Physics 24.1 Variable Heat Transfer (24 of 25) Thermos Bottle

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.

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[onaybilgen]

My k value is 0.063 W/m^2*K how can i convert cal/sec*cm*C

[abood-]

Thank you. However, are we taking into account here that the temperature differential is changing?

[abood-]

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.

[elsheikhmohamedahmedelshei]

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?

[lucasmarques]

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

[thaisnicole]

Por que não consideramos a convecção no cálculo

[hmata]

Awesome video! Your work is greatly appreciated!!

[jakubkusmierczak]

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.

[guenheejunheelee]

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.

[salvadorberberov]

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.

[aqeelshah]

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.