Talk:Heat of combustion

Importance of LHV vs HHV Debate

I would like to include some discussion - doesn't need to be an epistle - on why LHV is used (specifically in Gas Turbines) and how that sometimes causes confusion when comparing efficiency with other thermal plant like coal-fired boilers with steam turbines. Any thoughts or suggestions?--Graham Proud (talk) 06:12, 13 August 2013 (UTC)

Untitled

Can we obtain heat of combution of any product without experiment? is it same like following? A +o2 → Co2+ No2 then based on number of moles and standard heat of formation of Co2 and No2, can we take the obtained result as heat of combustion of substance A? if yes, then does heat of formation is exactly same (with opposite sign) that of heat of combustion? as if we reverse this equation, then heat of the reversed equation will be heat of formation. is this logic correct?

It would be nice if someone would make a sister page about heat of formation.

The reference to energy obtained from antimatter may be misleading as that is presumably the amount of energy contained in that weight of antimatter which would be released when combined with equal weight of matter. I won't vouch for the math in it, but the description is not sufficient, or in any case, might just be listed as the energy available in any mass, whether matter or antimatter, if that is the intent. —Preceding unsigned comment added by Uhpl508 (talk • contribs) 21:12, 21 June 2008 (UTC)

Improper Reference

The first reference is not specific enough to find the information that it references. —Preceding unsigned comment added by 128.32.154.142 (talk) 23:28, 12 February 2008 (UTC)

Nomenclature

Should the organic compounds be named according to the systematic nomenclature of IUPAC? I believe olefines should be alkenes, diolefines should be dienes, etc. i believe tthe use of trivial nomenclature is to be avoided in favor of systematic names. If the fuel has some water , is it true that the state of fuel's water is not important for LHV and HHV ? —Preceding unsigned comment added by 85.185.134.60 (talk) 10:12, 13 December 2007 (UTC)

Three Proposed Merges

Merge of Heating value here

It is proposed that Heating value be merged here. The two article each had a simple merge tag, but I have changed these to mergeto and mergefrom as I believe merging Heating value here is the best solution. Please discuss it. --Bduke 00:47, 22 August 2007 (UTC)

• Support "Heating value" is not a standard term and it really is just a heat of combustion. I suggest tidying it up and merging the content here. --Bduke 00:47, 22 August 2007 (UTC)

• Oppose I have found sulfur's heat of combustion to be ~4000btu/# in other resources, vs. the 2000btu/# given here. Where can this number be confirmed? —Preceding unsigned comment added by 74.0.223.151 (talk) 13:27, 11 September 2007 (UTC)

Higher Heating Value (HHV) is commonly used by the local air quality management authority in Southern California, perhaps by other air quality regulatory agencies as well. If this is combined with Heat of Combustion, "Higher Heating Value" should be such that it is searchable from a search engine such as Google, since many people, such as I, will search for HHV and not heat of combustion. —Preceding unsigned comment added by 65.169.176.254 (talk) 22:49, 14 November 2008 (UTC)

• Yes, merge - they seem to be exactly the same thing. — Omegatron 21:50, 27 January 2008 (UTC)

This MERGE appears to have been completed in Jan 2008. N2e (talk) 20:30, 8 August 2008 (UTC)

Merge of Higher heating value and Lower heating value here

It has been further proposed, in merge tags within each of the two Xxxxx heating value articles, that both are merged here. Both merge tags were added 2008-03-30 by User:Omegatron. One can thus assume that

• Omegatron Supports the merge, as the proposer.

• Support -- Rationale: both higher and lower heating values are physical characteristics for particular fuels and are thus part of the heat of combustion. N2e (talk) 20:30, 8 August 2008 (UTC)

Completed

All merges proposed here are now complete. D O N D E groovily Talk to me 03:41, 23 November 2010 (UTC)

H2S heat of combustion

This should be added. —Preceding unsigned comment added by 74.0.223.151 (talk) 13:45, 11 September 2007 (UTC)

Inconsistency in first table

The heat of combustion values in the 1st table are inconsistent for coal. The conversion between Mcal/kg and BTU/lb is correct, but the conversion to MJ/kg seems wrong. Although I have only checked the conversion of the units, I propose that these values are changed into 18.6 - 32.6 MJ/kg. - It is possible that the conversion went wrong the other way (and that MJ/kg are correct, and Mcal/kg and BTU/lb are wrong). I cannot find the reference.

Furthermore, all the values are inconsistent with another wikipedia page: http://en.wikipedia.org/wiki/Coal (see the 1st table). —Preceding unsigned comment added by 130.112.1.3 (talk) 13:12, 11 August 2008 (UTC)

The table at Heating values of some fuels is still inconsistent and poorly referenced. The HHV for coal is listed at 8000-14000 BTU/lb which converts to 18.6-32.6 MJ/kg, not 15-27 MJ/kg as stated in the table. Searching the reference yielded no easy source of information. --LRG (talk) —Preceding undated comment was added at 09:42, 30 September 2008 (UTC).

"Fuel needed to run a 100 W lightbulb for a year (876 kWh, or 3153.6 MJ)"section has to be changed/deleted

This section has no thermodynamical sense, which is outlighted by the text into parenthesis. Actually, it would be better to change it or to delete it. The deletion seems to me definitely required because it would have no sense to replace "to run a 100 W lightbulb for a year" by "to provide to 100 W of heat for a year". If someone finds usefull to keep relevant data from this section, he can revert or modify this deletion. 81.56.65.180 (talk) 14:20, 25 October 2009 (UTC)

"Lower heating values for some organic compounds at 15.4C"

A BIG citation needed here - What is the significance of 15.4C anyway? One source I found is here: "http://www.engineeringtoolbox.com/heating-values-fuel-gases-d_823.html" but I don't know how reputable that site is. Also, there's no reason to keep half of the table empty, since it only differs by a conversion factor. I added the value for carbon monoxide, since I used that value on my homework. Traversc (talk) 09:33, 28 October 2010 (UTC)

Is it kJ/L or MJ/L? — Preceding unsigned comment added by 83.6.186.1 (talk) 16:11, 25 August 2011 (UTC)

Table of Higher Heating Values

I just merged in Higher Heating Value to this article, with the exception of this table, which is difficult for me to go thru. Here it is:

Heating values for selected fuels

Name	HHV (MJ/kg)	LHV (MJ/kg)	HHV/LHV	LHV/HHV
Coal	34.1	33.3	1.024	0.977
CO	10.9	10.9	1.000	1.000
Methane	55.5	50.1	1.108	0.903
Natural gas	42.5	38.1	1.115	0.896
Propane	50.3	46.3	1.086	0.920
Gasoline	46.7	42.5	1.099	0.910
Diesel	45.9	43.0	1.067	0.937
Hydrogen	141.9	120.1	1.182	0.846

And here is a slightly different one taken from Lower heating value:

Heating values for selected fuels^,

Name	HHV (MJ/kg)	LHV (MJ/kg)	HHV/LHV	LHV/HHV
Coal	34.1	33.3	1.024	0.977
CO	10.9	10.9	1.000	1.000
Methane	55.5	50.1	1.108	0.903
Natural gas	52.2	47.1	1.108	0.903
Propane	48.9	45.8	1.068	0.937
Gasoline	46.7	42.5	1.099	0.910
Diesel	45.9	43.0	1.067	0.937
Hydrogen	141.9	120.1	1.182	0.846

If there's anything new here, feel free to toss it in. D O N D E groovily Talk to me 03:34, 23 November 2010 (UTC)

GHV definition is incorrect

I have just had a discussion with my partner who works on the thermodynamic analysis of complex plant as part of her PhD in energy engineering. She tells me "I think its wrong on the wikipedia page. GHV should be HHV, not LHV."

• http://books.google.de/books?id=AYjFoLCNHYUC&pg=PA850&lpg=PA850&dq=%22gross+heating+value%22++%22higher+heating+value%22&source=bl&ots=GPTrND5rHC&sig=5pYQUAOt_yNNxaeGhYBszuy_GJI&hl=de&ei=GpSATYaLCsT5sgai2rjsBg&sa=X&oi=book_result&ct=result&resnum=4&ved=0CDgQ6AEwAzgo#v=onepage&q=%22gross%20heating%20value%22%20%20%22higher%20heating%20value%22&f=false
• http://www.ecn.nl/phyllis/defs.asp
• http://www.engineeringtoolbox.com/gross-net-heating-value-d_824.html
• http://en.citizendium.org/wiki/Heating_value

I will refrain from making the necessary edits as I do not intend to maintain any kind of follow up on this page. Regards Robbiemorrison (talk) 11:28, 16 March 2011 (UTC)

I second this statment... The Gross Heating Value is HHV. The article is totally incorrect. —Preceding unsigned comment added by 65.200.157.177 (talk) 16:04, 11 May 2011 (UTC)

Are the figures in the column headed kJ/L in the later LHV tables actually MJ/L? — Preceding unsigned comment added by 80.177.3.114 (talk) 18:49, 31 August 2011 (UTC)

The heating values in the tables appear to be molar heating values not mass heating values. The reported units of BTU/lb, etc should be BTU/lb-mole etc — Preceding unsigned comment added by 209.173.113.108 (talk) 03:30, 10 February 2012 (UTC)

Incorrect unit conversion factors

Section "heating value" lists some conversions. Last one (Btu/lb = kcals * 1.8) is dimensionally incorrect: Btu/lb does not correspond to kcals . It should be kcals/[some unit for mass], and when this unit is chosen, the constant can be adjusted. DarkoS (talk) 18:09, 25 October 2012 (UTC)

Usage of terms

In my opinion Wiki should refrain from making subjective statements such as: "... and if they are not already then they should be doing so..." or "...based on the simple fact that it is correct..." 138.210.84.87 (talk) 10:21, 22 January 2013 (UTC)

Very poor quality article

This article appears to need considerable work. The most glaring issue that I see is that there appears to be no explanation of this property of a chemical. All we get is a few sentences, and then it's off to the races talking about higher/lower heating values. Essentially all of the textbook chemistry discussion is reduced to an introductory sentence and a few bullet points.

I came here hoping to remember which sign indicated an exothermic reaction. Guess what? There is no mention of a chemical which has a negative heat of combustion. It's not mentioned in this article.

Additionally, the writing is deplorable in the section "Usage of terms." Here is a gem:

• The difference between HHV and LHV definitions causes endless confusion when quoters do not bother to state the convention being used. -- How lovely? This sentence broaches the topic of eternity, so we might as well link to it?

Why I picked on that sentence is anyone's guess. There are so many to choose from in other sections:

• Most applications that burn fuel produce water vapor, which is unused and thus wastes its heat content. (Chemistry + Grammar = Wasted Energy?)
• Using LHV in other energy calculations brings similar errors, especially when pulled (incorrectly) into electrolysis calculations etc. (Pulling + My Leg = Electrolysis of my Sides Splitting from Errors?)
• Btu/lb = kcals * 1.8 (Was this error in unit conversion garbage what someone was really hoping to find here??)

Please, if anyone rates this article.... give it the lowest mark possible. IT'S A MESS! It is not fixable. I think it should be scrapped and started over. I like to saw logs! (talk) 05:51, 5 March 2014 (UTC)

150°C is NOT an arbitrary temperature

It is based upon the acid gas dew point for sulfuric acid (+ margin). Other acids (sulfurous, nitric, nitrous, carbonic) have an even lower dew point, so it is assumed that at 150°C. effectively no acids will condense. Hippocrocopig (talk) 22:22, 27 March 2016 (UTC)

Poor/dubious merge ? what units ?

We seem to have an article about heating values that doesn't define its current title of Heat of combustion. Is heat of combustion (a term used by chemists?) always/usually per mole ? Heating values seem to be engineering terms, usually per mass or per volume ? - Rod57 (talk) 11:57, 22 March 2017 (UTC)

Fringe theories

The statement recently re-added to the article is

Accordingly, the lower heating value is strictly proportional to the amount of oxygen consumed in the combustion.

The source given does not refer to the lower heating value at all. The higher heating value per amount of oxygen consumed differs significantly between fuels. According to [indirect calorimetry], it is "21.13 kilojoules (5.05 kcal), the heat released per litre of oxygen by the oxidation of carbohydrate, and $e_{f}$ is 19.62 kilojoules (4.69 kcal), the value for fat", a significant difference even for those common (similar) fuels. The Weir formula is also more sophisticated than the "strictly proportional" found here (but not in the reference).

I propose that this statement be removed; it isn't backed up by the reference, which makes clear it's a mere rough estimation for a restricted class of fuels.

IpseCustos (talk) 06:37, 10 June 2022 (UTC)

The sentence about the lower heating value being proportional to the amount of oxygen consumed is true. The cited reference (titled “Oxygen consumption as the definitive factor in predicting heat of combustion”) implies it, but I have now added another reference where the relation to the lower heating value is made explicit (the authors refer to “the water vapour content of the exhaust gases”, which is the characteristic condition distinguishing the lower from the higher heating value, obtained when the water condenses).

It is worth noting that IpseCustos does not even claim that the sentence in question is incorrect (which would be an untrue claim). Instead, all of the comments by IpseCustos refer to the higher heating value, which is different from the lower heating value because it includes the heat of condensation of the water formed in the combustion reaction. This accounts for the slightly different quoted numerical prefactors for carbohydrates and fat. The link to the Weir formula is not relevant, not only because it refers to the higher heating value but also because the units are not kJ or kcal per mole or gram, the conventional units of heat of combustion (the topic of this article), and the temperature at which the volumes of O₂ and CO₂ are calculated is not obvious; furthermore, one version of the Weir formula given has only one significant figure, so it cannot be very accurate.

In summary, no evidence has been provided that the sentence in question is incorrect or not relevant to heat of combustion. The added reference from Fire Safety Science confirms that this sentence summarizes rigorous experimental observations from hundreds of measurements that are relevant even under real fire conditions. In what way is that fringe science?

One could consider a longer sentence expressing the same facts: “Accordingly, the heat of combustion (corrected for the heat of condensation of any liquid water formed) is directly proportional to the amount of oxygen consumed in the combustion.”

Klaus Schmidt-Rohr (talk) 17:27, 10 June 2022 (UTC)

The sentence about the lower heating value being proportional to the amount of oxygen consumed is true

Irrelevant. It needs to be verifiable, and since it's such an extraordinary claim it needs to be verifiable extraordinarily well. I'm afraid Fire Safety Science is not the kind of source that does that.

Also, if it is proportional, what is the constant of proportionality? That information would be important!

It is worth noting that IpseCustos does not even claim that the sentence in question is incorrect

Oh, I do. There are compounds that differ in heat of combustion (low or high) but consume the same amount of oxygen in that process. Branched alkanes, unbranched alkanes.

But this is not a difficult question to research: unless the web search failed me, the LHV of hydrogen is stated to be 241.83 kJ/mol(H₂), or 484 kJ/mol(O₂). The HV of CO is 282 kJ/mol(CO), or 564 kJ/mol(O2). So, for those two fuels relevant in real-world fires, the statement is untrue.

The Weir formula is indeed specified in different units, but converts to a range of 368 to 472 kJ / mol(O₂).

In summary, no evidence has been provided that the sentence in question is incorrect or not relevant to heat of combustion.

No evidence has been provided that it is widely regarded relevant to that topic. The burden of evidence here is on the editor who wants to introduce a claim, not the one challenging it.

Please provide evidence that your theory is considered notable by others, so we can reference its inclusion in Wikipedia articles properly.

IpseCustos (talk) 20:40, 10 June 2022 (UTC)

The fact stated in this sentence has been known for more than a century, and maybe even since the time of Lavoisier. It is extremely well verified. I will add more references that make this clear. It is even the basis of a whole area of fire science, oxygen consumption calorimetry, which is used world-wide and was the basis of several national (ASTM E 1354-99 and ANSI/NFPA 271-1998) as well as international (ISO 5660-1:1993) standards. The constant of proportionality used in oxygen consumption calorimetry is 419 kJ/mol.

The paragraph to which this sentence belongs is clearly about organic fuels, so H₂ and CO having slightly higher heats of combustion is not relevant. But since it was brought up in this discussion, I will make "organic fuels" explicit.

If the Weir formula "converts to a range of 368 to 472 kJ / mol(O₂)", that's another way of saying that the heat of combustion is proportional to the amount of O₂ consumed. So more evidence for this fact of nature!

This sentence states a long-established fact. It is not a theory, and certainly not a fringe theory, since it is utilized in fire science and studies of metabolism. It is a simple, true, and quantitative statement about the heats of combustion of organic fuels. It is clearly relevant to this article on “Heat of combustion”.

Klaus Schmidt-Rohr (talk) 16:08, 11 June 2022 (UTC)

To take just one example, the abstract of the Huggett paper in 1980 states:

The method is based on the generalization that the heats of combustion per unit of oxygen consumed are approximately the same for most fuels commonly encountered in fires

Using that as a reference for the statement that the heat of combustion is strictly proportional to the amount of oxygen consumed (per mole of reactant) is stretching things quite a bit. Clearly Huggett was aware that he was generalizing and approximating things to achieve a rough estimate that was sufficient for the purposes of practical fire science. It's not sufficient for a theoretical chemistry article.

And it's not relevant enough to go in the lead section. It should go under "ways of determination", along with Dulong's formula and, ideally, the Weir formulae. IpseCustos (talk) 22:44, 11 June 2022 (UTC)

To address the stated concern, the word "strictly" has been taken out. The uncertainty (±3%) is already specified earlier in this paragraph. In 1980, Huggett had only a moderate amount of data and he was working under non-ideal conditions, but the proportionality has subsequently been confirmed on hundreds of organic compounds; importantly, the larger and more complex the molecule, the smaller the percent error. The proportionality holds well enough to be part of national and international standards in fire science. Since this is a short, relevant sentence pointing out a simple fact about the heat of combustion that is of significant utility in combustion science, I think the second half of the lede is a quite appropriate place for it. I don't see how it has much to do with "ways of determination". Other editors should comment. Klaus Schmidt-Rohr (talk) 01:26, 12 June 2022 (UTC)

"Strictly proportional" has been replaced by "directly proportional", which has the same meaning.

The 3% clearly refer to the 0.3h estimation method, which is different from the "mole of oxygen" method.

Statements that are good enough for fire science aren't necessarily good enough for theoretical chemistry.

If there is any error, we cannot say "directly proportional". We must make clear that we're then talking about an approximation, declare which class of fuel it is valid for, list exceptions, and provide good general sources in the context of theoretical chemistry, not fire science, that verify this approximation is considered good enough. All this makes the statement too long and bulky to go in the lead section. IpseCustos (talk) 06:56, 12 June 2022 (UTC)

To address these concerns, "directly proportional" have been revised to "proportional (±5%)". The LHV formula with 0.25h and the HHV formula with 0.3h differ only by 0.05h. Therefore, the LHV and HHV of organic molecules are similar in magnitude and in relative uncertainty. Furthermore, the correction for the condensation of water is identical (44.0 kJ per mole of H₂O formed) for theory and experiment, so it does not introduce additional uncertainty. As a result, the percent deviations of the HHV and LHV predictions from the experimental HHV and LHV values, respectively, are similar for organic molecules. This also applies for careful standard-state calorimetric data, e.g. as compiled by Domalski (1972) for over 500 molecules, which are used for "theoretical chemistry" (calculations of standard molar enthalpies of formation of organic molecules). The good agreement of the proportionality factor used by fire calorimetrists (-419 kJ per mole of O₂) with that from Domalski's standard-condition data (-418 kJ per mole of O₂) is impressive. The value of ±5% is a conservative estimate from the quoted literature. Klaus Schmidt-Rohr (talk) 17:17, 14 June 2022 (UTC)

This remains a case of violating WP:OR, WP:REFSPAM, WP:COI, WP:V, and WP:DUE.

This is your fifth attempt, if I'm counting correctly, and the fifth one that is wholly unacceptable.

The current attempt reads:

• Accordingly,

According to what? Your fringe theory?

• the heat of combustion of organic fuels

which fuels? It clearly does not apply to explosives, ring-strained molecules, etc.

• (when corrected for the heat of condensation of any liquid water formed)

"corrected" in which direction? Not even that is clear

• is proportional (±5%)

it either is proportional or it isn't. It isn't. Do you mean a range or a normalized deviation? If the latter, how did you select your fuels? There's no such thing as a usable random distribution on the set of possible molecules, so it has to be the former.

• to the amount of oxygen consumed in the combustion

"per mole of fuel"

And if we correct all those, we are left with a technically correct but ultimately uninteresting (IMHO), well-known statement that, far from being a fundamentally new discovery, is refined by, rather than contradicting, the Weir formula, Dulong's formula, the Joback method, what-have-you. That statement does not belong in the lede section of this article.

And I'm sorry to bring up conduct rather than content, but you have consistently misrepresented sources as agreeing with your claims when they don't, so I'm not sure I can trust references you give in the future. Since your conflict of interest is not just exhibited through citing your own work, but concerns the subject matter itself, I would ask you to please abide by WP:COI and refrain from making controversial edits (such as the last five ones to this article) before discussing them on the talk page. Thanks. IpseCustos (talk) 17:58, 14 June 2022 (UTC)

RfC about heat of combustion being proportional to oxygen consumption

The following discussion is an archived record of a request for comment. Please do not modify it. No further edits should be made to this discussion. A summary of the conclusions reached follows.

No discussion, but the claim was removed for reasons of WP:COI

---

Should the lead section contain a claim that the lower heating value is "directly proportional" to the amount of oxygen used in the combustion? IpseCustos (talk) 16:34, 11 June 2022 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

How to figure out HHV/LHV from Thermophysical databases

In a couple of the tables for HHV and LHV the NIST Chemistry webbook is given as a reference for the values but no specifics of how to get the information from the webbook. I think it would be useful for either the table notes or the reference to provide details 24.62.236.118 (talk) 13:55, 18 September 2024 (UTC)