Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.physics > #680304

Re: What color water tank is best?

Show all headers | View raw

Dne 08/04/2018 v 06:58 micky napsal(a):
> 
> Assume a large metal tank of water is placed on top of a house to
> provide hot water for the kithen sink and the bathroom sink and tub. 
> 
> Assume sundown is at 6.  What color should the tank be?
> 
> AIUI, white will not absord the heat as well, but it will keep the heat
> it does absorb longer, so there will be hot water until 7,8,9 PM
> 
> But black will absorb the heat faster, will be able to absorb more heat
> on grey days, and will have hot water ready by noon instead of 2PM.
> However it will cool off sooner and the tank will be losing heat even
> maybe before sundown and very likely the water will be almost cold by 7.
> 
> 
> Which of my statements, clauses, adjectives, are incorrect?
> 
> What color should the tank be for best hot water?   The most hot water? 
> 
> 
> Ignore the possibility of sometimes using a supplemental electric
> heater, except that the solar heater is to be designed to make that as
> little necessary as possible.. 

Why do you post the same question again,
when you have already got a lot of answers ?

The majority of absorbed energy is visible light, not heat,
as majority of incident power is in visible range.
The heat is created when the light is absorbed.

In thermal IR region, both black and white colours
are generally comparably "IR black or at least dark",
in sense of absorption and emission of thermal IR.

Therefore, heat loses difference is negligible.
( Blacking of electronic cooler radiators is
 because they are metallic, not light,
and difference is not drastic )

So, the solution is black. FIG 1

Optional, but with high advantage,
is to create a passive water circuit, FIG2
with the collector separated from a reservoir,
powered by water density difference.

The collector is best to have a low volume,
from set of black tubes,
surrounded by focusing reflecting surface,
like alufoil in half circle shape.
This would increase the water temperature

Separation of the collector and reservoir
has another reason for higher efficiency:

Until the reservoir is full,
the collector is still filled by cool water,
so water heating rate is not disturbed.


------------------------------------

Watch with a monospace font.

FIG 1

3
<-----o---------------------------o
      |                           |
      | water down                |  water up
      |                      ----------
      |                      |        |
      |                      |   2    |
      |                      |        |
..... |......................|........|.....
      |                      |        |
      |                      |        |
      |                      |        |
      |                      ----------
      |                           |
      |                           |           1
      \-------------------------- o---------<-

1 - a water supply
2 - a black reservoir
3 - to warm tap water
. - floating cold/warm water fuzzy boundary.


FIG 2
<-----o-<-/------------------\
  3   |   |      4           |
      |   \------------------/--<-\
      |                           |
      |                           |
      |                           |
      |  water down               | water up
      |                           |
..............................................
      |                           |
      |                           |
      |                           |
      |                      ----------
      |                      |  |  |  |
      |                      |  |  |  |
      |                      |  |  |  |
      |                      |  | 2|  |
      |                      |  |  |  |
      |                      |  |  |  |
      |                      ----------
      |                           |
      |                           |       1
      \-------------------------- o-----<---

1 - a water supply
2 - a black collectors with reflective focusing alufoil.
3 - to warm tap water
4 - insulated warm water reservoir ( any colour )
. - floating cold/warm water fuzzy boundary.



-- 
Poutnik ( The Pilgrim, Der Wanderer )

A wise man guards words he says,
as they say about him more,
than he says about the subject.

Back to sci.physics | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

What color water tank is best? micky <NONONOmisc07@bigfoot.com> - 2018-04-08 07:58 +0300
  Re: What color water tank is best? Libor 'Poutnik' Stříž <poutnik@privacy.net> - 2018-04-08 10:39 +0200
    Re: What color water tank is best? Libor 'Poutnik' Stříž <poutnik@privacy.net> - 2018-04-08 11:10 +0200
    Re: What color water tank is best? Gaston Levell <jno@itwjwg.tn> - 2018-04-08 10:53 +0000
      Re: What color water tank is best? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-04-08 17:28 +0200
      Re: What color water tank is best? Lofty Goat <rlwatkins@gmail.com> - 2018-04-08 20:12 -0500
        Re: What color water tank is best? Sergio <invalid@invalid.com> - 2018-04-09 12:30 -0500
          Re: What color water tank is best? Mahipal <mahipal7638@gmail.com> - 2018-04-13 22:59 -0700
            Re: What color water tank is best? benj <benj@nobody.net> - 2018-04-14 13:49 -0400
              Re: What color water tank is best? Libor P Striz <poutnik@privacy.net> - 2018-04-15 07:27 +0200

csiph-web