Fin and tube heat exchangers are used widely in residential, commercial and industrial HVAC applications. Invariably, indoor and out of doors air contaminants foul these heat exchangers. This fouling can cause decreased capacity and efficiency of the HVAC equipment in addition to indoor air high quality issues related to microbiological development. This paper describes laboratory studies to analyze the mechanisms that trigger fouling. The laboratory experiments contain subjecting a 4.7 fins/cm (12 fins/inch) fin and tube heat exchanger to an air stream that incorporates monodisperse particles. Air velocities ranging from 1.5-5.2 m/s (295 ft/min-1024 ft/min) and particle sizes from 1–8.6 microm are used. The measured fraction of particles that deposit in addition to information about the location of the deposited material indicate that particles greater than about 1 microm contribute to fouling. These experimental results are used to validate a scaling analysis that describes the relative significance of several deposition mechanisms including impaction, Brownian diffusion, turbophoresis, thermophoresis, diffusiophoresis, and gravitational settling. The analysis is prolonged to use to different fin spacings and particle sizes typical of these present in indoor air.

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