Thermal Conductivity: Exploring the Disparity in the Real World

[sasuke07]

Homework Statement

I was wondering why there is such a disparity between thermal conductivty and how they act in the real world.
Ex. If if have 3 cups filled with hot water. The 3 cups are made of glass, plastic and metal.
The metal will obviously have way higher thermal conductivity compared to the glass and plastic cups. But the temp. goes down slowly in all 3 cups and the rate that the temp. goes down. between the 3 cups are similar. The metal will drop in temp. faster than the other 2 but not that much faster. I was wondering why

Homework Equations

No Equations

The Attempt at a Solution

Said in 1.

 

[LawrenceC]

A cup loses heat through its walls as well as from its surface. Furthermore, in order for the sides to lose heat, the heat must be released via natural convection. Natural convection from horizontal surfaces is greater than it is from vertical surfaces (side of container). Natural convection is a relatively slow mover of heat so it tends to blunt the differences in thermal conductivities of the walls of the cup. What diffuses through the wall must be released to the surrounding air.

The cups also radiate energy. That must be a consideration as well. Water radiates.

 

[vivekrai]

Rates are similar in them but not equal. Probably your experiment and ambient is too small to judge any significant difference due to the nature of the matters. Rest is clarified by LawrenceC

 

[sasuke07]

Thanks a lot

 

[asteriatic]

person:
I can explain the disparity in thermal conductivity and its real-world application. While metals do have higher thermal conductivity compared to glass and plastic, it is important to consider other factors that affect the rate at which temperature decreases in a substance. One factor is the specific heat capacity of the material, which is the amount of heat needed to raise the temperature of a given mass by 1 degree Celsius. This means that even though the metal cup may have higher thermal conductivity, it may also have a higher specific heat capacity, requiring more heat to raise its temperature. Additionally, the thickness and surface area of the material also play a role in heat transfer. In the case of the cups filled with hot water, the metal cup may have a larger surface area, allowing for more heat to dissipate into the surrounding environment compared to the glass and plastic cups. Therefore, while thermal conductivity is an important factor in determining how quickly a material can transfer heat, it is not the only factor at play in real-world scenarios. Other factors such as specific heat capacity, thickness, and surface area must also be considered to fully understand the rate at which temperature decreases in different materials.