Convection from a cold window with simulated floor heating by means of a transiently heated flat unit

Windows play an important role in the energy performance of buildings. Measurements of the natural convection flow along a cold window surface have been carried our, in a climate chamber. A transient heating procedure was used, which was achieved by a heated flat unit placed horizontally below the window (similar to floor heating). The air temperature in the space outside the window was set to −12°C. The local Grashof number, Grx, ranged from 9.5 × 107 to 3.0 × 109. During heating, Grx was nearly unchanged at each measurement station along the window surface. The heating; procedure was found to have a negligible impact on the local heat transfer and on the distributions of velocity and dimensionless temperature in the near-window region. The local heat transfer data along the window surface are found to be correlated with Nux=0.0077 Grx0.46. The mean convective heat transfer is discussed, and compared with previous results for the natural convection along a vertical plane or in an enclosure with different end temperatures. The velocity and temperature data show good agreement with power profiles, by modifying the characteristic scales that have been generally used for the natural convection boundary layer flow along a vertical flat plate. The results of the correlation and modification are presented.