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Author Topic: Anyone tried adding a reflector?  (Read 35182 times)
wyleu
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« Reply #30 on: August 20, 2008, 05:27:42 PM »

This probably one of the best ways of appreciating the characteristics.
Get a tube with a core to understand the meaning of a greasy heat...   whistlie
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Colin_A
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« Reply #31 on: August 20, 2008, 07:27:33 PM »

Hi Wyleu
In my book the hands-on approach is the best way to learn and usually the most fun.
I am considering buying a single 70mm single wall tube to play around with. I would like to experiment with a parabolic trough using the evacuated tube as the receiver so hopefully i`m still on topic with the thread.
 
I think the length of the 70mm tube is around 1.5m but I can`t find any info regarding the diameter or length of the protruding end of the heatpipe.
 I wondered if a small bore copper tube wound into a tight spring which fitted over the end of the heatpipe would function as a reasonable heat exchanger or perhaps a proper "plug-in" type manifold is available off the shelf?

Situation normal.. more questions than answers Grin

Colin


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NickW
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« Reply #32 on: August 20, 2008, 11:12:23 PM »

Colin

if you want to have a play with solar concentrators like I did use a 47 or 58mm tube as they are twin wall. In contrast a 70mm would be useless as they are single wall glass.
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Colin_A
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« Reply #33 on: August 21, 2008, 12:17:54 AM »

Hi Nick,
I had it in my mind the heatpipe surrounded by air would be less effective than the 70mm tube with the vacuum surrounding the heatpipe.
I was a little concerned how well the still air tube could cope with the air expanding with the heat versus the 70mm vacuum tube...always assuming a diy parabolic trough could multiply the radiation to the tube by some significant amount Smiley

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Ivan
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« Reply #34 on: August 21, 2008, 01:04:52 AM »

definitely go for the 47 or 58mm. The air expansion isn't a problem - there's a tiny hole in the top to allow pressures to equalise. And you have so much more flexibility with the twin walled tubes - have a look at the news pages on the Navitron website - we've been cooking curries, soup, tea, coffee etc directly in the twin wall tubes.

Incidentally, if the weather's good, it migh be a good opportunity for demonstrating some solar cooking at the Navitron party. Might have a go at another solar curry...
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Colin_A
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« Reply #35 on: August 21, 2008, 01:21:28 AM »

Thanks Ivan
Ok, 47mm or 58mm it is..more scope for experimenting is good  Grin
Any thoughts on the coiled pipe heat exchanger or is there a tried and tested method for transferring the heat from a single tube?
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CeeBee
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« Reply #36 on: August 21, 2008, 11:05:09 AM »

Any thoughts on the coiled pipe heat exchanger or is there a tried and tested method for transferring the heat from a single tube?

Hi Colin, and welcome. Sounds as though you're thinking along the same lines as me (but more practically!). I've got a spare 47mm tube - thought it would be nice to have one at ground level to show people or to try 'solar cooking'. But I'd rather try leaving the heatpipe in-situ than removing it and putting the water/food/etc. in the tube. So the problem is: what's a good way of transferring heat from the heatpipe tip to e.g. a saucepan, bearing in mind that the the tip needs to be at the top (otherwise the heatpipe won't work), and the arrangement will need to be well-insulated?

What next having wrapped your copper pipe round the tip? Other than having a pumped circuit much the same as we have in a proper panel?

As for reflectors: I keep thinking of the light fittings for fluorescent tubes often used in offices - there's one above me as I type. They have nice curved reflectors, and indeed I've got several of these (scrap from a previous office) in my 'might come in handy' pile. Only thing is, even a 47mm tube would take up more of the reflector's 'aperture' than the relatively narrow fluorescent tube.

And this thread has caused be to wonder how the 70mm single-wall tubes work at all: without the vacuum gap, won't the outside surface of the tube tend to get hot and lose heat? Anyway, however it is that they work, can't see why they'd be any worse for reflector experiments than any other kind (provided, of course, that you're going to keep the heatpipe, since you can't remove it!).
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Colin_A
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« Reply #37 on: August 21, 2008, 02:29:28 PM »

Hi CeeBee and thanks for the welcome,
I don`t have any answers but luckily i enjoy a challenge.
I`d like to experiment with the tube purely as an add-on system to a greenhouse project i have underway.
It doesn`t really matter how well it works just the fact that its "different" makes it worth a go Grin

The 58mm tube may be the better choice for me as its a bit longer than the 47mm and a similar price to the 70mm.
Ideally i`d prefer it to be a thermosyphon based system so it runs when theres enough sun to drive it.
The only downside is needing the tank above the tube but i guess with a single tube it wouldn`t need to be that big.
Logically, even without a concentrating reflector, if the quantity of water is geared pro-rata to the number of tubes/area, the temperature should be similar.
 
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Ivan
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« Reply #38 on: August 21, 2008, 03:43:34 PM »

The 70mm tube is fully evacuated - ie heatpipe suspended in evacuated glass single walled tube.


The best way to use heat without removing the heatpipe would be something like this (this is a suggestion, rather than something I've actually tried): take a baked bean can, drill hole in bottom, solder in a piece of copper pipe into hole )blanking off the top of the copper pipe. Finally, insulate can, fill with beans and place in sunshine (It'll cook a lot faster directly in the glass tube, though!

Weather's good for the weekend, so we should be doing some solar cooking demos.
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sjaglin
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« Reply #39 on: March 21, 2009, 07:17:39 AM »

WAOOOOOOOOOOOOOOOOW!!!

Thanks for this thread, it made me discover the Kelly kettle, when I read about it I couldn t believe it! That's exactly what I was looking for. I ordered it strait away and received it yesterday.

So this morning I made my coffee with the  bits I cut off my garden last year when tidying my bush (nothing rude...). Works a treat, I boil  the water, put it in a big thermos and use it through the day.

I am also working on my solar cooker/oven, I have managed to raise water temp to 72 on wednesday, I made a cup of warm tea (i don t like it hot). I am changing the design now. Here is the "old design" (see piccie).



Stef


* SolarOven1March2009.jpg (91.77 KB, 480x640 - viewed 780 times.)
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sjaglin
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« Reply #40 on: March 24, 2009, 11:08:54 AM »

Hi There,

Following my  first attempt I decided to build another solar oven. I used only recycled material : an old draw, some plastic mirrors from a perfume display (was skipped by a shop, loads of mirrors...), some cardboard and paper for the insulation...

I will try it when the sun comes back, I also need to close the top of it (cling film probably).

http://farm4.static.flickr.com/3457/3382129328_7cb0ba7425.jpg?v=0
http://farm4.static.flickr.com/3604/3382129332_50030bd795.jpg?v=0



Stef bike
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Amy
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« Reply #41 on: March 24, 2009, 11:31:20 AM »

Thats a lot of pots of stew you have there.  Grin

I hope you get it all cooked before the clouds come over.
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sjaglin
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« Reply #42 on: March 24, 2009, 09:21:13 PM »

Hi hi hi, actually my goal is a vegetarian curry and some bread, June should do it !   wackoteapot
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Ivan
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« Reply #43 on: March 24, 2009, 11:56:59 PM »

have you seen this page - solar vegetarian curry cooked on an overcast summer day - http://www.navitron.org.uk/newsdetail.php?id=21

I made a similar curry at the Navitron party last year - so a few forum members have first-hand experience. Given the sunny days we've had recently, there'd be no problem making a curry on a good day in March.

The technique easily lends itself to pasta, spagetti etc.

P.S. we're using solar tubes for heating water most days now - for pre-heat for the evening's cooking and/or cups of tea.
« Last Edit: March 24, 2009, 11:58:35 PM by Ivan » Logged
sjaglin
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« Reply #44 on: March 25, 2009, 06:43:18 AM »

Hi Ivan,

I'll try that one but 3 full pots of curry powder! Is that to use your trousers next day to cook the rice Huh  Blimme you must like it hot, I'll have to stick to a couple of spoons of curry paste, and I'll still need some yoghurt!

Stef
 surrender
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