[Stoves] Top lit updraft combustors

[Philip Lloyd]

“Just remember that HHV is always less than LHV, and anything above 100% is WRONG and cannot possibly conserve energy or mass and is therefore unscientific.” 

HHV stands for Higher Heating Value; LHV stands for Lower Heating Value, so, to the contrary, HHV is always > LHV by definition.  

The units in SI are MJ/kg; any report of HHV or LHV in % is wrong.

Philip Lloyd

 

 

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Norbert Senf
Sent: Monday, December 18, 2017 6:43 PM
To: Law, Steven (MOECC)
Cc: mhatech at yahoogroups.com; Sauve, Terrence (OMAFRA); John Ackerly; Discussion of biomass
Subject: Re: [Stoves] Top lit updraft combustors

 

Thanks, Steven. That's great.

Our experience with domestic-scale cordwood in masonry heaters (50 lb batches @20% moisture) is that the "boiling of water" or latent heat loss is typically in the 13% range, using the Condar spreadsheet HHV calculation   heatkit.com/docs/condar.PDF

 

On Mon, Dec 18, 2017 at 11:24 AM, Law, Steven (MOECC) <Steven.Law at ontario.ca> wrote:

Hello all,

 

I have finally completed a proper study of reporting efficiency using LHV and HHV. It was much more complicated than I thought it would be, and now I know why this is such a mess!

 

Just remember that HHV is always less than LHV, and anything above 100% is WRONG and cannot possibly conserve energy or mass and is therefore unscientific.

 

When an LHV efficiency from Europe is 90% (which is actually a reasonable number), the HHV efficiency is a maximum of 84% or usually less, depending on the moisture content of the wood fuel and is more typically 75-80%. This is important, HHV efficiency is extremely dependent on fuel moisture whereas LHV is less so, but only for non-condensing boilers.

 

Again, this is for non-condensing combustion devices, because when you throw in high efficiency condensing heat recovery all the numbers get screwy and LHV no longer applies. Everything has to be re-done for condensing boilers and only HHV can be used, I will repeat LHV cannot be used for anything where condensation of the flue gas occurs in the heat recovery device!

 

I think I have a proper engineering calculation procedure mapped out to deal with all of the above issues and I will begin to roll this out a little bit at a time since I need to review it again before sending anything out. It is a scientific method that is based on conservation of mass and energy and I hope that this new calculation procedure will help to solve some current problems in the industry.

 

Best regards, Steven

-- 

Norbert Senf
Masonry Stove Builders
25 Brouse Road, RR 5
Shawville Québec J0X 2Y0
819.647.5092
www.heatkit.com

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