Heat transfer between resistance and water

In summary, the question is about the main mechanism of heat transfer between a solid copper resistance and liquid water. While some may argue that it is convection, it is actually conduction that is the primary method of heat transfer in this scenario. This is because in order for convection to occur, there needs to be a mass transport of the fluid, which is not possible in this situation. This confusion may arise from differing definitions of convection, but in this case, conduction is the correct answer.
  • #1
Carcul
8
0
What is the *main* mechanism of heat transfer between a thermal resistance and water?

My doubt arose in the context of a problem (from a high school national test) dealing with the following situation: a 500 W thermal resistance made of copper is immersed in a jar containing 500 g of water at 20ºC, with the purpose of heating it to 90ºC, and then it is asked what is the principal mechanism of heat transfer between the resistance and the water.

Even being copper a very goog thermal conductor, we have here heat transfer between a fluid and a hot solid surface, so shouldn't it be mainly by convection? The correct answer is supposed to be "conduction", but I don't agree.
 
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  • #2
Why do you say it is convection??

More importantly, why did you even consider convection? it never occurs in something where diffusion currents(of mass) cannot flow.
 
  • #3
Now you have confused me. Why can't occur here mass transport of water? Isn't it a fluid??!
 
  • #4
Carcul said:
Now you have confused me. Why can't occur here mass transport of water? Isn't it a fluid??!

Water is a fluid, and heat transfer in water takes place by convection, mostly.

But your question is, what is the method of heat transfer between a solid copper resistance and liquid water.. How can convection currents arise in solids and be transferred to liquids?? :wink:
 
  • #5
Thank you very much for your help, I understand now what you meant. I guess my source of confusion is/was the way convection is defined in some books. For instance, in the book Thermodynamics, an engineering approach, from Çengel, we can read "Convection is the transfer of energy between a solid surface and the adjacent fluid that is in motion, and it involves the combined effects of conduction and fluid motion." This doesn't look like the explanation you have given, however.
 

1. What is heat transfer between resistance and water?

Heat transfer between resistance and water is the transfer of thermal energy from a material with higher resistance to a material with lower resistance, through a medium such as water. This transfer of energy can occur through conduction, convection, or radiation.

2. How does resistance affect heat transfer in water?

The higher the resistance of a material, the more difficult it is for heat to transfer through it. This means that materials with higher resistance will take longer to heat up or cool down compared to materials with lower resistance. In water, resistance can be affected by factors such as salinity and impurities.

3. What is the role of water in heat transfer between resistance?

Water is an excellent medium for heat transfer due to its high specific heat capacity and thermal conductivity. This means that it can absorb and transfer large amounts of thermal energy, making it an effective medium for transferring heat between materials with different resistances.

4. How does the temperature difference between resistance and water impact heat transfer?

The greater the temperature difference between the material with higher resistance and the water, the faster the heat transfer will occur. This is because a larger temperature difference creates a stronger driving force for heat to flow from the higher resistance material to the water.

5. What are some practical applications of heat transfer between resistance and water?

Heat transfer between resistance and water is commonly used in industrial processes, such as cooling systems for machinery and heat exchangers. It is also essential for maintaining a comfortable living environment, as seen in heating and air conditioning systems that use water as a heat transfer medium.

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