3 replies to this topic

[ME OF COURSE]

I'm currently having troubles making a link between chimical properties of the gas (whish give me Cp and Cv at a defined temperature and pressure) and the common value we use in the industry as 1000BTU/ft3 dry.
I'm suspecting temp. to be a factor in some troubles we have and i wanted to make a chart of the gas volumetric heating value from known pressure and temp.
If you have any usefull reference, i'm open to learn on that.

[Zauberberg]

Heating value is a function of gas composition only.

What may bother you, is different flow of fuel gas at different pressure and temperature - so the actual energy flow (Btu/hr) will change as well. If there's a P-T compensation for the flow measurement, there should be no concerns.

http://www.documenta...ation Solutions

[chemtan]

speaking about heating value, it does not depend upon temperature of gas. However, wobbe number defines how much heat does a gas generate on burning.

For calculating the heating value of gas you need to do below steps:
1. Find molar\volumetric composition of gas.
2. calculate heating value of each component.
3. Multiply the component's heating value by its %age in composition.
4. Add the resultant heating values.

Alternate,
put the composition in a material stream of any simulation software (HYSYS, AspenPlus, PRO/II, UniSim) and see the properties, it will show you the heating value.

Edited by chemtan, 16 December 2009 - 12:30 AM.

[S.AHMAD]

I'm currently having troubles making a link between chimical properties of the gas (whish give me Cp and Cv at a defined temperature and pressure) and the common value we use in the industry as 1000BTU/ft3 dry.
I'm suspecting temp. to be a factor in some troubles we have and i wanted to make a chart of the gas volumetric heating value from known pressure and temp.
If you have any usefull reference, i'm open to learn on that.

Dear friend

You have not described your problem fully so we are not able to help without having full information.

Published heating value normally referred to a base temperature of 25C (derived from the enthalpy of formation). The heating value does change with temperature and you can calculate it by enthalpy balance between product of combustion and reactants at the temperature of interest with reference to the base temperature. You can refer to any Chemical Reaction textbook. However, the difference is not significant and that is why almost all practicing engineers just ignore the effect of temperature on heating value. Unless the temperature is far above the base temperature of 25C.

You can get a more precise answer if you provide us more information/data.

Edited by S.AHMAD, 11 December 2009 - 04:15 AM.