[Stoves] Heat-pipes/thermal-diodes

[Ronal W. Larson]

Nari:

   After reading about the lanstove, and seeing the word “heat pipe” above Table 1, I still do not understand how a heat pipe is functioning in your system.   The photo doesn’t show much of a distance between the top of the lantern and the cook pot.  Can you provide additional technical description?   What is the working fluid for instance?  What sort of material containing the fluid?  The length of the path for gaseous phase before recondensing?   Anything on costing, efficiency, etc?

   Also it seems that most of the power is going into lighting.  Can you describe how you calculate the very high (Tier3/4) thermal efficiency that you cite.  This is sort of like making charcoal, and properly accounting for the energy not getting into a cook pot.

  How much of the energy in the lighting is getting to the cook pot?

  Any reason that you could not add char making to this very clever arrangement?

  What sort of customer is buying these?

Ron


On Jan 29, 2014, at 9:43 PM, nari phaltan <nariphaltan at gmail.com> wrote:

> Hello stovers,
> 
> Let me share with you some historical perspective on heat pipes. These devices were developed during the hay days of NASA program for delivering large amounts of heat from one place to another in a constrictive space. Hence they used fluids which changed phase either in atmospheric pressure or any other pressure inside the pipe. Generally they had a wick which allowed suction fluid from one end to another.
> 
> This principle is being again looked very carefully in a constricted space of IC chips in computers where huge amount of heat/unit area has to be transferred for cooling purposes.
> 
> Our janta cooker used in the lanstove also works on heat pipe principle.
> 
> In late 1970s we developed a solar oven in our lab at University of Florida which used vegetable oils as heat transfer and storage medium from concentrated solar collectors to the oven. The device worked well but because of the breakdown of oils at high temperatures we had to change them very often. We tried various inert atmospheres like nitrogen and CO2 gases but were not successful. Since it was an M.tech project so after the project finished it was not taken up later on.
> 
> Cheers.
> 
> Anil
> 
> 
> 
> On Thu, Jan 30, 2014 at 9:49 AM, CPP GMail <crispinpigott at gmail.com> wrote:
> Dear Ron
> 
> I am wondering if the term 'heat pipe' is being used correctly here. I certainly know what a heat pipe is but the vacuum tube collectors used in these solar installations are not heat pipes. They are what is described in the text. 
> 
> They are vacuum insulated collectors being used in thermosiphon systems. The Mercedes cookers used a second thermosiphon to transfer heat from the main tank. That was not a heat pipe either though using a different working fluid it certainly could have and it might have solved the heat transfer rate problem. 
> 
> In my view that combination might be the best way to get solar cookers much more widely used, tackling the institutional market first. It allows the heart be collected any time, and the cooking to be done later. The heat pipe is the correct technology to draw the heat to the cooking vessel or surface. By varying the pressure in the tube the heat transfer rate can be controlled. 
> 
> Regards 
> Crispin 
> 
> PS re the firewalled papers: you can write to the author and ask for a copy and they usually send it.
> 
> 
> 
> Crispin and list:
> 
>     Thanks for the updated cite.  Makes at least two that are not behind paywalls.  Hope we can find some that are even more current and easy obtainable.  But there is a big literature on heat pipes outside the cooking arena.
> 
> 	I think we can learn a lot from the solar cooker side - but my interest is on biomass stoves and the ability to feed multiple pots from a single flame.  You talk also about thermo-siphoning and pumps.  I am describing neither of those - a heat pipe operates on a very different principle as I know you know.
> 
> 	The word “diode” is important here.
> 
> 	I talked with one of the last references in your cite - Mr.  C J Swet at about the time he wrote that 1974 article - on (I recall) a thermo siphon principle.
> 
> Ron
> 
> 
> 
> 
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> -- 
> Nimbkar Agricultural Research Institute (NARI)
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