Physics 24.1 Variable Heat Transfer (24 of 25) Thermos Bottle
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- เผยแพร่เมื่อ 9 ก.ค. 2018
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In this video I will calculate the time it takes for a temperature, t=?, for inside a cylindrical thermos from an initial temperature t0=100C to tf=50C.
Next video in this series can be seen at:
• Physics 24.1 Variable...
Awesome video! Your work is greatly appreciated!!
Thank you sir for working out this problem. I have been thinking about it for a considerable amount of time and finally came across your video.
I have a question. Your model considered only the heat capacity of the water and ignored its resistance/conductance to heat transfer. On the other hand, you considered only the heat resistivity of the cylinder and ignored its heat capacity. Is this a realistic model? I mean no need to consider heat resistance of the water and heat capacity of the cylinder? Or this is this just to simplify the problem and reach a closed-form solution?
My k value is 0.063 W/m^2*K how can i convert cal/sec*cm*C
1 cal = 4.186 J m^2 = 10,000 cm^2 K = C degrees
Sir, It seems like the bottom area of the bottle needs to be considered if the diameter isn't small enough because considerable amount of the heat from the liquid inside will also transfer through that side. then I think the equation dQ/dt would be different from the one you've reasoned out.
Hi there. I am doing a project on a similar case with changing temperature differential and would appreaciate if you have any references or textbooks which talk about cases like this.
Your videos are great ☺️
Thank you. However, are we taking into account here that the temperature differential is changing?
Yes indeed.
Like the videos. Working on a project similar to the one in your drawing. Need to construct a thermos with following dimensions. Dimension a=0.5in, dimension b=1.5in and dimension L=48in. Need to submerge the thermos in a fluid with a constant temperature of 200°C and time for the liquid inside to reach 200°C temperature in 100 hrs (with starting initial temperature of 20°C). I can use your calculation in reverse and find out what the thermos constant needs to be. However, how will I be able to construct a thermos with that constant. Need help in selecting materials ( type and thickness of insulator, vacuum thickness etc.) . Any help would be appreciated.
i am working on a project same like you. my subject is 24 hrs with acceptable %20 loss like 100 celcius to 80 celcius. so if you done your project. can you contact me i ask for your documents because i cant find any calculations on website i am bachelors student. i am in hurry so if you see this please respond me in a second
can someone help me? my problem is to know the time for a bottle go from 4 celsius to 10 celsius with Tinf = 25 celsius i have LN(-??) and i dont know who to solve it
Sorry Lucas. With the information you gave us, we cannot determine what the problem is.
Por que não consideramos a convecção no cálculo
For simplicity, to show just the conduction. We have an entire playlist that also includes conduction. See here: PHYSICS 24B CONVECTION TEST YOUR KNOWLEDGE starting with this video: Physics: Ch 24B - Convection: Test Your Knowledge (1 of 26) What is Convection? th-cam.com/video/7vg3EnX7ZWc/w-d-xo.html
Mr. Professor if the heat flow is in the opposite direction, do I have to change the temperature limits of integration and Ta and Tb? to calculate the time of interior heating? Best regards, Follower.
When you change the limits of integration you will get the exact same answer except of the sign (it will change to the opposite sign).
So the time for cooling is the same as for heating in such a conditions (reverse heat flow)?
The speed at which hear flows depends on the difference in temperature, the length of the path, the cross-sectional area and the heat conductivity of the material. If those are all the same, the time will be the same.
It is great news for me. Thank You. Mr. Professor I am trying to estimate the power of the sun by using solar panels. The solar panel is made of steel pipes and energy medium is water. Since the temperature of water is 40 oC and solar panel 70 oC, it is a little bit hard to recieve precise value of sun power in a period of time, since the rise of the temperature of the panel which I measure depends on two processes cooling and heating at once. Mr. Professor would You be so kind and make a video at this topic?
We haven't covered heat exchange with flowing water yet, which is indeed a complicated topic. You also have to remember that as the water absorbs heat, it will become warmer from one end of the pipe to the other end of the pipe, and then you need to exchange that heat through a radiator (or a condenser) depending on the final temperature of the water (or steam).
Very helpful video. Thank you Sir
Happy to help
@@MichelvanBiezen
Hi Sir, kindly share me similar equation for my requirement.
I am suppling heat Q-200W,
providing h-35 (fan air velocity~4m/s),
And having Ti (initial) of 80°C (steady), Ta (ambient) 25°C
Component Mass-1.5kg
Material-Copper
Cov Area - 0.1 m^2
I want to find two things
1) if I reduce h to 25 then how much time (t) will it take to reach Tf (final) of 90°C
2) if I increase Q to 300W (with h 35) then how much time t, it will take to reach Tf of 90°C
Thanks in advance
WhatsApp 8144011363
kamurudeenka@gmail.com
Sir I want to increase the time for liquid that it should remain hot for long time. What should I do I mean Please tell me what factor I can increase or decrease.. sir please reply me must it is very important for me.
Choose an insulation material with a lower "k", the heat conductivity constant, or make the insulation layer thicker.
@@MichelvanBiezen thank you so much sir