Radiators are heat exchangers in which a primary fluid, usually a gas, circulates, while a secondary fluid, used for heating or cooling, also circulates. As the gas flows over a bundle of finned or smooth tubes, heat exchange occurs with the fluid inside the tube, thus recovering heat from the combustion gases or cooling the process gas. The heat exchange surface area is maximized by fins mechanically attached to the tube, ensuring high efficiency in a compact format.

Radiators are primarily used in energy recovery systems to utilize combustion and process gases. They also have numerous other applications, including in drying ovens, chemical and food processing, exhaust cooling for compressors and engines, heating/cooling of fresh air in heating, ventilation, and air conditioning (HVAC) systems, and in the marine sector. A properly sized coil reduces fuel consumption and operating costs, increases efficiency by minimizing heat loss through the stack, and improves process temperature control.

The choice of radiator depends on the temperature and cleanliness of the gas, as well as the permissible pressure drop. Steam radiators provide rapid heating of rooms and ambient air; hot water and superheated water radiators offer safe solutions compatible with central hydronic systems; oil-filled radiators are preferred when stable heat transfer is required at high temperatures; for seawater radiators, the material is chosen for its corrosion resistance. If the gas is clean and the temperature difference is small, finned coils are compact and efficient; in pipes with high concentrations of dust and soot, finless or widely spaced finned models, which are easy to clean, are advantageous; finally, in pipes where pressure drop is critical, oval tube solutions are preferable.

Materials used for the tubes include carbon steel, stainless steel, copper, and special alloys such as Bafon and brass. Materials used for the fins include aluminum, copper, stainless steel, or carbon steel; their combination is determined by the process chemistry, temperature, pressure, and expected service life. The collectors can be designed with U-shaped, flat, or domed caps, while floating solutions facilitate thermal expansion management. The coils are manufactured using spiral fin, lamination, oval tube, or rolled tube methods; tube-to-fin contact and welding procedures are performed in accordance with TEMA practices. MIT designs are mechanically and thermally calculated according to Directive 2014/68/EU PED and EN 13445, as well as TEMA principles. Material and welding certificates and test reports are provided for projects deemed necessary.

To ensure optimal selection, the following information should be provided: gas inlet flow rate and temperature, target outlet temperature, gas composition and expected fouling level, permissible pressure drop on the gas side, type, flow rate, and inlet and outlet temperatures of the secondary fluid, operating time and load profile, configuration and accessibility for maintenance, required standards, and preferred materials. This information allows for optimization of the sensor area, fin spacing, number of rows, circuit, and type; capacity can be increased incrementally through a modular design, if necessary.

Regular cleaning ensures efficiency and prevents pressure losses. Pipes heavily fouled with soot and dust should be equipped with access hatches, soot cleaners, or a flushing system. If condensation is likely, condensate drainage and material selection are essential for corrosion protection. Appropriate external insulation reduces heat loss. During installation, it is best to opt for ventilation that prevents hot air recirculation, robust supports to absorb vibrations, and expansion-tolerant fittings. During operation, outlet temperature, pressure losses, and vibrations should be monitored, and any performance degradation should be addressed through preventative maintenance.