Yes to get 50 microns you need a double stage pump with fresh oil, I found is quite easy to make heat pipes from soft copper tube, pinch and solder both ends, drill a small hole at one end and solder a short length of 1/8 copper tube for the vacuum pump connection, squirt in the water with a syringe then place in the freezer for a few hours. Connect up the pump using a flexi connection leaving the heat pipe in the freezer, leave pump running for 10 minutes or so, a good vacuum gauge helps as it shows how close to a near vacuum you are getting, any water vapor will prevent a good vacuum and register on the gauge. Crimp the 1/8 pipe, cut and solder to seal.
To see how effective the pipe is dunk one end in luke warm water, listen with an ear to the pipe, you should hear it boiling, place in hot water, the other end gets hot instantly.
The U tube video shows acetone being used as this boils at a lower temp than water, I tried it and works as described, ok for solar where the temps > 40c, but it doesn't work below 40c, would have to evacuate the pipe properly, ...rather difficult when it doesn't freeze.
Heat recovery still being worked on, not enough hours in the day.
Mike
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