Message

Subject: Re: [FlyRotary] Re: Oil viscosity Date: Mon, 27 Sep 2004 09:32:39 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_84815C5ABAF209EF376268C8" ------=_NextPart_84815C5ABAF209EF376268C8 Content-type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable = Message

Some thoughts on Rusty's improved cooling with the lower viscosity=20 oil=2E If you recall, there was an earlier discussion about drilling o= ut the=20 oil passage in the iron end plate and taking the oil from there=2E I believe= Ken=20 Welter did this, and obtained about a (15 degree?) improvement in oil=20 temperature=2E The only way this effect could be possible is that the pump i= s=20 working less hard, and there is therefore less heat being generated in the o= il=20 by the action of the pump=2E

This could relate to Rusty's experience, namely a lower viscosity oil w= ould=20 require less power input to pump, and the heating due to the pump would be l= ess=2E=20 Add to this the beneficial effect of lower viscosity improving the heat=20 rejection in the heat exchanger, and I can believe the improvement is relate= d to=20 viscosity change=2E

There is an interesting NACA paper "Cylinder-Temperature Correlation of= a=20 single cylinder liquid cooled engine" published in 1946 where they studied t= he=20 effects of flow rate and coolant properties on cooling effectiveness=2E The=20= correlation of lots of data where they varied the ethylene glycol concentrat= ion=20 from 0 to 97% allowed them to determine the relative effects of heat capacit= y,=20 thermal conductivity, and viscosity of the cooling medium=2E They foun= d that=20 high specific heat, high thermal conductivity, and low viscosity are desirab= le=20 characteristics of a good cooling fluid=2E In order of importance,

Thermal conducivity (k) > heat capacity (Cp) > viscosity=20 (v)=2E

Rusty is not changing k or Cp with the lighter weight oil, and the=20 viscosity change only affects the heat transfer effect slightly, so I am lef= t=20 with the conclusion that it is the decrease in absorbed work that makes the=20= biggest difference=2E

Bill Schertz
KIS Cruis= er # 4045

----- Original Message ---= --

From: Russell Duffy [mailto:13brv3@bellsouth=2E= net]

Sent: 9/26/2004 4:39:16 PM

To: flyrotary@lancaironline=2Enet

Sub= ject: [FlyRotary] Re: Oil viscosity

5W30 seems a bit low=2E
>
>
I was thinking = the same=20 thing=2E Leon, will an
extremely light oil be able to keep the=20 seperation
between the bearings and shaft? On the other hand,
will=20= it 'wet' the walls of the cooler better and
thereby transfer heat more=20= efficiently?

Since when i= t 30 weight=20 oil is "extremely light"? You might call it extremely standard, or=20 extremely normal :-) As I understand it, the first number is the cold=20 rating, which is just for cold starting, so it doesn't have any effect on no= rmal=20 operation=2E

BTW, I made = about 3=20 trips around the airport (on the ground of course), and just made it to 140=20= degrees=2E I'm convinced it's cooling much better with the lighter (though=20= not extremely light ) oil=2E Can't wait to fly it, but next Sunday=20 is the earliest possible opportunity, and probably more like the next=20 weekend=2E

Rusty (Airbi= ke project=20 for sale cheap on eBay now, gotta make room in the garage)

<= /DIV>

------=_NextPart_84815C5ABAF209EF376268C8 Content-type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Some thoughts on Rusty's improved cooling with the lower viscosity oil=2E I= f you recall, there was an earlier discussion about drilling out the oil passage i= n the iron end plate and taking the oil from there=2E I believe Ken Welter did thi= s, and obtained about a (15 degree?) improvement in oil temperature=2E The only way= this effect could be possible is that the pump is working less hard, and there is= therefore less heat being generated in the oil by the action of the pump=2E This coul= d relate to Rusty's experience, namely a lower viscosity oil would require less power= input to pump, and the heating due to the pump would be less=2E Add to this the be= neficial effect of lower viscosity improving the heat rejection in the heat exchanger= , and I can believe the improvement is related to viscosity change=2E There is an= interesting NACA paper "Cylinder-Temperature Correlation of a single cylinder liquid coo= led engine" published in 1946 where they studied the effects of flow rate and co= olant properties on cooling effectiveness=2E The correlation of lots of data where= they varied the ethylene glycol concentration from 0 to 97% allowed them to deter= mine the relative effects of heat capacity, thermal conductivity, and viscosity o= f the cooling medium=2E They found that high specific heat, high thermal conducti= vity, and low viscosity are desirable characteristics of a good cooling fluid=2E I= n order of importance, Thermal conducivity (k) >heat capacity (Cp) > viscosity (v)=2E= Rusty is not changing k or Cp with the lighter weight oil, and the viscosity chang= e only affects the heat transfer effect slightly, so I am left with the conclusion = that it is the decrease in absorbed work that makes the biggest difference=2E =20 Bill Schertz KIS Cruiser # 4045=20 ----- Original Message ----- From: Russell Duffy [mailto:13brv3@bellsouth=2E= net] Sent: 9/26/2004 4:39:16 PM To: flyrotary@lancaironline=2Enet Subject: [FlyRotary] = Re: Oil viscosity=20 =095W30 seems a bit low=2E > > I was thinking the same thing=2E Leon, will an extremely light oil be able to keep the seperation between the bearings and shaft? On the other hand, will it 'wet' the walls of the cooler better and thereby transfer heat more efficiently?=20 Since when it 30 weight oil is "extremely light"? You might call it extremel= y standard, or extremely normal :-) As I understand it, the first number is the cold rat= ing, which is just for cold starting, so it doesn't have any effect on normal ope= ration=2E BTW, I made about 3 trips around the airport (on the ground of course), and = just made it to 140 degrees=2E I'm convinced it's cooling much better with the li= ghter (though not extremely light ) oil=2E Can't wait to fly it, but next Sunday i= s the earliest possible opportunity, and probably more like the next weekend=2E=20= Rusty (Airbike project for sale cheap on eBay now, gotta make room in the ga= rage) =09 ------=_NextPart_84815C5ABAF209EF376268C8--