Need help finding cheap thermo formable plastic!

Greetings! I need help finding a material for a project. I am looking for the cheapest Thermo-formable plastic that I can find. I need to be able to form it with a heat gun and keep its rigidity after forming. I also need to be able to paint it. I require a large amount so I am looking for the cheapest. Any suggestions would be greatly appreciated. Thanks

Posted by Jonas3 8 years ago


Help! Thermo Electric Generator

Just wondering if any of you knowledgable folk can help me out. Of late I have experimenting with solar cells and energy production. I have been calculating some interesting results, many of which due to the use of lenses, magnification and mirrors etc. Alas this has led to more that on fried solar cell due to the temperatures im dealing with. Is there any practical way to obtain/construct a Thermo electric generator as pictured? I have spent some time with my friend Google, leaving me with little more than the notion that perhaps this technology is out of reach of the home experimentor. Think giant light cannon that can melt pennies. How can I harness this heat directly as apposed to, going the boiler/steam powered engine method?

Posted by Lftndbt 9 years ago


thermo electric fan

I bought an ECOFAN and want to know if anyone has figured out how to make one?I see computer fans online for as low as $19 that seem to run the same way.Heres one I looked at;http://www.tigerdirect.com/applications/searchtools/item-details.asp?EdpNo=1272112&csid;=_21Will these work?

Posted by olddawg 9 years ago


Vacuum forming heat source

Hi! I am planning to build a vacuum forming machine that does not use a seperate oven to heat the plastic. For my 3D printing hobby I have come across many heated beds, also some on 230v. Could something like this (https://www.ebay.com/itm/30X30CM-750W-220V-Silicone-Heater-3D-Printer-Heated-Bed-Pad-30cm-Thermistor/401257671771?hash=item5d6cd22c5b:g:iVEAAOSwx6pYrp70) with a heat sink be used for such an application? Thanks!

Posted by ttreurniet 8 months ago


Would a glass, vacuum-insulated thermos be able to withstand the extreme cold of liquid-air?

I am in the middle of designing a system to produce liquid air using the von linde process. the termos would not be under any pressure, but it will get quite cold. can a thermos using a glass vacuum insulated inside be able to withstand temperatures below -180 degrees celsius?

Posted by pedrogabman 8 years ago


Just found out: Clean inside of a thermos - Simple!

I just had to clean my thermos prior the tournament tomorrow. A quick peek inside revealed some stubborn residue. Propably furring (chalky deposits) from the boiling water i use to make tea in them... (we have quite "hard" water with lots of calcium). The throat of the bottle (Full-metal thermos) was too narrow for normal cleaning-brushes... I fortunately had a bag of rice standing around and thought  "Hm... Hard and small things"! So i quickly added half a handfull of dry rice in the thermos and a bit of cold water (2-3 spoons). Then i shook it a bit and poured the rice out. The inside was quite clean and almost "pristine" again. This method should also work for thermoscans with glass-interiors. Another (better) way of doing that is propably (but ONLY if you have a METAL-Interior!) to add a hand of sand or fine gravel with some wather (Maybe even a bit of dishsoap) and give it a shake. Again: Only do the sand/gravel if your thermos does not have a glass-interior!! Have fun and enjoy a good drink while outside! :)

Posted by Orngrimm 5 years ago


Can a glass, vacuum insulated container withstand temperatures in the -180 degree celsius range?

Is it possible to store liquid nitrogen and oxygen in a vacuum insulated container for a short period of time? i have a thermos that i though might work, but i want to be sure that im not going to have the thermos explode in my face when i try it. this is an old beefy thermos that can take at least 190 degrees celsius, but im not sure about the other direction.  

Posted by pedrogabman 8 years ago


Looking for reversible thermo chromic pigment or paint

Hi, I am looking for reversible thermo chromatic pigments (or paint / ink, even paper) in europe. For now, the best I've found is 480€ including shipping and VAT for 1kg of pigment (32°C), which should allow to make about 5kg of paint, which would allow painting 20-25m² (one layer). If you add the price for white paint, is come to 25€ for 1 square meter, which is not so expensive, but I need half a square meter, not 20 ! Any advice ? Thx, tReg.

Posted by treg 9 years ago


Any knowledge on a peltier cooler thermoelectric cooling module

Needs help putting assembling a thermoelectric module for a possible inventing.  Suggestions on the supplies and parts needed

Posted by jayhead 6 years ago


Thermodynamics for Highschool

So, I work at a science center and we have our annual Engineering Olympics coming up and we've been brainstorming something about thermodynamics. The general format is 6 teams from different highschools in the area are given a task to complete from one engineering discipline, such as construct windmill blades to achieve the highest amperage from an attatched motor or insullate a container of water with random materials to prevent it heating up when submerged in boiling water. This year, I haven't really found an idea for thermo that really excites me. Thermo isn't the easiest thing in the world in highschool, and since we're dealing with kids from different schools, we have no way of knowing how advanced they are. So, any ideas of a project to test their thermodynamic mettle?

Posted by Dinkum Thinkum 9 years ago


room thermostat

First things first notice: Iam in Europe so it's probably a bit different than in USA. I have electric radiator in my room. i bought thermo switch but i don't know how to connect it between the socket and the radiator. I must mention that the radiator had already same thermo switch before but it broke down after 5 years and I didn't write notes how it was connected. I already blown 4 fuses during the attempt. The wire has three wires: blue ("live"), brown and yellow/ green ("earth"). In the switch there's sheme sticker -> www.shrani.si/f/C/Nr/42sKtVVC/thermo.png . so how do i connect the plug and the radiator??  www.imit.it/dati/schedaArticolo.php

Posted by Karletto555 8 years ago


smart window thermostat

Wanted: circuit to open window at night when it is cooler outside than in. Close it when hotter outside in morn. Probably add something to prevent it from opening and closing several times in the eve and morn with random fluctuations. Prefer 2 thermostats, 1 outside, one in, rather than a timer. I've a vague recollection of a circuit with 2 potentiometers, one on the motor, one on the control panel, such that turning the control pot will activate the motor until its pot is at the same position as ctrl pot.. Could a circuit something  like this control my window? But most thermostats are on/off, not continuous variable.   It would be simple to do a switch logic thing like:  “IF thermo ‘I’ is above 70 AND thermo ‘O’ is below 70, THEN OPEN “  but that only works at 1 temp.

Posted by Toga_Dan 1 year ago


Way Of Detecting Humans?

Is there ~~an easy way~~ a best way of detecting humans in the dark, or in a forest? Me and my friends play airsoft, usually in a forest, and it's hard to know where the enemy (other friends) are. I'm a sniper and I want an easy way to detect them. One way would be a thermo-camera, but those are expensive. Is there a better way?

Posted by guyfrom7up 9 years ago


modify wine cooler thermostat refrigerator thermostat operating temperature

Hello. Can someone please tell me how to modify the thermostat on a wine cooler (that uses a compressor). I want to change the temperature from running between 10c-18c to 0c-5c. Please post an instructable or give me ideas- even if generic, it would be helpful.I am specifically trying to modify a baumatic bw18.

Posted by drosengarten 8 years ago


Now I've gone and done it.

Gave notice at work today, strangely the boss was super enthusiastic about my leaving, oh well. So last day is officially the 26th, but I'll take a personal day and make the 22nd my last day. It feels really really strange. I'll be a full time student now, praise be to student loans. Spring 2008 Chem for eng solid mech dynamcs thermo.

Posted by Tool Using Animal 10 years ago


BATFINK

NOT Ratfink, but Batfink. Has anybody ever seen this show? You know, with Batfink's super sonic sonar radar, his wings of steel that cannot be harmed, evil genius Hugo-a-go-go, his sidekick Karate, the Battillac that looks like a VW-bug and always makes Batfink glad that it has a thermo-nuclear plutonium insulated something, the announcer that always stops right before something horrible will happen to Batfink and asks us what will happen, and the chief. I used to watch it on Boomerang, but they stopped airing it. It's a funny and cool show, made by Hal Seeger.

Posted by CLASSIFIEDINFORMATION 10 years ago


I ain't as dumb as they want me to think I am...

As some of you know, I left my job at Christmas to return full time to school to get an engineering degree, I'm kinda clever ;-), but my first full time semester was full of suck. I took Thermo, Dynamics, Solid Mech, and Chem for Eng. Chem for Eng was a joke, I never attended class and got an A. Thermo, the teacher, it was his first time, I learned from the book, got a B+ Dynamics, the teacher was a grad student, and he was incredibly passionate about teaching, great class, harder than hell, got a B. And then there is Solid Mech. The grade has been a sword of Damocles hanging over my head, I was doing so poorly that I even registered to take it again in the summer, the first test, I got a 39, and that was greater than one sigma below the mean. Well folks, I just dropped that summer class because I got a C. Yea freakin' ha!!! I never thought I'd be this excited to be average. LOL. So now I have all summer, only one class (materials) and maybe a part time job, expect to see more (low cost) instructables. Ghod, right now I feel awesome.

Posted by Tool Using Animal 10 years ago


Forum topics not appearing.

Over the last month, I have noticed that my forum topics do not show until a few days after posting. By this time they have sunken three pages in.One of my previous topics, did not show until Kiteman commented in it. I'm not sure how he found it.I have just posted another topic, which still hasn't shown up after a day.This has only occured of late as previous topics showed within 5 min.Thermo electric generatorand my recent topicSia preforms still MIAAny ideas?

Posted by Lftndbt 9 years ago


Mind Puzzler

All right everybody so I'm going tp post a little brain puzzle. The first one to get it will get followed by me. (NOTICE: PM me the answer,if you leave a comment it has a chance to be stolen.)  Puzzle: 3 men enter a steam room at a gyn. One of the men is carrying a thermos,the other a towel,and the third a water bottle. After 10 minutes later and the steam clearing away two of the men find that the other is dead. WHO KILLED THE MAN. After somebody has given me the answer I will post the correct answer in a edit of this forum. Good luck.  

Posted by didexo 6 years ago


Trigger Switch For Ray Gun

Greetings Space Cadets! I need help figuring out what sort of switch to use to activate the  thermo-nuclear disruptor beam of the ray gun I'm building out of a busted battery powered drill, a smoke alarm and a battery. Bet you didn't know this combination of junk is dangerous in the wrong hands? I need a switch that will work with DC current and switch on the circuit when pressed but not stay on.  Like a primitive projectile firing pistol of the 21st century this ray gun should only fire once when the power switch is pressed and not stay on continuously. Any suggestions? And yes, I'll post an 'ible when I get it done. Thanks!

Posted by 2lazy2work2nervous2steal 7 years ago


Want collaborators for a solar hot water project

I have had this idea for a while and I decided to try and make it a collaboration instead of just trying to do it by myself. I thought there was a way to start a collaborative instructable, but I don't see that option now. Does anyone out there know how to do a collaborative instructable? Maybe that option appears right before you publish it? I don't know if the best way to share ideas is this forum, or the collaborative instructable (if it exists). ******** Here is the idea: I have a solar box cooker, which is shown in this instructable. On days when I have nothing to cook, I often put a kettle of water in it, so when I get home from work I have very hot water that can be used for cooking pasta, making  tea, coffee etc. I pour that water into a thermos, and it will stay hot until the next day. I would like to design and build a solar cooker that is dedicated to this task with this tentative list of requirements: *It would be fairly small, just large enough to hold a kettle *It would be easy to put the kettle in and take it out *It would be weatherproof, so it could sit outside for months at a time *It would be designed in such a way that it would collect energy from the Sun during a large portion of the day, without need of any sun-tracking mechanism *Ideally, it would have a mechanism that would transfer the water to a thermos as soon as it boiled, or got to a certain temperature. Looking forward to hearing from people who want to collaborate on this. As soon as we have decided on where to share ideas, I'll post mine.

Posted by dlginstructables 7 years ago


mission of sputnik 1

Russian technology satellite. One launch, 1957.10.04. Tikhonravov's 1.4 metric ton ISZ satellite was to have been launched by the new R-7 ICBM as the Soviet Union's first satellite, during the International Geophysical Year.    But it was not ready in time, so Korolev hurriedly developed Sputnik 1 as a replacement. It became the first artificial satellite of the earth. Sputnik 1 had 1 watt of power, producing an 0.4 second duration signal on the 7 and 15 m bands. Four antennae were deployed at 35 degree angles. Power was provided by three silver-zinc batteries. Thermo-regulation was by a ventilator. The 580 mm sphere had a mass of 83 kg and was made of highly polished Aluminum AMG6T alloy 2 mm thick. It was built without drawings due to the quick time schedule. Korolev was everywhere, supervising all aspects of its construction. It functioned for 21 days.      AKA: PS-1. Gross mass: 84 kg (185 lb). First date: 1957-10-04. Number: 1 .     the word sputnik is russian word for traveller

Posted by Waren-Neutron 7 years ago


I am looking for advice on thermoforming to make a soaking tub from a 55gal HDPE drum

I thought I could make an inexpensive soaking tub by just fitting up an open top 55 gal plastic drum, but my body will not quite fit when I try to sit in it. I just need a couple more inches for my knees. So after viewing a you-tube on how those barrels are made, I have thoughts that I might be able to re-thermo-form the barrel. The more I think about it, if successful, there are lots of uses. Someone posted that HDPE melts around 265F, so I figure that I could get that air temp easily with a hot air gun, possibly inside the barrel, then using a resealable lid, add air pressure to the barrel and surrounded it with a new rigid mold. If I could figure out how to intrude with parts of the rigid mold, I could even make a seat. As I am imagining, the closer I can get it to the shape of my body in a sitting position, the least amount of water I have to use to fill and heat. And then I could add spray foam to the outside for insulation. Does anyone out their have experience blow molding or other recommendations?

Posted by tesselation 2 years ago


Master Minds Only (Coffee Mug "Forget me Not"

I am looking to design a coffee mug that reminds the user via a speaker attached to the door in some way, that they are leaving the house without their coffee.  The project will need a sensor at the door that can recognize a sensor built into the mug, I'm thinking Thermos style yet able to fit in a normal sized cup holder, that can be machine washed without damaging the inside components. (The design can have an attachable bottom to hold the hardware and battery source, so the main part is machine washable.)  And an additional sensor is needed on the users car keys to recognize the user is leaving the house. when both the mug sensor and the key sensor pass at the same time  a "have a nice day _______user name_____" voice recording plays when only the key sensor goes past the door receiver a " ____User name____ is forgetting their coffee" voice recording plays  My questions are for what type of sensors will I need to purchase in order to create this project? and how would I set up the code to recognize the combination of sensors vs. the single sensors by passing the door sensor? Thank you for your help Indestructable community  

Posted by Ragestine 3 years ago


Designing a better "non-electric" espresso-maker

For people who want a reasonably portable non-electric espresso-making solution that's also affordable, there are a few alternatives. A few examples: Pneumatic: https://www.instructables.com/id/Hand-held-Espresso-maker/ http://www.handpresso.com/ http://mypressi.com/ Brute force: http://unmodifiedpresso.blogspot.se/ Results are--of course--variable with all of these solutions. From what I've gathered, apart from issues with bad coffee, with grind setting/quality or with tamping, the major issues have to do with temperature and pressure. Then there're the issues of convenience/comfort. How would you like to address such issues? Re. temperature, there's the time-honoured method of preheating all the parts by rinsing with just-boiled water. I like the idea in principle but I'd like a way to ensure that the water used for extraction stays in the right temperature range for as long as possible. Possible solutions: 1. Phase change metals such as the ones used in Joulies: http://www.joulies.com/pages/frontpage (different temperature target of course; not DIY-friendly) 2. A large reservoir of hot water. Make the machine hollow so that it can hold a lot more hot water and ensure that this large volume can stay in contact with the extraction chamber. May make the machine more pleasant to hold and use :) a possibility may be to have a water container encircling the existing water chamber in the Presso. Or just pour a lot of near-boiling water in a tank from which only enough water for one or two shots is released into the extraction chamber. Eg. make the Presso's water-reservoir much larger but design it so that only enough for one or two shots is released when the handles are raised to the appropriate position. 3. Insulation. Design as a thermos in such a way that metal parts won't rapidly transfer heat away from the water. What're your ideas?

Posted by Aimless 6 years ago


Homes Protected from Raging Forest Fires

Every year we hear about countless homes being destroyed by forest fires. Unfortunately, the public isn’t aware that our current level of technology can readily address this problem. I have been examining a concept that has intrigued me over the past decade and which I call a “fire shield”. This shield functions by completely enveloping a private home and protecting it against encroaching forest fires. We’re talking about protection against a blazing fire storm generating high speed winds and flames in excess of 100 MPH. The shield would be a flexible structure that easily inflates like a balloon (needing perhaps three people for a day to erect) and forms a protective hemispherical, shell-like dome over the home (Fig-1). The structure would be impervious to penetration by high speed flames and their intense radiant heat, thereby keeping the enveloped home safe, cooled and protected. Each home would require a pre-fitted, customized buildup of a number of pre-built modular, balloon-like segments. They are manufactured and then assembled over the house only once, to get a customized tailored fit, then taken down and stored, and thereafter are ready to be deployed within a day’s advance notice of an encroaching forest fire. The Fire-Shield would be a modular, portable, inflated dome like those used for indoor tennis, which is prepared and custom-fitted to be later erected within a day. While typical inflated domes have their entire inner volume pressurized, our Fire-Shield will only require pressurizing a small volume contained between its double-walled structure that forms the dome as shown in Fig-1. The surface of its outer material uses NASA's radiatively reflective, aluminized Mylar to ward off the intense radiant heat of a fire storm. In addition this surface gets protected against the 100 – 150 MPH fire-winds, which are ready to impinge upon it, by injecting a high speed film of air (just like gas-turbine blades) produced by portable blowers. The actual heat-shield contains multiple, redundant pockets of cells directing the flow of air to both film-cool its surface and protect the shield against direct flame contact. Each major modular segment would contain its own portable, gasoline powered wind generator to supply the airflow. Depending upon home-size, several of these modules would be easily connected using Velcro plus redundant snaps and safety-stays. The shield gets attached over chimney tops and to pre-installed, grounded cement-posts, plus strategic hooks about the outside of the house. Special, inflated pillows are also strategically placed (between the shield and the house exterior) to facilitate the formation of a hemispherical shield that envelopes and protects our home against a high speed fire-storm. The Fire-Shield Design Concept The concept for a fire shield went through a gestation period of several decades as my career in thermo/fluids evolved. It started with the design of jet engine turbine cooling to thermal control of satellites, and finally to designing radiant heat barriers for cryogenics. These activities enabled receiving a score of patents as well. These activities inspired the concept for a rapidly deployable Fire-Shield to protect homes against a raging forest fire. The idea requires integrating several technologies ranging from inflatable commercial air domes to jet engine cooling to radiatively cooled spacecraft. Also included are flexible material coatings developed by NASA that radiatively reflects high temperature heat, making the deployable Fire-Shield a viable concept. Two key design principles are employed to protect both the heat shield and the home it envelopes. The first is shown in Fig-2 and uses a high speed film of air (faster than the anticipated fire-storm flame speeds of 100 – 150 MPH) that is locally directed to blow over the shield’s surface, cooling it and protecting it just like the metal turbine blades of jet-engines. The temperature of speeding flames impinging upon a jet engine’s metallic turbine blades is hot enough to easily melt them, yet the blades are protected by using this film cooling technology. The same technology will protect the heat-shield from meltdown when high speed flames of 100+ MPH attempt to impinge upon its surface. The second principle protects the shield against the intense radiant heat coming from a blazing forest fire where temperatures can exceed 2000 F. While this radiant heat does not physically touch the shield, as would a fire-storm’s flames, its presence is “felt” and is as deadly as the hot flames that would normally scrub over the shield without our film-cooling. We use a radiatively reflective, thermal coating barrier that repels this radiant heatload and protects the shield from melting. Such coatings were originally developed by NASA to protect satellites and spacecraft. The coating gets applied to the shield’s outer domed surface and will reflect better than 97% of all intensive radiant heatloads that are incident upon the dome’s surface. (Patent Pending; Original Concept Documented in 2006)  

Posted by RT-101 6 years ago


Technology Makes Cheap Drinking Water from Air

INTRODUCTION:   How can we best apply basic technology to help the underprivileged and/or disaster-hit countries like Haiti? Daily hygiene and nourishment are among the top needs for disaster ridden regions!  Simply put, no water means no hygiene. The Romans understood that over two millennia ago and created their complexly beautiful aqueduct networks for handling both fresh and wastewater! Other ingenious water systems like “air wells” have been found in the city of Theodosia (cf: discovered in 1900 by Zibold, see Zibold’s Collectors/Dehumidifiers) dating back to Greco-Roman times during the Byzantine Empire. These were strictly passive systems that naturally dehumidified air, collecting its potable water in underground basins. All air, even in relatively dry desert regions, will precipitate or release its natural water content (initially in the form of vapor) through condensation when it hits its dew-point temperature and below. That means you “chill” it to an appropriate level that is anywhere from 5F to 50F below its current air temperature, depending upon how much water content (relative humidity) it has locally absorbed. The condensation of the water vapor releases its internal latent heat (reheating the cooled air) which must be constantly dissipated (absorbed by something) in order for water formation to steadily continue. So how do we dissipate this resultant vapor-heat and chill our air without any infrastructure or electricity, in an underprivileged or disaster-ridden region? We simply bury a long cast-iron or any metallic drain-pipe sufficiently underground where the temperature of the earth is naturally held to a constant at around 45F to 55F. That’s our “free” chiller gift from nature. One end of the pipe, Figure-1,  sticks out of the ground to suck-in local outside hot air, and the other end dumps cooled dry air and water into an underground cistern where it gets collected and is piped to the surface to both exhaust the cooled dry air and connect to a water pump. We need a hand operated water pump to lift up the water above ground, and we need an electric fan to constantly pump air through the ground-chilled piping system. We can even force the cooled piped air to exhaust into a tent-like structure where it provides air conditioning as an added bonus, but this adds the penalty of both power and the increased fan size necessary to drive our required airflow further into an enclosure! While this concept is not “passive” (requiring electricity to work) like those clever Byzantine air-wells, it will produce much more potable water and within a smaller volume than those elegantly passive historic devices. The electricity for our fan power requirements can be produced by any one of four ways using either “active” or “passive” techniques: 1) An active playground or bike-pedaling-person or oxen-driven mechanism-generator, 2) A passive windmill generator, 3) A passive solar energy collection system that directly generates electricity, or 4) A passive thermo-electric system that directly generates electricity using the Peltier effect, operating solely on temperature differences between the cell’s top and bottom surface (we jury-rig the cool pipe and hot ambient air to contact separate sides of the cell). Depending upon how much water is needed, the required air volume plus pipe length and diameter, together with the fan will be sized accordingly. We can also configure groups of parallel fan-driven air pipes that are radially fed into the cistern. The sizing of this underground network depends upon the ambient air’s local average temperature and relative humidity (how much water gets absorbed into the air) plus buried pipe depth and effective underground temperatures achieved. The basic concept is one where we “wring” water from air at some given humidity content. The higher its relative humidity the more water is recovered from the air. The air-wringing process simply chills the air as it scrubs along the cooled internal pipe surface until it starts to rain inside the pipe from condensation onto its surface. The condensation is like the dew that forms on car windows, grass or any cooled surface in the early morning, before the sun comes out and evaporates the dew back into the heating air. A further bonus is that our dew-formed water is naturally distilled and very clean. It is potable water ready to drink without the need for additional sterilizing agents. Of course, we must make sure that the interior piping and cistern network is biologically cleansed before burying it underground. The hand pump with its 10 to 15 foot extended piping to reach the underground cistern must also be cleansed. The beauty of this constantly replenishable water supply is its convenient underground installation anywhere! After the in-ground installation, we have a virtual, partially passive, no moving parts, non-breakdown system containing above ground total access to all moving parts that could breakdown, namely the water pump and electric fan. Also, it is easily maintained, with few moving parts (water hand-pump and electric fan) and basically lacking any technical complexity which makes it ideal for technologically backward regions. The example below uses a relatively small industrial fan moving air at 1500 CFM (Cubic Feet per Minute) with a DC motor rated at 1kW. This fan together with our underground piping system will conservatively generate 12 GPH (Gallons Per Hour) of potable drinking water without need for any purification chemistry. Based on an average electrical cost of 14-cents per kWh (kilo-Watt hour), the typical commercial distillation of one gallon of drinking water costs roughly 35-cents as compared to our cost of only 1.2-cents. Furthermore, if we decide to go green and use solar energy for generating our water, it would effectively cost us nothing beyond the initial installation! USING A PSYCHROMETRIC CHART TO SIZE OUR WATER SUPPLY: The following gets a little technical and is only provided for those die-hards who are truly interested in how the science works. Those non-technically schooled may skip this part and not miss the basic concept. Figure-2 shows a Psychrometric Chart for air. This chart summarizes some of the basic thermodynamic properties of air throughout its typical range of operating temperature. The chart uses six basic air properties that defines the physical chemistry of water evaporation into air:  (1) the enthalpy or total energy contained within a unit of air which is a combination of its internal and external energy, expressed as the amount of BTU-energy per unit mass of reference dry-air, (2) the specific volume or the ratio of a unit volume of local air to its mass of reference dry-air, (3) the humidity ratio or the amount (mass) of moisture in a local unit of air divided by its reference mass of dry-air, (4) the percent relative humidity per unit of local air, or the mass ratio (expressed in percentage form) of the partial pressure of water vapor in the air-water mixture to the saturated vapor pressure of water at those conditions (the relative humidity depends not only on air temperature but also on the pressure of the system of interest),  (5) the dry-bulb temperature or the locally measured air temperature, and (6) the wet-bulb temperature or saturation temperature which is the local air temperature experienced during constant water evaporation (a wet-bulb thermometer is typically used:   a thermometer that measures resultant temperature while wrapped in a water wet-gauze and spun to generate local air movement and max-evaporation)  1.0   The Process and A Sample Calculation Our Psychrometric Chart uses six thermodynamic properties that help to determine the amount of water available for extraction from the local ambient air as a function of its temperature, pressure and relative humidity.  Let’s assume the following local ambient conditions for the region we plan to construct our water system at:  (1) Typical daily air temperature Td = 106F and one atmosphere pressure assumed at sea-level, (2) Relative Humidity, RH = 55%, and (3) Typical underground temperature down at six feet is measured at Tu=55F (at 12ft. it drops to ~45F). This yields the following calculated results for obtaining a steady-state supply (changes at night) of water to fill the cistern:      1)      In our example, the “local” air (dry-bulb) temperature is Td=106F, at a relative humidity of RH= 55%.  Fig-2 indicates that the resultant Humidity Ratio is HR= 0.0253 Lbs-water/Lb-Dry-Air (intersection of Td=106F line and RH=55% line, then horizontal to HR value).  We then determine the “gulp” of air volume containing the HR Lbs-water which corresponds to the point of intersection of Td and RH. Interpolating on specific volume “mv” yields mv=14.7 ft3/Lb-Dry-Air (this value sets the optimum unit airflow for our given ambient conditions, and creates a ballpark pipe length to diameter ratio needed later). It represents the basic unit of air volume that will enter our underground pipe per given time, and ultimately defines the size of our fan and piping network. For increased water creation, multiples of this unit volume will scale up the additional amounts of water that can be collected. 2)      As the inlet air cools down to a temperature of Tu=55F, from contact with the relatively cold underground pipe, we follow the constant enthalpy line (red upward left-diagonal) from the intersection of Td and RH to its saturated air temperature condition of Ts= ~88F, which is its dew-point temperature where the corresponding local RH=100%.  At this temperature or under, the air precipitates and releases its moisture content, resulting in water condensation onto the pipe walls.  Since our air will chill to a final pipe temperature of Tu=~55F, we follow the RH=100% saturated curve (green) down to yield an HR=~0.009 Lbs-water/Lb-Dry-Air. This is how much water is left in the air when it gets to 55F.  Therefore for every pound of local outside air that enters the pipe, mw=0.0253 – 0.009 = 0.0163 pounds of absolute pure, distilled potable water precipitates onto the inside pipe wall (per pound of dry air that is cooled and dehydrated) to gravity-flow out the pipe exit and into the cistern. 3)      We now convert pounds of air per unit time into a unitized volumetric airflow that yields gallons of hygienically pure potable water production per unit time. For every Va=100 ft3 of local volumetric air movement per minute (CFM) through the pipe, which translates into ma=Va/mv= 100/14.7 = 6.8 lbs. of dry air per minute or 6.8 * 60 = 408 lbs. per hour (PPH), to yield a water-flow of mwf=ma * mw = 408 * 0.0163 = 6.65 PPH or 6.65/8.345 = 0.8 GPH of water.  An industrial fan rated at 1kW DC will typically move 1500 CFM at a pressure of 8-iwc, to continuously produce 15 * 0.8 = 12 GPH of pristine potable water. 4)      Not shown here are the design details of sizing our pipe, fan and solar collection system for electric power requirements using heat transfer principles coupled with a thermodynamic heat balance, and aerodynamic fan performance assessment. These details help to size the electric power generation requirements plus margin used to properly size a solar collector containing further margins for overcast days. The engineering involved here is straight forward but beyond the scope of the current project.

Posted by RT-101 6 years ago