Comments on: A rare recantation http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/ the blog that is not dansdata.com Fri, 10 Feb 2012 14:00:21 +0000 http://wordpress.org/?v=1.5.1-alpha by: davolfman http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3217 Sat, 04 Oct 2008 15:42:11 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3217 I never realized you could run any old peltier in reverse. I'll have to see if I have that old 40 watt I bought intending to cool my Thunderbird with. I never realized you could run any old peltier in reverse. I'll have to see if I have that old 40 watt I bought intending to cool my Thunderbird with.

]]> by: Jono4174 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3211 Fri, 03 Oct 2008 17:56:09 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3211 In NZ (unlike Australia), "Engine Up" is allowed to advertise on TV. (It is an oil additive which does nothing) In NZ (unlike Australia), "Engine Up" is allowed to advertise on TV. (It is an oil additive which does nothing)

]]> by: j http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3209 Fri, 03 Oct 2008 16:04:36 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3209 I nabbed a look at your "magnetic wine" review this morning, and just happened to spot this article this afternoon: http://www.telegraph.co.uk/news/newstopics/howaboutthat/3115492/Ultrasound-machine-turns-cheap-plonk-into-fine-wine-in-30-minutes-says-inventor.html I smiled, then I sighed. I'm guessing the "inventor" actually does believe it works; he probably also buys special pure silver cables for his hifi. I nabbed a look at your "magnetic wine" review this morning, and just happened to spot this article this afternoon:
http://www.telegraph.co.uk/news/newstopics/howaboutthat/3115492/Ultrasound-machine-turns-cheap-plonk-into-fine-wine-in-30-minutes-says-inventor.html

I smiled, then I sighed.
I'm guessing the "inventor" actually does believe it works; he probably also buys special pure silver cables for his hifi.

]]> by: Daniel Rutter http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3208 Fri, 03 Oct 2008 15:49:49 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3208 A Peltier device is indeed, technically, made out of an array of thermocouples, but when you say "thermocouple" you're usually talking about the simple dissimilar-metals type, which is cheap and robust but which has quite miserable power output. If you put a bunch of thermocouples and a heat sink the size of a basketball on top of a kerosene lamp you can <a href="http://blog.modernmechanix.com/2007/10/05/kerosene-lamp-powers-radio/" rel="nofollow">just about</a> <a href="http://blog.modernmechanix.com/2005/11/18/kerosene-radio/" rel="nofollow">run a valve radio</a>, but that same contraption would have trouble powering one incandescent-bulb turn signal, let alone the rest of the crud in a car, even if you extended it to six feet of exhaust pipe. "Peltier" thermoelectric devices are always made out of semiconductor junctions (and there's some technical difference between the Peltier and Seebeck <a href="http://en.wikipedia.org/wiki/Thermoelectric_effect" rel="nofollow">effects</a> which I haven't the physics to quite understand), and have much better efficiency than simple dissimilar-metals thermocouples. A Peltier device is indeed, technically, made out of an array of thermocouples, but when you say "thermocouple" you're usually talking about the simple dissimilar-metals type, which is cheap and robust but which has quite miserable power output. If you put a bunch of thermocouples and a heat sink the size of a basketball on top of a kerosene lamp you can just about run a valve radio, but that same contraption would have trouble powering one incandescent-bulb turn signal, let alone the rest of the crud in a car, even if you extended it to six feet of exhaust pipe.

"Peltier" thermoelectric devices are always made out of semiconductor junctions (and there's some technical difference between the Peltier and Seebeck effects which I haven't the physics to quite understand), and have much better efficiency than simple dissimilar-metals thermocouples.

]]> by: davolfman http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3207 Fri, 03 Oct 2008 13:37:26 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3207 "Peltier-device heat-recovery units"? Isn't it a heck of a lot easier (and more understandable) to call them thermocouples instead, or are you quoting? "Peltier-device heat-recovery units"? Isn't it a heck of a lot easier (and more understandable) to call them thermocouples instead, or are you quoting?

]]> by: reyalp http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3204 Fri, 03 Oct 2008 09:48:27 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3204 Dan: AFAIK cooling your exhaust actually does impact performance somewhat, due to the effects of increasing the density. If you just add peltiers to the outside of your existing pipes, that wouldn't be an issue (in fact, it would probably retain even more heat), but you set things up to extract maximal heat, that could be a different story. Scavenging the heat from your oil, block or cooling water is OTOH is completely free, at the expense of a lower temperature differential. robinsonb5: I don't think scaling the process is a problem, but bouncing down the road might complicate things. The total size/mass might end up pretty large too, but I don't have a good handle on just how big. A fridge doesn't have much cooling power compared to an AC unit, since it mostly relies on insulation and thermal inertia. The traditional <a href="http://en.wikipedia.org/wiki/Absorption_refrigerator" rel="nofollow">ammonia cycle</a> uses compressed hydrogen gas and ammonia, which might lead to safety concerns. Alternately, you could try to use a <a href="http://en.wikipedia.org/wiki/Stirling_engine" rel="nofollow">stirling engine</a> for one or both sides of your AC. Dan:
AFAIK cooling your exhaust actually does impact performance somewhat, due to the effects of increasing the density. If you just add peltiers to the outside of your existing pipes, that wouldn't be an issue (in fact, it would probably retain even more heat), but you set things up to extract maximal heat, that could be a different story. Scavenging the heat from your oil, block or cooling water is OTOH is completely free, at the expense of a lower temperature differential.

robinsonb5:
I don't think scaling the process is a problem, but bouncing down the road might complicate things. The total size/mass might end up pretty large too, but I don't have a good handle on just how big. A fridge doesn't have much cooling power compared to an AC unit, since it mostly relies on insulation and thermal inertia. The traditional ammonia cycle uses compressed hydrogen gas and ammonia, which might lead to safety concerns.

Alternately, you could try to use a stirling engine for one or both sides of your AC.

]]> by: robinsonb5 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3201 Thu, 02 Oct 2008 20:57:02 +0100 http://dansdata.blogsome.com/2008/10/02/a-rare-recantation/#comment-3201 Something I've wondered a few times, actually - you know those camping fridges that use a gas flame to run an adsorption cycle? Is that technology remotely scalable? Could that waste heat from the exhaust be used directly to run some form of air-con, or would the coolant volumes/pressures be prohibitive? I guess the efficiency would be lousy, but efficiency matters very little when you can use waste heat for free, and in so doing take the load off another part of the system. Something I've wondered a few times, actually - you know those camping fridges that use a gas flame to run an adsorption cycle? Is that technology remotely scalable?
Could that waste heat from the exhaust be used directly to run some form of air-con, or would the coolant volumes/pressures be prohibitive? I guess the efficiency would be lousy, but efficiency matters very little when you can use waste heat for free, and in so doing take the load off another part of the system.

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