Convective heat transfer in rooms with ceiling slot diffusers
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Convection at the interior surface of a building represents a significant portion of the heat transfer in office buildings with large glazing areas. While a large number of these office buildings utilize ceiling slot diffusers at the glazed building perimeter, convection correlations specific to these diffusers have not yet been investigated. This paper describes convection correlations developed for ceiling slot diffusers and examines the effect of temperature, various window geometries, and diffuser jet momentum on these correlations. The paper also examines the effect of venetian blinds on the overall correlations at various blind angle configurations: open, partially open, and closed. The results of the examined phenomena are validated in both heating and cooling conditions. All together, this paper represents the effort of over 100 individual experiments. The results show that forced convection is dominant at all air flow rates, and correlations are developed as a function of air volumetric flow rate with supply air temperature utilized as the reference. The correlations are found to rely only on window position, and are independent of temperature difference between surface and supply, diffuser position, and diffuser jet momentum. With respect to the blinds, the only relevant parameter is the angle of the blinds except when the blinds are open. When the blinds are open and at 45º, convective heat transfer is enhanced. Conversely, convection is decreased when the blinds are closed and at -45º. There is also a decrease in the convective heat transfer with a full window in contrast to a half window when the blinds are open. Finally, there is little difference between the convection correlations developed for heated and cooled environments.