| Fouling of heat exchangers used in heating, ventilation, and air conditioning systems can cause increased energy use, decreased performance, and degraded indoor air quality. Particulate matter from both indoor and outdoor sources is a common fouling agent. This study simulates and measures particle deposition on HVAC heat exchangers and explores potential impacts including bioaerosol deposition and growth on heat exchanger surfaces, degradation of air conditioner efficiency and capacity in residences, and increased fan energy use in commercial HVAC systems.; The simulation of particle deposition on heat exchangers examines the role of Brownian diffusion to fin walls, inertial impaction on fin edges and refrigerant tubes, gravitational settling on fin corrugations, and air turbulence impaction in fin channels. When the heat exchanger is cooled, thermophoresis and the presence of condensed water cause additional deposition.; Particle size-resolved experiments on a 4.7 fin/cm test heat exchanger demonstrate reasonable agreement between the model and the measured data. When cooled and condensing, substantially more deposition occurs. Further fouling experiments with a test dust establish a relationship between mass deposited and pressure drop increase.; The experimental results demonstrate that common indoor bioaerosols will deposit on heat exchanger surfaces. The presence of moisture and nutrients can lead to fungal and bacterial amplification. A causal relationship between deposition and biological growth is undetermined, but the correlation between biological growth and sick building syndrome suggests that biological fouling merits further study.; Combining the experimental results with typical indoor particle and dust fiber concentrations indicates that a typical residential cooling coil will foul in about 4.2 years. This fouling, and consequent drop in flow, will lead to a 2–4% decrease in performance. In larger commercial systems, fouling can result in increased fan and building energy use. Preventing and mitigating fouling of HVAC heat exchangers will lead to increased building energy efficiency and improved indoor air quality. |
