TABLE 2. Summary of test conditions and performance of the louver-baffle To assist readers interested in making use of the coherent system of SI units, the exact conversion factors to be used with the above table are: (%) EFFECTIVENESS 100 200 300 400 500 600 FIGURE 12. Effectiveness of the louver-baffle mixing device for selected temperature patterns. at various downstream locations after the air accom TEMPERATURE DIFFERENCE BETWEEN PORTIONS OF THE AIR STREAM BEFORE MIXING FIGURE 13. Effect of air temperature difference at mixer inlet upon the (%) EFFECTIVENESS The overall distance of 2.5 duct diameters from the inlet of the mixing device to the downstream measuring station was held constant. FIGURE 14. Effectiveness of the louver-baffle mixing device relative to the spacing between mixing elements. The distance between the mixing elements was held constant at 0.92 duct diameter. FIGURE 15. Effectiveness of the louver-baffle mixing device as the overall distance from the inlet of the mixing device to the downstream measuring station was varied. FIGURE 16. Relation of mixer inlet velocity to effectiveness for the louver-baffle mixing device. STATIC PRESSURE DROP (INCH W.G.) EFFECTIVENESS (%) FIGURE 17. Relation of the louver angle to effectiveness for the louver-baffle mixing device. FIGURE 18. Pressure drop for the louver-baffle mixing device at selected louver settings. The louver-baffle mixer was found to be slightly more sensitive to variation of flow rate than the louvered strip mixer. Over the velocity range from 100 to 450 fpm, as shown in figure 16, the effectiveness increased approximately 3 percent as the mean stream velocity was increased over this range. Along with placement of elements, temperature patterns, etc., tests to determine how the effectiveness would change were made by varying the angular deflection of the air as it passed through the mixer. Tests were made at various louver angle positions from 0°, or along the axis of the duct, to 65° from the axis. As shown in figure 17, the observed effectiveness was maximum at a setting of 60°. Beyond 60° the pressure drop became prohibitively high without an increase in effectiveness. Figure 18 shows a plot of the pressure drop across the mixing device as the louver angle was changed while the flow rate remained constant. 4.3. Concentric Louver For the concentric louver mixing device, the angular setting of the louvers in the outermost area was selected to be 60° from the normal path of flow. At the 60° louver angle setting, the pressure drop was determined for a given rate of air flowing through the outer area. Then with the same flow rate,the angular set ting of the louvers in the two inner areas was adjusted to give a matching pressure drop for the two inner areas and the outer area. The resulting angular setting for the two inner areas was 49° from the normal path of flow. All test were conducted at these louver angle settings. A summary of test conditions and performance of the concentric louver mixer is given in table 3. TABLE 3. Summary of test conditions and performance of the concentric louver mixer. To assist readers interested in making use of the coherent system of SI units, the exact conversion factors to be used with the above table are: |