1eyedjack

Ah thanks. I wonder if greater efficiency could be achieved by using human effort to compress air into a bottle which would then gradually dissipate to drive a pump in a more conventional heat engine that uses (eg) ammonia in a reverse rankine loop.

Wasn't sure whether to post this in the physics forums or eng. forums. Sort of applied physics, perhaps. I was wondering if any of you kind readers could do some sums to work out how much effort it would be to run a human-powered refridgerator? I was thinking along the lines of a portable one that you could take camping where there is no power supply provided. I did some searching and could not see any on the market, so I sort of assume that it is not feasible, but would like to see it proven in black and white. After all, it wasn't that long ago that wind-up torches and radios were not available. I suppose that the short answer is that it the amount of effort would depend on how good a refridgerator you want. Ie, by how much do you want the internal temperature depressed? You could probably produce one that would reduce the temperature by about half a degree without working up too much of a sweat, but that would not result in a marketable product with profit potential. As regards how much ongoing regular physical repetition is required to maintain a desired internal temperature range, well that would depend on the efficiency of the insulation (assuming you don't go repeatedly opening and closing the fridge door), and doubtless a host of other variables (outside temperature perhaps being a critical one, size of refridgerator and specific heat capacity of contents (say water for this purpose) being another). We could perhaps simplify the problem by assuming a perfect insulator, so that once heat is extracted it stays extracted. Then I guess what I am looking for is a formula that shows how much effort in pedalling (or hand cranking) of a resistant wheel is required to reduce the internal temperature by so many degrees (and subject to whatever other key variables you consider significant).

Now, now, hold fire on the jargon, please, I know NOTHING. But I have a gadget powered by batteries (it is a timer for an automatic garden irrigation system). The instruction manual enjoins me to use alkaline, non-rechargeable batteries. I am abjured from using any other sort on pain of .... well, pain. The manufacturer of the gadget has no financial stake in whatever battery supplier I choose, so I reluctantly conclude that that the advice is at face value. But to me, a volt is a volt is a volt. Just as a dollar, pound or penny loses the identity of its source once it is in my wallet, I do not expect an item of electronic equipment to be overly "concerned" whether an ampere here or there comes from an alkaline battery, NI-Mh, Ni-Cad, lithium-ion, polymer or what the heck. If the potential diffence between plus and minus fits the spec, then great. Same goes for whether the battery has been run down, charged up, run down again however many times. For sure, I can well believe that one battery may maintain its charge longer than another, or that its long term life may be limited by recharge frequency etc. But I can cater for that by replacing the batteries or recharging at an appropriate frequency, and that is not the point being expressed in the manual. So, what's that all about? Thanks for any insight

If anyone asks me a question how to explain a quantum physics phenomenon to a layman I direct him to read Mr Tomkins in Paperback, by George Gamow. I certainly couldn't explain it better than he.