[Trikky2]

The air blows from the fan housing through the heat exchangers regardless of whether the flaps are open or closed. But that's a whole different kettle of fish.

Dave.

Yes but only a tiny bit compared to when the flaps are open and if your engine is in need of that tiny bit of extra air then I have some bad news for you - its going to blow anyway.

Maximum cooling is not just about volume , its about temperature differential.

The hotter the ambient temperature the less cooling effect the air will have. Hence if your engine is desperate for that tiny bit of bleed-off for the exchangers then a degree or two rise in ambient will cancel out any benefit - sorry

 

[Mr.Whippy]

So now your talking about a heater matrix to heat the car and a radiator to stop the water boiling in the system and a thermostat to control the two, plus a control valve to allow you to set the temperature in the vehicle, an electric fan to blow the air not to mention the construction of the exchanger itself and all the associated plumbing.

It could be done yes. But to claim its a less complex way of doing it than an Eberschpasser or a propex heater is frankly ludicrous. :lol:

As for using the oil to heat, yes that too could be done and would be equally complex but as has already been pointed out by previos posters, in the winter - when you need the most heat - the oil in an aircooled does not get hot. It will struggle to get above 50C. If you dont believe it then fit a guage and pootle about in winter temperatures for an hour or two.

Agree with you re. the oil heating - IMHO it will be too little too late to be of much practical use except maybe on very long trips.

I've had an eberspacher, (admittedley not a new one) and when it worked it was great but it just wasn't reliable enough and took up a lot of luggage room under the bonnet, plus it meant cutting large holes in the body for the hot air pipes, combustion intake and exhaust pipes. Spare parts are like hen's teeth and very expensive. Propex isn't practical in a Beetle if you want to carry luggage.

I think I'll be able to knock up a W/C system using readily available parts and keep it fairly simple. So far this is the idea.... I have most of the parts to hand, the difficult bit will be making a prototype heat exchanger, and making it water pressure tight with my mig welder.

I've already cut & shut a Mk1 Golf heater matrix unit with fan, so it will sit under the back seat opposite the battery. The water pipes come in and out via the bakelite tube on that side.

One homemade W/C heat exchanger on no.3 exhaust, range rover header tank from eBay with pressurised cap, Honda civic rotary fuel pump that should be good enough to shove the coolant around (I'll put it on the cold return side), if it's not up to the job then I'll buy a small electric coolant pump that they use for Karting, but they're a bit pricey so I'll keep with the second hand stuff for now.

Heat control using a stand alone Golf heater valve operated by the existing heater control cable. This simply sends coolant to either the heater matrix or radiator. A small motorbike bike radiator will fit in the rear arch or alongside the gearbox. If I get a radiator with built in fan switch then this can contol an electric fan on the radiator if I get stuck in traffic.

Junctions and pipework in 15mm copper pipe, with general purpose heater hose for the flexy bits.

Heater box under rear seat blows out via 50mm flexy air hose down each heater channel, and outlets under rear seat.

Well that's the idea anyway.

As for the fan housing, that's already modified with the outlets removed and the internal vanes redirecting all air to the cylinders and heads to make full use of the fan for cooling.

Dave.

 

[evilC]

I'll go along with all that - 'tis but a simple plumbing job.

evilC

 

[PIE O.C.]

You can get a diesel eiberspacher from a lorry breakers for around £80, dont use much diesel, my mate is fitting one in a bay behind the kick board that had all the heating system missing, fitted an electric washer bottle and is going to use the original washer bottle for the diesel. Thed new Danburys use one in a similar position as they have no heat exchangers

 

[the jester]

eberspacher is definately the way forward

if your going to that much bother would you consider fabricating some diy heat exchangers that work on hot air similar but bigger than stock

 

[PIE O.C.]

Some kit cars fit petrol Webasco's as standard they are quite compact

 

[Ratfink]

why not just make some proper big bore stainless heat exchangers?

step 1: buy the 'J' Tubes
step 2: got some billets of ali
step 3: take them to a machine shop and ask them to put lateral fins on them and route them so they go round the 'J' tubes, one each side.
step 4: find some way of bonding the ali blocks to the stainless tubes.
step5: find an old heat exchanger and cut in half, then copy the design, but make big enough to surround the ali blocks and goive good flow of air. the flap mechanism may be tricky to fabricate, so pull it off the old one.
weld it all together, and use the origional beetle heater system, and marvel at the pasty warming goodness :d

 

[jimcub]

Stainless is a bad medium for that application as it is not good at heat transfer but the principle sounds fine.

But I've just thought that a better alternative would be to have a water/oil cooler with a standard radiator to cool the water and a diverter to power a traditional heater. You could probably get away with a small rad - classic Mini? with an electric fan in the space above the transmission.

evilC

Here is the maths to work it all out.

The overall heat transfer coefficient for a wall can be calculated as:

1 / U A = 1 / h1 A1 + dxw / k A + 1 / h2 A2 (1)

where

U = the overall heat transfer coefficient (W/m2K)

A = the contact area for each fluid side (m2)

k = the thermal conductivity of the material (W/mK)

h = the individual convection heat transfer coefficient for each fluid (W/m2K)

dxw = the wall thickness (m)

The thermal conductivity - k - for some typical materials: .

Polypropylene PP - 0.12 W/mK
Stainless steel - 21 W/mK
Aluminum - 221 W/mK

More about conductive Heat Transfer
Thermal Conductivity for Several Materials
The convection heat transfer coefficient - h - depends on

the type of fluid - gas or liquid
the flow properties such as velocity
other flow and temperature dependent properties
Heat transfer coefficient for some common fluids:

Air - 10 to 100 W/m2K
Water - 500 to 10 000 W/m2K

Thermal resistance
The overall heat transfer coefficient can also be calculated by the view of thermal resistance. The wall is split in areas of thermal resistance where

the heat transfer between the fluid and the wall is one resistance
the wall it self is one resistance
the transfer between the wall and the second fluid is a thermal resistance
Surface coatings or layers of "burned" product adds extra thermal resistance to the wall decreasing the overall heat transfer coefficient.

Example - Heat Transfer in a Heat Exchanger
A single plate exchanger with media A transfers heat to media B. The wall thickness is 0.1 mm and the material is polypropylene PP, aluminum or stainless steel.

Media A and B are air with a convection heat transfer coefficient of hair = 50 W/m2K.

The overall heat transfer coefficient U per unit area can be expressed as:

U = 1 / (1 / hA + dxw / k + 1 / hB) (1b)

Using the values from above the overall heat transfer coefficient can be calculated to:

Polypropylene PP : U = 24.5 W/m2K
Steel : U = 25.0 W/m2K
Aluminum : U = 25.0 W/m2K

 

[HairyYeti]

VW had this very same problem on the VW Trekker / Thing......they used an Eberspacher under the bonnet.

In Canada and other very cold places their solution was to put an Eberspacher under the bonnet.

I have seen a conversion where hot air from the oil cooler was ducted / diverted.


My own solution is heated front and rear Beetle windows and a thick fleecy winter coat.! Oh and a 1992 Peugeot diesel so I dont have to drive a freezing cold bug.!

 

[billybug]

Yeah my Swedish '58 has an Eberspacher under the bonnet, works too - well it did until the fuel pump packed up!

 

[emtee]

You can get a diesel eiberspacher from a lorry breakers for around £80, dont use much diesel, my mate is fitting one in a bay behind the kick board that had all the heating system missing, fitted an electric washer bottle and is going to use the original washer bottle for the diesel. Thed new Danburys use one in a similar position as they have no heat exchangers

Won't they normally be 24volt?

 

[evilC]

why not just make some proper big bore stainless heat exchangers?

step 1: buy the 'J' Tubes
step 2: got some billets of ali
step 3: take them to a machine shop and ask them to put lateral fins on them and route them so they go round the 'J' tubes, one each side.
step 4: find some way of bonding the ali blocks to the stainless tubes.
step5: find an old heat exchanger and cut in half, then copy the design, but make big enough to surround the ali blocks and goive good flow of air. the flap mechanism may be tricky to fabricate, so pull it off the old one.
weld it all together, and use the origional beetle heater system, and marvel at the pasty warming goodness :d

I thought about it along the same lines but instead of the billet alloy blocks my thought was to fold 1mm alloy sheet into say 1" folded strips and then clamp them around the J tube in a sort of fan shape (try it with paper to get the idea). The heat exchanger casing could be a simple alloy split tube with rivetted/screwed ends like a hi-perf bike silencer with rivetted inlet and outlet tubes. I might have a go at this some time to see if it works.

evilC

 

[PIE O.C.]

They do the diesel eiberspacher in 12v send me a pm if you are interested in one I think me mate has a spare