Transcript: fan retrofit video

Hi. So, what the heck is a blast chiller? Aside from sounding cool, they've been around for decades. And if you're a chef, you've probably worked with one on a daily basis, or if you're an avid cook, you've always wanted one. Effectively, they are a refrigerator or a freezer on steroids. They can very rapidly cool off food. And there's a number of advantages to doing that. If, for example, you're in the process of cooking something and you need to reduce the temperature, you're making a marinade or a sauce or a pie filling or a pastry and you want to bring the temperature down so you can go to the next phase. Rather than putting something in the refrigerator for an hour, you can put it in a blast chiller for 20 minutes and keep going. It makes you more efficient. Another advantage is food quality. If you remember in our last video on rock candy, crystallization is all about time. When you take water and you freeze it into ice, the longer you take to do that, the larger the ice crystals get. And when they get large, they start to damage some of the fibrous material, the cellular structure in vegetables, fruit, and meat. And so when you thaw them out, those damaged structures mean that the vegetables get a little bit spongy or the fruit when you thaw it out will produce some juice in the bottom of the container that contains nutrients and flavor. And when you thaw meat, it gets kind of strange. It gets rubbery and dry at the same time because you've broken down the protein structures and driven out water. Because the blast chiller is able to refrigerate the material so quickly, the ice crystals are much smaller. As a result, it doesn't damage the food as much. Now, you might say, "Wait a minute. I go to the grocery store, I pick up frozen peas or frozen fruit, and when I thaw them out, they're in pretty good shape." The reason is that the food processors use blast chilling when they package the food. And as long as it's distributed and you bring it home and it stays frozen, the ice crystals remain small. Another advantage is food safety. You see, no matter how clean you are in your kitchen, it isn't a clean room. And so there's going to be mold, bacteria, spores that can get into your food from the air, from you, from your utensils. And when the temperature of that food is in what they call the danger zone between about 65 C and 5° C, that those bacteria, those pathogens have the perfect environment for reproduction. They've got water, food, and a nice comfortable temperature. So they multiply like crazy. So when you store that food in your refrigerator, it has a more limited lifespan. It might only last 2 or 3 days. use a blast chiller and it might last twice as long so you don't get as much food waste. So with all of those advantages, you might think, why don't we see these things all over the place? Well, the problem is these things tend to be relatively large. And so unless you're doing a remodeling project or you've got an enormous kitchen, you really don't have room for them. So they focus on the commercial market. And as a result, they build these things to commercial standards. heavy paneling, heavy duty hinges. They're strong to put up with the abuse of commercial use. They also have very large blowers or fans inside to distribute the heat and much more powerful refrigeration systems to draw the heat out. As a result, they're a bit of a niche item and so they're not manufactured in very large quantities. And so for the companies to remain viable, they have to charge a lot of money. A typical unit of about this size will cost you between about $5 and $8,000. You can get a really small unit for somewhat less or you can get a larger unit for the price of a new car. So, it's a real barrier to purchasing these things. But what we're going to show you today is how to construct a blast chiller at home for about $50. And if you're a slow, methodical worker, you can complete the project in under an hour. Now, you might think the guy's crazy. There's no way that this could be done. He's fooling us. No, I'm not. If you have a basic understanding of some simple physics and some engineering, you can accomplish this. And we're going to prove it. To begin with, we're going to modify an existing freezer. So, we don't have to buy a new unit, and we don't need more space for it. Secondly, you don't need commercial quality in a residential application. These things last for decades. I mean, when's the last time you've ripped the door off of a refrigerator not allowing for that frat party? In addition, you're also going to have to deal with the fans and the refrigeration system, and that's what we're going to focus on now. Now to begin with it's good to understand the principle about how food cools when you put it in a refrigerator or freezer. There's two processes going on. One is radiative cooling. Every object in the universe above absolute zero emits electromagnetic radiation and in the temperature range between say frozen water and boiling water that radiation is in the infrared region and it is very temperature dependent. It's actually temperature to the fourth power. So, if you doubled the absolute temperature of some item, it's going to radiate 16 times more energy. Because I'm warmer than the walls in this room, I'm emitting more energy than they are sending back to me. So, I'm cooling off. And the same thing happens in the freezer when you put in warm food and the cold walls of the refriger. But that's a minor component. The major factor is convective cooling. When you put the hot object inside of the freezer, the air molecules that contact the surface gain energy. They warm up. They become less dense and they begin to float away. Cold air comes in to replace it and continue the process. But it's very, very slow. That air rises at millimeters/ second and as the food cools that rate of rise continues to slow. But if we put a powerful blower inside of the freezer, we can increase that rate of heat transfer a thousandfold. And as the food cools, the fan just keeps pumping at the same rate. So it's a much more effective way to get the heat out of the food. So the first thing we need to do is we need a fan. We need a powerful blower. Now, you're not going to want to use something like a table fan. It's too bulky. you're going to use up half of the room inside of the freezer and it's going to make it impractical. But you also want to focus on a very efficient fan because we are going to be locating it inside of the chamber, it's going to add its heat load to the load of the food that we're trying to cool. Now, if you were to get, say, an instrument fan, a computer fan, one of these muffin fans that I'm sure you're familiar with, they're very efficient and they can produce a high velocity blast on the food we're trying to cool, but they don't move a lot of air. We effectively want to move that air past the surface of the food, but we also want to distribute it through the chamber in order to dump that heat. So, we need a pretty large fan. Typically, you want to use a fan that has a cross-sectional area that's about 40% of the cross-sectional area of the freezer. So, there is room around the fan for the air to circulate back down and continue the cooling loop. And it turns out there is an ideal solution for this problem. Radiator booster fans. If you've never heard of these things, these are sold on Amazon. They're sold in auto supply places that are used when you have a car or a truck that is pulling say a heavy trailer or a camper. And the load means that the engine's working hard. It's making a lot of heat, but you're not driving very fast or maybe even in traffic. As a result, to keep the engine cool, this thing augments the flow through the radiator to blow more air through it and keep the engine at a low temperature. That's nice. In addition, because they're designed to operate inside of an engine compartment, they tolerate vibration, dirt, bugs. They're really robust and you don't take them off in the winter. So, they'll tolerate road spray and very, very low temperatures. The primary reason for that is that the motors on these are sealed. And that's a good thing for us because we're not going to be spilling lubricants inside of the chamber. Now, another interesting thing about these is because they're sold in the millions per year, they're cheap. Really cheap. The two examples I have here on the table cost $50 for a pair of them. So, you can really pick them up at a low cost and they come in a variety of sizes to match the size of the inside of the chamber of your freezer or your refrigerator. Pretty neat. In addition, because they are DC powered, you can alter the direction of flow, which is very convenient because typically you'll mount these on a radiator and they will blow through the grill side or the rounded side. But for our installation, we actually want the flow through the flat side. And the way you change the direction is simple. Find the leads and attach the positive lead to the black, which is normally the negative. that will reverse the direction of the motor. But these fan blades, which are quite efficient, are designed to operate in only one direction. So, we also have to change the orientation of the fan. We're going to put a link in the description below to the Amazon page where we picked up these fans because they're particularly easy to modify. If you look carefully, you'll see this single nut right here. Simply take a nut driver and release the nut. Take the fan blade off. Reverse it. Put it back down. Get it to settle onto the post. Put the nut back on. Tighten it up. and you've now completed about 50% of the assembly work for the whole project. So, as you can see, it's pretty easy. In addition, mounting these is easy because they are designed to mount on a radiator. They often have holes or tabs that allow you to attach them to the radiator. I think the most effective way to mount them inside the freezer is simply to use tie wraps. They're inert. They're inexpensive. And when you attach them, you can actually tuck tuck the little tabs down. So even the shelf that you put this thing on is going to be usable. And because they are very flat, they occupy very little volume. Let me show you inside of the freezer here. If you look carefully, you'll see that the fan is mounted down here. And you can even see the little tie wraps that I've attached here and tucked in. They're flush so you can use this shelf. And because it's flat enough, you can still use the bin below to get out your vegetables and your fruit. And in addition to that, they're very, very powerful. I've got this power supply set to 5 vols. >> I'll look over at this camera. Turn this down. 6 vol 7 vol 8 vol 9 vol 10 vol and 12 vol. This thing really roars. One other thing I want you to notice is this little blue line I have over here. This is the temperature probe that's mounted that we're going to be using for the test that monitors the air temperature inside of the freezer. We'll get into that in a little bit. Now, you might be concerned and think this thing is going to blow my pasta all over the inside of the refrigerator. But that's not true because in fact, as much as this has a tremendous amount of capacity, we don't actually want to run it at 12 volts. There is a sweet spot of efficiency with this fan. And the way I was able to identify that is this little setup back here. I'm not going to run it because it's pretty obvious what I did. I took another variable power supply, a mounted fan, an animometer placed at a fixed distance from the fan, and simply ramped up the voltage and measured the air velocity. And at about 8 to 9 volts, this thing will move about 80% of its maximum air flow and use less than half of the power. So that's why I'd recommend you use this. Now, in addition to that, you're going to wonder, what do you use for the power supply? Well, I kind of like these variable power supplies. They're pretty nice, and they come with a switch. They also have a voltage control like I just demonstrated, so you can do your own experiments. And they actually give you a wattage of power used, so you can evaluate how much it's costing you to do that in terms of heat load. However, even though you can pick these up for less than $50 online or on Amazon, if you really want to save money, you can get a wall wart that has enough voltage and amperage capability to drive these fans, and you'll spend less than half of that. That's where we came up with the $50 price. Now, we come to what theoretically could be the dealer in the project, the refrigeration system. Typically, if you take a look at a website or a sales brochure about using a blast chiller, you'll see a chef will go in and take the um food and they will load it into an empty blast chiller, close it, and hit blast, and they'll cool it off. The problem we have is that that system has to have an enormous heat system to remove all that heat and send it into the room. Now, if we were to get an HVAC system or a new modification of this by getting the equipment, the skills or somebody in to do this, it would enormously increase the price and the the effort that you have to put into the project. But there's a way around that. You see, a normal freezer or refrigerator is really designed primarily to keep food at a temperature. As a result, it has a puny compressor system. If you look at the power meter right here where this system is plugged in, it's running at 90 watts. It runs anywhere from about 75 to about 94 watts. That's full power. That's as much as it can refrigerate. And it runs a duty cycle of about 50%. 50% of the time on, 50% of the time off. that's necessary to just compensate for the amount of heat coming in from the outside environment through the insulation. So effectively what we've got available to us to do the refrigeration of what we're putting in there is half of that number or about 45 watts. To put that in perspective, if you take a kilogram of hot liquid or warm water and you cool it off and turn it into ice, you have to remove about 700,000 jewels or 700,000 watts for a second. So, you can imagine it would take a heck of a long time to draw the heat out of the system. But it turns out we get lucky because we are modifying an existing system that's already loaded up with food. We have a huge heat sink that exists inside of here. You'll see this better when we're doing some of the video, but this system here will run typically at about -20 to 25° C hard frozen food. And if you look at your freezer, and we studied ours, you probably have 20, 30, 40, 50 kg of high water content thermal mass already in there. So what the fans are effectively doing is rather than trying to draw the heat out of the system, they're transferring the heat from the small item that you added to the huge heat sink that already exists there. Yes, it will warm up five or six degrees in the process, but still be way below freezing while the thing that you put in there has now frozen. Meanwhile, that little compressor that could is going to continually remove heat. So, when you're done cooking through the night, it will bring everything back to the equilibrium temperature of about -20 or 25° C. That is what makes this whole project possible. And so in order to do the test, let me show you the meters and what they represent. And basically, we'll go through how you're going to read this when we do the time lapse. Now, the first is the power. >> Move that one to your left. >> This one here. >> Yep. >> Okay. Now, for the time lapse, you'll get a better view because we're going to set these up so it's a real clear, crisp view. But as long as you can at least see the numbers here, you can see that right now it's using the nominal full power of about 88 87 watts. Occasionally you'll see this drop all the way to 0.3 watts. That's when the duty cycle is in the off mode. The.3 is just what's keeping the electronics alive. You may, and it's not certain you will, but you may rarely see this shoot all the way up to about 280 watts for a few minutes. This is the defrost function that occurs in these freezers and you can't defeat it and it can occur anywhere from every 6 to about every 18 hours. It's unpredictable, but it represents such a short period of time that it's not going to really affect our tests. But it will explain that if you see that short period of time when the power shoots up and then comes back down. Even though that adds some noise to the testing, nevertheless, it is realworld situation. what you're going to find when you install this. So, the clock is pretty obvious. We're going to be running the time frame and the time lapses on this clock. Over here is the temperature meter. The top probe is the one with the blue line that's measuring air temperature. And the bottom number is this probe that's going into the sample that we're going to be testing. Now, let me show you what the testing involves. Over here we have 800 cc's of distilled water and a 1 kilogram stainless steel pot. I'm going to pour the water in here. Every last drop. And then I'm going to turn on the heater and we're going to bring this up to 50° C. This represents sort of the warm liquid that you would cool off if you were saying using this for the efficiency in cooking operation and you just want to reduce the temperature somewhat. When we see this cool off, we'll see how rapidly it cools off in the first control test. But then we're going to keep running this test until we freeze this to solid hard ice so we can evaluate what's the crystallization time, the actual freezing time of that sample of water. So, when this gets up to 50°, we're going to put it in and we're going to start the time lapse. See you in a bit. Okay, we got 50° here. So, let's go ahead take out the probe, pick up the pot. Going to bring it over here. Open her up. Place it in here like this. Put the thermal probe in here like that. Make sure it doesn't come out good. And we'll start the timer. All right. So, keep an eye on the time, power, and the temperature. And you'll notice just incidentally, this temperature went well up from minus 255 just because of the air that entered when I put the pot in. But you can see it dropping very very rapidly. Now we've just got to wait. See you in a bit. All right, we've gotten down to minus one degree. So, let's take a look and see what it actually looks like in here. Oh, yeah. So, this is hard frozen. completely frozen. And you can see that it took us 426 minutes in order to freeze this without the fan. Standard mode of operation. Now, what we're going to do is I'll empty out the pot. We're going to refill it with the water and we're going to run the test again, but this time we're going to turn the fan on to 9 volts and we're going to do a similar time lapse and we'll see what the differential cooling rate is, both for warming the liquid and for freezing the ice. See you in a little bit. Okay, so let's do the second test. 800 cc of distilled water, 1 kg stainless steel pot. Put this in here. Get it all in. Put down the probe. That'll do. and we'll start the heating process. And we want to bring this to the same temperature we did for the first test, 50° C. So, I'll see you in a bit. All right, we're actually at 51° here. So, let's get this out of here. Take the pot out. I'm going to put it into the freezer. Same position. Open that door as much as possible. Yeah, like that. Place the probe in here. Good. Sure. We put it in carefully. Okay. We're going to start the timer. You can see that the temperature warms up a lot because I just opened the door. We're at 50°. Start the blower. About 98 watts. 17 seconds. This is quickly lowering simply because we really didn't add much heat just by opening the door. And we're going to watch this number slowly drop. So, we'll see you in a bit. >> [music] >> All right, that looks good. We're still at about 93 watts. We're at 66 minutes. Still the 9 volts. Good. All right, let's take a look and see what we've done. Yep. Yeah. Frozen. >> You want to show it a little bit closer? >> Okay. Like this. >> Frozen. There like a little bubble at the top maybe, but that's it. Okay, so obviously this does work. This is a pretty impressive result. and we're going to give you a summary and a comparison. But one thing I want you to note from the live streams, if you take a look from the from the um time lapse, is that the temperature of the air temperature during the uh long duration test was consistently higher in the blast chiller uh version simply because we're removing the same amount of heat from the same sample, but we're doing so in a much shorter period of time. So, are loading more heat into the system. So, let's see what it looks like if we do a direct comparison. Let's take a look at a graph. You might have noticed that we looked pretty tired by the end of the video. We are exhausted with the duration of both of these tests. This was probably the longest single session that we've ever done on our channel. But let's put aside the uh complaints and let's look at the actual data. Now the graph as it's displayed shows on the horizontal axis time in minutes in 15minut segments 0 15 30 45 and the vertical axis is temperature in degrees Celsius. Both samples are shown on the display and the red line represents the control, the freezer operating simply as a freezer. The blue line represents the blast chiller, the freezer with the fan on. Both samples start out at 50° C and rapidly cool once the pot was put inside of the freezer. You'll notice that the red line has a shallower slope. It takes approximately 2 hours 0 minutes to 120 minutes for that liquid to have cooled down to 0° C. While if you look at the blue line which represents 50° C to the same 0° C, it occurs in approximately 60 minutes. So the chilling function of the blast chiller is about twice as effective, twice as rapid. Then you'll notice with both lines that they follow a fairly horizontal period and that represents the transition of the 0°ree water to 0° ice the crystallization process. Now when water crystallizes it releases a great deal of heat. So the heat being removed from the samples is being uh is allowing the water to be converted phase converted into ice. And so rather than cooling, you're simply converting more and more of that water into ice. In the case of the red line, this starts at about 120 minutes into the test and continues all the way out to the right side of the graph at 420 minutes. In other words, it took about 300 minutes for this phase transition to occur. If you look at the blue line, the 0°ree water begins at 60 minutes into the test and is completed at 165 minutes or in other words, 100 minutes. So, the freezing function with the blast chiller is approximately three times as fast. So, I think these were pretty impressive results. I think this is likely comparable to a blast chiller that costs thousands of dollars. Now I know this is not like our projects uh involving directed energy defense systems. Um and just as an aside we are currently working on two of them actively right now. But this kind of a project is neat because it is simple, it's inexpensive, you can do it quickly, and it's clearly very effective, and it's something that you can do uh set up and accomplish in less than an hour. Something that you might be able to do between drone attacks. So, I hope you liked this video. Uh it was a lot of fun to do it. It did take a long time. And if you like the kind of content that we're producing on this channel, please take just a couple of seconds and subscribe. It doesn't cost you any money at all. And if you add a thumbs up and a comment, these three actions induce YouTube to distribute our videos to a much broader audience. And the larger we get, the more we can afford [music] to do. And if you really like what we're doing, take a look in the description below the video where we link to our [music] Patreon community. The Patreon community provides direct support for the channel and it is one of the reasons that we've been able to avoid those annoying invid promotions that many content creators have had to resort to and we plan to keep it that way. And in addition to that, you should also realize that we do not make any money on our channel. We put all of the money that we receive both through YouTube and Patreon directly into producing more videos. We do this because we enjoy it. And finally, we are going to be following this video like every other one with a live stream this coming Sunday at 9 at 6:00 p.m. Eastern time. At that point, you can ask us questions. You can make comments about this video. You can give us criticisms. And it's an opportunity to discuss what is obviously just a one-way presentation. When we do the video, we can also discuss any of our other videos that we have done or any topics in science, engineering, and physics that you find interesting. I think you'll like it because we really enjoy doing it and it gives people the opportunity to have interaction with us and a live forum. So with that, stay safe, have fun, and we'll see you Sunday night.