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Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 10:18 am
by Smidge204
Here's how I'd do it:

Image

It's exactly identical to the presumed system the manual seems to describe, except there is a bypass and 3-way valve which has the ability to divert flow from the motor cooling loop into the cabin heating loop. The valve only opens when the fluid in the motor cooling loop is hot enough to contribute and only when heating is required. You wouldn't even need particularly fancy controls on the valve either: simple min & max setpoints (no modulating) would suffice for this.

It would add maybe $150 to the cost of the vehicle but would help in cold climate driving where heating would be a significant factor in power consumption. Provided, of course, the motor/inverter gets hot enough, soon enough. As turbo2ltr mentioned, the coolant system seems capable of running while charging, so that may help "pre-warm" the system.
=Smidge=

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 10:27 am
by edatoakrun
Smidge204 wrote:Here's how I'd do it:

Image

It's exactly identical to the presumed system the manual seems to describe, except there is a bypass and 3-way valve which has the ability to divert flow from the motor cooling loop into the cabin heating loop. The valve only opens when the fluid in the motor cooling loop is hot enough to contribute and only when heating is required. You wouldn't even need particularly fancy controls on the valve either: simple min & max setpoints (no modulating) would suffice for this.

It would add maybe $150 to the cost of the vehicle but would help in cold climate driving where heating would be a significant factor in power consumption. Provided, of course, the motor/inverter gets hot enough, soon enough. As turbo2ltr mentioned, the coolant system seems capable of running while charging, so that may help "pre-warm" the system.
=Smidge=

Are you sure this is not already in use?

One of the few things I find objectionable in LEAF design is using precious battery storage capacity to heat the cabin.

Seams to me a heat pump using the main coolant system as the heat source, backed up with resistance, would greatly expand cold weather range.

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 10:43 am
by kmp647
edatoakrun wrote:"it uses a pump, resivoir and heater core and is a seperate system from the inverter-charger-motor coolant circuit."

And there is no heat exchange between the two systems?

the owners manual lists 2 seperate capacities for the main traction cooling system and the heater circuit

1.8 qts for the heater circuit (something close)

seems like combining them could help but I guess they didnt for some reason

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 10:58 am
by smkettner
If it was hot out there is no need to circulate the motor coolent through the cabin.
When it is cold out there is no need to warm the motor.

There is not a circumstance to share the heat.
I speculate the engine coolent may not get more than 20 degrees over ambient.

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 11:15 am
by GroundLoop
If you look at the cutaway pictures of the Leaf motor, you can clearly see water cooling channels.

The manual specifically mentions:
"Water pump noise while charging"
EV-8

Combining the cabin heater and inverter/motor coolant seems like a really bad complication of two individually simple systems.

Unlike an ICE, the motor has no real need to warm itself for efficiency, and no guarantee of prompt surplus heat.

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 11:20 am
by Smidge204
smkettner wrote:If it was hot out there is no need to circulate the motor coolent through the cabin.
When it is cold out there is no need to warm the motor.
Agreed. A 3-way valve and injection loop prevent both of these scenarios from occurring.

smkettner wrote:There is not a circumstance to share the heat.
Disagree. After ~10 minutes of steady driving I'd wager the motor and inverter have generated enough heat to be worthwhile. Similar to an ICE, but an EV would probably have significantly less thermal mass. Add to this the speculation that heat is generated during the charging process - which would mean there is less warming up to do.

smkettner wrote:I speculate the engine coolent may not get more than 20 degrees over ambient.
Maybe not with a radiator, but even if that is the case (and I speculate otherwise) heating water that is already +20 above ambient is better than heating water that is at or close to ambient.

The viability really depends on how much waste heat the motor/inverter generates, and the max temp the components are allowed to reach. Heat would vary considerably with speed, but if we assume 90% efficiency that's still several kW on average. Max temp is likely up around 200F so that's plenty hot. Throw in supplemental resistance heat and call it good I say.
=Smidge=

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 11:33 am
by edatoakrun
Does seem to be a lot of heavy battery energy to waste.

Particularly if it were possible to use the ac compressor (in heat pump mode) to utilize a coolant heat exchanger , to use the heat when the coolant was below the temperature for cabin heating.

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 12:45 pm
by GroundLoop
If only Nissan had Engineers to figure this stuff out and chose an efficient, reliable design..

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 1:07 pm
by Smidge204
GroundLoop wrote:If only Nissan had Engineers to figure this stuff out and chose an efficient, reliable design..
If only we had perfect engineers who worked in a perfect world where every possible idea could be thought of and no compromises ever had to be made... :roll:

If they didn't set it up to use motor coolant for cabin heating, there is obviously a reason why. "They didn't think of it" is among the possible reasons, right alongside "They didn't think it was worth it" and "Technicalities prevented it." Only the actual engineers know for sure so let us have our fun, k? :D
=Smidge=

Re: Does the Leaf have a radiator?

Posted: Mon Dec 20, 2010 1:08 pm
by edatoakrun
GroundLoop wrote:If only Nissan had Engineers to figure this stuff out and chose an efficient, reliable design..
And introduce it with the "cold climate" option...