SHORT:

I want a valve functionally equivalent to a car's "thermostat" as used in
vehicle radiator system but MUCH smaller.
Use is temperature regulation of a low volume flow.
(Somewhere in 0.1 cc /s  - 5 cc/s range). (eg may be 0.1 - 1 or 1-5 etc) tb=
d
Some leakage bearable as long as << min flow rate

Temperature entering valve rises when flow restricted.
Temperature entering valve falls when flow occurs.
Time constants ideally < to << a few seconds

Could be :

- Electrically controlled (solenoid etc) with external temperature sensing.
Ideally zero current when not adjusting
or
- Mechanical with  no-electrical power - eg bimetallic ...

Example solution:

A miniature servo with cam constriction of a flexible pipe (a la
peristaltic pump) + electronics would work well.
Care needed with size, lifetime.  No servo current when temperature is
stable.


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

More

Temperature controlled valve wanted suitable to control liquid flows in 0.1
cc /s  - 5 cc/s range.
Self switching using bimetal or other means "nice".
Electrically switchable valves also of interest - see below.
Linear change in flow restriction over a small delta T useful if it allows
self adjustment to stable temperature.

Set point temperature needs to be at least settable by design and ideally
field or factory adjustable.

Size - smaller is better.
Two dimensions:
5 - 10 mm awesome,
10 - 20mm OK,
20 - 30 ~~=3D,
30mm + -> magic needed

Third dimension
5 mm <=3D good <=3D 10 mm <=3D bearable <=3D 15mm <=3D not really unless st=
unning <=3D
20mm <=3D Needs top be magical

Sensing by capillary tube or similar OK if price right and may be useful.

Cost: "low"  (Divide anything in McMaster Carr catalogue by factor of 10 to
50 in $ and size).
$1 Good
$1-$5 ~~
More -> magic needed.

Volume: Large.

___________________________________


This is a bit 'stream of consciousness'
Ask for clarification if possibly able to help.


EE / TECH / OT - decisions decisions ...

Nasty hybrid / anciem cgs like units - for various almost good reasons.
(cc of water ~=3D 1 gram and various things not covered here get easier on
the brain).
mm creep in.
Some of these will not get used here.

cm =3D 10 mm
cc =3D cm^3 =3D E3 mm^3 =3D E-6 m^3
l =3D litre =3D 1000 cc =3D ...
SG =3D density of water =3D 1.000000... (on planet concerned)
g =3D 10 m/s/s

I require a "valve" with functionality similar to that of a car radiator
thermostat but for uses with
  lower temperatures and
   average flow rates somewhere in the range 0.1cc to 5cc/second.  !!!

      0.1 - 5 cc/s      =3D ~ 0.4 litre to 20 litres an hour.
               (Fills a 200cc coffee cup  in 30 minutes to 36 seconds

If 5 mm ID circular tubing/piping ... is used.
Area at 5mm ID =3D 20 mm^2 =3D 0.2 cm^2

At 0.1cc/second flow velocity is 0.5 cm/s =3D 5mm/s
At  5 cc/s V =3D 25 cm/s =3D 250 mm/s

I'm seeking to control a very low volume water flow in order to regulate
temperature.

Car thermostats have no external housing and are fitted into a premade
housing - in my case either a standalone thermostat or one which needed a
housing would be acceptable.



Several flow rate ranges may be required - not necessarily the same valve
in each case but a common one would not hurt.

In each case it is desirable that the when the valve and connecting pipe
assembly is placed on a flat surface with all pipes in the same plane as
the surface (aka flat on a desk or whatever) then the 3rd dimension /
vertical height be minimised.
  5mm 'height" would be marvellous
  10mm height is getting 'large'
  15mm to 20mm is rather larger than I would like but MIGHT be OK if all
other features were superb. Unlikely.


Minimum operating hours >=3D  64 x $cost :-)
Longer and dearer better
40 hours minimum
Much longer fine if $ suitably low.


     Russell
--=20
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