Oil spray cooling of rotor 1

[UKpete]

I need to design an oil-spray cooling system for the rotor of a high-speed motor. The plan is to spray each end-face of the rotor using the bearing oil supply. The rotor speed is 40krpm and the temperature approx. 160degC, the oil temperature is 75degC. The rotor internal losses amount to about 300W.

I have seen some likely looking spray nozzles, but I need to estimate the heat transfer coefficient on the rotor surface. Does oil spray cooling work in the same way as water spray cooling?

Can anyone help please?

 

[quark]

The oil spray cooling is not like water spray cooling. There will only be sensible heat change in the oil.

For example, 1 kg of water can absorb 1 kCal of heat if it's temperature should not rise by 1⁰C. Where as 1 Kg of water can absorb 550 kCal of heat upon evaporation. So you require less water flow rate to cool the things upon evaporation.

If you are using oils with a boiling point lower than 160⁰C then it is ok. But there will be other problems of metal compatibility.

If everthing works out to be ok, you can consider total 300 Watts being transferred to the oil provided you make a fine mist of the oil.

However, it is helpful if you provide some data regarding the oil to be used and the spray system.

Regards,

 

[UKpete]

quark, thanks for your reply. I have been trying quite hard to get some info but there doesn't seem to be a lot out there.

I understand your comments, the reason I mentioned water is because I have read of its use for spray cooling eg industrial food processing, but as you say a different mechanism (evapouration) is being used.

My application is automotive-related, so the oil is a standard SAE 10W-40 engine oil such as Castrol Magnatec. I have quoted an oil temperature of 75degC as we already have an oil cooler on board.

The nozzles I have seen are from a US company called Lee (I can't remember any other details), and I was just curious to know what approximate heat transfer coefficient I could expect from a surface spinning at high speed.

 

[quark]

Pete!

I am very sorry that I couldn't be of much help. None of my HT books deal with this subject. I could have tried some conventional methods to get a rough solution but chances of evaporation on the rotor surface (which may restrict the heat flow) and high rotational speed (liquid particles may be thrown away, thus minimizing contact period) are bothering me.

However, upon searching yahoo I got one exact reference about a paper by a PhD student at this link.

http://www.eas.asu.edu/~mae/05_res/combustion_lab/personnel.html

(third paper from bottom)

I think you will get better advice from academic engineers(because most of the references I got from yahoo search are research papers).

I wish you good luck.

Regards,

 

[UKpete]

ok but thanks for looking. I think I need to go into a search of academic papers, see if I can find some experimental results. I would do some experimental work myself but it's expensive.

Regards