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States that a roof ventilator is often used to increase the draught of a chimney or a ventilator pipe. Establishes a method for testing and rating ventilator draught. Finds that air pressure near the ventilator inlet must be measured as a function of both the external wind speed and the flow rate of air through the ventilator. Gives data for three ventilator types and for an open pipe. States that results show that ventilator draught is increased by separation of the wind stream as it flows over the ventilator and decreased by the pressure losses as air exits the ventilator. Draught can be found by matching a ventilator performance curve to a system curve for a given building. Dimensionless analysis suggests that ventilators can be rated using two dimensionless groups – a pressure coefficient and a loss coefficient.
KEYWORDS: Testing, rating, air flow, calculating, chimneys, cowls.
Citation: ASHRAE Transactions, vol. 96, pt. 2, St. Louis 1990
Product Details
- Published:
- 1990
- Number of Pages:
- 5
- File Size:
- 1 file , 580 KB
- Product Code(s):
- D-18670
