Calculating Heat Given by a Flame

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Discussion Overview

The discussion revolves around calculating the heat produced by a flame resulting from the combustion of ethanol in a Stirling motor. Participants explore various methods for determining this heat to assess the motor's output, focusing on concepts related to enthalpy and combustion.

Discussion Character

  • Exploratory, Technical explanation, Homework-related

Main Points Raised

  • One participant seeks to calculate the heat from the combustion of ethanol for a Stirling motor and considers using the Free Enthalpy of Combustion.
  • Another participant suggests that the standard enthalpy of reaction might be more relevant than free energy and indicates that this data is readily available.
  • A different participant proposes that enthalpy can be a good approximation for heat in most cases and recommends posting the question in the engineering forum for more specialized advice.
  • The original poster expresses intent to gather more precise information about their motor's plans before proceeding further.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method to calculate the heat from combustion, and multiple approaches are suggested without resolution.

Contextual Notes

There are limitations regarding the assumptions made about the relationship between enthalpy and heat, as well as the specific conditions under which these calculations apply.

LorDjidane
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Hello

First of all, I'm french, as a consequence my scientific language might be difficult to understand. I'm sorry for this.

So, I'm studying a little Stirling motor.
I evaluated the Work given by its cycle. It functions with an external combustion, produced by the burning of Ethanol (C2H5O).

I want to calculate the Heat given by the flame provided by this combustion in order to calculate the output of my motor.

Does anyone have an idea ? I thought about the use of the Free Enthalpy of Combustion, but I don't understand how to use it.

Maybe I could use the expression :
Variation of enthalpy = C*variation of temperature ?

Thanks for your help =)
 
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Are you referring to free energy? You might want to find the standard enthalpy of reaction instead. The data is quite easy to find.
 
That must be that (attached with the post).

But with that, how could I calculate the heat given by my flame ?
 

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I think that enthalpy is a good approximation of the heat q in most cases,
to be sure and perhaps obtain more professional advice you'll need to post this question in the engineering forum and be sure to mention "Sterling Motor."
 
Ok, thanks a lot for your help =)

I'll first try to get the plans of my motor to be more precise.
 

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