<html><head></head><body lang="en-US" style="background-color: rgb(255, 255, 255); line-height: initial;"> <div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Dear Kirk</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><span style="font-size: initial; line-height: initial; text-align: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif;"><br></span></div><br><div id="_originalContent" style=""><meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<div>>The power level is 1.6 kw to 6kw with cushion on each end. What ever cooking arrangment design you use is up to <br>
you and heat flux will change accordingly. If the people in Java can use a <br>
stove with 1.6 to 6 kw, and can use that heat effectively, then the power <br>
level is adiquate for Java or anywhere else. The same combustor principles <br>
can be used on larger or smaller stoves if this range is not adiquate.<br>
<br>
(raising the skirt)"This will reduce the draft and reduce the burn rate and <br>
reduce the heat transfer efficiency (aka thermal efficiency)."<br>
I don't necessarily agree. Some of the draft may be lost, but the flow <br>
resistance will be reduced which will counter the draft loss. I am <br>
intending to do some testing on the effect of raising the pot stand, so I <br>
intend to find out. Also I want to do some tests on the effects of ambient <br>
conditions on the stove. The skirt needed raising only when the ambient <br>
temperature was higher. Most cooks will not even use a skirt so the <br>
question may be less important than we think. Without a skirt there would <br>
be no problem with ambient temperature on turn-down.<br>
<br>
Don't forget the low emissions. Don't get fixated on narrow issues.<br>
<br>
Kirk H.<br>
----- Original Message ----- <br>
From: "Crispin Pemberton-Pigott" <crispinpigott@outlook.com><br>
To: "'Discussion of biomass cooking stoves'" <br>
<stoves@lists.bioenergylists.org><br>
Sent: Saturday, June 04, 2016 1:11 PM<br>
Subject: Re: [Stoves] kgharris stove test<br>
<br>
<br>
> Dear Kirk<br>
><br>
> From your original post:<br>
><br>
>>The high power used in the tests was around 3.25 kw.<br>
><br>
> What was the cooking power during the hot start test? That means, from <br>
> ambient to boiling, the heat gained divided by time to gives Watts <br>
> (J/sec), and further, what was the heated area of the pot? I want to <br>
> calculate the heat flux to see if the cooking power is acceptable to, for <br>
> example, people in Central Java.<br>
><br>
>>At 24C room temperature there was no problem keeping the water in the 93C <br>
>>to 97C test simmering range. At 30C room temperature the simmering water <br>
>>temperature could not be held below 97C. The pot skirt had to be raised <br>
>>to release some heat to maintain the test temperature.<br>
><br>
> You do not 'fail' by not having the water between those temperatures. Yes, <br>
> as a result it will increase the evaporation of water from the simmering <br>
> pot.<br>
><br>
>>Raising the skirt....<br>
><br>
> This will reduce the draft and reduce the burn rate and reduce the heat <br>
> transfer efficiency (aka thermal efficiency).<br>
><br>
> The effect of this on your calculated result is important. If you <br>
> evaporate more water, you get a smaller number of litres at the end. This <br>
> is divided into the mass of fuel you burned (well, not the mass of fuel, <br>
> but the dry fuel equivalent of the energy that was released from the mass <br>
> of fuel that went missing).<br>
><br>
> The result is that for any given dry mass of fuel equivalent, you get a <br>
> higher SFC number. Because the number of litres has not effect on the fire <br>
> (at all) we do not really know what the fuel consumption is, only what the <br>
> dry fuel equivalent divided by the number of litres remaining is.<br>
><br>
> It would be helpful for us if you reported the dry fuel equivalent, or <br>
> better yet, the actual mass of fuel needed to complete the whole test (hot <br>
> start and simmer). The reasons is that we can consider what effect the <br>
> various conditions such as skirt elevated or not, have on the performance.<br>
><br>
> For example I would be very interested in the power (burn rate) with the <br>
> skirt in the two positions, and the Heat Flux as well. That is very useful <br>
> information, particularly if the skirt increases the firepower and set the <br>
> minimum power level. It is quite legitimate to make a stove with a skirt <br>
> and the instructions for turning it down include - 'raise the skirt', or - <br>
> 'remove the skirt'.<br>
><br>
> The Chinese heating and cooking stoves almost all have a mechanical insert <br>
> that is placed in the top of the stove when turning the power down to a <br>
> long 10 hr burn. Without that device they can't possibly burn 8 or 10 kg <br>
> of fuel for 10 hrs and have enough left to raise the flame back to life <br>
> (which is part of the national test).<br>
><br>
> You get the idea? There is no problem with having 'mechanical controls' <br>
> on the stove to bring the power down to 0.5 kW.<br>
><br>
> Regards<br>
> Crispin<br>
><br>
><br>
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