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LannyQ1
Joined: 07 Jul 2007 Posts: 2 Location: USA

Posted: Sat Jul 07, 2007 12:41 am Post subject: Specific heat of pintos 


Specific heat of pintos
I am pleased to find this forum.
I am interested in developing biomass fired appliances and when testing for fuel efficiency I noticed that it took less fuel to boil 5 liters of water with pintos, than it took to boil 5 liters of just water.
So to calculate the fuel efficiency of my stoves I need to know the “specific heat” (amount of heat needed to raise the temp 1 deg) of pinto beans also rice and maze (corn).
I have not been able to find this data can anyone help?
Thanks Lanny 

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Watt Guest

Posted: Sun Jul 08, 2007 11:55 am Post subject: Re: Specific heat of pintos 


LannyQ1 wrote:  Specific heat of pintos
I am pleased to find this forum.
I am interested in developing biomass fired appliances and when testing for fuel efficiency I noticed that it took less fuel to boil 5 liters of water with pintos, than it took to boil 5 liters of just water.
So to calculate the fuel efficiency of my stoves I need to know the “specific heat” (amount of heat needed to raise the temp 1 deg) of pinto beans also rice and maze (corn).
I have not been able to find this data can anyone help?
Thanks Lanny 
did you measure the water volume of each, or just make up to a mark? 

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LannyQ1
Joined: 07 Jul 2007 Posts: 2 Location: USA

Posted: Sun Jul 08, 2007 12:30 pm Post subject: Re: Specific heat of pintos 


Watt wrote:  LannyQ1 wrote:  Specific heat of pintos
I am pleased to find this forum.
I am interested in developing biomass fired appliances and when testing for fuel efficiency I noticed that it took less fuel to boil 5 liters of water with pintos, than it took to boil 5 liters of just water.
So to calculate the fuel efficiency of my stoves I need to know the “specific heat” (amount of heat needed to raise the temp 1 deg) of pinto beans also rice and maze (corn).
I have not been able to find this data can anyone help?
Thanks Lanny 
did you measure the water volume of each, or just make up to a mark? 
I use 5 liters of water and 5 lietrs of water with beans (total volume).
Beans, rice and corn have a higher mass than water but must have a lower specific heat. lanny 

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Antinome Guest

Posted: Wed Jan 28, 2009 4:58 am Post subject: Latent Heat of Vaporization and smaller volume of water 


Is it possible that this effect is due to the bean/rice/corn absorbing a significant quantity of the water? Everything would still reach 100C in nearly the same timeframe (actually I'd guess that the one with added beans would reach 100C slightly slower), but only the free water would be absorbing the same amount of heat needed for the Latent heat of vaporization prior to actually boiling and there's less of that in the ones where a lot of liquid got absorbed. Latent Heat of Vaporization is so much larger than the specific heat that I'm pretty sure it has to be the dominating effect.
5 000cc * 4.18600 J/cc*1/C * (100C  23C) = 1,611,610 J to heat the water up to 100C, but the same amount of added heat again only boils off 15% of the water at 2260J/cc.
Another theory is that the dissolved starch makes a good site for steam bubble formation, and that you only see the boiling start on he pinto bean pot sooner, where they are actually both converting water to steam at close to the same rate.
...or possibly you did this on different days with wildly different ambient pressures? Or you used two different burners? Or one started with a cold pot and the other just came out of a dishwasher?
really we would need to see when the pots hit 100C side by side, not when they started boiling. knowing that and the mass of the beans as well as the water (volumes are fine here since we know 1gm=1cc) we could work out the specific heat of the pinto bean with no problem. 

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Antinome Guest

Posted: Wed Jan 28, 2009 5:05 am Post subject: Coeerection 


Just realized that the bean+water is 5L Total. This makes me more sure that latent heat of vaporization is the answer. Once the beans reach 100C they just sit there occupying space. The water however, continues to absorb heat until it has enough energy to start turning to steam. That takes less time when there is less water. Absorption of more water may make this effect even more pronounced.
But only the experiment I proposed will tell you for sure. 

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