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

Groups > sci.electronics.design > #447477

Re: Window Heater

Show all headers | View raw

On 2/12/2017 7:57 AM, bill.sloman@ieee.org wrote:
> On Sunday, February 12, 2017 at 5:02:38 PM UTC+11, rickman wrote:
>> On 2/11/2017 11:57 PM, bill.sloman@ieee.org wrote:
>>> On Sunday, February 12, 2017 at 2:02:37 PM UTC+11, rickman
>>> wrote:
>>>> I sit directly under a window much of the time (don't suggest
>>>> I move, there just isn't another practical option).  When it is
>>>> cold the window has a draft that is downright brutal.  I
>>>> plugged the window with a 3/4 inch piece of Styrofoam
>>>> insulation and the draft persists (sealed with tape around the
>>>> edges).  Seems even a couple of degrees difference with the
>>>> room air can create a draft that is cold enough to be a bother.
>>>> The wall around the window reads 66 degrees while the Styrofoam
>>>> reads about 64 degrees.
>>>>
>>>> I thought maybe the way to deal with the draft is to fight
>>>> cold with fire.  So I bought a few power resistors in the metal
>>>> cases that can be mounted.  I wired them in series and
>>>> connected a variable supply as I didn't know how much power I
>>>> would need. Turns out a fair amount.  If I crank up the heat to
>>>> around 30 to 40 watts with the resistors right behind me on the
>>>> sill of the window, the draft is gone.  Not bad.
>>>>
>>>> But I was wondering how best to mount them.  At this wattage
>>>> they get pretty warm, around 200 degrees!  I was looking at
>>>> sheet aluminum to mount them to thinking just a couple/three
>>>> inches of height would do the job.  But now I am wondering.
>>>> I'm not sure a string of resistors along a three inch wide
>>>> sheet of aluminum would reduce the temps that much and I'm not
>>>> at all clear on how that might affect the airflow.
>>>>
>>>> I am thinking of a much wider sheet that would not get so hot.
>>>> I am also thinking it would help better to cut the draft by
>>>> being larger. I'm thinking it would give rise to a reverse
>>>> draft and possibly require less heat.
>>>>
>>>> So which is better, a small hotter heat source or a spread out
>>>> lower heat source.  I suppose covering the entire windows with
>>>> aluminum would be the best approach, but I'm not ready to do
>>>> that. So maybe 12 inches of aluminum sheet?
>>>
>>> A more sensible approach would be to replace the single layer of
>>> glass in the window with double-glazing. You can use a second
>>> sheet of polycarbonate space off from the glass by about 10mm to
>>> dramatically reduce heat losses.
>>
>> What part of my post made you think the glass was single pane???
>
> The fact that you could feel a draft.

Yeah, that's what I thought.  I expect I would feel the draft from the 
wall if I were sitting with my back to that.  It's not a windstorm, it's 
a slow, cool draft that makes my shoulders ache.


>>> In the UK this was called secondary double glazing and you could
>>> buy a kit of parts at do-it-yourself shops. Typically it went
>>> onto the window frame, rather than onto the glass itself.
>>>
>>> If the window is deep enough, you can just measure the dimensions
>>> of the window, order a suitable double-glazed pane from your
>>> neighbourhood glazier, and replace the existing single pane of
>>> glass with the double-glazed assembly.
>>>
>>> I've done both. The replacement pane is neater. Don't forget
>>> that window glass isn't a tight fit inside the window frame - you
>>> need a 6mm (0.25 inch) gap between the glass and the frame which
>>> is filled by putty or non-setting glazing compound - to take up
>>> differential expansion.
>>>
>>> Triple glazing is even better. Apparently the Swedish love it.
>>> The panes get a bit deep.
>>
>> I tried it.  The window is already double glazed and I added a
>> layer of plastic sheet (they sell kits for this).  It helped, but
>> no more (likely less) than the 3/4 inch Styrofoam.  I don't recall
>> if I've tried both.
>
> Making the gap too big allows convention currents between the panes.
> Styrofoam is essentially stabilised air - the individual cells are
> too small to allow convection.
>>
>> My original idea with the heater was to add the plastic with the
>> heater in the space between the plastic and the Styrofoam.  I
>> expected that to use very little extra heat.  But I don't like the
>> plastic sheet and wanted to try this.
>>
>> Now that I think of that, heating the space behind the plastic
>> reminds me of your ultra fine temperature controller.  You put the
>> sensor and the heater at the thin spot in the insulation.  Heating
>> the space in the window would completely stop the draft.
>
> The "ultra-fine" temperature controller was aimed a getting tight
> control of temperature over a volume about 1cm square and less than a
> millimetre thick.
>
> As the paper said, we could have done better if we could have
> insulated the volume of interest better, and hadn't had to leave
> clear spaces for access.
>
> You want to get rid of a specific temperature gradient, essentially
> from the middle of your window to the wall surrounding it.
>
> Putting a heat source in the middle of your window may well do it.

There is no reason on earth to heat the middle of the wall.  Heating the 
surface would be much better, less heat loss to the outside.


> The high-tech solution - as used in car windows which you don't want
> to mist up - is an electrically conductive and transparent layer of
> tin oxide.
>
> http://www.techbriefs.com/component/content/article/ntb/tech-briefs/materials/3363
>
>
>> The surprising part of the whole thing is just how small a
>> temperature difference will result in a draft.  I only measure 2 or
>> 3 degrees difference between the Styrofoam and other objects in the
>> room, yet the draft forms when it is very cold out.  Likely the
>> walls also create a draft, but not as pronounced.  Sitting with my
>> back to the window doesn't help, but like I said, no practical way
>> to deal with that.
>
> Curtain? A draft is just a convection current, and if you confine
> that convection current so that it doesn't actually run down you
> back, you should be fine.
>
> If you wanted to go very high tech, you could work out the Rayleigh
> number.
>
> https://en.wikipedia.org/wiki/Rayleigh_number
>
> It does depend on the cube of the characteristic length, and making
> the convecting volume thin does help.
>


-- 

Rick C

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

Thread

Window Heater rickman <gnuarm@gmail.com> - 2017-02-11 22:02 -0500
  Re: Window Heater bill.sloman@ieee.org - 2017-02-11 20:57 -0800
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 01:02 -0500
      Re: Window Heater whit3rd <whit3rd@gmail.com> - 2017-02-11 23:07 -0800
        Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 03:52 -0500
          Re: Window Heater whit3rd <whit3rd@gmail.com> - 2017-02-12 18:32 -0800
            Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 21:42 -0500
              Re: Window Heater "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-13 10:04 -0600
                Re: Window Heater makolber@yahoo.com - 2017-02-13 10:17 -0800
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-13 15:30 -0500
                Re: Window Heater "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-13 15:39 -0600
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-13 20:28 -0500
                Re: Window Heater krw@notreal.com - 2017-02-13 20:48 -0500
                Re: Window Heater Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-13 13:47 -0800
            Re: Window Heater dagmargoodboat@yahoo.com - 2017-02-14 06:56 -0800
              Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-14 07:17 -0800
                Re: Window Heater dagmargoodboat@yahoo.com - 2017-02-14 13:20 -0800
                Re: Window Heater George Herold <gherold@teachspin.com> - 2017-02-14 16:17 -0800
                Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-14 16:28 -0800
                Re: Window Heater George Herold <gherold@teachspin.com> - 2017-02-14 17:42 -0800
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 21:18 -0500
                Re: Window Heater dagmargoodboat@yahoo.com - 2017-02-14 19:20 -0800
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 22:42 -0500
                Re: Window Heater George Herold <gherold@teachspin.com> - 2017-02-15 06:51 -0800
                Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-15 06:06 -0800
                Re: Window Heater George Herold <gherold@teachspin.com> - 2017-02-15 06:54 -0800
                Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-15 09:15 -0800
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-15 15:02 -0500
                Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-15 16:38 -0800
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-15 19:50 -0500
                Re: Window Heater Martin Brown <|||newspam|||@nezumi.demon.co.uk> - 2017-02-17 11:18 +0000
                Re: Window Heater Martin Brown <|||newspam|||@nezumi.demon.co.uk> - 2017-02-16 08:28 +0000
              Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 14:07 -0500
                Re: Window Heater dagmargoodboat@yahoo.com - 2017-02-14 12:57 -0800
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 17:32 -0500
                Re: Window Heater dagmargoodboat@yahoo.com - 2017-02-14 19:12 -0800
              Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 14:16 -0500
                Re: Window Heater dagmargoodboat@yahoo.com - 2017-02-14 12:53 -0800
                Re: Window Heater John S <Sophi.2@invalid.org> - 2017-02-14 16:14 -0600
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 17:35 -0500
                Re: Window Heater John S <Sophi.2@invalid.org> - 2017-02-15 10:45 -0600
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-15 15:06 -0500
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-15 16:46 -0500
                Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 17:34 -0500
      Re: Window Heater bill.sloman@ieee.org - 2017-02-12 04:57 -0800
        Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 18:19 -0500
      Re: Window Heater Winfield Hill <hill@rowland.harvard.edu> - 2017-02-12 10:42 -0800
        Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 18:30 -0500
    Re: Window Heater Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-12 08:45 +0000
      Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 03:57 -0500
        Re: Window Heater Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-12 09:34 +0000
  Re: Window Heater Jon Elson <elson@pico-systems.com> - 2017-02-11 23:52 -0600
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 01:07 -0500
      Re: Window Heater Martin Brown <|||newspam|||@nezumi.demon.co.uk> - 2017-02-14 10:40 +0000
        Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 06:00 -0500
          Re: Window Heater John S <Sophi.2@invalid.org> - 2017-02-14 16:17 -0600
            Re: Window Heater Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-14 14:28 -0800
            Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-14 17:36 -0500
  Re: Window Heater Mikko OH2HVJ <mikko.syrjalahti@nospam.fi> - 2017-02-12 14:54 +0200
    Re: Window Heater Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-12 08:56 -0700
      Re: Window Heater Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2017-02-12 20:14 +0200
        Re: Window Heater Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-11 00:30 -0500
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 18:56 -0500
  Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-12 06:35 -0800
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 19:01 -0500
      Re: Window Heater "dcaster@krl.org" <dcaster@krl.org> - 2017-02-12 17:29 -0800
        Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 21:37 -0500
          Re: Window Heater Jon Elson <jmelson@wustl.edu> - 2017-02-13 15:08 -0600
            Re: Window Heater Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-13 13:32 -0800
  Re: Window Heater Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-12 08:20 -0800
  Re: Window Heater "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-12 11:48 -0600
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 19:03 -0500
      Re: Window Heater "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-13 09:58 -0600
        Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-13 15:33 -0500
          Re: Window Heater Jon Elson <jmelson@wustl.edu> - 2017-02-13 15:10 -0600
            Re: Window Heater Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-13 13:36 -0800
            Re: Window Heater "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-13 15:40 -0600
            Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-13 20:34 -0500
          Re: Window Heater krw@notreal.com - 2017-02-13 20:52 -0500
  Re: Window Heater Tim Wescott <seemywebsite@myfooter.really> - 2017-02-12 12:02 -0600
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 19:05 -0500
      Re: Window Heater Tim Wescott <seemywebsite@myfooter.really> - 2017-02-14 17:49 -0600
  Re: Window Heater bitrex <bitrex@de.lete.earthlink.net> - 2017-02-12 13:06 -0500
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-12 19:05 -0500
  Re: Window Heater Clifford Heath <no.spam@please.net> - 2017-02-13 11:21 +1100
  Re: Window Heater krw@notreal.com - 2017-02-12 19:28 -0500
  Re: Window Heater Martin Riddle <martin_ridd@verizon.net> - 2017-02-12 21:57 -0500
    Re: Window Heater "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-13 10:01 -0600
  Re: Window Heater Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-13 13:49 -0800
    Re: Window Heater rickman <gnuarm@gmail.com> - 2017-02-13 20:36 -0500
  Re: Window Heater rickman <gnuarm@gmail.com> - 2017-03-01 19:44 -0500
    Re: Window Heater George Herold <gherold@teachspin.com> - 2017-03-01 17:33 -0800

csiph-web