatures well below 0°C, such as in air liquefaction plants. The second category involves transfer of heat at temperatures near atmospheric up to 1000° C and above. Heat transfer at low temperatures is normally termed refrigeration or cryogenic technology and the fluids involved in such cases are therefore called refrigerants. The subject of this text is the second category, involving temperatures above ambient and the term heat transfer fluids is generally reserved for heat transfer media in this high-temperature range. The most common fluids applicable in this range Include air, products of combustion (flue gases), and water; organic fluids comprise the next largest category; and in the final category, molten salts and molten metals serve a small but important sector of industry. The nature of the fluids involved, in particular combustion products and steam, and the urge to conserve energy, establish a strong link between simple indirect heat transfer and energy generation and conservation. This means that efficient heat transfer includes features of power generation and fuel conservation.
