[Stoves] Top lit updraft combustors

[Law, Steven (MOECC)]

As per my previous email, please see the clarification below:

“In the email below I am referring to the HHV or LHV reported efficiency, not the calorific value. If LHV efficiency is 90% then HHV efficiency is <84% dependent on moisture content. You are right that if we are referring to calorific value in MJ/kg then HHV is always greater than LHV, on either a consistent wet or dry basis. This is also a function of moisture content if expressed on a wet basis and can vary widely.”

Please let me know if this makes sense or if further clarification is required.

From: Philip Lloyd [mailto:plloyd at mweb.co.za]
Sent: December 18, 2017 9:39 PM
To: 'Discussion of biomass cooking stoves'; Law, Steven (MOECC)
Cc: mhatech at yahoogroups.com; Sauve, Terrence (OMAFRA); 'John Ackerly'
Subject: RE: [Stoves] Top lit updraft combustors

“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<mailto: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<http://heatkit.com/docs/condar.PDF>

On Mon, Dec 18, 2017 at 11:24 AM, Law, Steven (MOECC) <Steven.Law at ontario.ca<mailto: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<http://www.heatkit.com>
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