REFLECTOR: Oil temps

[John Dibble]

Al - Yes, greater flow will result in a greater delta T.  With the
cooling air temp remaining the same, the oil exiting the cooler MUST be
warmer.

Chuck - I'd love to see some data with the TC on the inlet.

John

Chuck Jensen wrote:

> Al,Good explanation.  Hard to believe but I could actually get my head
> around the thermodynamic explanation.  Perhaps the higher oil temp is
> a combination of the two; higher horse power as Scott surmised and
> greater oil flow as John postulated.  Even though the amount of heat
> rejected by the oil cooler is higher with higher oil flow, a temp
> sensor downstream of the oil cooler may still be hotter with the
> higher oil flow at higher rpm.  As always, everything is related to
> everything. Chuck Jensen
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
> On Behalf Of Al Gietzen
> Sent: Monday, May 28, 2007 6:49 PM
> To: 'Velocity Aircraft Owners and Builders list'
> Subject: REFLECTOR: Oil temps
>
>
> I see higher oil temps at higher rpms also.  I think the reason is
> that the oil pump is a positive displacement pump which means the
> amount of oil pumped is proportional to rpm.  The cooler can not cool
> a greater flow down to the same temp as a lower flow.
>
> John
> SERG/Franklin
>
> Other things being equal; higher flow results in a higher heat
> rejection capability.  It decreases the fluid side temp drop, which
> increases the average temperature, and if the air temp is the same;
> increases the average delta T from fluid to air, increasing the heat
> rejection.  I know; it may seem counterintuitive, but the
> thermodynamics works that way.
>
> The increased rpm increases the hp a bit, and would increase the oil
> temp.
>
> Al
>
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