ASHRAE Journal - April 2012 - 18

90 Degree Elbow Throw Corrections in Direction of Horizontal Duct Distance Between the Outlet and Elbow (Equivalent Diameters) 3 Table 43 1.5 Table 44 0 Table 45 Throw Corrections in Opposite Direction of Horizontal Duct Distance Between the Outlet and Elbow (Equivalent Diameters) 3 Table 46 1.5 Table 47 0 Table 48

Total Pressure Correction Factors for Rigid and Flex Elbows, With and Without a Damper tn the Full Open Position Distance Between the Outlet and Elbow (Equivalent Diameters) 3 Table 49 1.5 Table 50 0 Table 51

NC Additions 90 Degree Elbow Are Applied, Both Flex and Rigid and With and Without a Damper Distance Between the Outlet and Elbow (Equivalent Diameters) 3 Table 52 1.5 Table 53 0 Table 54

Close Coupling Throw Corrections in Direction of Horizontal Duct Vertical Duct Height (Equivalent Diameters) 3 Table 55 1.5 Table 56 Total Pressure Correction Factors Vertical Duct Height (Equivalent Diameters) 3 Table 61 1.5 Table 62 0.5 Table 63 3 Table 64 0.5 Table 57 3 Table 58 Throw Corrections in Opposite Direction of Horizontal Duct Vertical Duct Height (Equivalent Diameters) 1.5 Table 59 0.5 Table 60

NC Additions With and Without a Damper Vertical Duct Height (Equivalent Diameters) 1.5 Table 64 0.5 Table 64

Note: Table numbers are listed per the final report on RP-1335: Effects of typical inlet conditions on air outlet performance.

Table 1: Index of the tables and content within the final report of ASHRAE Research Project 1335 (RP-1335). If that device is installed with a damper and the damper is adjusted to a 50% restriction, the actual total pressure is above 0.90 in. w.g. (22 410 Pa). Figure 2 also shows if an occupant reduces the 3 Diameters velocity from 1,000 fpm (using manufacturer’s 1.5 Diameters data) to 500 fpm to obtain a desired comfort level 0 Diameters at a 50% restriction to the damper, the total pressure remains relatively constant. As with the previous example for NC, it can be Figure 3: Tables 43 through 54 apply to 90 degree elbows with the distance concluded that a damper located at the diffuser between the outlet and elbow equal to 3, 1.5 and 0 equivalent diameters. should not be used to make major reductions in flow to balance a system. The damper can be used to fine-tune 44, and 45 show that the discharge pattern from a diffuser with an a device to obtain a reduced flow to maximize the occupant’s elbow is not symmetrical and give the factor to be applied based comfort. Adding a damper to a diffuser adds an approximate on no damper, and with a damper listing the damper full open and 0.20 in. w.g. (4980 Pa) of total pressure if the damper is in the positioned relative to the airflow. The throw corrections are listed full open position. for throw in the direction of the horizontal supply duct. Tables 46, The results of the testing for the corrections factors to trans- 47, and 48 can be applied to the same as the previous but with the late from catalog data to actual installed performance for throw in the direction opposite the horizontal supply. throw, pressure and NC were summarized in a series of tables Tables 49, 50, and 51 provide the total pressure correction that are easy for designers to use. The tables allow a designer factors for rigid and flex elbows with and without a damper in to quickly and accurately convert the ideal performance ob- the full open position. tained from Standard 70-2006 to typical installed conditions Tables 52, 53, and 54 provide the NC additions obtained (Table 1). A review of the available tables is listed next. from a manufacturer’s catalog data when 90 degree elbows are applied, both flex and rigid, and with and without a damper. Descriptions of Tables Tables 55 through 64 are factors to be applied when the difTables 43 through 54 from the final RP-1335 report apply to fuser is installed using a close coupling configuration shown 90 degree elbows with the distance between the outlet and elbow in Photo 1. The tables are for inlet duct heights of 3, 1.5 and .5 equal to 0, 1.5 and 3 equivalent diameters (Figure 3). Tables 43, equivalent diameters.
18 ASHRAE Journal ashrae.org April 2012

ASHRAE Journal - April 2012

Table of Contents for the Digital Edition of ASHRAE Journal - April 2012