20 horses and still no cold beer?

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trowell

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when i was a student, (many years back), i found a job on a farm for the summer holidays that involved spraying liquid pig feaces from the back of a tractor onto a carrot crop. The towed slurry tank was pressurized using the PTO (power take off) from the tractors engine.

I dont spray sh*t anymore but unfortunately i still, albeit on very rare occasions, have to analyse the human variety at my place of work. That aside, I pondered today whether there is a way in which I can tap into my 20 horse power boat engine and use it in the same way to power a heat exchanger to cool the bloody beer down....

surely there is a way to create cooling when a diesel engine is running. Some of the posh Audi's have refrigerated glove boxes to keep the sarnies fresh...how does that work?

any ideas gratefully received
 
You need to get an air 'conditioning' unit from a car and connect it to your engine using pulleys etc. You just then need to connect all the pipework back up to the cooler, recharge and it may work. The other and easier option is to buy a small electric cool box.
 
Those Audi's have air conditioning. Effectively the engine drives a fridge compressor. You could have an engine driven fridge, but its simpler to run a 12volt fridge or coolbox from power provided by the alternator.
 
No idea what the shit has to do with it, but engine-driven fridge compressors are a perfectly standard thing. More common in the US than here, for whatever reason. They're used with a much bigger cooling plate in the fridge, that has magic fluid in it that holds the cold a long time, so it stays cool even when not running the engine.

Pete
 
trowell said:
when i was a student, (many years back), i found a job on a farm for the summer holidays that involved spraying liquid pig feaces from the back of a tractor onto a carrot crop. The towed slurry tank was pressurized using the PTO (power take off) from the tractors engine.

I dont spray sh*t anymore but unfortunately i still, albeit on very rare occasions, have to analyse the human variety at my place of work. That aside, I pondered today whether there is a way in which I can tap into my 20 horse power boat engine and use it in the same way to power a heat exchanger to cool the bloody beer down....

surely there is a way to create cooling when a diesel engine is running. Some of the posh Audi's have refrigerated glove boxes to keep the sarnies fresh...how does that work?

any ideas gratefully received
Click to expand...

Used to be pretty common on charter boats out here but less so nowadays.

See here for what you need. http://www.seafrost.com/Engine Drive.html
 
Engine driven compressor for fridge

Can be an excellent solution to fridge problems. The car aircon compressor tends to have huge cooling power. So you need a keel cooler for the condensor and as said you need a way to store the huge cooling power in eutectic plate. (is that the name?) Then you need to run the engine perhaps daily to keep everything frozen. Of course you would need a fridge compartmentalised so beer is not frozen but icecream is. As said very efficient and no battery worries but expensive compared toa small 12v compressor cooler.
Which can run on solar as well as engine or shore power.
Good luck olewill
 
As above, it is/was a common system on charter boats, as most of them run the engine at least once per day. Much less satisfactory for cruising when you want to anchor for days at a time.

There is quite a lot about these engine driven compressors in Nigel Calder's maintenance and engineering book.
 
little_roundtop said:
We have a Frigoboat system to cool the fridge, in addition to a 12v compressor.
Click to expand...

That's interesting, I've often considered the idea of such a dual system in a real cruising boat. Are they two completely independent circuits, or two compressors in parallel with one plate in the fridge?

Pete
 
A car system (as has been said) has immense cooling power compared to that required for a fridge! It has to keep the whole volume of a car cool despite huge solar gain because cars are poorly insulated and have a big surface area. The smallest 2 seater car compresor would be more than ample. Something like a Smart Car. They have a compresor driven by the engine, which sends compressed refrigerant to a condenser, usually mounted in front of the radiator. In here, it liquefies and then goes through a receiver with a filter and some dessicant in it. It then passes through a small hole where it is allowed to discharge into a lower pressure area (the evaporator) where it turns back into a gas - taking heat from its surroundings to do so. It then passes back to the compressor, to begin the cycle again.

The chilled glovebox thing just takes a bit of the cold air from the evaporator area and ducts it through the glovebox.

I'm not sure a car system would be good for a small volume like a fridge because it takes ambient air and blows it (with the heater fan) over the fins of the evaporator and sends the cooled air into the passenger compartment. You probably wouldn't want to blow air into your fridge / freezer and if you did, you'd need to provide somewhere for it to go. You might be able to just put an evaporator in the fridge somewhere (with no air flowing through it) and see if that gets cold enough to keep the rest of the volume cold. They nearly always have thermostatic switches on them which cut the compresor out when the evaporator core gets to a particular temperature.

The condenser, would, as has been said, need to be changed for something that dumped its heat into the seawater ratehr than the air.

The most common refrigerant in cars these days is R134a and you'd need specialist equipment to charge the system up. Obviously, unlike a fridge, if the compresor is engine driven, you'd need flexible hoses to allow for engine vibration. You could also maybe look at cannibalising a chiller unit from a refrigerated van.

Unless you want air conditioning for the rest of the boat into the bargain, you might be better just getting the engine to drive a bigger alternator and running a conventional (self-contained) fridge-freezer unit from an inverter.

If you want to pursue the car route, I've had excellent service from these people:

http://www.fenair.co.uk/

Ask for Pat. They do a lot of agricultural stuff. Long way from Anglesey though!
 
prv said:
That's interesting, I've often considered the idea of such a dual system in a real cruising boat. Are they two completely independent circuits, or two compressors in parallel with one plate in the fridge?

Pete
Click to expand...

They're completely independent. The 12v compressor has a regular (quite thin) evaporator plate. The Frigoboat has a box like structure in the fridge and it gets real cold with the compressor on. We generally run the Frigoboat for the 20 or 30 mins that we're under power when motoring into an anchorage, looking for a suitable spot and then getting the hook in. It cools the fridge enough that the 12v compressor comes on very rarely overnight.

That said, I'm not impressed enough with it to say I'd fit one if it wasn't there (it was on the boat when we bought her). It needs re-gassing every couple of years, apparently these systems get moisture in the gas very easily (no idea how) and then the efficiency falls off.
 
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