mklotz
Well-Known Member
I want to build a fluidyne Stirling pump so I decided that it might be a good idea to see if I could get a liquid piston Stirling to operate.
The prototype is butt-ugly
to the point that it's difficult to see how it operates. The glue used to secure the plastic blocks that form the engine, in combination with the heat from the resistor, caused the plastic to craze.
The back view shows the leads from the resistor but still isn't terribly revealing.
This diagram
will explain the operation.
Plastic blocks (crosshatched) cemented between two plastic sheets form a compartment which is partially filled with water. A volume of air is trapped by the blocks and the water. On the 'hot side' of the engine, a 22 ohm, 5 watt power resistor (labeled R in the diagram) is immersed in the water. Its leads project through the back of the engine (via holes sealed with silicone cement).
When the resistor is heated by an external 13 VAC transformer, the entrapped air is heated and expands, pushing the water in the main cavity down and causing the water in the channel labeled A to rise.
The air cools when it contacts the water in the far right channel. The water level falls to the level shown and the whole process repeats as long as power is supplied to the resistor.
The net effect is that the water column at A oscillates up and down. Not at all spectacular visually but the clever mind will note that this oscillation can be harnessed to pump water.
Imagine channel A connected to a bog-simple pump - a length of tube with two ball check valves and the connecting T between these two valves. As the water pressure in the A channel oscillates, so will the water pressure between the two valves oscillate with the result that water is pumped.
I took the design for this prototype from an article in Scientific American's "Amateur Scientist" column (which means the plans are copywrite protected).
It's fascinating to watch this thing, ugly as it is. With no moving parts (save a quantity of water), the water in the output tube magically rises and falls.
Next step is to build a larger version using pipe and add the pump.
The prototype is butt-ugly
to the point that it's difficult to see how it operates. The glue used to secure the plastic blocks that form the engine, in combination with the heat from the resistor, caused the plastic to craze.
The back view shows the leads from the resistor but still isn't terribly revealing.
This diagram
will explain the operation.
Plastic blocks (crosshatched) cemented between two plastic sheets form a compartment which is partially filled with water. A volume of air is trapped by the blocks and the water. On the 'hot side' of the engine, a 22 ohm, 5 watt power resistor (labeled R in the diagram) is immersed in the water. Its leads project through the back of the engine (via holes sealed with silicone cement).
When the resistor is heated by an external 13 VAC transformer, the entrapped air is heated and expands, pushing the water in the main cavity down and causing the water in the channel labeled A to rise.
The air cools when it contacts the water in the far right channel. The water level falls to the level shown and the whole process repeats as long as power is supplied to the resistor.
The net effect is that the water column at A oscillates up and down. Not at all spectacular visually but the clever mind will note that this oscillation can be harnessed to pump water.
Imagine channel A connected to a bog-simple pump - a length of tube with two ball check valves and the connecting T between these two valves. As the water pressure in the A channel oscillates, so will the water pressure between the two valves oscillate with the result that water is pumped.
I took the design for this prototype from an article in Scientific American's "Amateur Scientist" column (which means the plans are copywrite protected).
It's fascinating to watch this thing, ugly as it is. With no moving parts (save a quantity of water), the water in the output tube magically rises and falls.
Next step is to build a larger version using pipe and add the pump.