Experimental simulation of wind driven cross-ventilation in a naturally ventilated building

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 29).A device was designed and constructed to simulate cross-ventilation through a building due to natural wind. The wind driver device was designed for use with a one tenth scale model of an open floor plan office building in Luton, England. The air flow patterns produced by the wind driver were observed, and the uniformity of the velocity of the flows into the model windows was measured for the three settings of the wind driver fans. The temperatures and velocities of flows on the interior of the building and at the exhaust windows were also examined. The wind driver device was capable of producing uniform velocities across the face of the model to within 20 to 27%, depending on the fan setting. The consistency of certain features of the velocity distributions produced by the wind driver operating at different speeds suggest that improvements made to the design of the wind driver could lower this variation to about 15%. The velocities measured on the interior of the model seem consistent with interior velocities in the Luton building, although further experimentation is needed to confirm this trend. Cross-ventilation was effective in reducing interior model temperatures by up to 10⁰C from the natural convection case.by Erin L. Hult.S.B

Blower-door techniques for measuring interzonal leakage

AbstractThe standard blower door test methods, such as ASTM E779, describe how to use a single blower door to determine the total leakage of a single-zone structure such as a detached single-family home. There are no standard test methods for measuring interzonal leakage in a two-zone or multi-zone building envelope such as might be encountered in with an attached garage or in a multifamily building. Some practitioners have been using techniques that involve making multiple measurements with a single blower door as well as combined measurements using multiple blower doors. Even for just two zones there are dozens of combinations of one-door and two-door test protocols that could conceivably be used to determine the interzonal air tightness. We examined many of these two-zone configurations using both simulation and measured data to estimate the accuracy and precision of each technique for realistic measurement scenarios. We also considered the impact of taking measurements at a single pressure versus over multiple pressures. We compared the various techniques and evaluated them for specific uses. Some techniques work better in one leakage regime; some are more sensitive to wind and other noise; some are more suited to determining only a subset of the leakage values. This paper makes recommendations on which techniques to use or not use for various cases and provides data that could be used to develop future test methods