Consider window blinds that are installed in the air space between the two panes of a vertical double-pane window. The window is H = 0.5 m high and w = 0.5 m wide, and includes N = 19 individual blinds that are each L = 25 mm wide. When the blinds are open, 20 smaller, square enclosures are formed along the height of the window. In the closed position, the blinds form a nearly continuous sheet with two t = 12.5 mm open gaps at the top and bottom of the enclosure. Determine the convection heat transfer rate between the inner pane, which is held at Ts,i = 20°C, and the outer pane, which is at Ts,o = - 20°C, when the blinds are in the open and closed positions, respectively. Explain why the closed blinds have little effect on the convection heat transfer rate across the cavity.

Transcribed Image Text:

1 = 12.5 mm L = 25 mm - Ts0 H = 0.5 m Txi Baffle Baffle Closed Open 1 = 12.5 mm