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pradeepdhoni
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Join Date: Jul 2011
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Calculation for Total Air Flow in Boiler

07/13/2012 9:12 AM

I am newly working in Thermal power plant. I have come across a logic for calculation of total air flow, for this they have taken flow(measured using DP),Pressure & temperature of the air. Please explain me why they are using this. And in the calculations they further using some constants which i cann't understand. These constants are different at other total flow calculations.
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lyn
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#1

Re: Calculation for Total air flow in Boiler

07/13/2012 9:16 AM

Can you give an example calculation, showing all the steps you take and explaining each in detail?
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pradeepdhoni
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#2

Re: Calculation for Total air flow in Boiler

07/13/2012 9:49 AM

These are calculations,

1.Sqrt (Air box inlet flow)*5743*1.23 = A

2.(air box inlet temperature)+273.15 = B

3.(air box inlet pressure)+101.32 = C

4.602.15/B = D

5.C/103.63 = E

6.(Sqrt(D*E))*(A/1000) = (Total air flow in boiler through FD fan).

Please explain the constants & calculations.
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tonykuphaldt
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Location: Bellingham, WA
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#3
In reply to #2

Re: Calculation for Total air flow in Boiler

07/14/2012 12:02 AM

The constants in lines 2 and 3 should be familiar from your studies in basic physics: they are converting measured values of temperature and pressure into absolute units. 273.15 is the offset value between degrees C and Kelvin; 101.32 is the offset between kPa gauge and kPa absolute.

Incorporating these absolute pressure and absolute temperature variables into the flow equation compensates for density changes in the air, which is necessary for accurate DP-based flow measurement. The Ideal Gas Law is the basis for this compensation, relating the volume of a gas to its absolute pressure and absolute temperature.

Those constants which differ between installations at your facility are accounting for factors such as the geometry of the differential producer (e.g. pitot tube, venturi).

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