The Science Of Heat Exchangers
Heat exchangers are single-purpose devices designed for optimal transfer of heat between mediums. In processes that generate large amounts of heat and/or must contend with high environmental heat, efficient heat removal is necessary for optimal productivity. In theory, optimal heat exchange is a relatively simple matter. In the real world, achieving it is often complex due to the many variables involved. Computer programs used to design an optimal heat exchanger for a given scenario have made this process significantly easier.
How a Heat Exchanger Works
Heat is energy. In a medium that is hot, the atoms within it are moving at a fast pace. In a medium that is cold, the atoms are moving within it very slowly. The term absolute zero refers to the state where the atoms within a medium have stopped moving completely. The fundamental principle of a heat exchanger is that energy seeks equilibrium. When two mediums are in contact, those mediums will exchange energy until they are both at the same temperature. Heat exchange is a natural process, and heat exchangers occur in nature. The goal of a mechanical heat exchanger is to optimize the process so that the maximum amount of heat moves as quickly as possible.
Different Types of Heat Exchangers
Exchangers are available for commercial, industrial and personal use in a wide range of configurations. The most basic heat exchanger uses two canisters of water. The water can be cooled by an additional mechanism or simply drained and replaced. The most common exchangers are somewhat more complex. Common examples include direct contact, shell and tube, plate, plate and shell, plate fin, pillow plate, fluid based, waste heat recovery, dynamic scraped surface, phase-change and spiral. Each format has its own pros and cons, and the heat exchange rate is often not the only consideration. For instance, a plate fin configuration is often used when the exchanger must withstand high pressure.
Common Applications for a Heat Exchanger
Espresso machines use a fluid heat exchanger in order to extract the espresso, which requires cooling super-heated water. Many aircraft and motor engines employ a plate fin heat exchanger because it has a large exchange surface area and is able to withstand high pressure. A waste heat recovery unit is often used by refineries to capture the exhaust gas from the manufacturing process. Spiral heaters are used for pasteurization and heat recovery, and a direct contact exchanger is used in air conditioners, humidifiers and water heaters.
Modern heat exchangers plays an important, but often undervalued, role in our modern lives. Exchangers improve many processes in our daily lives by making them more energy efficient and thus more affordable.