Chosing the right needle valve

[lurklaban]

Hi all!

We're running a CM machine and for control of reflux condenser water flow a needle valve was purchased. However, it turned out not to bee as easy to adjust as hoped - of the 1 and 3/4 turns available on the valve, less than 1/4 of a turn was used (that is, from closed to full reflux, less than 1/4 of a turn was needed leading to Verry sensitive adjustments where you really wasn't sure if you had moved the turning wheel at all but still sometimes could make quite a big difference in output)

Now my naive brain thought that since the current needle valve was 10 mm (about 3/8 inch), a needle valve of 1/8 inch would give about 1/9 of the cross-sectional area and hence make the available range for adjustment greater. A needle valve of 1/8 inch was ordered from Aliexpress, but - to my great dissapointment - the results was still quite the same as with the 10 mm valve.

Any sugestions on what's wrong and how to know what needle valve to use or if there is another way to make the adjustments less sensitiv? (We did lower the pressure from the water outlet from 2kg to 1 kg and it made some difference, but not much...

Regards
LurkLaban