Heat recovery in air handling unit systems
Air handling unit systems – AHU systems for short – filter, heat, cool, humidify or dehumidify room air from recreation and work areas with the aid of fans. To ensure comfort, extract air is generally extracted and replaced with fresh air. A heat recovery unit is used to transfer heat or even cold from the extract air to the fresh air (tip 1: heat recovery).
Key requirements
In most countries, there are prescribed minimum values for heat recovery efficiency (European Union; EU Regulation 1253/2014/EC). These values must be observed. Similar considerations apply to the potential leakage of extract air into the fresh air. This must be avoided or minimised (tip 4: leakage). As the system runs all year round, very low outdoor temperatures also have to be tolerated. Condensate is therefore to be expected in the extract air.
(Tip 5: condensation in the extract air, tip 6: frozen condensate).
(Tip 5: condensation in the extract air, tip 6: frozen condensate).
Special Features
Humidity can also be transferred with the rotary heat exchangers, thereby increasing comfort and saving costs for air-conditioning systems (tip 7: humidity transfer). In the case of sorption rotary heat exchangers, a suitable coating must be applied to ensure that no odours are transmitted. The heat recovery efficiency should be controllable due to the internal heat loads that are usually present.
Cost-effectiveness
Heat recovery in AHU systems is standard practice today (as of 11/2024) and is a legal requirement in most countries (European Union; EU Regulation 1253/2014/EC). An economic efficiency calculation is therefore only worthwhile for systems that have a higher output than required.
Solutions from Hoval
Hoval supplies plate heat exchangers (crossflow and counterflow) and rotary heat exchangers (condensation, enthalpy and sorption rotary heat exchangers) for this application. As a pioneer in heat recovery, Hoval has decades of application experience and the consultancy expertise required. What’s more, its involvement in international expert panels means it is always up to date with the latest developments.
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