Varmeveksleren

Varmeveksleren, or heat exchanger, is a device designed to transfer thermal energy between two or more fluids at different temperatures while keeping the fluids separate. Heat transfer occurs through a solid wall, typically a metal barrier, by conduction, while the fluids experience convection on their respective sides.

There are several common types of varmevekslere. Shell-and-tube heat exchangers consist of a bundle of tubes inside a shell and are suitable for high pressures and temperatures. Plate heat exchangers consist of corrugated plates forming many small channels, offering high heat transfer efficiency in a compact footprint. Finned-tube and air-cooled exchangers are used where cooling air is available, such as in automotive radiators or power plants. Brazed- or gasketed plate-and-frame variants are common in compact applications.

Design considerations include the overall heat transfer coefficient (U), heat transfer area (A), and the number of transfer units (NTU) to evaluate performance. The logarithmic mean temperature difference (LMTD) or effectiveness relations are used for design. Fluid properties, flow arrangement (counterflow or parallel flow), pressure drop, and fouling influence performance and maintenance needs. Materials are chosen for corrosion resistance, temperature, and pressure.

Applications span HVAC systems, power generation, chemical processing, refrigeration, and various industrial processes. Efficiency, reliability, and maintenance are important, with attention to leak prevention and cleaning to manage fouling. Emerging trends include compact plate-and-frame and brazed plate heat exchangers, microchannel designs, and advanced coatings.