Formaldehyde transfer in residential energy recovery ventilators

Abstract

like to thank Doug Sullivan for his role in setting up experiments, calibrating instruments and balancing the system, as well as Sebastian Cohn and Marion Russell for sample preparation and analysis. AbstractThe rotary enthalpy wheel design used in many energy recovery ventilators (ERVs) is designed to transfer heat and moisture between supply and exhaust air streams. The wheel, however, can also transfer formaldehyde and other indoor contaminants from the exhaust stream to the supply stream through air leakage, entrainment in the porous wheel, and adsorption/desorption to the filter medium. This contaminant transfer reduces the benefit of the mechanical ventilation provided by the device. Field and chamber experiments were used to quantify the formaldehyde transfer efficacy (the fraction of formaldehyde transferred from the exhaust stream to the supply stream) in a common ERV model under varied conditions. In field experiments, the transfer efficacy was approximately 29%. Chamber tests showed formaldehyde transfer efficacy between 10 and 29%. The bulk of the transfer was due to air leakage and entrainment within the wheel, with up to 30% of the transfer attributed adsorption/desorption from the filter medium. The transfer efficacy decreased with increasing air exchange rate and supply air temperature. The transfer efficacy increased as the supply and exhaust streams were unbalanced in flow rate. Overall, the air leakage through the device substantially exceeded the product rating of 10%, with 27-28% air leakage measured in field experiments and 12-19% air leakage in chamber experiments.

Formaldehyde and acetaldehyde exposure mitigation in US residences: in‐home measurements of ventilation control and source control

“…One factor not included when calculating kL and C eq is the re-entrainment of contaminant-loaded exhaust air within mechanical ventilation systems. For the ERV used in H5, up to 30% of formaldehyde in the exhaust stream can re-enter the conditioned space through air leakage and adsorption/desorption from the rotary wheel (Hult et al, 2014), lowering the effective ventilation rate through the ERV. If this process were included in Equation (1), the fitted value of kL would be lower proportionally to the reduction in the effective A.…”

Contaminant transport in membrane based energy recovery ventilators

“…However, an earlier study reported between 1% and 9% crossover for formaldehyde in five different "rotary enthalpy exchangers" (Andersson et al 1993). More recently, a study of an enthalpy wheel installed in a test house was reported to have formaldehyde crossover of up to 29%; the same wheel had 19% formaldehyde transfer in chamber experiments, and a large portion of this transport was associated with air leakage and entrainment as opposed to media adsorption (Hult et al 2014). Other studies have demonstrated crossover (EATR) in wheel-type ERV systems up to 33% when a differential pressure was applied across the wheel with higher pressure on the contaminant side; however, when the pressure was low or in the opposing direction, EATR was in the range of 1% (Shang et al 2001).…”

Investigation on the performance of a heat recovery ventilator in different climate regions in China

“…Similarly, the accumulative sensible heat recovery capacity ̇ of the integrated system can be calculated by, ̇= ∑ ℎ, =0 (8) where H also stands for the running hours of the HRV/integrated system.…”

“…Although the heat recovery efficiency of the ERV is higher than that of the HRV, the maintenance fee and the initial cost of the ERV are higher than that of the HRV [2,5] . Moreover, in an ERV the contaminants would be transferred from exhaust to supply air [6][7][8] . The problem of balancing energy conservation and cost is more complicated owning to different climates, indoor design conditions and heat exchange efficiency of the HRV or ERV, etc.…”