If you could store 1.5 gallons of hot engine coolant would it help MPG's....

Phantomofheat · Mar 18, 2013

In the heat calculations above there are a things missing like mass of the engine and oil, amount of heat lost to the exhaust iirc is about 30-35% of total heat.

Here is an article I found on PCM heat storage for Diesels http://ehakem.com/index.php/IJoT/article/viewFile/266/244
I have not read it yet but there is only so much time at lunch.

Diesl · Apr 1, 2013

I feel there is still stuff left to be said in this thread. It died before its time. Maybe the overly specific title put people off?

SD26 · Apr 2, 2013

I don't think it's dead...it's just different from what other people are thinking.

Considering options for a new house build in passive solar design, and my thoughts kind of some back to this thread considering various concepts.

josh8loop · Apr 2, 2013

Diesl said:
I feel there is still stuff left to be said in this thread. It died before its time. Maybe the overly specific title put people off?

I sure hope it's not dead-Hopefully other folks will experiment a bit and post some results. I would but have been extremely tied up with other things

Keep up the great discussion fellas!

josh8loop · Apr 2, 2013

James & Son said:
From what I see Josh does not calculate anything, but he does do some testing. He mainly is trying to conserve heat rather than waste it. I am sure he agrees with you that there is plenty of heat to store, he has even commented in one post about using a 50 liter water tank or using the fuel tank for storage. Somehow this is got something to do with him wanting to purify water I would imagine.
Basically he is going to have his trunk or back seat conserving heat and purifying water whether we like it or not.
Another way of looking at cool down rate which in the first 1/2 hour as tested by Josh at 70 F ambient is 203 to 172 F or 62 F degrees per hour. I have done some testing and I think the average motor cool down rate in summer from 190 F to 100 F is about 5 hours or 18F per hour(average).
How about the warm up side. Most people say it takes 15 minutes to warm up from lets say 68F to 190F or 488 F per hour.
I think these are realistic numbers. There will be no equilibrium reached at 204 degrees as Josh thinks.(heat loss vs. heat gain).
You will be trying to reheat 200lbs of block and head(.18 average sp. ht x 200 = 36 lbs.) with 1.5 gals of water or wax for that matter which is about 12 lbs of water at 1sp. ht.
The motor mass and the specific heat of the mass amounts to the [equivalent of 36 lbs of water], plus the 8 liters of coolant adds another 17 lbs for a total of 53 lbs.
This means Josh will be using 12 lbs at 170 F to try and heat 53 lbs at lets say 120 F. if he is well insulated. Possibly a gain of 16F. Starting the motor will realize that 16 F in 2 minutes of normal operation.[ 16/488 x 60 = 2 min. using info from above warm up cycle paragraph).

I think you have a pretty good feel for where I would like to go with this

Basically try to conserve heat energy- albeit may be low value and perhaps not worth the effort and certainly not give financial payoffs. Perhaps I might get a bit more comfort (quicker heat in winter time) or perhaps make the car perform a function that it wouldn't other wise be able to do namely possibly purify water or some other task. I figure if I can't make it get higher MPG's then maybe it can do a bit more for me that will make it more useful

Remember that on every trip I may not realize excess waste thermal energy for example very short trips. Long trips(which I rarely ever do) on the other hand may net some additional thermal energy that could be used for something rather than shunted to the environment. This may involve purifying water, or perhaps drying a dessicant matrix for evaporative AC. Anyone else have any additional ideas on what to do with the waste low value heat?

VeeDubTDI · Apr 2, 2013

Installing a 1.5 gallon dewar flask is a lot different than deleting your radiator and the other stuff that this thread progressed into. The 1.5 gallon flask may have its merits, but going larger than that will just kill your fuel economy and storage due to the extra weight and bulk of the additional items you're installing.

That's my $0.02 on this whole project.

Diesl · Apr 2, 2013

Variation on this idea: instead of heating the engine, is there any way to heat the various cats in the exhaust system so the car doesn't spend as much extra fuel getting them up to operating temp? For that to work we need heat at a higher temperature (like, 250°C or more); but not higher than you could get with superheated water.
Most of all, I think the system, whether used to preheat the engine, or the engine oil, or the exhaust system, needs to be robust. There's no point in adding a lot of complexity and potential failure modes just to save the equivalent of a tenth of a gallon (wild guess, I didn't do any estimate) of fuel on every cold start. I'm surprised that they (VW engineers) added all those control loops for the various cats and filters (oxidizing cat, particulate filter, NOx cat, H2S cat); but maybe they had no other choice to meet the emissions regulations.

robnitro · Apr 3, 2013

The ALH engines don't really know if the cat is hot or not. There's no feedback from there. On PD there may be, with the O2 sensor, but it can probably be tuned out.

CR is another story, lol.

josh8loop · Apr 3, 2013

Diesl said:
Variation on this idea: instead of heating the engine, is there any way to heat the various cats in the exhaust system so the car doesn't spend as much extra fuel getting them up to operating temp? For that to work we need heat at a higher temperature (like, 250°C or more); but not higher than you could get with superheated water.
Most of all, I think the system, whether used to preheat the engine, or the engine oil, or the exhaust system, needs to be robust. There's no point in adding a lot of complexity and potential failure modes just to save the equivalent of a tenth of a gallon (wild guess, I didn't do any estimate) of fuel on every cold start. I'm surprised that they (VW engineers) added all those control loops for the various cats and filters (oxidizing cat, particulate filter, NOx cat, H2S cat); but maybe they had no other choice to meet the emissions regulations.

I wasn't really going the superheated water route due to pressures and temps involved. The coolant system on a stock TDI just won't create enough heat to produced superheated water AFAIK. I don't have a CAT so no issues for me there.

robnitro · Apr 3, 2013

http://www.engineeringtoolbox.com/boiling-point-water-d_926.html

It would take 575 psi to be able to have 250 C liquid water. Steam is not too useful for storing heat, very low heat capacity per volume compared to liquid.

david_594 · Apr 3, 2013

I'll throw out an opinion and say I doubt adding the 1.5 gallons of heat to the system would be of any real benefit toward fuel economy. The heat capacity of 12 pounds of coolant would be pretty insignificant compared to total the heat capacity of the 365 pound ALH engine.

I think your biggest and easiest gains would be in insulating the engine and swapping in a higher temp thermostat.

VeeDubTDI · Apr 3, 2013

david_594 said:
I'll throw out an opinion and say I doubt adding the 1.5 gallons of heat to the system wouldn't be of any real benefit toward fuel economy. The heat capacity of 12 pounds of coolant would be pretty insignificant compared to total heat capacity the 365 pound ALH engine.

I think your biggest and easiest gains would be in insulating the engine and swapping in a higher temp thermostat.

I fixed it for you.

gerardrjj · Sep 21, 2014

I was browsing the thread and didn't read all the posts but here's my thoughts on some of the stuff I've read:

1. The engine warm-up cycle is pretty short. Even in winter my TFI only takes a few minutes to get to normal temperature and the thermostat opens.
2. Let's say it takes 5 minutes to warm up the engine coolant and at ambient air temperature the engine runs at 95% of the efficiency that it does at operating temperature. That means that over the 5 minutes the car operates at an average of 97% efficieny. A 30MPG car would be operating at 29.1MPG.
3. To add more coolant and the equipment to contain the coolant under pressure and switch to/from the hot storage tank you'd add, I guess, 15 pounds of weight to the car
4. The question is, does running for 5 minutes at 1 1MPG reduction in efficiency offset the extra load and reduced MPG due to carrying around an extra 15lbs of dead weight.

Personally, I'd think no.

914fan · Sep 21, 2014

On my 97 jetta, the temp usually runs in the lower 3rd of the range. My mileage had always been 46-47, unless I drop my speed. Then it goes between low to high 50s. Perhaps the newer cars are different.

If you could store 1.5 gallons of hot engine coolant would it help MPG's....

Phantomofheat

Veteran Member

Diesl

Veteran Member

SD26

Veteran Member

josh8loop

Veteran Member

josh8loop

Veteran Member

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast

Diesl

Veteran Member

robnitro

Veteran Member

josh8loop

Veteran Member

robnitro

Veteran Member

david_594

Top Post Dawg

VeeDubTDI

Wanderluster, Traveler, TDIClub Enthusiast

gerardrjj

Member

914fan

Veteran Member