冷凝水管路尺寸計算

1、無The condensate pipe sizing chartThe condensate pipe sizing chart (Figure 14.3.5) can beused to size any type of condensate line, including:Drain lines containing no flash steam.Lines consisting of two-phase flow, such as trapdischarge lines, which are selected according to thepressures either side

2、of the trap.The chart (Figure 14.3.5):Works around acceptable flash steam velocities of 15- 20 m/s, according to the pipe size and the proportionof flash steam formed.Can be used with condensate temperatures lowerthan the steam saturation temperature, as will be thecase when using thermostatic steam

3、 traps.Is used to size trap discharge lines on full-loadconditions. It is not necessary to consider anyoversizing factors for start-up load or the removal ofnon-condensable gases.無May also be used to estimate sizes for pumped linescontaining condensate below 100C. This will bediscussed in Tutorial 1

4、4.4.Fig. 14.3.5 Condensate pipe sizing chart無Using the condensate pipe sizing chart (Also available inAppendix 14.3.2)Establish the point where the steam and condensate pressuresmeet (lower part of the chart, Figure 14.3.5). From this point, movevertically up to the upper chart to meet the required

5、condensaterate. If the discharge line is falling (non-flooded) and the selection ison or between lines, choose the lower line size. If the discharge lineis rising, and therefore likely to be flooded, choose the upper linesize.Note: The reasoning employed for the sizing of a steam trap isdifferent to

6、 that used for a discharge line, and it is perfectly normalfor a trap discharge line to be sized different to the trap it is serving.However, when the trap is correctly sized, the usual ancillaryequipment associated with a steam trap station, such as isolationvalves, strainer, trap testing chamber,

7、and check valve, can be thesame size as the trapping device selected, whatever the dischargeline size.A steam trap passing a full-load of 1000 kg/h at 6 bar g saturatedsteam pressure through a falling discharge line down to a flashvessel at 1.7 bar g.As the discharge line is non-flooded, the lower f

8、igure of 25 mm isselected from the chart (Figure 14.3.5).無Fig. 14.3.6 A non-flooded pressurised trap discharge line (referto Example 14.3.3)A steam trap passing a full-load of 1000 kg/h at 18 bar g saturatedsteam pressure through a discharge line rising 5 m up to apressurised condensate return line

9、at 3.5 bar g.Add the 0.5 bar static pressure (5 m head) to the 3.5 barcondensate pressure to give 4 bar g backpressure.As the discharge line is rising and thus flooded, the upper figure of32 mm is selected from the chart, (Figure 14.3.5).無Fig. 14.3.7 A flooded trap discharge line (refer to Example14

10、.3.4)A steam trap passing a full-load of 200 kg/h at 2 bar g saturatedsteam pressure through a sloping discharge line falling down to avented condensate receiver at atmospheric pressure (0 bar g).As the line is non-flooded, the lower figure of 20 mm is selectedfrom the chart, (Figure 14.3.5).無Fig. 1

11、4.3.8 A non-flooded vented trap discharge line (refer toExample 14.3.5)A pump-trap passing a full-load of 200 kg/h at 4 bar g saturatedsteam space pressure through a discharge line rising 5 m up to anon-flooded condensate return line at atmospheric pressure.The 5 m static pressure contributes the to

12、tal backpressure of 0.5bar g.As the trap discharge line is rising, the upper figure of 25 mm isselected from the chart, (Figure 14.3.5).無Fig. 14.3.9 A flooded trap discharge line (refer to Example14.3.6)Consider a condensate load of 200 kg/h to a receiver and pump.The pump discharge rate for this me

13、chanical type pump is taken assix times the filling rate, hence, the condensate rate taken for thisexample is 6 x 200 = 1 200 kg/h.Because the condensate will have lost its flash steam content toatmosphere via the receiver vent, the pump will only be pumpingliquid condensate. In this instance, it is only necessary to use thetop part of the chart in Figure 14.3.5. As the line from the pump isrising, the upper figure of 25 mm is chosen.Note: If the pumped line were longer than 100 m, the next largersize must be taken, which for