Archive for the ‘IR’ Category

The time of infrared imaging in classrooms has arrived

January 9th, 2014 by Charles Xie
At the Consumer Electronics Show (CES) 2014, FLIR Systems debuted the FLIR ONE, the first thermal imager for smartphones that sells for $349. Compared with standalone IR cameras that often cost between $1,000 and $60,000, this is a huge leap forward for the IR technology to be adopted by millions.

With this price tag, FLIR ONE finally brings the power of infrared imaging to science classrooms. Our unparalleled Infrared Tube is dedicated to IR imaging experiments for science and engineering education. This website publishes the experiments I have designed to showcase cool IR visualizations of natural phenomena. Each experiment comes with an illustration of the setup (so you can do it yourself) and a short IR video recorded from the experiment. Teachers and students may watch these YouTube videos to get an idea about how the unseen world of thermodynamics and heat transfer looks like through an IR camera -- before deciding to buy such a camera.

For example, this post shows one of my IR videos that probably can give you some idea why the northern people are spraying salt on the road like crazy in this bone-chilling weather. The video demonstrates a phenomenon called freezing point depression, a process in which adding a solute to a solvent decreases the freezing point of the solvent. Spraying salt to the road melts the ice and prevents water from freezing. Check out this video for an infrared view of this mechanism! 

InfraMation Keynote Delivered

November 6th, 2012 by Charles Xie
Orlando is the center of the thermal imaging universe in November 6-8 when it hosts the largest infrared imaging conference in the world: InfraMation. Invited by FLIR Systems, I gave a Keynote Speech on the educational applications of IR imaging in this morning's Opening Plenary and I felt that it was very well received. The PEPSI joke about how to use an IR camera to produce a PEPSI logo (see the second image in this post) was a hit. Everyone laughed.

Here is the link to download my slides in PDF format (34MB). 

Once again, I was thrilled by the power of IR imaging and how this kind of technology can knock down the barrier between disciplines.Even if we are an educational technology firm with a primary mission to teach science, we are in no place to be humble because the science we are seeing through our IR cameras is exactly the same as the science the industry folks are seeing through theirs. Our original discoveries, intended to teach students science concepts, were equally recognized by world leaders in IR imaging technologies such as Prof. Dr. Michael Vollmer from the University of Applied Sciences in Brandenburg, Germany in their publication intended for researchers and professionals. With cutting-edge and yet easy-to-use technologies like IR imaging, the line between research and education is never so blurry. This ought to get science educators to think about the possibilities opened up by new technologies. We keep hearing some educators pushing back by asserting that children are not scientists and cannot think or act like scientists. This kind of argument largely neglects the advancement of technology and throws away the opportunities they bring along. It is time for a change, at least a try.

Think Molecularly: An Infrared Imaging Experiment Opens a Door to Deep Scientific Explorations

October 20th, 2012 by Charles Xie
Figure 1
The most fascinating part of science is the search of answers to strange phenomena. In the past nine months, I have posted more than fifty IR videos on my Infrared YouTube channel. These experiments are all very easy to do, but not all of them are easy to explain. In this blog post, I will try to explain one of those experiments, with one of my other skills -- molecular simulation.

This simple IR experiment concerns with putting a piece of paper above a cup of room temperature (nearly) water (Figure 1). I hear you saying, what is the big deal of it? You have probably done that several times in your life, for whatever reasons.

If you happen to have an IR camera and you look at this process through it, you may be surprised. Many of you know that water in an open cup is slightly cooler ( 1-2°C lower) than room temperature because of evaporative cooling: constant evaporation of water molecules from liquid water brings away thermal energy from the cup and causes it to remain a bit cooler than the room environment (which is why you feel cold when you step out of a swimming pool). You may think that the paper would also cool down because at room temperature paper is a bit warmer than the water in the cup and, based on what your science teacher has told you, heat would flow from the warmer paper to the cooler water, causing the paper to cool down.

Figure 2 (Watch it in YouTube)
But the result is exactly opposite -- the paper actually warms up (Figure 2)! And the warming appears to be pretty significant -- up to 2°C can be observed in a dry winter day. I don't know your reaction to this finding, but I was baffled when I saw it because I was expecting to see cooling and this effect appeared to be a violation of the Second Law of Thermodynamics (which, of course, is impossible)! In fact, the reason I did this experiment was to figure out how sensitive my IR camera could be. My intention was to exploit the small temperature difference resulting from evaporative cooling of water as a stable lower-temperature source. I was examining if the IR camera could catch the miniscule heat transfer between the water and the paper.

Figure 3 (Watch it in YouTube)
I quickly figured out that the culprit responsible for this strange heating phenomenon must come from the water vapor, which we cannot see with the naked eye. But what we can't see doesn't mean it doesn't exist. When water molecules in the vapor encounters the surface molecules of the paper, they will be captured. When more and more water molecules are captured and condense onto the paper surface, they will return to the liquid state and, according to the Law of Conservation of Energy, release the excessive energy they carry, which causes the paper to warm up. In other words, the paper somehow recovers the energy lost in the cup through evaporation. As you can see now, this is a pretty delicate thermodynamic cycle that connects two phase changes, evaporation and condensation, in two different places and their latent heats. The physicists among us would appreciate if I say that this shows entropy at work: evaporation is an entropic effect that is caused by water molecules wanting to maximize their entropy by leaving their more organized liquid state. The interaction between the vapor and the paper acts to reverse this process by returning the water molecules to the condensed liquid state and a certain amount of net energy can be extracted from this (known as the enthalpy of vaporization).

Figure 4: Sensor results.
At this point, I hope you have been enticed enough to want to try this out yourself. If you don't have an IR camera, you can use a temperature sensor or an IR thermometer as a substitution to observe this phenomenon (of course, nothing beats an IR camera in terms of seeing heat -- with a point thermometer you just need to be patient and be willing to do more tedious work).

But wait, this is not the end of the story!

If you keep observing the paper, you will see that this condensation heating effect will diminish in a few minutes (Figure 3). This trend is more clearly shown in Figure 4 in which the temperature of the paper was recorded for ten minutes using a fast-response surface temperature sensor. What happens?

Figure 5 (Watch it in YouTube)
The answer to this question can be illustrated using a schematic molecular simulation (Figure 5) I designed to explain the underlying molecular physics (in that simulation water molecules are simplified as single round particles). After water molecules condense onto the paper surface, a thin layer of condensate will form. When it becomes thick enough, water molecules will evaporate from it, too, just like from the surface layer of water in the cup. When the rate of evaporation equals the rate of condensation, there is no more net heating: The condensation heating and evaporative cooling will reach the "break-even" point. Reaching this equilibrium state doesn't mean that condensation and evaporation on the surface of the paper will stop. In fact, water molecules will keep condensing to the layer and evaporating from it. This is known as "dynamic equilibrium." If you move the paper, you will break this dynamic equilibrium. Figure 6 shows a pattern in which evaporative cooling and condensation heating occurred simultaneously on a single piece of paper after the paper had been shifted a bit. In Figure 6, evaporation dominated in the blue zone that was shifted out of the cup area, condensation dominated in the white zone that was shifted into the cup area, and the overlap zone in the middle remained close to the equilibrium state because it was the zone that still remained inside the cup area -- so business as usual.

Figure 6 (Watch it in YouTube)
As you can see, there is a lot of science in this "simple" experiment! Nothing we have done so far requires expensive materials or supplies. Everything needed to do this experiment is probably within the reach of your arm if you are reading this article at home (and you happen to have a digital thermometer, or better, an IR camera, nearby). If you are a science teacher, this experiment should fascinate you because you know this will be a perfect inquiry activity for your students. If you are a building professional, this experiment should fascinate you because you know how important hygrothermal dynamics is in driving moisture transport in the building envelope. If you are a scientist, this experiment should fascinate you because what I have shown you is in fact an atomic layer deposition experiment that anyone can do -- some Fermi calculation suggests that the thickness of the layer is in the nanometer range (only a few hundred layers of water molecules or 1/10,000th of the diameter of your hair). What we are seeing is in fact a signal from the nanoscale world! Isn't that cool?

Figure 7 (Watch it in YouTube)
Does our story end now? Absolutely no. The new questions you can ask will be practically endless if you keep "thinking molecularly." The following are six extended questions I have asked myself. You can try all of these without leaving your kitchen.

When will the paper cool down?

Returning to the original purpose of my experiment (looking for cooling due to heat transfer), can we find a situation in which we will indeed see cooling instead of heating? Yes, if the water is cold enough (Figure 7). When the water is cold, the evaporation rate drops. There will be less water molecules hitting the surface of the paper. The energy gain from weaker condensation heating cannot compensate the energy loss due to the heat transfer between the paper and the cold water. (By the way, I think the heat transfer in this case is mostly radiative, because air doesn't conduct heat well and natural convection acts against heat transfer in this situation.)

What if the paper has been atop the water for a long time?
Figure 8 (Watch it in YouTube)

If you leave the paper atop the cup of water for a few hours and you come back to examine it, you would probably be surprised again: The paper is now cooler than room temperature (Figure 8). I wouldn't be surprised if you are totally confused now: This heating and cooling business is indeed quite elusive -- even though everything we have done so far has been limited to manipulating paper and water. To keep the story short, I will tell you that this is because water molecules have traveled through the porous layer of the paper through capillary action and shown up on the other side of the paper (this molecular movement is often known as percolation in physics). Their evaporation from the upper side of the paper cools down the paper. The building science guys among us can use this experiment to teach moisture transport through materials. Can the temperature of the upper side be somehow used to gauge the moisture vapor transmission rate (MVTR) of a porous material? If so, this may provide a way to automatically measure MVTR of different materials. The American Society for Testing and Materials already has established a standard based on IR sensors. Perhaps this experiment can be related to that.

Different materials have different dew points?

Figure 9 (Watch it in YouTube)
Do water molecules condense to other materials such as plastic? We know plastic materials do not absorb water (which is why they are good vapor barriers). If plastic materials are not cold enough, water molecules do not condense to them. Figure 9 shows this difference by using a piece of paper half-covered by a transparency film taped to the underside. Heating was only observed in the paper part, indicating water molecules do not condense to the plastic film. This experiment raises an interesting question: The so-called dew point, the temperature below which the water vapor in the air at a constant barometric pressure will condense into liquid water, may not be an entirely reliable way to predict condensation. Condensation actually depends on the chemical property of the material surface. Hydrophobic (water-hating) materials like plastic tend to have a low dew point, whereas hydrophilic (water-loving) materials tend to have a high dew point. The porosity of the material should matter, too, because a more porous material will provide a large surface for interaction with water molecule -- paper happens to be such a material because of its fiber texture. If you are a building professional and you worry about moisture, you probably should have this in your mind.

Figure 10 (Watch it in YouTube)
Vapor pressure depression

What will happen if we add some salt (or baking soda or sugar) to the water? Figure 10 shows that the condensation heating effect becomes weaker. For our chemist friends, this is known as vapor pressure depression. The salt ions do not evaporate themselves, but their presence in a solution slows down the evaporation of water molecules.

A vapor column?

Figure 11 (Watch it in YouTube)
What will happen if the paper approaches the water from a different angle like in the vertical direction? How does the shape of the water vapor distribution above a cup of water look like? Does it look like a steam from a cup of coffee? Figure 11 could probably give you some clue.

What about alcohol?

So far we have used only water. What about other liquids? Alcohol is pretty volatile. So I tried some isopropyl alcohol (91%). Once again, I was baffled. Our experience with applying rubbing alcohol to our skin says that alcohol cools faster than water. So I expected that when the isopropanol  molecules condense, they would release more heat. But this is not what Figure 12 suggests! Given the fact that the enthalpies of vaporization of alcohol and water are 44 and 41 kJ/mol, respectively, the only sensible explanation may be that the heating effect is not only due to the condensation of the vapor molecules, but also the interaction between the vapor molecules and the surface molecules of the paper. If the interaction between an alcohol molecule and a paper molecule is weaker, then the adsorption of the alcohol molecule onto the paper surface will produce less heat. I don't know how to prove this now, but this could be a good topic to research.
Figure 12 (Watch it in YouTube)

Final words

Even if this is a lengthy blog post (and thanks for making it to the end), I am pretty sure that the scientific exploration does not stop here. There are other questions that you can ask yourself. For me, I have been intrigued by the fascinating thermodynamic cycle and have been wondering if that could be used to engineer something that can harvest that latent heat. In other words, could we turn a cup of water into a tiny power plant to charge my cell phone? The evaporation of water molecules from an open cup is a free gift of entropy from Nature. Perhaps something could be done about it.

A simple IR experiment to prove that the North Carolina Sea Level Rise Bill is just flat wrong

July 5th, 2012 by Charles Xie
Last month, North Carolina's Senate passed a bill that would have required the state's Coastal Resources Commission to base predictions of future sea level rise along the state's coast on a steady, linear rate of increase. This has sparked controversies across the nation amid the record heat waves in many states.

If the lawmakers had done our very simple IR experiment on visualizing thermohaline in a cup, published in the July issue of last year's Journal of Chemical Education (see the image to the left), they would have had a better understanding about the possibility of the nonlinear acceleration of ice shelf melting: The less salty the seawater is, the faster the ice shelf above it melts. And the faster ice melts, the less salty the seawater will become. This creates a positive feedback loop that accelerates the melting process. If the speed of ice melting in systems as simple as a cup of saltwater is not as nice as the "steady, linear" rate some of the lawmakers would like to see, who can be sure that systems as complex as the Earth would follow a "steady, linear" trajectory of change?

If you bother to read on, this experiment uses just a cup of tap water, a cup of salt water, and some ice cubes. The two cups are placed next to each other on a table for comparison. (a) An IR image right after an ice cube was added to a cup of freshwater (left) and a cup of saltwater (right). (b) An IR image taken after four minutes showing a downwelling column in the freshwater. (c) An IR image taken after nine minutes showing the tabletop was cooled significantly near the freshwater cup. (d) An IR image taken after 16 minutes showing that the bottom of the freshwater cup became cooler than the top whereas the bottom of the saltwater cup remained warmer than the top.

To see the entire process caught under an IR camera, you can watch the embedded YouTube videos in this blog post. Feel free to send these videos to your representatives if you happen to live in the coastal area of North Carolina. Or send to a science teacher in North Carolina in the hope that the bill will be revised in the future to consider the possibility of nonlinear acceleration.

Note that these videos do not represent any political view and should not be considered as in support of any agenda, my purpose is only to provide a humble scientific demonstration to prove that things do not always go smoothly as we wish.

Investigating thermoimaging in augmented multisensory learning about heat transfer

July 2nd, 2012 by Charles Xie
Jesper Haglund from Linköping University presents a poster about our Sweden-US collaborative research on thermal visualization at the 2012 World Conference on Physics Education held in Istanbul, Turkey. Below is the abstract of the poster:

"Infrared (IR) thermal imaging is a powerful technology which holds the pedagogical potential of ‘making the invisible visible’, and is becoming increasingly affordable for use in educational contexts. Science education research has identified many challenges and misconceptions related to students’ learning of thermodynamics, including disambiguation of temperature and heat, and a common belief that our sense of touch is an infallible thermometer. The purpose of the present study was to explore how thermal imaging technology might influence students’ conceptual understanding of heat and temperature. This was carried out by investigating three different conditions with respect to students exploration of the thermal phenomena of different objects (e.g. wood, metal and wool), namely the effect of students’ use of real-time imaging generated from a FLIR i3 IR camera, students’ interpretation of static IR images, and students’ deployment of traditional thermometer apparatus. Eight 7th-grade students (12-13 years old) worked in pairs across the three experimental conditions, and were asked to predict, observe and explain (POE) the temperature of a sheet-metal knife and a piece of wood before, during and after placing them in contact with their thumbs. The participants had not been exposed to any formal teaching of thermodynamics and the ambition was to establish if they could discover and conceptualise the thermal interaction between their thumbs and the objects in terms of heat flow with minimal guidance from the researchers. The main finding was that a cognitive conflict was induced in all three conditions, as to the anomaly between perceived ‘hotness’ and measured temperature, with a particular emotional undertone in the real-time IR condition. However, none of the participants conceptualised the situation in terms of a heat flow. From the perspective of establishing a baseline of the understanding of thermal phenomena prior to teaching, extensive quantities, e.g. ‘heat’ or ‘energy’, were largely missing in the participants’ communication. In conclusion, although an unguided discovery or inquiry-based approach induced a cognitive conflict, it was not sufficient for adjusting the students’ conceptual ecologies with respect to the age group studied here. Future research will exploit the promise of the cognitive conflict observed in this study by developing a more guided approach to teaching thermal phenomena that also takes full advantage of the enhanced vision offered by the thermal camera technology."

If you happen to be at WCPE 2012, drop by his poster: Session - 1.04, Date & Time: 7/3/2012 / 13:00 - 14:00, Room: D406 (3rd Floor).

If you don't know what thermal visualization is, visit our InfraredTube website.

YouTube Physics features our infrared videos

June 1st, 2012 by Charles Xie
AAPT's Physics Teacher runs a column called YouTube Physics edited by Diane Riendeau, an award-winning physics teacher. In May, the entire column featured five intriguing YouTube videos from our IR website and recommended instructional strategies to use them effectively in the classroom.

Diane recently wrote about the YouTube Physics Column: "Through the use of YouTube, we can show our students demos that we do not have the capability of doing in class. We can use these videos to inspire them and show them some of the cutting-edge discoveries in our field. We can also show them videos from around the world. Students need to realize that the physics community is global, not just national. They should learn to marvel in the discoveries made by physicists from all nations."

We resonate with her vision, which is why we are publishing our IR videos on YouTube to allow students from all over the world to learn thermodynamics, heat transfer, chemistry, and other science subjects in everyday phenomena through IR vision. In the long run, we hope this effort will give birth to an "IRTube" that collects IR views of many scientific phenomena. With the introduction of thermal imaging technology into the classroom, we hope students will begin to upload their own IR videos to the IRTube. Darren Binnema, a student from the King's University College in Edmonton, Canada, has contributed the first IR video to the "IRTube." His IR video visualizes the heat of solutions of NaOH and KCl (see the above image).

For more IR videos, please visit the IRTube website.

Visualizing the latent heat of fusion of ice

February 27th, 2012 by Charles Xie

Latent heat is the heat released or absorbed by an object during a change of state without the change of temperature. The latent heat of fusion is the energy absorbed when a substance melts or released when it freezes.

The two videos in this post present a visualization of the latent heat of fusion of ice. Three containers, one filled with brine, the other two with freshwater, were stored in a freezer for two days. The temperature of the freezer was enough to freeze the freshwater in the two containers but not the brine. They were then taken out and put on a foam board. The left one was the brine.

The first video shows the temperatures of the three containers shortly after salt was added to the middle one. The second video shows their temperatures after about an hour. Both videos show that the middle container was the coldest. Two factors contributed to the cooling of the middle container. One is the latent heat of the melting of ice due to the contact of salt. The other is the negative heat of solution of salt--that the dissolving of salt absorbs heat.

Initially, the brine container on the left was colder than the third container on the right. After an hour, the brine container became significantly warmer than the third container. What was cooling it? It is the latent heat of fusion due to the melting of ice in the container. Since the brine was in liquid state all the time, there was no latent heat involved and all the heat it absorbed from the room was used to increase its temperature.

25 IR imaging experiments added

February 12th, 2012 by Charles Xie
I have added 25 experiments and their videos to the world's first website for IR imaging experiments launched last month. These experiments are all easy to do.

For example, to the right is an experiment that involves only a paper strip and a cup of tap water. Hang the paper strip above the water and slightly lower it into the water. Guess what you will see? Wait for a while and look at the IR view again. What will you see?

The first video shows what an IR camera recorded when the paper strip was just lowered to touch the water. You may expect that the paper would cool down because it has touched the water that appeared to be cooler than the ambient temperature. But, on the contrary, the paper warmed up! How is that possible? We all know that heat flows from hot to cold. How could heat flow from the cool water to the warmer paper strip and warm it up even more?

The second one shows what an IR camera recorded 20 minutes later. It shows that, on the paper, the thin strip just above the surface of water appeared to be the coolest.

Can you explain these temperature distributions and their time variations? I will leave these questions to you.

A partnership with HOBOS

January 21st, 2012 by Charles Xie
Prof. Dr. Jürgen Tautz
We are honored to announce a partnership with the HOney Bee Online Studies (HOBOS) Program, directed by Prof. Dr. Jürgen Tautz at Universität Würzburg, Germany, to promote science education through the application of IR imaging technology. HOBOS uses bees to stimulate students' interest and promote their inquiry skills, including enhancement of the ability to "think critically, integrate and synthesize knowledge, draw conclusions from complex material, understand the natural and physical worlds, grasp the processes by which scientific concepts are developed and modified, develop the mathematical and quantitative skills necessary for calculation, and analytical thought and problem solving." These are exactly our goals on the other side of the pond. We hope this international collaboration will help us integrate our resources to promote these shared visions.

Prof. Tautz is a renown biologist whose work have been widely reported by New York Times, BBC, and so on. HOBOS has been supported by UNESCO and nominated for the 2011 Cleantech Media Award.

Thermal vision is a critical technique in bee research. HOBOS currently provides an online IR camera that allows anyone to observe bees in real time. We envision that this partnership will allow us to jointly explore broader applications of affordable IR imaging (and other applicable technologies) in biology education. We are looking forward to the return of bees, bugs, and other insects in the spring to start this journey!

The world’s first website for IR imaging experiments launched

January 19th, 2012 by Charles Xie
We have launched the world's first website dedicated to IR imaging experiments for science and engineering education: http://energy.concord.org/ir.

This website publishes the experiments I have designed to showcase IR visualizations of natural phenomena. Each experiment comes with an illustration of the setup and a short IR video recorded from the experiment. Dozens of IR videos will be produced and added to the website as we move along. Teachers and students may use these YouTube videos without purchasing IR cameras (the price for the basic versions of which have come under $900 in the United States).

Among other things, we are developing a unique approach that uses affordable handheld IR cameras to visualize unseen energy transfer processes occurring in easy-to-do science experiments. Using this approach, thermal energy can be readily visualized through an IR camera. Other types of energy that convert into thermal energy can be inferred from thermal energy visualizations. This allows many invisible physical, chemical, and biological processes that absorb or release heat to be discovered and investigated.

By lowering the technical barrier to authentic scientific inquiry and presenting compelling visualizations of energy flows and transformations in everyday life, the tool will enable more students in diverse schools to develop a deeper understanding of energy concepts and their broad applications.