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Energy : Thermal

Telescopic insulation cladding
  [vote for,

Hot fluid pipe is normally covered with insulating material and whitish cladding (aluminium/ galvanized iron etc.). The white colour functions as poor heat radiator. The proposed telescopic system would have additional black cladding that can be extended/ retracted through temperature/ photo sensor set point based motor operation. During bright sun when ambient temperature would be high, black cladding would come out and absorb solar radiation. This would maintain low or negative temperature difference between fluid and cladding surface. So either there would be reduction in heat loss or some heat transfer across insulation to the fluid. And during low ambient temperature black cladding would retract. White cladding,as usual will have minimum radiation loss.
vedarshi, Aug 05 2004

Heat sensitive paint changes color http://www.blackwel...sionid=hvDZQjiUmNC6
maybe simpler to use a variant on this? [csea, Oct 04 2004, last modified Oct 21 2004]

Smart glass products http://www.smartgla...tter-Summer2004.pdf
<< .pdf >> data data data [dpsyplc, Oct 04 2004, last modified Oct 21 2004]


       would't this be expensive?
my-nep, Aug 05 2004

       [my-nep]this is a halfbaked idea. now we need to perform cost-benefit analysis. another important aspect- this would be more useful in the places with sunshine available for major period of the year. a further consideration (it may be an independent idea but i am mentioning here)-for reasonably long fluid piping in corrosive environment coated with anti-corrosive paint & exposed to sun;if the fluid at ambient tenperature goes to some HX for getting preheated, rather than painting with fancy colours, can it be painted black or covered with airtight black cladding ? benefits are obvious.
vedarshi, Aug 05 2004

       I wonder if this can be done using auto-dimming glasses technology.
Worldgineer, Aug 05 2004

       As a limitation, wouldn't this telescoping sheath only work on straight sections of pipe, and even then not be able to retract fully?   

       Solar water heating is quite common in my neck of the woods. Would it be an improvement or alternative to existing solar panels? Is it to regulate the temperature of the fluid being heated by regulating the energy input?   

       The white material is an insulator to hold in the heat that has been absorbed, right? Putting the black cladding around the insulator doesn't seem optimal. I'd think copper tubing painted with black automobile radiator paint (minimal insulation because it goes on thin yet still covers well) with a retractable insulating sheath would be a reasonable arrangement.   

       ...just wondering and rambling, 'cause some of what you propose seems backward to my brain (which is a very poor indicator of whether something is right or not)...
half, Aug 05 2004

       [half]very true-white material must hold absorbed heat. still retractable black cladding would work. simple argument-normally temperature of white material which covers insulation, 8~10degC above ambient is OK. If white material temperature reaches 50 degC and our telescopic black cladding unfolds in bright sunlight, it would quickly acquire temp.greater than 50 degC. won't this reduce heat loss to ambient from the fluid flowing in the pipe?
vedarshi, Aug 06 2004

       I dont understand the retraction... Wont black on the outside white/silver on the inside be optimal all year round?
madness, Aug 06 2004

       I guess maybe I don't understand the primary purpose of the proposed system. Is it to keep heat in or to absorb heat from the environment? I assume that you intend to do both.   

       Applying an insulating material directly to the tube would certainly prevent the contents from transferring heat to the ambient air. Indeed, a black surround would gain heat from the sun. However, the placement of the insulation as described would cause the heat gain to be minimized due to the very nature of insulation.   

       Sorry, I guess I must be missing something. Maybe it would help me if you provided a clear problem statement and an explicit application scenario.
half, Aug 06 2004

       Trying to get energy out of thermals, eh? j/k   

       Interesting, but the way you go about it wouldn't benefit very much. If there was a way to lose the insulation while the sun was shining on the black surface, then we'll talk bun.
destructionism, Aug 06 2004

       [half]ok i realize that my description was poor enough to cause confusion. i would describe it again (please read it thoroughly-there is redundancy in description only to remove confusions) : ..... HB IDEA NO. 1 : Take the example of superheated steam pipe covered with rockwool and aluminium cladding (i.e.white colour). for economy, as a standard practice, rockwool thickness is selected such that if temperature on its (rockwool) outer surface or the temperature of cladding is 8~10 degC above ambient (when steam is flowing at its normal design pressure, temp.)it is tolerable wrt heat loss. white cladding naturally minimizes radiation loss. .....NOW COMES THE SUGGESTION : on the portion of such pipe covered with rockwool and white aluminium cladding & exposed to sun (i.e. excluding the pipe portion running through shaded area),if a telescopic black coloured cladding is provided which would unfold or retract on the basis of certain positive temperature difference between outer black cladding surface temperature & inner white (existing permanent aluminium cladding) surface temperature, radiation loss to ambient may be reduced. in other words, if white cladding surface temp is 50 degC and black cladding surface temp is 55 degC (or much higher depending on intensity of solar radiation/ money you put in for selective radiation absorption material for black cladding)the radiation loss from inner permanent white cladding to ambient would reduce BECAUSE a) there would be some air gap between white cladding & retractable black cladding & b)heat will flow from black cladding to white cladding. When black cladding temp.drops due to whatever reasons (sunset,overcast sky etc.), the black cladding would retract & only white permanaent cladding would be there as usual.IMPORTANT- if there is no air gap between white cladding & black cladding, it may or may not in fact increase radiation loss from steam piping to ambient. .....HB IDEA NO.2 : Fluid piping in corrosive environment is coated with anti-corrosive paint.In situations where such pipe runs through open area (i.e.directly exposed to sun)and the fluid being pumped at ambient temperature goes to some HX for getting preheated, rather than painting such pipe length between pump & HX with fancy colours it can be painted black or covered with airtight black cladding (there would be no insulation in this case). Now you have nothing to lose. During availability of enough solar radiation, fluid would be preheated to some extent depending on obvious governing factors. And when there is no radiation, the fluid would remain equal to ambient temperature (micro analysis would tell that there would be little heat loss because very slight increase in fluid temperature across the pump would again drop between pump & HX due to black body radiation). ..... I am sorry to use many words again & again and also being too redundant but I feel this would make it clear to you, what I had in my mind. Now please comment whether it can graduate from HB to B or I need to do another B - Bury this idea :)!!!
vedarshi, Aug 06 2004

       Wait a minute...If you have a insulated super-heated steam pipe(+200*F?) whitch has an external temp. of +8*F, and you put it in a green house (that is effectivly what this is) 20*F warmer than ambeint, doesn't it only reduce the temp. difference between pipe and air by .8*F?   

       That hardly seams worth-while.
my-nep, Aug 06 2004

       [my-nep]a)how have you arrived at the figure of temp. difference between pipe and air = .8*F? b)any comments on HB idea no.2 - whether it is worthwhile or not.
vedarshi, Aug 07 2004

       [my-nep] Adding an amount of heat less than the total temperature doesn't cool the object any. Nor will it make it any hotter, but, the heat appplied will increase the time it takes for the object in question to cool down.
destructionism, Aug 07 2004

       At this point, my thoughts on the subject would be:
hitting enter twice in your text will create a paragraph break.
Typing <br>will create a line break
If you have two separate ideas, post them separately.

       So, about the idea I've been focusing on...I think it will have some of the effect that you're hoping for. But, for all your explanation I still wonder if you might not just be better off with more insulation. Either that, or use a conventional solar water heater and it's controls along with some sort of coaxial tube or other heat exchanger inside the insulated tubing arrangement.   

       I'm not saying that your concept won't work. I'm just saying I wouldn't implement it that way. If there is some need to implement the arrangement you discuss, then I'd be forced to focus on the design of the retractable sheath. It would be difficult to make it retract as it would need to have segments somewhat like a car antenna and would only stack down to so small an area. If someone paid me to implement a black sheath around a white insulator, I'd probably split the black sheath lengthwise and have it open "clamshell" style.
half, Aug 07 2004

       [half] you have a very good sixth sense. i was in fact struggling about how to create paragraph break/line break. Many thanks for the tips. Another problem I always face is that after posting new idea, the boxes to be filled in don't disappear. What is the correct way to avoid it ?   

       I would repeat that these are half baked ideas (they are more or less the same hence I did not post them separately) and open for any variation.
The goal for idea no.1 is to reduce/minimize heat loss from fluid piping using solar energy at minimum cost.
For idea no.2 the goal is to simply change some practice involving no additional investment but gaining something in return, even if it is minor.
vedarshi, Aug 07 2004

       You're most welcome.   

       After posting an idea, it is normal for the boxes to still be available to you. This is by design. It permits you to edit the idea after posting.   

       It is fairly common practice to revise one's ideas to provide clarity by adding something or removing some ambiguity.
half, Aug 07 2004


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