Model engineering heat pumps

Stirling heat pump. They work great, and have fewer lubrication problems than Stirling engines. And no stainless or superalloys. You can make them out of aluminum screw-machine stock. One end is hot, the other end is cold.

I've had thoughts of making a Stirling cooler myself.

-- Ed Huntress

Richard J Kinch fired this volley in news:Xns9C7ABE1B9B0Fsomeconundrum@216.196.97.131:

Richard, that would be roughly 1/4HP for five minutes.

That's a LOT of muscle.

LLoyd

Learning how to do gross calculations really took a lot of fun out of pipe dreams ;)

Wes

We have overblown project ideas on our to-do-who-knows-when lists. I have a grand idea of converting a 3m sat dish into a parabolic solar steam boiler to feed a steam engine generator followed by an absorption chiller. Don't know if I'll ever get a round-tuit, but it's a neat idea.

"Pete C." wrote in news:4a9f0260$0$32192$ snipped-for-privacy@unlimited.usenetmonster.com:

Why I was a lad, we had plans for a soda can "un-toaster". We had a bunch of Peltier effect cooling modules from the local surplus yard, and the idea was to make a clamping arrangement with four of them to suck the heat out of a soda can. It would have drawn about 240 Watts. The crowning touch was to be a lever arrangement to lower the can against a spring so it would pop up when it was cool.

Many years later, I finally have an adequate shop & skills to build the mechanism, but no time & no Peltier modules.

Doug White

1 KWH can pump 10,000 BTU in a 10 SEER heat pump. If we equate 746 watts to 1 HP, then you get 7460 BTUs pumped with 1 HP-hour. So pumping 50 BTUs would take 50/7460 = 0.0067 HP-hour. That's about 0.08 HP for 5 minutes. But who knows what efficiency you could build in that size. And how thirsty you are for a cold one.

Richard J Kinch fired this volley in news:Xns9C7AD5563B921someconundrum@216.196.97.131:

I stand corrected. I failed to account for the fact that energy moved isn't equal to energy input.

HOWSUMEVER... I'm not sure most 'mature' guys could output nearly a tenth of a HP for five minutes, either. But I concede the error .

LLoyd

Sounds pretty much like the 60 Watt wine chiller I bought for $3 a couple Saturdays back - took a 1 litre bottle of water from room temperature to freezing in about 3 hours. Gerry :-)} London, Canada

300W continous out of the legs of a trained cyclist is a reasonable number. 56W hand cranking seems a bit ambitious.

I got it, bar stool with pedals ;)

Wes

Neat idea.

The engineer in me says, "simplify". So, just build 1/2 a heat pump. If you pull a vacuum on a properly selected fluid (IPA???) it will boil and cool. So, all you'd need is a little vacuum pump and a double wall container sized for a beer can.

I'd further consider a cylinder with "O" rings for seals and read valves. Just move it back and forth for your power.

There's one concept anyway.

Karl

If the fluid boils low enough (R134a etc) then you don't even need to pump it. But that's cheating to vent the refrigerant. This is supposed to be a closed system other than the crank input and heat output.

[ ... ]

Hmm ... glass container? Mess? (And what is the freezing point of wine instead of water?)

Enjoy, DoN.

I doubt that any ice would have formed - just held at 0 deg. C. I haven't investigated the actual structure but the inner, metal cup seems uniformly cold. Actually I bought it for the 12V, 5A power supply. Gerry :-)} London, Canada

This 'mature' guy (AKA oldfart) survivor of quintuple bypass and now bearer of an ICD can output rather more than 74.6 watts (0.1HP) for considerably more than 5 minutes. I did better than that in rehab last summer and I'm considerably stronger now than I was then.

I joked at the time that they tortured us pedalling furiously to produce energy they sold to third-world places like Iowa.

Hour-record cyclists put out something over half a KW for that hour.

75 watts for 5 minutes is more than button pushing on a remote, but not that hard.

I've got a copy of a series that ran in The Model Engineer, late '30s or '40s. Used methyl chloride for the working fluid and was just about big enough to make an ice cube. An absorption unit would probably be easier to build, once you can braze hydrogen-proof joints.

Stan

Everything is easy for the man that never does it.

--Winston

Winston fired this volley in news:h7rknb02j66 @news7.newsguy.com:

Especially considering that so far, we've only accounted for the heat. Assuming a perfect Stirling machine is about 54% efficient, how much work do you think we'll have to add for losses to get the delta-T desired?

LLoyd

A wine chiller that goes below freezing probably won't be too wine-friendly. ;-)

Cheers! Rich