Radiator question, for thermodynamics/heat transfer experts Options

[bondo]

Hopefully I can get some input on this without too much of the inevitable "that won't work" (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

I'm cutting down a large tall radiator into a shorter one.. 1/3 the height to be exact. The 3 layers of radiator will be set up in a cross flow, sequentially. The hottest water will enter the rearmost later, travel across, then across again in the middle layer, and across yet again in the front layer. The idea is the hottest water gets the hottest air, and the coldest water gets the coldest air. This way delta T stays pretty constant.. I'm thinking of it as trying to heat the air as much as possible, which would cool the water as much as possible.

So I realize that cooling capacity will be reduced, as I will be dealing with 1/3 as much air. But then the cooling capacity must be more than 1/3, because it's 3 layers thick instead of 1. My question is what percentage of the original cooling capacity should I be expecting? Would it do me any good to do 5 layers instead of 3? (by adding 2/3 of a second radiator)

The original radiator cooled the same engine just fine, in a heavier car, with an AC condenser preheating the air. I will be running an electric pump, so I will have an advantage at idle.

[ArtechnikA]

QUOTE (bondo @ Feb 2 2005, 02:22 PM)

Apparently by the time the termostat opens, and the hot water runs up to the radiator, cools, and comes back to the engine, it can already be too late. My idea to solve this problem (and the problem of firewall interference) is to place the entire LT1 water pump assembly in the front trunk

seems to me that when the thermostat opens sending hot water to the radiator, it is also opening the path that admits the ambient-temp water in the radiator and lines from the radiator to the engine. that oughtta produce an immediate cooling effect ...

but i am way outta my depth dealing with water-cooled plumbing issues ...
(however, that's the way it works with oil coolers with thermostats in the circuit...)

i do not like the idea of trying to suck a fluid. how many high-mounted water pumps do you see? you get one good bubble in there - steam pocket, leftover from filling, slosh from bumpy road, whatever - and you (theoretically at least) run the risk of cavitation and loss of prime.

also - pulling a vacuum on a liquid depresses its boiling point, but pressurising it by pushing it increases it.

maybe modern electric-drive water pumps handle all this stuff in stride nowadays.
but it would scare me ...

[bondo]

The pump will be mounted at the bottom of the front trunk, lower than its stock location, but probably about the same height as the belt driven pumps used on most conversions.

I agree about the ambient temp water from the radiator.. I was just thinking that since I need to add a reservior anyways, I might as well put it where it can assist that effect.

[ArtechnikA]

QUOTE (bondo @ Feb 2 2005, 02:43 PM)

The pump will be mounted at the bottom of the front trunk, lower than its stock location, but probably about the same height as the belt driven pumps used on most conversions.

it's still 10 feet of hose away from the engine.

i'd be concerned about (for instance) parking on a hill. but as i said - this is an area i don't claim to know much about. if it's not a problem, i'm not trying to make it one...

[bondo]

QUOTE (ArtechnikA @ Feb 2 2005, 12:47 PM)

QUOTE (bondo @ Feb 2 2005, 02:43 PM) The pump will be mounted at the bottom of the front trunk, lower than its stock location, but probably about the same height as the belt driven pumps used on most conversions. it's still 10 feet of hose away from the engine. i'd be concerned about (for instance) parking on a hill. but as i said - this is an area i don't claim to know much about. if it's not a problem, i'm not trying to make it one...

Hmm, hill. More variables I haven't though of. I think I'm getting to the "gotta try it and see" phase. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[SLITS]

Just for fun, a couple of more variables to play with.....

1. Any bend in the piping system will create a resistance to flow and lower the gph capability of your pump.

2. The material you use for piping will have an effect on flow (frictional resistance).

Plumb it like a Fiat X1/9 with two copper pipes running under the car (they're placed there after the original thru body pipes rust out). Then we can bash you for being Vino oriented rather than rice oriented. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[ewdysar]

Another attribute that Scott discussed with me that seems to point to thinner cores is the fact that the heated air expands requiring more space to flow through. This is a real problem on 6 core rads, the flow is limited to the amount of expanded air that can fit through the last pass. It seems that cores that increase in area as you move farther back in the flow could help, but I have never heard of this being done. This concept is fairly new in car design, all my old trucks had 4 pass rads, but any of my recent cars or trucks have had only 2, at the most. Each of the new car rads that I've looked at have fairly large surface areas, so this trend may be a function of that.

Just more possible stuff to consider...
Eric
PS. The only thing that I could complain about my RH setup, is that it may cool too well. I guess it could be worse...

[bondo]

QUOTE (SLITS @ Feb 2 2005, 01:15 PM)

Just for fun, a couple of more variables to play with..... 1. Any bend in the piping system will create a resistance to flow and lower the gph capability of your pump. 2. The material you use for piping will have an effect on flow (frictional resistance). Plumb it like a Fiat X1/9 with two copper pipes running under the car (they're placed there after the original thru body pipes rust out). Then we can bash you for being Vino oriented rather than rice oriented. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

Hmm.. ok, bends are bad, rough is bad. Good to know.

[bondo]

QUOTE (ewdysar @ Feb 2 2005, 01:19 PM)

Another attribute that Scott discussed with me that seems to point to thinner cores is the fact that the heated air expands requiring more space to flow through. This is a real problem on 6 core rads, the flow is limited to the amount of expanded air that can fit through the last pass. It seems that cores that increase in area as you move farther back in the flow could help, but I have never heard of this being done. This concpet is fairly new in car design, all my old trucks had 4 pass rads, but any of my recent cars or trucks have had only 2, at the most. Each of the new car rads that I've looked at have fairly large surface areas, so this trend may be a function of that. Just more possible stuff to consider... Eric PS. The only thing that I could complain about my RH setup, is that it may cool to well. I guess it could be worse...

Interesting.. My mustang has a 3 row radiator, and each row is about 1/2" deep. This radiator I'm hacking up for experimentation has a single row that's more like 1.25". I wonder if that's why.

Thanks to all this discussion I have some new ideas to try, if there's room.

[914GT]

QUOTE (bondo @ Feb 2 2005, 12:43 PM)

The pump will be mounted at the bottom of the front trunk

The best location for the water pump is low in the engine compartment. My electric pump is mounted on the engine mount bar. The reason for this is when you accelerate forward the water naturally pressurizes toward the rear and that assists the pump when you need it most. Having it at the lowest point in the system also helps somewhat, obviously, as compared to up high where air pockets could reside.

[v82go]

On my application I use aluminum condit instead of rubber hose under my car. I think this should also help get rid of alittle heat.

[v82go]

CONDUIT (yes I can't spell)

[914GT]

Bob,
The conduit looks good. Hell of a lot easier to work with than the steel pipe I used.

[bondo]

Nice, where do you get aluminum conduit? The stuff I've used (for electrical wiring) is all galvanized steel or PVC. Aluminum would be ideal.

[v82go]

Check with any electrical supply place. They also can supply you with long radius 90's.
The conduit also welds very nice.

[BIGKAT_83]

v82go the fan and shroud look like they are from one of the first orginal Renegade brass and copper radiator setups. I also see a ac drier.
Does the car have AC? Also is this the car that was for sale in Orlando a couple of years ago. Looked real nice from the pictures.


Bob (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

[bondo]

Whenever I need to design something unusual I turn to... garage floor engineering!

Here's the latest idea... semi-paralell, semi series. Solves the air expansion problem as the rear layer has twice the area of the front layer. This still may not work, but I think it has a better chance.

[SpecialK]

Good thinking on the aluminum coduit v82go, definitely some added cooling vs rubber lines. Did you run the aluminum tubing all the way to the engine compartment? Which route, down the rockers?

[BIGKAT_83]

Bondo I've seen and ridden in 2 914's that had junkyard radiators from a corvette and both of these cars ran cool in the heat of the summer. I really don't see a need for anything special.
I think the main thing is to have a expansion tank that will bleed the air from the system. If you look at the pictures of BOXSTR new yellow V8 914 you can see how it needs to be plumbed up with a larger hose from the bottom of the expansion tank to the low pressure side of the radiator(feed to the water pump) and then a feed line from the high pressure side(hot water from engine) of the radiator to a point about 1" from the top of the expansion tank.
This will bleed all of the air pockets from the system. On my V8 car all I do is put water in and bleed the air from the top of the radiator and drive.
If you look at most of the new cars this is the way they are plumbed. Here is a picture of the expansion tank I'm using on my new V8 car

[BIGKAT_83]

Here is Boxstr new yellow 914 this is what I was trying to explain.

(IMG:http://www.914world.com/bbs2/html/emoticons/headbang.gif) Bob

[MattR]

You guys are all wrong, the 914 is AIRCOOLED!!!

(IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

okay, back to your real conversation. I'll chime in after MAE 91 - intro to thermodynamics (should be next spring)