Creating fluid flow in an insulated system

[beerbaron]

I'm searching for ways to create a liquid flow to increase heat transfer.

The coolant temperature is -15 celcius so as the ambiant temperature. Problem is that this system is insulated and therefore I cannot use an outside electrical current to power a pump.

Here are my stats:
Create a medium flow to increase heat transfer of about 30-40%
Volume of 4 liters of fluid coolant
Operating temperature of the system -15 celcius
Flow must last 3 minutes

Here are the solutions I found:
Use a small water pump and some batteries (problem is batteries are weak at those temps)
Use some sort of mechanical system that would create a flow (maybee spring system like those used in toys)
Put the system on a spring and give it initial movement, spring will oscillate and keep the flow for some time.

Any suggestions will be appreciated!

BeerBaron

 

[JJPellin]

I'm not sure if I fully understand the question. But the first thing that occurs to me is to pipe the system so as to maximize thermosiphon. Put the heat source at the low point in the system and the cool source at the highest point. Slope the piping and place the connections so the heat tends to rise and the cold to drop. Thermosiphon circulation is commonly used for mechanical seal barrier fluid system. Even if you plan to use a pump or other method, piping for thermosiphon would make the system more efficient and increase circulation. Of course all of this assumes that you have a close loop system that recirculates the same coolant.

 

[louieho]

Would using magnetism a possibility? This way you can drive your system from outside.

 

[stanier]

if you had bottled gas you could use a gas/liquid accumulater

 

[beerbaron]

Louieho: No, magnetism woudln't be possible. It's in has a cage of Faraday around it (metal box).

Stanier: Gas/Liquid accumulater... what exactly do you mean?

BeerBaron

 

[stanier]

Basically its acylinder with a gas supply to one side and liquid on the other. As you apply the gas pressure the piston moves and expels the liquid.

An alternative might be a ferrous plug in your pipe with a mag lev device on the outside to acceleratoe the plug thus moving the liquid.

 

[beerbaron]

Thanks stanier... interresting even tough I can't use is in my application.

BeerBaron

 

[sterl]

The heat is that of fermentation? Where is the Temperature Difference we're trying to shorten or at least raise the slope of?

The thermosiphon sounds like a very nice solution though at this scale I think I would simply source some heat pipes...They are commercially available and need only a few degress of TD to work reasonably well.

But either system requires Temp Diff and specific orientation/ installation arrangements....Where's the TD?