- 63
- 124 020
Denis YW Yu
Hong Kong
เข้าร่วมเมื่อ 25 ก.ค. 2020
Educational videos about energy, materials and other science topics
What is special about this Escher picture?
Check out the symmetry elements in this Escher picture
มุมมอง: 160
วีดีโอ
How many balls are in the container?
มุมมอง 94ปีที่แล้ว
Check out the little secrets about invisibility
Smart windows on airplanes
มุมมอง 171ปีที่แล้ว
Learn how an electrochromic window works in this video
Why is the sky blue? And why is the sun reddish at sunset?
มุมมอง 206ปีที่แล้ว
A simple explanation on why the sky is blue and related phenomena
How much thermal insulation (R-value) is a material?
มุมมอง 60ปีที่แล้ว
See this video for information about heat conduction, thermal insulation and R-value
Can you tell the difference between sunrise and sunset?
มุมมอง 18Kปีที่แล้ว
In this video, I will discuss about the difference between sunrise and sunset
How hot is a dolsot bibimbap?
มุมมอง 496ปีที่แล้ว
Find out how hot a Korean stone pot rice is and how long does it take to cool down.
What is the energy efficiency of a gas stove and what are the losses?
มุมมอง 1Kปีที่แล้ว
Experiments to estimate the energy efficiency of a gas stove, to understand the losses, and also to study the effect of a pot cover
Convection - how much heat is carried away?
มุมมอง 852 ปีที่แล้ว
A simple experiment to estimate convection heat transfer coefficient
Maillard Reaction
มุมมอง 872 ปีที่แล้ว
Learn about how food is charred to give us great taste (student video competition - gold award)
Reducing radiation with shiny surface
มุมมอง 1152 ปีที่แล้ว
See how effective is the reflective coating on reducing heat transfer
How does a dehumidifier work?
มุมมอง 34K2 ปีที่แล้ว
Learn how a dehumidifier works and also its energy efficiency in this video
Understanding psychrometric chart - advanced
มุมมอง 2672 ปีที่แล้ว
This part of the video explains the specific volume, wet bulb and enthalpy lines on the psychrometric chart
Understanding psychrometric chart - beginner
มุมมอง 6192 ปีที่แล้ว
Understanding psychrometric chart - beginner
Measuring humidity with a sling hygrometer
มุมมอง 2262 ปีที่แล้ว
Measuring humidity with a sling hygrometer
Skin effect and proximity effect - how they change resistance of wires
มุมมอง 13K2 ปีที่แล้ว
Skin effect and proximity effect - how they change resistance of wires
Wireless charging, induction and transformers
มุมมอง 2412 ปีที่แล้ว
Wireless charging, induction and transformers
Understanding inductor and inductance with demonstrations
มุมมอง 3402 ปีที่แล้ว
Understanding inductor and inductance with demonstrations
What online lectures were like during COVID-19
มุมมอง 1133 ปีที่แล้ว
What online lectures were like during COVID-19
Basically turn on your air conditioner
Lyerys 😢
Thank you for the effor you put into the video
What number should I programme humidistat button for a damp room?
Thanks
Hi, thanks for the video. What is the voltage of the ultrasonic membrane?
Hello. It is not clearly written what is the voltage of the ultrasonic membrane, but the AC adaptor has an output voltage of 24V, so most likely it is 24V
Very nicely shown and explained, interesting math and charts, thanks! Yet MY OWN cheap China humidifier puzzles me: it consists of two thin 15mm diameter ceramic wafers with centrally mounted metal membranes. Apparently a high (108kHz?) vibration is induced by the piezo effect. The bottom ( and NOT the top!) speaker like metal sheet has many tiny 5um holes. These seem to generate the cool mist visible above the SOLID (no opening AFAIK!) MEMBRANE on top of this diffuser. A wick feeds the bottom punch-hole sheet with water. How does the water get from in between these two thin metal sheets to the top surface, escaping the speaker-like membrane?? If the TOP membrane had these 5000+ holes (through a microscope they look odd, probably LASER burnt?) I'd understand the principle, but the switched order of these metal sheets puzzles me endlessly. These 50c atomizer plates are not very reliable, yet they do generate a quite impressive mist at a really low power: less than 1W feeds the circuit board, the activator membranes and the LED illumination. Of course this small scale device does not really change the room climate, but with a little fragrance added it creates a neat aroma in its vicinity. Just HOW the "speaker" gets access to the mist underneath it's top membrane escapes me..just like the mist..
Thank you for your comments. It is hard to tell without photos how the Chinese humidifier works, but my guess is that maybe the water goes in by capillary action
@@denisywyu7864 third attempt, as Google deletes my replies within seconds (the digital age is coming to its mindless AI end..).. Thanks! It is obvious that the bottom metal membrane with its thousands of tiny holes will generate a mist of droplets when oscillating at high frequency, as it is in contact with the moist wick underneath. Yet the mist escapes on TOP of the upper (unpunched) membrane with its speaker-like solid dome. I can even see the tiny droplet streams in the mist with my myopic eyes. They seem to come THROUGH the SOLID TOP MEMBRANE, which makes of course no sense. Somehow the 'atomized' moisture must crawl around the cave between the two metal sheets along its outer rim (15mm diameter, held by a rubber ring), reach the top dome and get shaken off it by the oscillation. Magic at work. You can buy a bunch (3) of these atomizers with all the electronics, switches and LEDs for US$3 at AliExpress, or thousands for US$0.20 each at AliBaba. Fascinating stuff. I could fix my humidifier by replacing the ceramic oscillator element; strong mist is generated again. How long? Will the added aroma oil clog the 5um holes soon, certainly a risk. I already use distilled water, to avoid any mineral clogging of these elements. I took photos of my defective unit with an old digital microscope. The miniscule 5um holes are impressive to look at, in comparison of a stamp print and a human hair. Since my attempt to publish a link yielded in the removal of my reply (thank you, Google, for nothing!) here another one at "App""Box""COM" add this string by replacing the '-' with '/': -s-deqtsjt77vykpnfhn4d20hq834m070at-file-1663152839535 There is a lot to be found on YT about these humidifiers, your clip is the most comprehensive and scientific one I could dig up. Hence my contribution here. Thanks!
as expected bro is asian
b looks 9pm 8pm 7pm 6pm 5pm backwords 2:52
thanks good video
At 4:19 Did you mean to say Copper "Rod" not "Tube" because a tube is also hollow, which is what I thought was what made a Heat Pipe a heat pipe?
A heat pipe has a little bit of water in it so the water can evaporate and conduct the heat faster
That's a really good explanation. Thank you!
I did not know that proximity effect is so evil. That would explain, why some inductors perform so poorly even though the wire is smaller than the skin depth. Thank you!
Aren't you forgetting the LED in you watt usage calculations? 9.7-0.6-[LED draw]
thank you for the comment. The weight measurement was done with the LED off.
That can’t be true about the dust. I live on the ocean. I believe it’s because of the glare of the water from the ocean.
Very stupid experiment. Why did you include water evaporation??
Excellent sir
🌌
The main difference is the size of the condensing unit. Scale it up to much and you only get cold air, without noticeable condensation.
When the coils are close, the magentic field of each individual wrap has an affect on many neighboring individual wraps. When the coil is spread, the magetic field only affects the closest neighbors. See inductive choking.
Informative. Synthetic fuels almost eradicate the soot from its combustion. Thank you very much.
Excellent explanation. Thank you very much.
amazing thx u!
Wow, I guess them perfectly just from the feel.
Is AC resistance (skin or proximity effect) increased with higher currents ?
this is a good question. I think the skin effect and proximity effects affect the area of the wire that can carry a current, which in principle does not depend on current. However, in reality, higher current means that there will be more heat generated, and so the temperature of the wire will increase, and resistance is temperature-dependent (usually higher resistance with higher temperature)
Thank you for this simple but effective demonstration. I had been studying skin effect for coils I am making, but was puzzled why litz wire was specified with a much smaller area wires for a frequency than the skin area alone would suggest. I believe this must be due to minimizing the proximity effect.
Thank you for the comment. I think litz wire needs to account for the proximity effect as well, so they are thinner
Very nice video I was impressed
The sky at sunrise appears red and the sky at sunset appears yellow. If light is more scattered in the evening, shouldn't the sky be red rather than yellow?
Thanks Denis very informative
This was great.
I want you to be tutor for my son
Superman may not see temperature differences, but he may see that one of those "rods" is actually a pipe!
thank you for the comment. Sorry, I forgot to clarify that both of the rods are pipes, one without water inside and one with water inside.
Great video. On to Part 2.
I’m looking for an efficient way to create clouds in the sky. Could this principle be used?
I guess in principle, you could, but you need a water source to start out with. The ultrasound turns the water into water droplets. The other possible way to create clouds in the sky is to do what the airplane does in cold wet days (contrails) where the steam from the engine condenses in air to form cloud trails.
If you seal the cup / put a lid on and had the heat pipe go through the lid, would the heat pipe cool down the water to room temperature? Would that happen fast?
yes, the heat pipe will cool down the cup faster, as it conducts heat out of the cup faster
Just check if PM or AM and you'll know the answer.
The point is to tell the difference without using any clocks. Mainly if you are ever out in the wilderness or forests.
@@damonsonnier34 yes how would you ever identify sunset vs sunrise in the wilderness without a clock
besides remembering if it was dark outside 30 mins ago
@@omnacky Because campers and hikers do not always fall asleep at nighttime.
Hahahahahaaa. Too funny. Great joke.
Excellent video! If you feel like it, please do one about the humidifiers that have the piezo transducer at the top of a wick sticking out of the water (or link to it if you already did one). Thanks!
This is great!
The earth is not rotating.
? Curious
Prove it. No balls.
Everything i thought was true is a lie??
Thanks for creating this vid; the explanations are very intuitive and easy to follow :) .
🙏🙏🌹🌹
Good explanation 🙏🏽👍🏽
Denis y w.. we have the same humidifier. It was working fine but suddenly when we adjust the timing of humidifier and as it starts the small fan… the motor stops its own. Why does this happen? How can we fix this humidifier back to normal?
Very good videos the others are so dumb and don't explain
OMg! such a great video!
Out of all the dumb, disastrously long videos on the internet about humidifiers, this was the best one, not dumb at all, and was the most informative with actual testing and data. Thank you for cutting through the stupidity. What a breath of fresh air.
Perfect. Answered all the questions and then some.
Great video
This was really well presented 👍🏽 thank you! The Smashing Pumpkins song "Soot and Stars" brought me here ✌🏽
love it