Bush/Camp freezer

[FNQ Bunyip]

I read this on a fishing site I goto now and then and its got me thinking ....

I have a 200l BUSH FREEZER using a CAR A/C coupled to a 5.5hp honda motor plus an alternator for charging the odd battery and my freezer pulls down to -42 degrees using a commercial temp gauge. My bush freezer has 50mm of insulation and I only run it for 4 hours a day @ a little above idle for about .4L / day petrol. It will completely freeze a 20l plastic bucket of tap water into an ice brick in 6 hours. By using a 12v bilge blower and directing the air onto the open carton it will freeze the carton of VB stubbies in 20 minutes.

Any Ideas, sugestions ,advice ,plans ,help would be great.
I can get a hold of all types of stuff and have a few condenser coils and things laying around ...

Cheers fnqbunyip

[frank]

Any Ideas, sugestions ,advice ,plans ,help would be great.

What do you want to do - make one of these things?

Are you mechanically minded. Do you have the correct tools?

Do you just want a link to the appropriate web site?

[FNQ Bunyip]

Hi Frank , yes I would like to build somthing along these lines.
Yes I'm machanically minded ( Deisel fitter ) . Also have a background in distilling essential oils ( steam& Solvent )
If I havent got the tools I can borrow them . ( vac pump )
So any tips or have you seen anything along these lines ?
I'm just fishing for ideas at this stage and recon that I should be able to have built somthing (that works ) by xmas .
Thanks
Cheers fnqbunyip

[frank]

Well, If this unit you have read about can freeze a slab of VB in 20 minutes then it's no good building one of these as you can't drink frozen beer

Obviously, the important thing to think about with a mobile fridge/freezer is how do you power it. If you want to take it into the bush while camping then it has got to be 1) portable and 2) have a portable power supply.

There are Peltier type fridges that work well for camping as these do not have any moving parts and are easily portable. Small battery or propane powered absorption fridges are also good for camping but are not easily built by the amateur or indeed by the professional

The idea of using easily obtained car AC parts and having them driven by a portable generator/motor seems to be a good idea. It will be a large machine though and not easily carried. I would think that it would have to be mounted on a trailer or something similar. What you must do though is make sure that you get the compressor, condenser coil, evaporator coil and metering device from the same car so that they are balanced.

Basically, you need to couple the compressor up to the engine via drive belts, pipe up the disharge outlet from the compressor to the condenser (having a fan to blow across the condenser to reject the heat) pipe up the condenser outlet to the metering device which is then piped up to the evaporator coil (in the chilled box with a fan blowing over it to absorb the heat) and finally pipe up the evaporator outlet to the compressor suction inlet. Do you have access to refrigerants?

To control it all you will need to wire in a thermostat, low pressure control, high pressure control and an on/off switch as a basic minimum.

What you are trying to do took most of us on this forum at least 4 years of learning. And we are still learning every day. There are many things that can and do go wrong with refrigeration circuits and even if you managed to do a little pipe strangling, brazing (do NOT soft solder any of the joints) you would not know if the unit was working fine if you managed to get it started. I remember an apprentice some time ago getting out the ohm meter and taking some measurements on a system. I said - well, whats wrong then, he said - I don't know but it's 32k ohms. Just shows that he can read the display but could not translate it into what may have been wrong with the system.

The cost alone makes me think it would be cheaper to either buy a ready-made unit or get a pro to assist you. At least then you would not lose all your hard work after maybe a few weeks/months when it all goes t*ts up.

The best advice I can really give is for you to buy/lend/borrow a book on the principles of refrigeration. If, after you have read up un the basics, you still want to have a go, post again with specific questions and I'll try to help further.