Net Heating Value or High Heating Value
Net Heating Value or High Heating Value
(OP)
I'm a bit (well, ok, a lot) confused on when to use NHV vs HHV. In particular: working on a Flare project where we have to keep a minimum of 300BTU/scf of vent gas to the flare. If we are sending N2 (no BTU content), we need to supplement with Natural Gas.
The gas provider has indicated their gas (dry) is 1010 BTU/scf as tested by calorimeter. Would this be NHV or HHV?
Since we are adding the Nat Gas to be combusted, not heating something (like a boiler), do we use the NHV or the HHV of the gas in our calculation of total BTU content?
The gas provider has indicated their gas (dry) is 1010 BTU/scf as tested by calorimeter. Would this be NHV or HHV?
Since we are adding the Nat Gas to be combusted, not heating something (like a boiler), do we use the NHV or the HHV of the gas in our calculation of total BTU content?
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RE: Net Heating Value or High Heating Value
Gross Heating Value (also known as High Heating Value) is the heat given off during complete combustion of a fluid. It is measured with a caliromiter. A portion of this heat is used in the reaction to boil the water that forms as a combustion product.
Net Heating Value is a theoretical value (i.e., is not measured) that starts with gross heating value and subtracts the latent heat of vaporization of the theoretical water combustion product. I say "theoretical water combustion product" because the amount of water can not be measured and must be estimated from the reaction chemistry.
The only reason that I can think of for specifying a minimum BTU/SCF content in a flare is that the lower the HV, the higher the ignition temperature and the system might be designed in a way that less than 300 BTU/SCF gas might not reliably ignite. Just a guess. If that guess is in the right direction then you would use GHV instead of NHV.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Net Heating Value or High Heating Value
Im not sure that i follow your initial definition?
Isnt GHV the energy that comes from combution+condensation of water formed during the burning of the fuel?
Opposed to LHV that dosnt consider this (since many burners and e.g. a flare) does not condens the water and hence does not have a possibility of achieving GHV.
Im a bit unsure wrt to net (i may google it later
But i do agree that its a bit strange to specify a min energy flow rate to the flare, although specifying a minimum GHV (without flow) could be usefull.
RE: Net Heating Value or High Heating Value
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Net Heating Value or High Heating Value
-Upper heating value: Heat of combustion including the energy you can recover if all the water formed during the combustion is cndensed and cooled to a std. temperature. Modern natural gas burning water heater will ususally have this feater and have an efficeny close to the UHV
-GHV= Same as upper?
-NHV=Same as lower heating value? You say its a "theoretical value and i dont quite know how to understand this
-Lower heating value: The energy that can be used if you dont condense any water. Older (and newer cheap) house water heater using natural gas will usually be of this type.
I know its splitting hairs but i just want to get the english words right.
Best regards
Morten
RE: Net Heating Value or High Heating Value
NHV, and LHV are the same thing.
We measure GHV in a calorimeter. We use mathematical relationships to derive NHV from GHV. That is why I call it theoretical.
I'm not sure that the modern high efficiency home heaters and water heaters actually cool the exhaust stack below the dew point of the water vapor. If they did that, the exhaust stack would accumulate liquid water and freeze in cold climates and accelerate corrosion in all climates. I have a high efficiency water heater and don't see any liquid accumulation around the exhaust pipe so I don't think we're actually getting to recovery of all the heat of combustion. I'm also not sure that would be a good idea.
David Simpson, PE
MuleShoe Engineering
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"
RE: Net Heating Value or High Heating Value
Besides, in some countries the terms used are LCV and HCV for low and high calorific values, respectively.
The words in Spanish: poder calorífico inferior [PCI] and poder calorífico superior [PCS].
RE: Net Heating Value or High Heating Value
Weisman makes them for domestic use (think it was a Weisman) http://www.viessmann.dk/da/products/gas-brennwertk... in danish sorry
Best regards
Morten
RE: Net Heating Value or High Heating Value
RE: Net Heating Value or High Heating Value
http://www.herramientasingenieria.com/_english/Gas...