The manufacturer's product data sheets often contain the information for the heat recovery rate and the heat supply rate, although the latter is always slightly higher.
The efficiency of a ventilation system is called the heat supply efficiency and is defined in the DIN V 4701-10 and DIN V 18599-6 standards. It describes the ratio of the enthalpy supplied to the supply air in relation to the enthalpy difference between the exhaust air and the outside air. The temperature transfer ("sensible heat") and the energy content of the humidity ("latent heat") are taken into account, but also the waste heat of the device, which results from the operation of the fans, for example, and thus increases heat transfer.
Degree of moisture recovery: Regenerators are able to transfer not only the sensible heat (i.e. the heat that can be read on the thermometer), but also the latent heat that is stored in the moisture content of the air. Therefore, caution is advised when comparing the heat recovery rates with recuperative devices, because they are based on different measurement methods. Most regenerative devices use the condensation of the air during the transition from hot to cold air within the heat exchanger to recover moisture. In this process, the moisture is deposited on the plates of the heat exchanger and is transported back into the rooms by the incoming outside air. In order to achieve an even higher degree of moisture recovery, some heat exchangers are also provided with a hygroscopic coating, which significantly increases moisture recovery even further. Other systems use vapour-permeable membranes that transfer moisture to the incoming outside air (enthalpy heat exchangers). With all variants, special attention must be paid to hygiene due to the transitions between the systems, which can mean, for example, increased cleaning effort due to shorter maintenance intervals.
Source: bauwion
