Liquid air heaters (heaters and coolers)

Liquid or water heaters are used for both heating and cooling air (gases). The most common heating medium for heating is superheated water, less often thermal oil. As a coolant for cooling air (gases), glycol solutions are used. Water heaters are manufactured in rectangular shape and are designed for installation in rectangular air ducts. Hot water heaters, as a rule, have a multi-pass design and are installed horizontally. The coolant moves through the tubes at a high speed, which ensures a high heat transfer coefficient.

The basis of the design of a water heater is a copper "coil" through which a heating coolant or an antifreeze solution of glycol circulates if the heater is located outside the building. Aluminum plates are staggered between the legs of the "coil" (or bimetallic plate-finned copper-aluminum tubes are used). The circulating coolant transfers heat to the copper, which in turn heats the aluminum plates. The flow of supply air passing through the duct washes the copper circuit and aluminum plates, absorbing their heat, and is fed further into the room. Aluminum plates are needed to increase the heat exchange area with the passing air flow. To operate the air heater with higher temperature heat carriers, coils and tubes are made of stainless steel.