[Stoves] Heat Exchanger in Pots

[Frank Shields]

Hi Crispin,

Nice bends in the copper tubing. Whats the trick to doing that? 
It looks like a very good system and so simple. The water flow could be by constant head to keep it constant going in, perhaps. So after the experiment with flowing water is completed you remove the coils and mix and determine the heat energy in the water left? 

If I am thinking that elevation (done at sea level or 12,000 ft) will not be of concern as you are looking at relative heat changes(?) and that is not dependent on altitude? That saves a LOT of potential error from the standard WBT and trying to maintain a temperature at simmer. 

Frank




Frank Shields
franke at cruzio.com


> On Jun 22, 2015, at 11:55 AM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Friends
>  
> Here is a new example of a copper tube heat exchanger in a pot:
>  
> <image007.jpg>
>  
> This was made at the YDD Lab in June.
>  
> <image008.jpg>
>  
> <image009.jpg>
>  
> <image011.jpg>
> The white cable ties were covered with epoxy to seal them.
>  
> This is a smaller pot that normal and holds 5 litres. Now we have two and can test a two pot stove.
>  
> Here is a set of temperature profiles during a test.
> <image015.jpg>
> The top Cyan line is the water temperature in the pot not rising higher than 60 degrees.
> The second brown line is the temperature at the gas sample point.
> The 3rd green line is the heat exchanger (water out)
> And the 4th line, light blue, is the inlet side of the heat exchanger. The difference can be read to 0.01 degrees and the noted drift between the two RTD’s was 0.004 max.
>  
> The two low lines, red and blue, are the chiller temps – the gas is chilled using a vortex tube and compressed air to drop the water vapour before going to the gas analyser. This approach is very simple, cheap, and can be used in a high humidity environment for continuous testing even with very high water vapour loads. By changing the compressed air pressure, the chiller can be brought down to 2 C or even lower. The gas warms on the way to the analyser and the relative humidity drops dramatically ensure the cells are not contaminated. The system has no moving parts after the compressor.
>  
> The calculated heat gain by the pot is 
> Water mass x 4.186 x Delta T in the pot, 
> plus the flow rate though the heat exchanger x Delta T x 4.186.
>  
> The shorter 3-metre tube in the large pot is able to handle more than 3 kW of heat gain. The second pot has about 6m of tubing.  The flow rate is typically 34-35 cc/second. This is calibrated before and after each test using a bucket and a scale and has proven to be very constant. The 10 second resolution is a few tens to a few hundreds of Joules.
>  
> Any burn cycle can be conducted on the stove and the heat gained by the pot determined for any selected interval. It can faithfully report the heat transfer efficiency at any time when combined with a gas analyser that detects water vapour, O2, CO2 and CO (at a minimum).
>  
> Regards
> Crispin
>  
> _______________________________________________
> Stoves mailing list
> 
> to Send a Message to the list, use the email address
> stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org>
> 
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org <http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org>
> 
> for more Biomass Cooking Stoves,  News and Information see our web site:
> http://stoves.bioenergylists.org/ <http://stoves.bioenergylists.org/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20150622/98cd4126/attachment.html>