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HVAC
The main aspects to consider when choosing a heat recovery unit for paint booths are described below.
Efficiency The efficiency of a heat recovery unit represents the heat that it is actually capable of exchanging between two fluids, compared to the theoretical maximum. This depends on several factors, such as the type of fluids involved, the heat exchange or transfer area, the layout and design of the device. The highestefficiency heat exchangers feature a high density of fins and small spaces for the air to flow through, giving a larger heat exchange surface for the two air streams. Generally, heat recovery units have an efficiency that can range from 40 % to 90 %. In painting processes, which use air streams with a high particle content, maximum efficiency must be weighed against the risk of fouling due to paint sticking to the fins. If the heat recovery units have a very narrow fin pitch, there is a risk of the channels being clogged by paint deposits. In the painting sector, therefore, it is difficult to achieve high heat exchange efficiency. Regulation 1253 / 2014 of the European Commission, based on the“ Ecodesign” directive 2009 / 125 / EC of the European Parliament, defines the installation of heat recovery systems in NRVUs( Non-Residential Ventilation Units) as mandatory, specifying 73 % as the heat recovery efficiency target. The exceptions are ventilation units“ exclusively specified as operating in a potentially explosive atmosphere as defined in Directive 94 / 9 / EC of the European Parliament” and those“ exclusively specified as operating [...] in toxic, highly corrosive or flammable environments or in environments with abrasive substances”. In most cases, however, the paint booths that come under these classifications do not reach the target of 73 % efficiency, and aim for slightly lower values( 60-68 %) in order to find an optimal balance between heat recovery efficiency and the need for periodic cleaning.
Pressure drop“ Pressure drop” refers to the fall in pressure that occurs due to the resistance provided by the heat
Plate heat exchanger made up of two side-by-side modules, equipped with control dampers, and separated by a central bypass section with damper.
Paint booth with 100 % outside air.
exchanger to the flow of air. This pressure drop depends on the speed of the air that flows through the heat exchanger, i. e. on the air flow-rate and dimensions, or more precisely the cross-section available for the air to travel through the fins( a function of the fin pitch) and on the length travelled by the air inside the heat exchanger. It follows logically that while heat efficiency increases with the fin pitch( higher heat exchange surface), the pressure drop also increases. Average pressure drop values for paint booths range from 150 to 250 Pa, and allow for the right balance between heat exchanger efficiency and more work required of the fans. Excessive pressure drop slows down the air flow, requiring the use of more powerful ventilation systems to circulate the air, thus increasing operating costs. Pressure drop is therefore a key aspect to consider when choosing a heat exchanger.
Silicone-free The presence of silicone inside paint booths can compromise the quality of the process. In fact, silicone particles adhere to the surface being painted, forming small craters on the surface, commonly known as fish-eye. To ensure high-quality results, it is therefore essential that the heat exchangers installed inside paint booths do not contain silicone materials or residues, for example resulting from raw material processing processes or the use of silicone sealants( used for high temperatures). Similarly, non-silicone components must also be used in the heat recovery unit bypass and control dampers.
Modular solutions In large paint booths, it is often more cost-effective to adopt heat recovery systems made up of multiple units. In fact, heat recovery units, especially plate heat exchangers, can be quite large and bulky, given the large heat transfer surfaces required. Installing multiple independent smaller heat recovery units www. heat-exchanger-world. com Heat Exchanger World October 2026
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