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cabin heat off of oil cooler?

Desert Rat

Well Known Member
I was just looking at the thread with the firewall mount oil coolers (something that I'm going to have to pursue in the near future) and was struck with a thought.

In a lot of those applications, the cooler is pretty close to the inlet flapper for the cabin heat. has anybody ever though of taking air downstream of the oil cooler to use for cabin heat, instead of off of an exhaust stack? Thats not really very different in concept to how a car heater works.

Is the air coming across the top of the engine too noxious to be plumbed into the cabin? Also, any of the big brains out there care to comment on the thermodynamics and heat exchange rates i.e is this practical at all, or do physics make it impractical?
 
I was just looking at the thread with the firewall mount oil coolers (something that I'm going to have to pursue in the near future) and was struck with a thought.

In a lot of those applications, the cooler is pretty close to the inlet flapper for the cabin heat. has anybody ever though of taking air downstream of the oil cooler to use for cabin heat, instead of off of an exhaust stack? Thats not really very different in concept to how a car heater works.

Is the air coming across the top of the engine too noxious to be plumbed into the cabin? Also, any of the big brains out there care to comment on the thermodynamics and heat exchange rates i.e is this practical at all, or do physics make it impractical?

My plane is configure this way. The builder fashioned a heat box which the oil cooler is mounted on, and there is a cable actuated door which is normally closed over a hole in the firewall shelf, letting the air from the oil cooler exhaust into the rear cowling. When the door is actuated, the air off the oil cooler goes over my right leg.

Heat wise it’s acceptable but it’s not an exhaust muff either.
 
Yesterday it was about 30F when I did my BFR. In an hour's flight, the oil temperature never got over about 140. Point is, when you need cabin heat, an oil to air heat exchanger may not supply what you need. That's been the experience of every account I've ever seen where someone went with that approach.

Thankfully, I have a traditional heat muff around the exhaust pipe and it provided plenty of heat yesterday.
 
I’ve heard that in some planes, when it’s cold enough that you want heat, the oil might not be warm enough to heat well. Dunno.
 
Math...

Empirically, I don't think there's enough heat coming off the oil cooler to warm the cabin air when compared to other methods.

Consider:

A 2" duct blasting air into a shroud surrounding a stainless steel pipe which is at +/- 1200°F and thence into the cabin makes the air "pretty warm."

-vs-

A ~3" duct blasting air into an oil cooler that is +/- 220°F and thence into the cabin might be "warm-ish"

--

I'm sure that with the right data points you can model this accurately. Google search for "LCHX Performance Curves" and look for the Calculated Heat Rejection charts that match your particular oil cooler (provided its close to the SW/South Wind variety)
 
When it is cold enough that you want heat, the engine oil temps are low enough that the vernatherm is not diverting much oil to the cooler and you are blocking off airflow to the cooler to get oil temps up. Ergo, no usable heat for the cabin.
 
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