[PSUBS-MAILIST] Motor Pod Ventilation

[Sean T. Stevenson]

A couple of things - first, the specific heat capacity of water is much
greater than that of air, so effective cooling can be effected even with
small delta-T's.  Second, if you think about the latent and sensible
sources of heat generated by the submarine's systems and its occupants,
if you can't lose that heat to the seawater, where else is it going to
go?  Even circulating the air to cool the motors will result in a
temperature rise of the air, which is subsequently transferred to
everything it touches.  When surfaced, you have two ways of losing that
heat: to the air, or to the surrounding water.  When submerged, the
water is your only option.  Now, this can be done passively, which
necessitates relying on a delta-T between the sub and the water, or
actively, which requires energy input (i.e. air conditioning) but
permits you to expel water or air at a higher temperature than the
ambient medium.  Either way, if you can't lose heat to the environment,
the only possible outcome is a rise in temperature of your closed system.

Sean


On 2014-04-13 19:33, Joe Perkel wrote:
> Sean,
>
>  Northern climates have nice cool seas,  but I'm dealing with tropical
> temps here averaging in the 80's in summer. With hot seas, which
> scheme would be best? I simply am not certain, my gut says relying on
> the ambient water may not do the job. I could be wrong.
>
> Joe
>
> Sent from my iPhone
>
> On Apr 13, 2014, at 9:16 PM, "Sean T. Stevenson" <cast55 at telus.net
> <mailto:cast55 at telus.net>> wrote:
>
>> Airflow in constrained spaces is often difficult to model.
>> Alternatives include water cooled motors, or simply effectively heat
>> sinking the motor housings to the hull and using passive water
>> cooling to the ambient seawater. Ultimately, that's where the heat is
>> going anyway. Unless you can use it for some purpose (cabin heat,
>> humidity control etc.) you might as well sink it as directly as possible.
>>
>> Sean
>>
>>
>>
>> On April 13, 2014 6:45:39 PM MDT, Joe Perkel <josephperkel at yahoo.com
>> <mailto:josephperkel at yahoo.com>> wrote:
>>
>>     I am considering a scheme for dealing with electric motor cooling
>>     and would like input on the viability of the idea and any pros or
>>     cons that I may be missing.
>>     In looking at my SeeHund replica, note that the torpedo/pod(s)
>>     length exceed needed battery capacity.  So the idea being that
>>     the aft ends of both will house electric motors that are isolated
>>     from the battery compartments.
>>     I'm thinking to ventilate these aft motor units into the aft
>>     machinery space within the main hull. Incidentally, the hull
>>     diameter will be 42" and the torpedoes #14 pipe. This will leave
>>     a significant airspace around these motor units allowing me to
>>     use fan cooled motor cases.  Each motor pod could be connected
>>     with vent pipes for intake and output airflow, then the machinery
>>     space itself force vented to the outside with  main induction and
>>     exhaust vents.  All this for continuous surface running of
>>     course. Submerged, the motor units would be intermittent duty.
>>     The centerline unit would be fully enclosed and not vented,
>>     therefore not as attractive for continuous duty due to thermal
>>     constraints.
>>
>>      
>>
>>     Joe
>>

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