Hello,
After reading couple threads about cheap Chinese water cooled spindles I came to conclusion, most people here have no idea how much cooling does your spindle need, so in here we will calculate:
How much water flow do you need?
How large radiator/much air flow you need?
Here we will use school level thermodynamics, so everybody should understand what we discuss.
Here we go, we will analyze how much water flow does a 2.2KW spindle need.
Assumption1 spindle is 80% efficient, so 20% directly goes to heat. Or 0.44KW is needs to be absorbed by water. In reality your spindle is not ruining 100% load all the time, so these are worst case numbers.
Wasted_power = 440W
Water_specific_heat = 4200J*kg/C How much heat does 1kg water need to absorb to rise temperature by 1C.
Water_temperature_rise = 20C We assume that water after spindle heats by 20 degrees. 20C is very conservative, in reality it can be up to 60C
Water_flow = Wasted_power / (Water_temperature_rise * Water_specific_heat * Water_density) =440W / (20C * 4200J*kg/C * 1kg/l )= 0.005l/s or 19l/h so any water flow is enough for this spindle
That is under 20 liters per hours for 2.2kW spindle under FULL LOAD
For a diy machine we will use a cheap 120mm PC water cooling radiator.
Water_temperature_rise = 20C
Air_flow = 100m3/h = 0.028m3/s In reality 120mm fan has air flow similar to 130M3/h, but lets assume that radiator provides some air resistance.
Air_specific_heat = 1000J*kg/C
Air_density = 1.3kg/m3
Air_temperature_rise = 0.5 * Water_temperature_rise = 10C
Power_dissipation = Air_flow * Air_specific_heat * Air_density * Air_temperature_rise = 0.028m3/s * 1000J*kg/C * 1.3kg/m3 * 10C = 360W
A 120mm pc radiator with fan will dissipate 360W of power if you are ok with spindle temperature 20C above room. Or a 120mm pc radiator with fan will cool a 2.2kW spindle, under FULL LOAD, with temperature rise of 25C above room temperature.
In reality 40-60C above room temperature is safe for most spindles.
PS: hope this sticks.