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Ted Krapkat
537 posts
TimePosted 02/01/2014 05:27:14
Ted Krapkat says

re converting heat value

Hello Nael,

I have seen exactly the same text on that website in another place and it showed 10^2 and not 102. So I assumed that the ^ symbol did not translate correctly in the font that was used.

If you use 10^2 instead of 102, the result is 9.41 kcal/ Nm3.

 

Regards,

Ted.

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Nael
72 posts
TimePosted 15/01/2014 10:20:41
Nael says

re converting heat value

Hello Ted,
I was confused with your wrong calculation and right answer (= 9.41) but now I have got it, it is “qbmconsultants.com” mistake.

Thanks for your clarification


Regards

Nael

 



 



 

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Nael
72 posts
TimePosted 15/01/2014 10:59:23
Nael says

re converting heat value

Hello Abdulla;

This converting factor is very important as there are a lot of cement plants using un accurate factor for converting their gas consumption from Nm3 to SCF by using the general converting factor:            [1.0 Nm3 = 35.315 SCF]  or [1.0 BTU/SCF = 8.9 kcal/Nm3] .. Actually this factor is accurate if both standard (Nm3 & SCF) has the same standard temperature and pressure but if standard cubic foot (SCF) corresponds to 1 cubic foot of gas at 15.6 °C (60 F) and 1.0 atm and  normal cubic meter (Nm3) of gas corresponds to 1 cubic meter at 0 °C and 1.0 atm , the above mentioned converting factor cannot be used before making both measured standard temperatures equivalent to each other as the following:                                           

Let us take 1.0 Nm3 as Basis:  

1). Converting the normal cubic meter value 1.0 Nm3 (at 0°C & 1 atm) to normal cubic meter (at 15.6°C & 1.0 atm) by using the following formula:

V (15.6°C) = V(0°C) x [P(0°C)/P(15.6 °C)] x [T(15.6°C)/ T(0°C)] 

As;

V(0°C)= 1.0 Nm3   

P(0°C)  = P(15.6 °C) = 1 atm

T(15.6°C) = 15.6 + 273.15 = 288.75 °K

T(0°C) = 0 +273.15 = 273.15 °K

Then;

V (15.6°C) = 1.0 Nm3 x [1/1] x [288.75/273.15] = 1.0571 Nm3

2). Only now; after converting our Nm3 value at 0°C standard temp to 15.6 °C standard temp which is equivalent to SCF standard temp (15.6°C), the above converting factor can be used to convert the value from Nm3 to SCF as showing below: 

1.0571 x 35.315 = 37.332 SCF

Which mean that your new factor changed to:

1.0 Nm3 = 37.332 SCF                    [at 15.6 C & 1.0 atm]

To convert from BTU/SCF to kcal/Nm3:

1.0 Btu/SCF =37.332 x 0.252  kcal/Nm3 = 9.41  kcal/Nm3

1.0 BTU/SCF= 9.41  kcal/Nm3

 

Regards

Nael

 

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