Keeping Engine Coolant Hot

[Blue Bomber]

The issue with that is, you have to wait 30 min - 1 hr before driving. The Prius' system is instant. Adding a block heater as well will defintely help considerably, though, especially with engine wear and drag created by thick oil.

The easiest way I can think of for an instant system is to tap the coolant drain plug on the block and run a braided line to an accumulator. These are usually made for oil for prelube purposes, but should also be able to use coolant. It's a piston inside a chamber that will release and collect fluid depending on pressure, or by using a hand operated valve. Just insulate it, open the valve to collect hot coolant (pressure is much higher when hot), close the valve and shut the car off. Get back in later, open the valve to release the warm/hot coolant, and start the car. There are even remote mount electronically controlled valves if you don't want to mount the accumulator in the cabin.

The only issue I see here is with the capacity of the system. The largest normal oil accumulators I've seen are 3qt, but it's possible they may be produced in larger sizes. Does anyone know how much coolant the Prius collects?

[dutchboy]

Originally Posted by Blue Bomber

The only issue I see here is with the capacity of the system. The largest normal oil accumulators I've seen are 3qt, but it's possible they may be produced in larger sizes. Does anyone know how much coolant the Prius collects?

The Prius uses a 3L "thermos" reservoir.

[DonR]

It's called an accusump.

Canton Racing Products

1, 2 & 3 quart accumulators. You would have to insulate it yourself. Electric valves are available.

Normally they are used with drysump oil systems with a large resovoir. The small cooling resovoir may present a problem. There may not be enough volume to empty the accusump.

A system with a pressurized "overflow" bottle may be the way to go. You could increase the size of it with an auxillary tank with an upper & lower hoses. You need to make sure the tank has air in it.

Don

[wwelder]

You can't always heat the coolant or the oil except with propane type heaters.

[Piwoslaw]

I was looking through old PopSci magazines and I found an article about using a thermos with molten salt to keep the engine's heat (Popular Science, June 1994, p.38).
It's called a Schatz heat battery and was apparently available in 1994 VW Golfs and Jettas. I wonder how well this system worked, and if it can still be found in junk yards?

[Daox]

Awesome idea. Use the phase change of the material to hold much more energy. I know I've read about it before, just not related to cars. Its really a great idea I think.

[Thymeclock]

Originally Posted by Duffman

This is not a worthwhile mod guys, just slap on a oil pan heater (use block heater too) and plug your car in 30min-1hour before you are going to use it.

Unless you live in a climate that is extremely cold and has inexpensive electric rates, it usually doesn't pay to do this either. The small amount of gas you save is offset by the cost of the heater itself plus the cost of operating it.

[Piwoslaw]

Here's another PopSci: Popular Science, June1990, p.29.
I also found this link on the Schatz heat battery: Engine waste-heat storage.

...the heat battery is a 10-kilogram cylinder 37 centimeters long and 17 centimeters in diameter. The container's core consists of a stack of flat sheet-metal envelopes filled with the heat-storage medium-readily available barium hydroxide crystalline salt. The envelopes also serve as turbulence generators for the engine coolant that flows through the container, Schatz wrote. The core is surrounded by a high-vacuum insulating jacket.

If the coolant temperature is higher than that of the storage medium, it warms the salt, which eventually liquefies at its melting point (75 [degrees] C). The device has a heat capacity of 600 Watt-hours when cooled down from 80 [degrees] to 50 [degrees] C. During discharge, the storage medium solidifies.

600Wh is about the same as what you'd get from a block/coolant heater, but it's free and remote, and lasts for a few days.

This article said the melting temperature of barium hydroxide is 75*C, Wikipedia states 78*C. That may be a little high. My coolant temp hardly ever exceeds 78*C (during winter only on long uphills), and there are more efficient turbodiesels than mine (like 1.2TDi, of VW Lupo and Audi A2 fame), which have even lower temps, so the medium may never melt. On the other hand, any thermal help for a cold engine is good.

I googled around, but it seems that this in the news in the early '90's, VW and Saab fooled around with it, and then Hush! I wonder why it never went mainstream? Cheap oil, like usual?

[Galane]

Insulation technology has come a long way in recent years. I just finished up work on a Can-Am Commander 1000 X.

Installed a heater and insulated the interior panels around the engine and floor under the seats, both to reduce noise and to keep heat out of the interior in summer and hold heat in the interior in winter. (The rig has a Mammoth Skins rear panel and side curtains, BRP factory plastic roof and windshield option.)

I used two different materials. One is a non-woven fabric, about 1/4" thick with aluminized plastic on both sides, reinforced with a mesh, probably fiberglass. Supposed to withstand very high non-contact temperature. The other is Hushmat, a black, tarlike substance with heavy gauge aluminum foil on one side. Somewhat less expensive than DynaMat.

What might work well for insulating a hot coolant tank or PCM heat storage is cast in place foam. Smooth-On has silicone and urethane foams in a range of density and hardness. A low density, rigid foam would be what you'd want for stopping convection and radiation heat transfer.