. Power, heating and ventilation ... a treatise for designing and constructing engineers, architects and students . 92 40 39 46 44J 8 200 10 0 931 66J 76 66 102 44 43J 52S 50 10 ducted tests made by one of the leading manufacturers of fansupon their standard steel-plate blowers and exhausters. Whilethe results thus obtained apply particularly to fans of their ownmake, they may be used with a faiir degree of accuracy for anyfan of similar type and proportions. 198 HEATING AND VENTILATING PLANTS Pressure and Velocity. Before taking up the subject further, let us consider briefly thediflferent fo
. Power, heating and ventilation ... a treatise for designing and constructing engineers, architects and students . 92 40 39 46 44J 8 200 10 0 931 66J 76 66 102 44 43J 52S 50 10 ducted tests made by one of the leading manufacturers of fansupon their standard steel-plate blowers and exhausters. Whilethe results thus obtained apply particularly to fans of their ownmake, they may be used with a faiir degree of accuracy for anyfan of similar type and proportions. 198 HEATING AND VENTILATING PLANTS Pressure and Velocity. Before taking up the subject further, let us consider briefly thediflferent forms of pressure involved in the action of a can best be explained by the use of a practical illustration. Let Fig. 146 represent a blower with a short pipe attached tothe outlet. A and B are U-tubes, or water gauges, for indicatingthe pressure within the pipe. A has the lower end of the tubebent at right angles and turned toward the fan, while the tubeleading from B is straight. Dynamic Pressure.—If the fan be revolved with the end of thedischarge pipe wide open, the water in the two legs of tube A. Fig. 145. Laying Out a Fan to Scale. will stand at different levels, thus indicating a pressure withinthe pipe, while the water in tube B remains unchanged. The pres-sure indicated by A is called the dynamic pressure, and is causedby the air blowing into the end of the tube which is turnedtoward the fan; or in other words, it is the pressure due to themovement or momentum of the air. As the end of the dischargepipe is wide open, allowing the air to pass through freely, thereis no radial pressure created, and therefore none indicated by thetube B. Static Pressure.—Let Fig. 147 represent the same apparatus,but with the end of the air pipe partly closed. Tube A in thiscase shows a higher pressure than before, and there is also a FANS 199 pressure indicated by B. The latter pressure, which is similar tothat in a steam boiler, is called the static pressure. Velocity Pressur
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectventilation, bookyear
