Natural ventilation for passive cooling: measurement of discharge coefficients

摘要: Abstract For the design of natural ventilation systems for passive cooling in buildings, engineers and architects are interested prediction rates as a function position size openings. In common use, there both simple detailed (i.e., multizone) models which rely basically on same Bernoulli algorithm to describe airflow through large An important source uncertainty is related attribution discharge coefficients. The present study was undertaken improve our knowledge velocity coefficients when measured real buildings. experiments were performed naturally ventilated three-level office building where staircase acted exhaust chimney. order keep flow pattern stable, condition air measurements be reproducible, windless nights only driven by stack pressure. Air patterns traced with smoke tracer gas. first set experiments, velocities, contraction neutral pressure level (NPL) have been measured, second resulting effective area combination two openings series. derived from open doorways found agreement obtained constant injection gas technique, an ± 20%. coefficient φ = 0.7±0.1 jet ɛ 0.85±0.1 shown generally accepted value Cd 0.6±0.1, giving new justification its use models. Basic configurations ventilative given illustrate how qualitative modeling used can give valuable information designer.