An experimental investigation of air flow and convective heat transfer in enclosures having large ventilative flow rates

The prediction of convective heat transfer in enclosures under high ventilative flow rates is primarily of interest for building design and simulation purposes. Current models are based on experiments performed forty years ago with flat plates under natural convection conditions.

In order to investigate convective heat transfer in buildings, a full-scale experimental facility was developed with several unique features: fifty-three individually controllable heated panels which allow the room surfaces to be near isothermal, thus minimizing radiation; capability of using two different inlets; a ventilation system capable of providing temperature-controlled air at flow rates between two and one hundred air changes per hour; an air speed and temperature measurement system; and a flow visualization system.

A large number of experiments were performed with varying inlet locations and sizes, inlet temperatures, and flow rates. The room outlet temperature was identified as the most suitable reference temperature for the calculation of film coefficients. Film coefficients were successfully correlated to the jet momentum number, J. The correlations form the basis for a new convective heat transfer model that was implemented into the Building Loads Analysis and System Thermodynamics program. The new model was exercised and shown to yield much more accurate results than the current, natural convection based model.

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