El jueves, 19 de julio de 2012, 6:57:11 (UTC-5), Richard Rasker escribió:> Hello, > > I'm designing a 'thermo table', consisting of a 150 x 150 x 4 mm aluminium > surface (6" x 6" x 1/6"), which has to be kept at a precise temperature > throughout (+/- 0.1 degree centigrade). Since both heating and cooling are > required, the whole design is based on one or more Peltier elements. > > Ideally, one would use a Peltier element of comparable size as the aluminium > surface, to minimize temperature differences due to small local heat > losses. However, for reasons of cost and available electrical power (100W > max), I'm limited to commonly available Peltier elements with a 40 x 40 or > 50 x 50 mm surface area. > > So I thought I'd use four identical 25W Peltier elements (40 x 40 mm) > instead of one 100W Peltier element (50 x 50 mm). My question: is it better > to connect these Peltier elements in parallel or in series? In other words: > is a Peltier element's heat transport mainly determined by voltage > difference or by current? Any ideas are appreciated. > > And oh, I thought about using much thicker aluminium to minimize local > temperature differences, but with the above dimensions, I already have a > heat capacity of > 200 J/C, so with 100W power it already takes at least 2 > seconds to heat it up by one degree. > Doubling the thickness also doubles this time, and that quickly becomes a > problem: users will want to change the temperature often, and don't want to > wait several minutes every time until the temperature settles to its final > value. > > Thanks in advance for any ideas. > > Richard Rasker > -- > http://www.linetec.nland to think im a total newbie who stubled upon this trhead while looking for a correct way of conecting 2 peltier modules using an xbox 360 power supply a 1209 temp control and pc parts for an upgrade to an old black and decker BNA17B peliter cooler.... god i love internet!!!!
Muliple Peltier elements: parallel or series?
Started by ●July 19, 2012
Reply by ●May 21, 20202020-05-21
Reply by ●May 21, 20202020-05-21
On Thursday, May 21, 2020 at 4:53:28 PM UTC+10, cristhia...@gmail.com wrote:> El jueves, 19 de julio de 2012, 6:57:11 (UTC-5), Richard Rasker escribió: > > Hello, > > > > I'm designing a 'thermo table', consisting of a 150 x 150 x 4 mm aluminium > > surface (6" x 6" x 1/6"), which has to be kept at a precise temperature > > throughout (+/- 0.1 degree centigrade). Since both heating and cooling are > > required, the whole design is based on one or more Peltier elements. > > > > Ideally, one would use a Peltier element of comparable size as the aluminium > > surface, to minimize temperature differences due to small local heat > > losses. However, for reasons of cost and available electrical power (100W > > max), I'm limited to commonly available Peltier elements with a 40 x 40 or > > 50 x 50 mm surface area. > > > > So I thought I'd use four identical 25W Peltier elements (40 x 40 mm) > > instead of one 100W Peltier element (50 x 50 mm). My question: is it better > > to connect these Peltier elements in parallel or in series? In other words: > > is a Peltier element's heat transport mainly determined by voltage > > difference or by current? Any ideas are appreciated. > > > > And oh, I thought about using much thicker aluminium to minimize local > > temperature differences, but with the above dimensions, I already have a > > heat capacity of > 200 J/C, so with 100W power it already takes at least 2 > > seconds to heat it up by one degree. > > Doubling the thickness also doubles this time, and that quickly becomes a > > problem: users will want to change the temperature often, and don't want to > > wait several minutes every time until the temperature settles to its final > > value. > > > > Thanks in advance for any ideas. > > > > Richard Rasker > > -- > > http://www.linetec.nl > > and to think im a total newbie who stubled upon this trhead while looking for a correct way of conecting 2 peltier modules using an xbox 360 power supply a 1209 temp control and pc parts for an upgrade to an old black and decker BNA17B peliter cooler.... > > god i love internet!!!!If you e-mail me at bill.sloman@ieee.org I'll send you a reprint of my paper on the subject. Sloman A.W., Buggs P., Molloy J., and Stewart D. “A microcontroller-based driver to stabilise the temperature of an optical stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor” Measurement Science and Technology, 7 1653-64 (1996) It hasn't been cited all that recently - nothing since 2018 - so there may be something better around. It covers the theory, if not in any great detail - there's only so much that you can squeeze into ten pages. -- Bill Sloman, Sydney
Reply by ●May 21, 20202020-05-21
On 2020-05-21 02:53, cristhian.hellsing@gmail.com wrote:> El jueves, 19 de julio de 2012, 6:57:11 (UTC-5), Richard Rasker > escribió: >> Hello, >> >> I'm designing a 'thermo table', consisting of a 150 x 150 x 4 mm >> aluminium surface (6" x 6" x 1/6"), which has to be kept at a >> precise temperature throughout (+/- 0.1 degree centigrade). Since >> both heating and cooling are required, the whole design is based on >> one or more Peltier elements. >> >> Ideally, one would use a Peltier element of comparable size as the >> aluminium surface, to minimize temperature differences due to small >> local heat losses. However, for reasons of cost and available >> electrical power (100W max), I'm limited to commonly available >> Peltier elements with a 40 x 40 or 50 x 50 mm surface area. >> >> So I thought I'd use four identical 25W Peltier elements (40 x 40 >> mm) instead of one 100W Peltier element (50 x 50 mm). My question: >> is it better to connect these Peltier elements in parallel or in >> series? In other words: is a Peltier element's heat transport >> mainly determined by voltage difference or by current? Any ideas >> are appreciated. >> >> And oh, I thought about using much thicker aluminium to minimize >> local temperature differences, but with the above dimensions, I >> already have a heat capacity of > 200 J/C, so with 100W power it >> already takes at least 2 seconds to heat it up by one degree. >> Doubling the thickness also doubles this time, and that quickly >> becomes a problem: users will want to change the temperature often, >> and don't want to wait several minutes every time until the >> temperature settles to its final value. >> >> Thanks in advance for any ideas. >> >> Richard Rasker -- http://www.linetec.nl > > and to think im a total newbie who stubled upon this trhead while > looking for a correct way of conecting 2 peltier modules using an > xbox 360 power supply a 1209 temp control and pc parts for an upgrade > to an old black and decker BNA17B peliter cooler.... > > god i love internet!!!! >Welcome. You're accessing this group using the Google Groups WWW interface, but in fact this is a Usenet newsgroup, sci.electronics.design. Usenet started in 1979, and covered the whole world within a couple of years, at least for folks that had Internet access at that time. It was and is based on the NNTP protocol, rather than HTTP/HTTPS. That makes it a decade older than the World Wide Web, and 19 years older than Google. It's the original social media platform, and has virtually none of the censorship problems associated with the Big Tech-dominated platforms. If you dislike somebody's posts super badly, you don't try to get them banned, you just set a filter so you don't see them. Democracy and freedom, right? Some groups, such as this one, include folks with world-class expertise. C'mon and join the fun! You can view Usenet with Google Groups, which does have a pretty deep archive of posts (*) (you would probably have had trouble replying to an eight-year-old post on Twitter, for instance). However, the best way is to get a real newsreader such as Thunderbird or Forte Agent, and an account on a free news server such as aioe.org or eternal-september.org. There are also nearly-free ones such as Giganews and Supernews, which also have deep archives, but have recently been experiencing some performance problems. Cheers Phil Hobbs (*) Google bought out the original Usenet archiver, DejaNews, in 2001, and acquired both its extensive archive and its Usenet search technology. -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●May 21, 20202020-05-21
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in news:ra6vu5$b82$1@gioia.aioe.org:> On 2020-05-21 02:53, cristhian.hellsing@gmail.com wrote: >> El jueves, 19 de julio de 2012, 6:57:11 (UTC-5), Richard Rasker >> escribió: >>> Hello, >>> >>> I'm designing a 'thermo table', consisting of a 150 x 150 x 4 mm >>> aluminium surface (6" x 6" x 1/6"), which has to be kept at a >>> precise temperature throughout (+/- 0.1 degree centigrade). >>> Since both heating and cooling are required, the whole design is >>> based on one or more Peltier elements. >>> >>> Ideally, one would use a Peltier element of comparable size as >>> the aluminium surface, to minimize temperature differences due >>> to small local heat losses. However, for reasons of cost and >>> available electrical power (100W max), I'm limited to commonly >>> available Peltier elements with a 40 x 40 or 50 x 50 mm surface >>> area. >>> >>> So I thought I'd use four identical 25W Peltier elements (40 x >>> 40 mm) instead of one 100W Peltier element (50 x 50 mm). My >>> question: is it better to connect these Peltier elements in >>> parallel or in series? In other words: is a Peltier element's >>> heat transport mainly determined by voltage difference or by >>> current? Any ideas are appreciated. >>> >>> And oh, I thought about using much thicker aluminium to minimize >>> local temperature differences, but with the above dimensions, I >>> already have a heat capacity of > 200 J/C, so with 100W power it >>> already takes at least 2 seconds to heat it up by one degree. >>> Doubling the thickness also doubles this time, and that quickly >>> becomes a problem: users will want to change the temperature >>> often, and don't want to wait several minutes every time until >>> the temperature settles to its final value. >>> >>> Thanks in advance for any ideas. >>> >>> Richard Rasker -- http://www.linetec.nl >> >> and to think im a total newbie who stubled upon this trhead while >> looking for a correct way of conecting 2 peltier modules using an >> xbox 360 power supply a 1209 temp control and pc parts for an >> upgrade to an old black and decker BNA17B peliter cooler.... >> >> god i love internet!!!! >> > > Welcome. You're accessing this group using the Google Groups WWW > interface, but in fact this is a Usenet newsgroup, > sci.electronics.design. > > Usenet started in 1979, and covered the whole world within a > couple of years, at least for folks that had Internet access at > that time. It was and is based on the NNTP protocol, rather than > HTTP/HTTPS. > > That makes it a decade older than the World Wide Web, and 19 years > older than Google. It's the original social media platform, and > has virtually none of the censorship problems associated with the > Big Tech-dominated platforms. If you dislike somebody's posts > super badly, you don't try to get them banned, you just set a > filter so you don't see them. Democracy and freedom, right? > > Some groups, such as this one, include folks with world-class > expertise. > C'mon and join the fun! > > You can view Usenet with Google Groups, which does have a pretty > deep archive of posts (*) (you would probably have had trouble > replying to an eight-year-old post on Twitter, for instance). > However, the best way is to get a real newsreader such as > Thunderbird or Forte Agent, and an account on a free news server > such as aioe.org or eternal-september.org. > There are also nearly-free ones such as Giganews and Supernews, > which > also have deep archives, but have recently been experiencing some > performance problems. > > Cheers > > Phil Hobbs > > (*) Google bought out the original Usenet archiver, DejaNews, in > 2001, and acquired both its extensive archive and its Usenet > search technology. >You need a hot (or cold) slurry between the heat or cold source and the surface you wish to have a homogenous temperature across its surface on. First off, you cannot go to big or even local room currents will throw you off. I used to make black body calibration source 'ovens' for IR Thermometry some decades ago, and we used a huge, 6" diameter Aluminum ingot with a single rod heater shoved about 40% of the way up its ass. The face had a concentric set of sawtooth wave grooves across it at about 1mm height, and the best damned carbon black black body high emissivity surface coating around. The outer half inch was obscured by the front aperture plate/cabinet opening, and it sits back about 30mm behind that. The surface temp homogeneity was pretty damned good for simple IR thermometry. But for a larger surface a thick slab front surface was needed and a liquid oil behind that with the homogeneous temperature to spread. So for the peltiers run them at full tilt in whatever direction you desire (hot or cold) and use that to heat or cool a vessel and pump assembly to heat the oil that lies behind the panel surface. But a huge 50 kilo block of Al thick enough to allow several backside heat/cold sources to soak through enough thickness of media to homogenize the temperature on the front side surface works good too. That array would all have to be individually managed and calibrated in, likely for each big set point jump. OR put a nice sloshy oil chamber between them and let it soak into the front mass evenly. The surface has to be recessed back into the cabinet it is in as room air currents mess it up, and IR imaging devices don't like calibrating from 'bad' surfaces. We used to calibrate Optical tube, resistor bolometer thermometry devices with it from a 1" focus to my 4" gold mirrored, 1.5 foot long tubed, rifle scope aimed, rifle stock fitted IR thermometer with about a 50' focus that electrical linesmen used to look at insulators and transformers for overheating and leakage from the ground. Now we just use IR imagery. Did not have that back in '86, without HUGE bucks and LN handy. So we sold a lot to the power company guys. Cool thermometer too. I probably built this one... <https://picclick.com/MIKRON-PORTABLE-INFRARED-THERMOMETER-GUN-10-to- 272283002167.html>
