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Room heat transfer?

Greetings all, I live in a solar powered house which is heated by a single log burning stove which is situated in the main living area. Is it possible for me to transfer heat to the colder rooms by simply putting ducting between the top sections of the adjoining walls (seeing that hot air travels to cold areas - in theory!) or will I have to use a fan? I am trying to use as little power as possible or ideally non at all. Has anyone got any experience of this or know of any suitable solutions? Many thanks in advance.

Question by peachvw    |  last reply


Heat Transfer Project

I need help with this project!!!

Topic by hj212121    |  last reply


Heat transfer through cement

I have a garage on top of garage because my land is on a hill. The lower garage is all concrete all the way around including the ceiling. The floor in the upper garage is the cement from the roof of the lower garage. I want to heat the upper garage, but I know the floor will always be really cold because it is cement and the lower garage is not heated. The lower garage does stay quite a bit warmer than outside temps.My question is this, If I heat the lower shop, will the floor in the upper garage and the upper garage that is insulated be warm as well? Or am I better off just heating the upper shop and having a cold floor? I spend a lot of time in the garage and would like it comfortable when I am in there. ThanksJed

Question by jedidieah    |  last reply


how to calculate heat transfer rate through a heat pipe ?

Objective: maintain a temperature of water feed into an equipment to be ( 0C-20C). he surrounding temp is about -15 C in Winter and 40 C in summer. I would consider the soil as a heat sync. Any equation to calculate the amount of heat the heat pipe can transfer or  be dissipated  ? Thanks !!

Question by sultan86    |  last reply


If a material is heated from the one side (100C), does it require the same amount of cooling (-100C) to get it cold?

If a material is heated from the one side and it takes 10min to transfer the energy to the other side, how long will it take to get the material cool to it's original temperature? (10min?) Does it depend on heating versus cooling. in other words, if it is heated at 100degrees, do you need to cool it at -100degrees to equal the time it takes to enter versus the time it takes to exit?

Question by deadend_designs    |  last reply


Temperature rate of rise on unexposed side of material with resistance R?

If a material with a thermal resistance R is exposed to an elevated temperature, how do you calculate the temperature of the unexposed side as a function of time?

Question by agingengineer    |  last reply


Induction Heating

High frequency induction heating is basically a very efficient way to heat ferrous metals. Induction heating uses an powerful magnetic field to induce currents within the surface of the metal being heated. This means that the coil will not get hot unless the material being heated transfers heat to it. Induction heating is very efficient because no heat is wasted, no heat is wasted because the coil does not produce heat, the heat comes from the workpiece being heated only.

Topic by lyzyrdman    |  last reply


Distribution of Solar Heated Water and Any Other Heated or Cooled Water

I started this project about a week ago after seeing the Instructable – https://www.instructables.com/id/How-to-build-a-strikeheliostatstrike-paraboliI made mine out of cardboard and then coated the cardboard – front and back – with fiberglass resin for stiffness. I covered the inside with tinfoil to test it out and find the focal point. It worked great with the focal point at the center of the dish even with the lip of the curve. I then removed the tinfoil and replaced the tinfoil with mirrored Plexiglas. Now it works awesome. I have a 30� parabolic mirror that can ignite wood almost instantaneously at the focal point of the light.Next I constructed the heating coil to run water through. This is made from a large 1 Kg coffee can, 16’ of ¼� copper tubing with end fittings, and the glass lid of a small sauce pan (handle removed). The outside of the coffee can is painted flat black as is the copper pipe. The copper pipe is coiled to a coil 4� in diameter and 6� in length and inserted inside the can with the ends extending from the side of the can through two drilled holes. The inside of the can is not painted, but left shiny. The glass lid is then taped over the hole with aluminum metal tape covering a minimum amount of the glass – about 1/4� around the edge.The coffee can is then suspended over the mouth of the parabolic mirror by a three point 6� chimney pipe stand-off. The can’s mouth is centered at the focal point of the mirror so all of the light being reflected by the mirror must enter the coffee can. Hoses are hooked up to the copper pipe fittings and these lines go to the feed/storage tank.The problem with the conventional set up from here is that the speed the water moves at (slow) to be heated to a great degree causes such great loses through convection, this system is not really feasible. I propose a new idea – or a new twist on an old idea.I noticed that the solar heat generating station use a black water pipe inside a glass vacuum tube to generate heat from the sun for heating water. I said to myself that this is a great idea and plan on building the next heating coil in a vacuum chamber. But, I also came up with the idea that the if the water is heated in this manner, why can’t it be transferred to the storage tank in a similar manner.If the feed lines were suspended inside a larger outer line and the outer line sealed tight and vacuumed the heat transfer due to convection would be almost nil. I estimated that with a total convective area at 100% the use of plastic stand-offs (8 @1/8� thick over 12’) the convective area would be reduced to 0.6%. Unbelievable! Even if this rose to 5% it is far beyond anything in use today by the home owner. Stretches of pipe going 100s of meters would no longer be un-heard of. You could place the dish in a close by field away from the trees and house and pump the heat back without losing it to the ground.This would also work for outdoor wood furnaces if use today. An outer pipe could be added over the existing pipe work, sealed, and vacuumed – almost all heat lose would be gone. And much larger stretches of pipe could be used here also. They would no longer need one furnace for the barn and another for the house. With this system, the pipes could even be run above ground, if desired, in some cases.This could also be used to replace insulation on cooling lines also.The key to the system is minimal contact between the inside and outside lines, and the vacuum between the two lines. Remember, there is no transfer of heat through convention within a vacuum, because there is no air for the heat to transfer through.As with all the new ideas this could get costly depending on the scale of piping you are dealing with – but the savings from reduced heat lose will far out way these cost in the near future.I may get an Instructable out for the Energy efficiency contest, but will be hard pressed.

Topic by strmrnnr    |  last reply


How practical is using bismuth for stovetop heat transfer? Answered

A stove that heats pots by induction is a nice idea, but it is still not common and will not work with all pots.Suppose, instead, the pot and resistive heating element were placed in a well that was filled with bismuth or another metal that has a low melting point. How would the efficiency of this compare to a pan sitting on an induction cooker, gas stove, or ordinary resistive heating element? What would be some important practical considerations, if this were implemented?

Question by NobodyInParticular    |  last reply


PCB toner transfer? Answered

Hey all- back with another dilemma. Whilst trying to make a PCB for the second time (first failed miserably), Im stuck on toner transfer. I printed my design out from eagle and laid it out, and Ironed it for about 2min on each side (mostly because the first time i tried i did it for about a minute and i only got about half the design on). When it cooled down i took it off and nothing got transferred. I got some residual lines from I think heat stress on the paper, but I was able to take them off. So naturally I tried again- but this time with a different method. I found some t-shirt transfer paper upstairs, and tried that. NEVER doing that again. I ended up having to sand my board down for like 5-7 min trying to get all the gunk off. Any ideas why my printer method doesnt work? Im using the same brand of photo paper as last time (Costco Kirkland brand), but a different printer- a canon instead of a brother. I have access to the brother printer, a hi quality photo printer (1200 dpi I believe), a dell laser printer, and the canon. I think I used the brother printer last time I tried (or possibly the photo printer- also a canon). Could that be the problem? Thanks in advance- Astroboy907 P.S I also have some transparency sheets if anyone has a method to get that to work.

Question by astroboy907    |  last reply


Can I turn a Laser.LED Keychain Light to where it can (light stuff on fire) transfer heat?

Can I turn a Laser.LED Keychain Light to where it can (light stuff on fire) transfer heat?

Question    |  last reply


Why dont they use alcohol in closed system steam engines? Other than safety?

By closed system i mean constant mass of working fluid.  i.e. no steam leaving system, like an air conditioner. My point is that alcohol has a lower boiling point that water, (some kinds can boil from the heat of your hand!). SO other than the safety problem of alcohol being flamable, alcohol could operate with a lower heat input than water.    With the addition of a cold resivoir, the closed system alcohol steam engine could work right? Or why not use a refridgerant gas in a closed system steam engine cycle,? >Which would effectively absorb the heat input any ideas? addition*  I mean for use in any steam engine with a closed loop cycle, like the Rankin cycle   http://en.wikipedia.org/wiki/Rankine_cycle

Question by MechEngineerMike    |  last reply


Induction Heating large scale

I am working on a project and have a large tank full of product kind of a greasy substance trying to heat up to temp of 180 degrees. the tank currently has a 4 inch pipe running inside wall all around tank for heat transference.. At this location a boiler is not a option at this time . I was curious if anyone ha s ever attempted a large induction heater build one that would encase a 4 inch pipe and heat liquid inside so thermal transfer would heat our product. Sorry for not including all details at this time i just curious if large induction heat was possible or efficient ?Thanks,

Question by andy1917  


Will concrete conduct heat well? Answered

See the picture for  more detail, but I basically need to know if this design of rock-steel-concrete-pipe will transfer heat to the oil in the pipe well. Thanks in advance, I don't need big fancy explanations, I just need to know if this will be a substantial heat source.

Question by jj.inc    |  last reply



Vortex cooling / heating tubes

I am currently gathering information about vortex tubes for my repulsine project. There are plenty to choose from on a commercial base but I struggle to find any technical drawings with proper dimensions. Several home made varities can be found as well but wither with poor performance or incomplete drawings. So I was thinking that someone here either uses a commercial product at home or work and might be able to take some basic measurements for me? I am most interested in the relation between inner tube diameter and lenght for the hot and cold ends as well as the size for the vortex chamber itself. If there is an orifice used on the cold end the hole diameter would be required as well. My aim is, based on a properly working original, to create a device that might be less efficient but can be used without a compressor. Would like to see, correct transfer of dimensions given, a vortex tube like system was used in the repulsine. Some old documents state that there was a "seperator" which removed "heavy air particles" and created a temperature differencial between top cone of the repulsine and the wave disks.

Question by Downunder35m    |  last reply


I am looking for a material that is thermally conductive, but electrically insulating. Answered

I need a thin sheet of this material to electrically Isolate my transistor from the heat sink without hampering the heat transfer...I tried Mica ..is there something better?

Question by vinod nicholas    |  last reply


expanded graphite heat-sink? Answered

Okay , I've searched and searched and cannot find what I'm looking for. Maybe the other diy'ers can help me. 1.What I'm looking for is a heat-sink made of expanded graphite or (carbon, graphite (∥) as it might be known as well) that is actually in the shape of a traditional aluminum heat-sink with the fins and NOT in the shape of thin film as it is very commonly available. I don't even know if it exists or is manufactured by any company. I've tried contacting some companies about it but they have yet to get back to me. The reason I want this is for the tremendous increase in heat conductivity as in this chart shown on this webpage http://physics.info/conduction/ . The application I am trying to use it for needs a raised, elongated surface area to displace heat semi-uniformly, hence why I need fins like a traditional heat-sink instead of the commonly available film expanded graphite online. 2. If it does exist or is able to be manufactured, would it be a ridiculously priced part or would it be a reasonable priced part? (Just doing small scale tests for now so it would be the size of a FET finned sink). 3. From what I've read it seems possible by maybe layering the films into a stacked lattice, keeping heat transfer perpendicular to the lattice, but what are your thoughts all? (I question bonding the layers myself but I don't know if you could hard press the layers together without a bonding agent since any bonding agent being used I believe would reduce the thermal conductivity quite a bit, but I'm not incredibly familiar with expanded graphite). Any and all help would be appreciated from this wonderful community Best regards, Velesh

Question by velesh    |  last reply


Most efficient way to recover heat from 130 degree F water and transfer this heat to 140 degree F water?

I am making a solar still and I need to recover as much heat as I can from the 130 degree F water (bringing the water temp down to near ambient, 72 degrees F) and then transfer this heat to 140 degree F seawater. I have a limited amount of solar collectors to heat brackish water, send it through an evaporator tower and then a condenser tower to make fresh water. As the fresh water goes through the condenser it gains a great deal of latent heat, thus the 130 degree F water. In order to increase production and regain otherwise lost energy I am trying to recapture a portion of this heat to further warm up the brackish water (currently at 140 degrees after exiting the evaporator tower) before being further heated with the solar collectors. I am operating off grid, so the solution must utilize solar heat or PV panels as the power source.  Does anyone know of a heat pump that operates best in this temp range? What about using TEC (aka TEG, TEP or TEHP) to perform this task? Is there a better or more obvious solution that I am oblivious to? Any advice would be much appreciated. 

Question by MichaelMichael    |  last reply


Protecting wood from heat from fire ? Answered

Hi all, I have been thinking of trying to set a small fire pit into a patio table. Its a fairly solid low "coffee table" type outdoor table so is capable of holding the weight, but im not sure if I can just cast a fire cement bowl to hold the wood/charcoal and set it into the table or would it eventually catch fire through heat transfer. Thanks in advance for any replies. 

Question by Squibo    |  last reply


breakin in a soldering iron

Is it just me or do you have to "break in" a soldering iron before it's really usful? I've had a new soldering iron for about amonth (using it about 4 hours to 8 hours a week) and it only started to solder really well in the past couple of days. Anybody know why? Also my soldering iron kind of has a hot spot, where you the solder melts really well, that normal?

Topic by guyfrom7up    |  last reply


Heated concrete garden seats question?

Next year I want to use the garden a lot more, so this winder I'm building a gas bottle wood burner like btop & maybe a BBQ like Babe-BQ from abitdifferent (have access to a few bottles of various sizes) and some concrete (maybe papercrete, if i can gather enough old paper for the whole job) bucket style seats, as I have lots of left over cement from a previous project where the inlaws over estimate (by a large amount!) So i can use it longer through the year, I'd like to have them heated with some pipes going through them being heated off the burner. I'd have a copper coil at the burner end, but ideally to keep costs down, i'd like to use PEX in the seats.  Will this transfer enough (if any) heat outside the pipe? and also will the concrete absorb the heat?  I was thinking of placing the pipe 10/15mm deep and having it coil back and forth from front of the seat  by the knees to the back by the shoulders and back again, 2 or 3 times per seat. It will be a modular design, for smaller molds and adjustability, with each seat connected to the last. I've added a quick drawing i made. Hope it makes sense. Was also thinking that I could also set up a solar heater as a pre heater to heat them in the to just take the chill off, but thats a different project for another time Any suggestions or advice greatly appreciated. Tuns 

Question by tuns    |  last reply


Inkless printer- Laser or Heat to engrave Paper

Hello,I am currently searching for projects that print on paper using heat, lasers or other inkless technology. The problem I ran into is that a search for burn, laser and thermal in combination with printer and paper allways brings many results that are irrelevant (laser printers, thermal transfer printers and such).What I did find is http://www.flickr.com/photos/jabella/438212343/in/set-72157600033633262/ for example. Though commercial laser solutions seem a bit "too much" and overpriced to plot a bit on paper.Does anyone here have any links to projects that use heat or other methods to print on paper?I guess it could be as simple as a plotter using a weak soldering iron ;-)

Topic by schorhr    |  last reply


A Deceptive Thermal Question for PCB Layout? Answered

Alas ... I was never strong in thermodynamics. This is for you  Printed  Circuit  Wizards Here is my problem in a White LED  layout,  See first picture Trying to pass excess LED heat to back side copper through VIAs I know the larger the VIA Dia the lower the thermal impedance. Intuitively as the hole grows it will eventually make heat transfer much worse  What or how do I find the OPTIMUM VIA Diameter for Heat TRANSFER ??

Question by iceng    |  last reply


Cooling of Laptops - It it possible to use copper pipe and heat convection to achieve this?? Answered

I have a compaq laptop that runs the cpu at 55 °C which is equal to 130 - +°F. I have constructed a fan extraction system using my computer desk that has two fans underneath extracting the hot air from the bottom of the laptop unit and 2 fans directing cool air into the laptop  from behind. I am only getting a 5C temperature drop. That is when the computer is idle. If the computer is actively processing this temperature goes up. The core temperature is constant 4 degrees high the cpu. I have read that using a hot water bottle is an effective way of reducing the temperature. I actually tried this method and it gave me much the same result as the fans. see this site http://digitalcomposting.wordpress.com/2008/04/30/water-cooled-laptop-stand-6/ Has anyone tinkered with the notion of using  a sealed copper coiled tubing with water or coolant. That the laptop can sit on via a thin aluminum plate as its base and acting as a heat transference agent then using the  natural heat convection en.wikipedia.org/wiki/Heat_transfer to cool the laptop. This is achieved by having one of the sealed ends of the copper tube immersed into cold liquid. The convection would presumably happen due to the heat and cold differences. Your opinions and further Ideas are welcome.

Question by spiderfurby    |  last reply


Small heating element, possibly ceramic, to sense and maintain temperature.

I am trying to make a heating element that would only turn on once the element itself reaches a certain temperature. This element, possibly ceramic, would be dormant until it reached an internal temperature from an external source (liquid) of 100 deg F. Once it is triggered, it would produce heat to maintain the liquid at 100 deg F. Ive been trying to figure out the best way to do this and how much power would be required. Say the liquid, well go with water, was 12 fl oz. how would I build a circuit that can be sensing temperature without using power, and once it reaches the desired temp, turns on the heater until the temperature either goes too high or drops too low so that it is not trying to work too hard. Open to suggestions on heating element types or anything that could help with my project. Thanks in advance!

Question by AndrewN144    |  last reply


DIY radiator design considerations?

I plan to build a radiator for a room. I can do the physics i.e. heat transfer etc. My question is really to any heating engineers out there: Are there any design considerations that I need to include so that the new radiator does not upset the existing central heating system (that heats the whole house). Thanks in advance.

Question by alexhalford    |  last reply


Carburettor Heater - need help

Hi All, Hope this is in the right section. I am working on a project to heat the body of a carburettor (Bing 84) in order to prevent carb icing.  No commercial solution exists for my carburettor.  My engine (for paramotoring) is air cooled so can't use water from cooling system. My idea was to strip out the nichrome heating element from a car cigarette lighter and use that.  The heat needs to be applied to the metal casing of the carburettor, preferably being hottest near the air intake side of the carb.  I decided the best place was where the air filter is attached - a 12mm long metal throat with a 35mm diameter The trouble is, I don't know I can transfer the hundreds of degrees of temperature from the nichrome to the metal body of the carb without just shorting out the battery.  If I am to have a layer of insulation between the nichrome and the carburettor, what can I use that will conduct heat but not electrical current, and withstand around 300 degrees of heat?  I also thought about reducing the current and spreading the heating over a larger portion of the metal casing, which would allow the temperature to be lower. I have also been experimenting with motorbike hand grip heaters that run of 12v but they don't generate enough heat - I need to be pumping in around 8-10A as the internal cooling effect of the fuel vaporising rapidly causes sub zero conditions inside the carb even when the outside air temperature is well above freezing.  I have a 7Ah li-ion which I would only switch on when required (maybe have a latching push button on throttle control). It may not be doable but its an interesting project nonetheless and something I am going to play around with.  Any ideas? Thanks, Dug

Topic by dugaldcurtis    |  last reply


Is someone willing to give me a good amount of technical advice concerning heat dissipation using a Peltier device ?

Ok, I have a laptop that I use to play many videogames with, and as you can imagine, it has an overheating is a problem. I have software that monitors the GPU and CPU temperatures while I play. The GPU and CPU are rated at a 100c max temperature. Now that the summer season has started, my laptop gets hotter and hotter as I play. I am usually forced to Under-volt my computer so that it stays below safe temperatures. Now, I was digging around online and came across something called a "Peltier device". It is a small ceramic plate (with electrical nodes inside) that when electrified, transfers the heat from one side to the other. The peltier I got is rated at 545 watts, 32 amps, and 18vdc, and gets as cold as -60c, 150c. I ordered a desktop power supply online, along with 2 CPU cooling systems. (I.E.  2x Professional grade heat-sink, and 2x 120mm fan) The Power supply outputs 430watts, 28 amps, and 12vdc. I planned on taking these parts and simply sandwiching the peltier between 2 heatsinks, having 1 hot heatsink+fan and 1 cold heatsink+fan. I planned on pumping the cold air into the air intake on the bottom of my laptop, and just pump the hot air into the room.  Unfortunately, the problem I face (and this is a really stupid mistake) was that I did not measure out this whole assembly. It turns out, the peltier face plates are roughly 2.5" x 2.5", whereas the heat-transfer faceplate of the heatsinks are only about 1.5" x 1.5". Now, I wired this all up, and put it all together, ignoring the parts of the peltier that were hanging off and lo' and behold, the peltier worked as designed, one side got extremely cold, and the other got hot. The only problem is, over time, since nothing was drawing the heat away from the edges of the hot side, it transferred over to the cold side, thus warming it up to about room temperature, negating the entire purpose of the contraption.  This is the part that I need help on, would simply taking some aluminum plates that are large enough to cover the entire surface of the peltier, smother both sides in my remaining thermal compound, and then connect this aluminum (with more thermal compound) to the heatsink? This contraption is essentially meant to be a laptop cooling pad. Mounted inside of an old computer case. So it needs to be mobile (IE, liquid cooling is not an option). Can anyone think of a better solution to this? 

Question by schwerlin    |  last reply


Solar - PV versus Solar Oven with Peltier

I was browsing the site as I am often wont to do, and spent quite some time revisiting old 'ibles covering various solar projects, almost all of which are heat related. I understand from general consensus that PV (photo voltaic) solar systems are very inefficient and one of the worst ways to harvest solar energy (when considering the cost of construction and the energy transfer capacity, etc.) Almost everyone who knows what they are doing suggest that the best (and easiest) way to harvest solar energy is to collect the heat - be it to heat air or water, cook food, or other such purposes.Now, I have recently been fascinated by a discovery relatively new to me, peltier units. These devices, for those who don't know, can work in one of three ways. They can harvest and/or produce either heat, cold, or electricity.Basically, if an electric current is run through a unit, it produces heat on one side and an equal amount of 'cold' on the other. Yes I know you can't produce cold - but for the layman, that is what we call it.Or, if one side is heated while the other side is cooled, the unit produces an amount of electricity from the difference in temperatures. One example I have seen and plan to make use of is in vehicles - if you place one or more of these on your exhaust manifold, or any other location where the engine produces waste heat, and airflow can reach it to cool the other side, you generate electricity from the waste heat energy that would otherwise just be . . . well, wasted.But it occurred to me today, if you had a unit attached in the middle of a solar collector, focusing sunlight on one side of the peltier unit, and isolate the other side of the unit in some cooling medium (perhaps even just air with a heat sink of some sort - more likely a cooling liquid though), how effective would this be at harvesting solar energy (heat) into electricity?Actually, I have been using the more common name of peltier, but I believe that for this application a seebeck unit (which is nearly the same, but different) would be required. As I understand it, Peltier units are used more as coolers and are almost always constructed with Bismuth Telluride (Bi2Te3) and used around room temperature and below; while Seebeck units are good for power generators are often constructed of PbTe or, SiGe as well as Bi2Te3 and are used at much higher temperatures.From http://en.wikipedia.org/wiki/Thermoelectric_effect :The effect is that a voltage, the thermoelectric EMF, is created in the presence of a temperature difference between two different metals or semiconductors. This causes a continuous current to flow in the conductors if they form a complete loop. The voltage created is of the order of several microvolts per degree difference.((more info can be found at the referenced wiki page on formulae etc.))Just curious on if this would ever be a decent way to harvest solar energy into electricity. I have also thought up using a thermal siphon solar heating system in which the liquid flows past one or more water wheels which power a small (and obviously slow) generator - but at that point I believe it would be so inefficient and limited in use as to just have absolutely no practical application. The peltier unit (used as a seebeck unit) would probably do better, but I am not certain, which is why I post the question.

Topic by karossii    |  last reply


I have an idea for a personal cooler... do you think it will work? Answered

I'm thinking of placing one or two peltier cooler units on the side of a large aluminum container, which is filled with water. the peltier units also have heatsinks with fans on them. the fans blow the cold air on the user, while the heat is transferred into the aluminum and thus into the water. the aluminum box would be insulated to keep it from heating up the surrounding air, and the heated water could be dumped and refilled to dispose of the heat. this would allow for a sort of personal cooler without expelling hot air out the other side.

Question by codongolev    |  last reply


Printing on plastic labels

I'd like to make some waterproof sticky labels.There are special waterproof papers that work with some inkjets and some inks but I wondered if there might be an alternative.Thoughts so far.Use a fabric dye like Dylon (tm) in an inkjet cartridge to print onto the plastic label directly.Or print as above onto paper and transfer the image onto plastic labels using chemicals and/or heatCould laser toner be transferred onto plastic using similar methods ?

Topic by scubascooby    |  last reply


I want to Etch clear through Brass on a table-top Answered

I want to make some fake gears and such to decorate steam punk and sci-fi stuff.  I'd like to take brass or copper and etch clear through, and have a "clean" edge.  Sharp I don't really want. I need to transfer an image from a computer-drawn source.  Heat transfer with toner I know, etching, well, not so much.    I'd also like to do this on my kitchen table.

Question by hardlec    |  last reply


Best dark metal for solar absorbance.

What's the best metal for absorbing sunlight? ie, darkest. It needs to be immersed in ethanol, which will dissolve pretty much any paint etc. I've tried steel with some kind of enamel or anodised layer, but the eths started eating that too. Also whatever it was seemed to reduce the heat getting into the ethanol. And are there ways of making metal darker, chemically or through heating? I've been recommended getting something rusty and using a rust converter, which turns the oxidised layer into a phosphate, which is dark and might work well. Also.. are there other characteristics I should be paying attention to in order to maximise the amount of heat transferred to the fluid, like conductivity, emissivity, etc? Cheers.

Topic by SolarFlower_org    |  last reply


Idea for a non-ideal Carnot cycle based engine.

Initial Stirling engine conceptFor some time I was contemplating an idea for a Stirling engine that would work quite differently than the other designs that I came across. Whole internal volume of an engine may be viewed as a closed-loop pipe, trombone-like slide mechanism allows this pipe to change its length. Electrical fan replaces displacer and pumps working fluid throughout the engine constantly and in one direction. Some portion of the pipe is replaced with branching structure that consist of two heat exchangers (hot and cold) and regenerator. On both ends of this structure special valves are located that connect one of the structure’s parts to the main pipe, so that whole engine forms one closed-loop. While this happens, both of the unused parts are completely bypassed.This design should have many advantages. Working gas is in constant motion and little energy is wasted on accelerating it. Gas may pass many times through heat exchangers, allowing for much better approximation of isothermal processes. Disconnecting unused heat exchangers from the rest of the engine should minimize volume of dead spaces.There are some drawbacks to. Slide mechanism allows only very small changes of total volume (compression ratio is low), and that limits engine’s ability to operate with higher temperature differences. Piston, which is part of the slide mechanism, and especially valves, are heavy and this makes them unsuited for high speed operation, making the whole engine bulky. I also except that an area of all surfaces that are sliding against each other and produce friction would be higher than in traditional Stirlings.Problems with Stirling cycleIdeal Stirling cycle (Fig. 4) consist of two isothermal processes (constant temperature) during which work is performed, and two isochoric processes (constant volume, no work performed). Isochoric processes function is only to change temperature of the working gas, and this takes a lot of energy to do so (especially if gas with high heat capacity is used). Regular Stirling engines try to minimize this inefficiency with regenerator. But when I tried to analyze this process mathematically, I noticed that even regenerator with very high heat capacity cannot store more than half the energy needed to perform next isochoric process (see lower left part of the spreadsheets for more details).Fig. 5 represents heat pump (or refrigerator) working in a modified Stirling cycle. Isochoric processes represent transfers of heat to and from the regenerator. Rest of the temperature change is performed by polytropic processes, during which heat flows to or from the heat exchangers and also work is performed. I chose to represent heat pump, instead of a engine because engine working with this modified cycle wold require isochoric processes to be performed midstroke (or transfers of heat to regenerator would have to be performed during polytropic processes, when working gas changes its temperature also due to work being performed).Note that I am using word polytropic to indicate processes where gas changes its energy both due to heat transfers and work performed. When special cases of polytropic process are mentioned (isothermal, adiabatic, isochoric) I use their specific names.Solving those problems with Carnot cycleLegendary Carnot cycle consist of two isothermal processes (just like Stirling cycle), but changes of temperature are accomplished by the adiabatic processes (no heat transfers with the surroundings), instead of isochoric ones. This has huge advantage, because when energy is added to the working gas during adiabatic compression, all of it can be later recovered during adiabatic expansion.Design I previously mentioned can easily be adapted to work as a Carnot engine. Only change that is necessary, is replacement of regenerator with the empty pipe (ADIABATIC PIPE in Fig. 2). When valves connect this empty pipe to the rest of the engine, there is no heat transfer between working fluid and thermal reservoirs. Any changes of engine volume modify temperature and pressure in a approximately adiabatic fashion. To model what happens with the engine I used slightly modified Carnot cycle (Fig.3). Just before adiabatic process end, short polytropic process begins. It is done so that loses associated with valves connecting both adiabatic pipe and heat exchanger to the main part of the engine for a short period of time can be better simulated. Heat pump working in this cycle is shown in Fig. 6.Design detailsEngine uses special valves, which external shape resemble truncated cone. Smaller base of this cone faces main part of the engine, larger one heat exchangers. Inside there is a pipe, with one opening right in the center of smaller base. The other opening is located off-center on the larger base, so it can connect to the one of the heat exchangers or adiabatic pipe (which are situated just like chambers of a revolver’s cylinder in respect to each other). As this engine engine will most likely operate under low RPMs, flywheel will have to be connected through a transmission with very high gear ratio. The flywheel will have to be quite bulky as well. This poses another challenge, as the pressure inside engine’s tubing will be higher than atmospheric, and at least space around the other side of the “piston” will have to be pressurized as well. If only the immediate surroundings will be pressurized, and gears, flywheel, electric motor/generator will be outside of the container, then very inefficient seal will have to be employed. If everything will be located inside the pressurized container, then fast moving parts will be working against dense gas. Pressure in this area ideally should have such a value, so that on every piston stroke energy is both added to the flywheel and extracted from it as to make energy storage requirements more manageable. This requirements may also be further reduced by employing some other energy storage form. And of course exchange of heat between main part of the engine and this pressurized section must be taken into consideration.Then, there is problem of heat exchangers. They can be either large diameter pipes with fins, or smaller diameter ones that are densely packed (this seems to be must popular configuration in Stirling engines). As heat transfer with the outside of the engine takes around half of the piston stroke, it might be a good idea to employ two pumps of heat transfer fluid per each of the two heat exhangers. One would work constantly to transfer heat from some large heat reservoir, the other would transfer heat to the working fluid only when it is necessary. Some another heat exchanger would have to be placed between those two circuits.And there is also a question of the piston. Basic trombone-like version could be replaced by the something similar to the design drawn in Fig. 7, where two parallel tubes, connected by U-shaped piston, are replaced by the coaxial pipes with volute on the outer section that allows connection another parallel pipe. Piston itself has then small tubular part attached which allows working fluid to pass from outer section to the inner section. This design has only one high pressure seal, is possibly lighter, but fan that pumps working fluid will probably need to be more powerful. Problem of sideways motion of the piston must also be analyzed, and it can be either resolved with piston skirts or the crosshead. Interesting aspect of this problem is that while most frictional forces in the engine are mostly independent of the engine speed, forces associated with this sideways motion of the piston increase with engine rotational speed.Another possible improvement would be making adiabatic pipe shorter than the heat exchangers, which would reduce volume of dead spaces.Engine parametersIn case of a engine that uses helium as a working fluid, has minimum volume of 46.7 liters, maximum volume of 70 liters, operates at temperatures of -5°C and 37°C with the speed of 15 RPM you can expect that it will produce 1138W of power at 8.13% efficiency.In the case of heat pump that operates at the same parameters you can expect that it will require 2300W of power and achieve COP 4.95You can find calculations, diagrams and the detailed descriptions inside non-ideal_carnot_engine.zip (it is unfortunate that Instructables do not support uploading .zip files and other file formats any more, and I have to use another website just to upload few spreadsheets).Possible applicationsI started thinking about this concept when considering applications of thermal energy storage. In more northern latitudes largest factor in domestic energy consumption is heating. So, at least in my opinion, any movement toward replacing fossil fuels with renewables should focus on this largest contributing factor. And this actually is quite fine because storing 1 kWh in a tank filled with water, rocks/concrete or simply in the ground is much cheaper than storing it inside lithium-ion batteries. And general idea behind this low temperature engine, was that some part of this large amount of energy stored to be later used to heat buildings, could be converted into electricity.It should also be able to work in reverse as a heat pump or refrigerator.

Topic by rarinn  


Can anyone tell me how butane gas hair straighteners work?

I'm trying to use the same/similar technology for a project but struggling to find out any information on how the butane gas transfers to heat energy without a flame.  These in particular - http://www.argos.co.uk/webapp/wcs/stores/servlet/ProductDisplay?storeId=10151&catalogId;=19551&langId;=110&productId;=557918

Question by ey14    |  last reply


a thermal conductor that does not conduct electricity? Answered

I am looking to heat water to a boil in a pipe, using nichrome wire. the nichrome wire will be wrapped around the pipe. my problem is i don't want to short circuit the nichrome wire, so i need to insulate it, but i need it to still transfer as much heat as possible to the pipe.   any suggestion would be great, including other ways to, using electricity, bring water to a boil within a pipe. *UPDATE: does anyone know of an affordable insulating paint or coating?                     i found some (called Glyptal) but it cost $50, which is too much for me                    rust-oleum is an enamel paint. will it insulate?

Question by jg156    |  last reply


EXOTHERMIC WINDSHIELD DEFROSTER?

I've been thinking about rigging a device to automatically defrost my car windscreen about half an hour or so before I get in the car. Since it's got to be able to turn itself on while I'm still asleep, it's got to work off batteries. I think that pretty much rules out my first idea of a heating element / fan setup. My next idea was to use some kind of exothermic reaction and either directly transfer that heat to the glass by conduction, or with a similar convection / fan setup as previous. My questions are: 1) Does this sound at all feasible? If not, any better ideas to achieve the same aim? 2) What reactants would be good to use? The spec is: It has to produce a decent amount of heat over a decent enough period to give (at least a decent chunk of) the windscreen a chance to warm up and defrost without cracking the glass in the process. Also the products of the reaction should preferably be non toxic and easy to deal with (no masses of liquid, poison gas etc!) 3) Has anyone heard of anything like this being attempted before that I could sneakily steal?Ta very much.Adam?

Question by adamnewt  


Gas stove top burner covers?

I have a fairly small kitchen, and as such, I would like to make a burner cover for it. What I was thinking was something could be folded. Not only to save space when I don't need it on the stove at all, but in hopes of being able to keep it on half the stove, fold it up, and have access to two burners. However, I am unsure what to use to do this. I know that the heat from an active burner would burn most woods, and produce a fire hazard. But, I don't know what other materials would be workable enough to do such a thing. I was thinking of just covering the bottom of some MDF to reduce heat transfer through the MDF, as right now, that is what I am using when I am not using the stove at all.

Question by DoctorWoo    |  last reply


Solar Energy

Hi, i would like to ask for opinion, i am building a solar system where my system start from using a fresnel lense to collect the sun and use it to heat up a boiler, the boiler transfer steam into my tesla turbine and the turbine will turn my generator to produce electricity. Do anyone have any idea of building an own boiler instead of using a pressure cooker that i had seen this idea in somewhere, And, is there any places can provide cheaper fresnel lense as the sun focusing tool?? i will need a cheaper price lense cause of shortage in my budget of my final year project... 

Topic by 000123000    |  last reply


Perpetual motion & free energy is it possible? Answered

Hi Eric/Instructables, Basically I have been looking at perpetual motion and am led to believe that it is impossible due to the laws of thermodynamics meaning heat/energy has to be transferred somewhere, so I came up with a few designs which may challenge this theory.  Without wanting to reveal my designs and ideas too much I will explain what I am trying to accomplish and would love your opinion as to whether you think they are viable. I have 2 ideas, one is to use 'rare' magnets (which aren't rare at all so cost and obtaining them is not as hard as it sounds!) and have the magnets propelling round like a wind turbine design using the opposite poles effect to repel the magnets and get the turbine started.  Once the turbine is in motion I will harness the electricity created by the movement of the turbine/motor in a capacitor or kinetic store. This stored  electricity  can be used to keep the magnets magnetized by wrapping wire coils round the magnets and passing the stored current through the coil to keep the magnets repelling each other and spinning the turbine. Idea number 2 is a similar concept just dropping the use of magnets and using the method of so called free energy where you can get a small voltage from using a radio antenna, capacitors and germanium diodes (there are several example videos on the internet) again using a wind turbine effect to keep re-fueling the capacitors so the voltage drop when the load is applied is nulified. Perpetual motion is the dream and I think the transfer of heat/energy caused by friction can be harnessed and put back into the workings of the appliance/design, Many thanks for your time in reading this and hope for any replies positive or negative the dream will live on in my head and heart  :)  Mark Smith 

Question by McJesus    |  last reply


External HD wont power down??

Hey guys, i was wondering if perhaps someone has a similar drive like mine.For some reason, on my ibook, when plugged into firewire, it powers down automatically after 5 or so minutes of not being used, that's good. But I just cleared it off and formatted it for NTFS and put it on my server, via firewire aswell, and while data transfer and everything seems to be fine, the hard drive does not spin down, ever. And when I feel it, I can feel the heads clicking, when there's no program accessing it on my server that I can see. Perhaps it doesn't get the chance to spin down..Either way, I'm concerned about the heat it makes, and mostly, about it's longevity. Does anyone have a solution?? Is there some patch for xp that makes external drives power down??

Topic by Punkguyta    |  last reply


PCB trouble?

I transferred this circuit to a circuitboard, but it didnt work. So, I tried just taking an led and soldering it to a pcb, but when I touched both leads with a battery, nothing happened. I didnt not clip the leads, I knew the cathode and anode. I was worried that when I put the led on it, I burnt it out from the soldering heat. So I desoldered it, but when I tested it OFF the pcb, it worked. The traces it was connected to was NOT connected to anything else. Any circuit I try putting on a pcb never works, none of them. Even when I just tried soldering a buzzer on it and connecting it to a battery, it only worked when it was off of it. I cant figure out why, but I am really frustrated about this. Tell me if you need to know anything else.

Question by 101yummYYummy101  


Solar Power Towers Efficiently Using Brayton Cycle

I want to point out a solar to electric generation concept that has yet to be seen anywhere, even though it originated back during the Carter Administration's ERDA programs of the late 70's. I’m talking about solar power towers that convert solar energy into electricity at the hundreds of mega-watt level. While power towers do exist today, and the world currently does have a handful of them as shown in Fig-1, none use the Brayton Cycle nor can they boast an energy conversion efficiency at the mid to upper thirty percent level.  A group of engineers got together at a think tank organization called Sanders Associates in Nashua, N.H., several decades ago, and designed a unique Brayton Cycle, 100 MW solar Power Tower concept for generating electricity. This was accomplished under ERDA (Energy Research Development Administration) who gave us a phase-2 follow-up contract that took our phase-1 design and built a working scale model at the 10 KW level. This model was tested at the Georgia Tech Solar Research Facility and "registered" ~37% electric solar conversion efficiency. The system used ambient air as its working fluid, and was to be located in open-spaced desert regions. Phase-2 was lost to competition using a closed-loop liquid sodium system that boiled water into superheated steam at 900F to run a turbine that generated ~21% overall electric conversion efficiency.  Apparently, at that time ERDA would rather haul water out to the desert than use ambient air to generate electricity? The politics of their decision is beyond reason and clashes with improving the world’s development of green technology energy.  ERDA shut out our better technological performer and safely locked it away for another day! ERDA's official reason for turning us down: "this technology uses excessively high temperatures (2500F versus 900F) that are dangerous to workman maintaining the equipment". But that was back in the 70’s, maybe we’ve learned to deal with high-temp heat by now?   Solar Energy Concept Using Low Pressure Storage Our solar power tower would collect the sun’s energy by locating its ceramic heat exchanger on top of a tall tower as shown in Fig-1. The tower was located in the center of a field of active sun-searching mirrors (heliostats, Figure-2). These mirrors reflected sunlight onto our ceramic honeycomb heat exchanger, producing a concentrated flux intensity level that heated it to around 2500F. At the same time, low pressure fans generating only a few psi pressure would suck the ambient air through the honeycomb, heating it to just under the 2500F and then passing it through energy storage silos which stored the heat down to ~150F. We purposely designed the energy storage charging phase of our hot air system to work at only a few psi above ambient as a safety feature. The sun effectively acts as the combustor of our jet engine or Brayton cycle engine. Once the sun heats the air, it passes through heat exchangers consisting of a labyrinth of underground silos that are temperature segregated. These silos receive our 2300F airflow and cool it down to about 150F, transferring this heat into solid salt containers which turn to liquid once they have absorbed sufficient heat. Figure-3 is a schematic of this underground energy storage facility and shows the airflow being heated by a fully charged set of silos containing liquid salt-bricks. This airflow direction is reversed when we charge the silo’s salt-bricks. The bricks are kept in specially insulated, high pressure silos (located underground for added insulation) that store the heat energy at one atmosphere for later use. These underground silos act as our energy storage batteries, and when needed would discharge their heat energy accordingly into the moving airflow. This energy storage concept permitted the generation of electricity at night and during overcast days. Two sets of storage systems are required for continuous operation. One would be charging at low pressure while the other is discharging at high pressure through the Brayton engine to generate electricity.   Electric Energy Generation at High Pressure Electricity would be created by turning an electric generator at high speed. The generator was turned by running a jet engine connected to it.  The engine’s combustor for heating the air is effectively the sun, hence the name Brayton cycle for generating our solar electricity (Figure-4). The heat from the molten salt containers would increase the energy of the high pressure air coming from the compressor, and would then force it through a typical turbine that turns this energy into high rotational speed to run the generator and make electricity. Our solar jet engine sucks in ambient air using its compressor, as all jet engines do, and blows it through a series of silos at high pressure whose stacked bricks are held at different temperature levels. We start our airflow through a silo held as low as 150F and work our way up to ~2300F as we pass through our last, hottest silo which acts to complete the effective solar combustion process. This air preheating technique dramatically improves our energy turnover capability and allowed us to convert solar energy into electricity at near 37% efficiency. During our electric energy generation phase, the silos of our Brayton system requires operating at many atmospheres of pressure just as in any jet engine combustor using petroleum-based JP-fuel.      

Topic by RT-101    |  last reply


Building an ultrasonic soldering station ?

I have some strage projects coming up that will require me to solder things together that usually don't really like this.In my past job this was quite easy as we had an ultrasonic soldering bath and several ultrasonic soldering stations.Well, the access to those is gone :(At first I thought "How hard can it be to build one?"Not really too hard for a half decent soldering bath but a lot harder for a soldering iron...The soldering stations we used operated in the range of 50-60kHz.Commonly available transducers and their drivers however you find for 28 and 40kHz.Finding small ones in the range of 10 to 20W is also not easy.I can deal with a soldering iron that ends up in the size of a 500W wood burning iron as long as the tip is replacable.But what are the frequencies really required to solder for example on ceramic, titanium or lab grade glass?Does anyone have experience with doing this on lower frequencies than what the professional stations use?Last but not least:Is there any software available (preferably free or as an online tool) to simulate the quite long feed horn that is required with a soldering tip?Going with 1/4 wavelenghts is logical but how could I get the info on the actual shape required without simulating it first?I was thinking of using a heater cartridge like used for the hotend on a 3D printer to heat the tip.However, tests on my ultrasonic actuator showed the entire thing disintegrates within a few minutes, at least the filler and "glue" used to hold it all together.Would a free standing heating coil around the tip work?Heat transfer would be a pain and losses high, but should be possible?In case you wonder why: I just don't ave the thausands of dollars at hand required to buy one of these soldering stations....

Question by Downunder35m    |  last reply


I'm converting an old gas char-Broil outdoor grill,now used as a charcoal grill, to an electric smoker. See details.

For my initial design I'm using junk box parts (electronic hobbyist/pack rat).  The heating element is a 120vac, 500w burner previously used as an electric charcoal lighter.  The grill cavity is 15"H x 14"D x 25"W, with two rack heights leaving room for the burner, water pan, and possibly lava rocks/bricks.     The question is about temperature control.  I understand 500w may or may not be enough.  I'm considering a DIY full wave open loop SCR control, as I have many of the parts.  The purely resistive load is @2.4-2.5 amps and should be able to be temperature controlled using  demand oriented transfer or phase angle firing w/diacs.  I want maximum control cheaply and am having trouble selecting an appropriate design.  I have larger current SCR's in case I need a larger wattage elment. What can contributors suggest? 

Question by X-nfamous    |  last reply


Making water cooled shoes need some advice about thin copper tube fittings.

Essentially i want to make water cooled shoes from some of the spares i have from my old pc water-cooling set up.  I want to run some thin copper tubing around the shoe which will connect to the some metal fittings that will then connect to my rubber tubing and then to the pump and the radiator. Now i know about the fittings that are available for the regular copper tubing that runs in houses but this tubing will be around 4mm and im not sure how to connect this tubing to my metal fittings which are about 3/8th of an inch i believe.  I was thinking to just use some epoxy putty or something but im sure there are better ways to do this. so any ideas?  im sure fittings are available but i dont know what they're called i couldn't get anything with a quick google search.  Edit: i didn't realise response here would be so thoughtful and all. I dont want to be able to walk around in these i just want to sit in my room and be comfortable. The heat difference probably wouldn't be too large between my feet and the air for a huge transfer so i also had thought to add a small water bath with a second small radiator init.  The copper tubing doesnt have to be directly under my feet i realise they'd probably be crushed otherwise. but the heat conduction through them must be so much better then the plastic tubing. 

Topic by rajr110    |  last reply


Automatic Bottle Filler, Seal and Capper and Label Applicator.?

HELP!!! OK, I have put together a awesome new group of liquid based products for a variety of uses (being vague bc it's to much to go over now). But before my investor group will commit to stage 3 of funding (stage one was a small infusion for the chemistry and product development, and stage 2 is on my own dime). Now I have 30 days to come up with plans and a protoype assembly line to produce the first 500K in units...it needs to be fully automatic, not semi-automatic...at least for each individual process. I have researched the net and there are alot of semi-auto systems i can fully automate, and the big boy systems are just out of my reach until I get stage 3 funding...i have to produce a min of this much product in an effort to get it on the shelves of the clients we have setup. I need to fill round bottles (2.5 and 4 oz and 12oz), fill flat sided quarts and gallons, and hopefully at some point round and flat sided 3,5,and7 gallon buckets. i know that this can be one machine with different run setups or 3-4 different similar systems. then I need a sealer, basically applies the pressure sensitive seal then heats it and seals it form spilling, tampering etc. then a separate system that screws the cap on finally and importantly applies either the peel and stick pressure sensitive pre-printed labels, or heat transfer label or silk screening... OK before anyone says a thing...i know its very complex, I know it's gonna cost some money, but I do know it can be done DIY style... so your thoughts, input, links to similar parts and pieces or ideas, etc...

Question by IdeaVault    |  last reply


And now I'm left feeling slightly empty

Finals are OVER! And I should be ecstatic, but I'm just exhausted. I had Fluids, knocked that mutha outta the park. Modeling Methods (ugh!) think I did good, even a zero on the final would still net me a B in the class. Circuit analysis (yech), somewhere between a 60-90 in that class, the class was incomprehensible, the online test was broken and you can't learn with 220 people chatting over the prof. and lastly Machine Design- I'm worried about that one, I had a 90% going into the final, but I forgot to put J & I for a solid shaft on my formula sheet, oops, that cost me a shaft design problem, and when the heck did we cover welding? dammint. Next up Vibrations, Heat Transfer, Mech Properties of Materials and CadCam. BUT!!!! in between, well I have an interview tomorrow, I'm undecided on if that is a good thing, and then it's a week of floating around the Caribbean. Woot! And I'm now a member of Tau Beta Pi, which I'm pretty darned proud of. But FINALS ARE OVER!!!! No more spending until 1am in the library until we're all so tired we can't even read the problems. YEA!!!!!! nap time.

Topic by Tool Using Animal    |  last reply


Steppers and EMF.? Answered

I have build this Bi-Polar stepper circuit and it works great on the bread board. I etch a board 3 times, 2 with heat transfer and 1 with photo resist. I use 2 completely separate power supplies but with the PCB's i think i am experiencing EMF or feed back. I am using an adjustable schmidt trigger for the clock. What happens is i can hardly get any rpm's, sometimes if the trigger is set just wright it will turn up fairly well, at that time if i try full step the stepper stops turning or will reverse sometimes, if i try ccw it may or may nor reverse and i may stay in what ever direction and any given time . Now at a slow rpm full step normally work's and cw/ccw may or may not work, also it can trigger the half or full step. Also i can disconnect one coil and the stepper will continue to turn, If i try that with the other coil the stepper will stop. So it looks like it is only running on one coil. Is that possible? Keep in mind i have bread boarded it and work's fine. Its just on the 3 pcb's that all this happens. As for the diodes it seams to work better with 1N4001's than 1N4148's I have checked every trace with an DMM and made sure they are going to the correct pins ect. I have tried different IC's L297 and L298 and steppers 2 different kinds and multiples of each. So i am thinking this is EMF, feedback, or a design problem. I have tried to eliminate most every thing i can think of. Comments?     

Question by WWC    |  last reply