32 posts

### specific heat

Can anybody tell me what is the average spcific heat of flue gas flow 296229 Kg/Hr with temp and pressure is 0.08 Bar . Note the gas is flue gas coming after the cement plant. I need this value to calculate Heat duty by using mcp(t1-t2)

HARY

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138 posts

### Re: specific heat

guddu,

Below is a Visual Basic program that can compute what you need.

You can paste this code in Excel and use it then in a spreadsheet.

To do that, open a new Excel sheet, then try to go to Visual Basic using the ad-hoc toolbar.

Then create a new Visual Basic Module and paste this code in the module.

Then, go back to the Excel sheet.

You can test that it works fine by typing this test in a cell:

(you may need to replace "," by ";", depending on your computer settings)

=CpNm3_FlueGas(0.209, 0.791, 0, 0, 273, 373)

This should return the average heat value of air from 273K to 373K.

The value should be 1.293 kJ/Nm³/K.

As you can see below, the average heat value is obtained from a difference of enthalpies. When making an heat balance, you don't need specific heats, you need enthalpies. (actually I never use specific heats, except for heat transfer calculations)

You can find a lot of other data on the web.

I recommend specially the nist site.

It is more difficult to find data for clinker solids at high temperatures.

I have used the book by Ishan Barin for some data.

I also had some use of Mchedlov, but found many mistakes and inconsistencies.

There are also many papers for precision data on simple systems like (Al2O3,CaO).

The code below is based of the book by Ishan Barin.

Function HNm3_FlueGas(O2, N2, CO2, H2O, T) ' kJ/Nm³,

' analysis are volume fractions between 0 and 1, T in Kelvin

HNm3_FlueGas = (O2 * H_O2(T) + N2 * H_N2(T) + CO2 * H_CO2(T) + H2O * H_H2O_g(T)) / 22.414

End Function

Function CpNm3_FlueGas(O2, N2, CO2, H2O, T1, T2) ' kJ/Nm³/K

' analysis are volume fractions between 0 and 1, T in Kelvin

CpNm3_FlueGas = (HNm3_FlueGas(O2, N2, CO2, H2O, T2) - HNm3_FlueGas(O2, N2, CO2, H2O, T1)) / (T2 - T1)

End Function

Function H_O2(T)

Const A0 = 29.154

Const B0 = 6.477 / 2

Const C0 = -0.184

Const D0 = -1.017 / 3

Const H0 = -9.589

y = T / 1000

H_O2 = 1000 * (H0 + y * (A0 + y * (B0 + y * D0)) - C0 / y)

End Function

Function H_N2(T)

Const A0 = 30.418

Const B0 = 2.544 / 2

Const C0 = -0.238

Const D0 = 0 / 3

Const H0 = -9.982

y = T / 1000

H_N2 = 1000 * (H0 + y * (A0 + y * (B0 + y * D0)) - C0 / y)

End Function

Function H_CO2(T)

Const A0 = 51.128

Const B0 = 4.368 / 2

Const C0 = -1.469

Const D0 = 0 / 3

Const H0 = -413.886

y = T / 1000

H_CO2 = 1000 * (H0 + y * (A0 + y * (B0 + y * D0)) - C0 / y)

End Function

Function H_H2O_g(T)

Const A0 = 34.376

Const B0 = 7.841 / 2

Const C0 = -0.423

Const D0 = 0 / 3

Const H0 = -253.871

y = T / 1000

H_H2O_g = 1000 * (H0 + y * (A0 + y * (B0 + y * D0)) - C0 / y)

End Function

32 posts

### Re: specific heat

Dear Mr lalbatros

Shake hand.

Sir, concrete thanx for patronizing me with the above panecea.

I bgun to form the spread sheet as enlightened by you,but since i didnt prepare the same in my life, which pose me to proceed furthur. Poin is i will be grateful to you for forwarding the tailored spread sheet whcih you already have on my personal mial id

Well this could be the impeccable scenario to follow. As if i start with tailoring the same , there is more likely that i would not be on the platform which i want

Awaiting for your valuable reply

Thanks for your generosity

gudu