In this paper, we will present a numerical model for estimating the thermal performance of unglazed transpired solar collectors located on the Breck School campus in Minneapolis, Minnesota. The solar collectors are installed adjacent to the southeast facing wall of a field house. The collectors preheat the intake air before entering the primary heating unit. The solar collector consists of 8 separate panels (absorber plates). Four fans are connected to the plenum that is created by the absorber plates and the adjoining field house wall. All fresh air for the field house is provided by the solar collectors before being filtered and heated by four, independent two stage natural gas fired heaters. Moreover, the following data were collected onsite using a data acquisition system: indoor field house space temperature, ambient air temperature, wind speed, wind direction, the plenum exit air temperature, the absorber plate temperature, and the air temperatures inside the plenum. The energy balance equations for the collector, the adjacent building wall, and the plenum are formulated. The numerical model is used to predict the air temperature rise inside the plenum, recaptured heat loss from the adjoining building wall, energy savings, and the efficiency of the collectors. The results of the numerical model are then compared to the results obtained from the onsite measurements; which are in good agreement. The model presented in this paper is simple yet accurate enough for architects and engineers to use it with ease to predict the thermal performance of a collector.

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