AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Optimal Cleaning Strategies for HVAC Heat Exchangers
AMIN ENGARNEVIS, James Montgomery, Sheldon Green, Steven Rogak, University of British Columbia
Abstract Number: 696 Working Group: Indoor Aerosols
Abstract It is well known that the heat exchangers used in building heating, ventilating, and air conditioning (HVAC) systems become fouled by airborne particulate matter. These systems must be cleaned periodically to maintain good performance. However, the optimal cleaning time to save money, energy and maintain good indoor air quality is not known. A model has been developed to predict the energy use and annual operation cost of finned tube air-to-liquid heat exchangers commonly installed in HVAC air handling units. This model accounts for the changing properties of the coil and upstream filter throughout operation and provides a method of determining the optimum filter selection and coil cleaning time to minimize the annual cost of operating the unit. The optimal cleaning strategy has been shown to vary depending on system specifications such as the filtration efficiency, filter and coil bypass rates, coil geometry, and particle concentration. The sensitivity of the results to model parameters showed that the concentration of particles in the air stream, filter selection, and the electricity cost had the largest effect on annual cost of operation. Increasing the concentration of particles and the electricity cost, increase the cost of operating the system and make more frequent coil cleaning more economically attractive. Upstream filter selection can result in either a net savings or an additional operating cost, depending on the type and efficiency of the filter. Selection of high-efficiency filters compared to low-efficiency filters has likely a small effect on net system energy consumption, but increases the operating cost due to higher initial costs. These results imply the need for caution when considering high-efficiency filters to protect finned tube heat exchangers, and suggest that optimal finned-tube heat exchanger operation involves a compromise between an upstream filter that satisfies the indoor air quality requirements and a periodic coil cleaning program.