Pressure | 8631 Venturi
PERMANENT PRESSURE LOSS and UPSTREAM PRESSURE
T o determine Total permanent pressure loss when the Venturi is installed in line and with an upstream piping run:
Permanent Pressure Loss Example:
8631-24 designed for 600,100 scfh has a throat differential pres- sure of 2.3"w.c. The permanent pressure loss across the Venturi would be 2.3"w.c. x .123 = 0.28"w.c. The initial acceleration and entry loss would be 2.3”wc x 0.33 = .76"w.c. Total permanent pressure loss when the Venturi is installed in line with an upstream piping run = 0.28"w.c. Total permanent pressure loss when no inlet piping is used and when the “required” inlet bell (cap/filter) is installed = 0.76” + 0.28” = 1.04"w.c.
The estimated total permanent pressure loss when installed after the combustion air blower can be approximated as 12.3% of the throat DP. To determine Total permanent pressure loss whe the Venturi is installed in line with no inlet piping used and when the required inlet bell (cap/filter) is installed: The estimated total permanent pressure loss will be a sum of the permanent pressure drop across the venturi loss (as noted above) plus the combination of initial acceleration of the air and entry configuration loss. The estimated values will be 12.3% of the throat DP plus an acceleration and entry configuration loss of 33%: or approximately 45.3% of throat DP. This total permanent pressure loss value can then be used to determine the “negative” inlet pressure value for accurate flow calculations when inlet is open to atmospheric pressure.
Bulletin 8631 page 5
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