Calculating Heat Transfer Between 3 Mediums: Copper, Ground, Water

In summary, The conversation is about calculating the heat transfer between three different mediums (copper, ground, and water) in a geothermal system. The thermal conductivities of each medium are given. The person is wondering how to quantify the heat transfer and if using a different material for the pipe would affect the transfer rate. They mention using engineering tables and reference material to find idealized formulas, and also note that the specific heat of the water is a factor in determining how long it would take to heat up. They also question if a larger pipe wall would result in less heat transfer.
  • #1
James Brady
105
4
I had a quick thermal dynamics question... I'm looking into geothermal systems and I was wondering how to calculate the transfer from the ground, through a copper pipe into water. I know how to calculate the heat transfer from air of different temperatures though a medium, but I do not know how to calculate the heat transfer in watts between three different mediums:

Thermal conductivities (W/m*k):

Copper: 400
Ground: 1
water: 0.58

Just wondering how to do some basic calculations, thanks.
 

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  • #2
You do know that the amount of heat that transfers from the ground is equal to the amount of heat that transfers through the copper pipe and into the water.
 
  • #3
Yes, I know that heat out = heat in. I'm wondering how to quantify that though. For instance, if I used an iron pipe, would that heat transfer be slower?
 
  • #4
MAYBE some tips you can use here:
http://en.wikipedia.org/wiki/Ground_source_heat_pump#Thermal_efficiency

I'm guessing you will likely need some standard engineering tables for different environmental and mechanical systems. In other words, idealized formulas are probably in the realm of experts in the field and may not match real world situations easily.

NOTE the organizations mentioned in the article...
maybe they have reference material online...
 
  • #5
Ok thanks. You know what I was thinking of how long it would take for the water to heat up. That's a function of specific heat, I just couldn't put my finger on it. But I should be able to turn it into a differential equation now.

Just be sure though... A larger pipe wall will result in less watts going into the fluid, correct?

Heat in = thermal conductivity*surface area*deltaT/wall thickness...?
 

1. How is heat transfer calculated between three mediums?

The heat transfer between three mediums can be calculated using the formula Q = U * A * (T1-T2), where Q is the heat transfer rate, U is the overall heat transfer coefficient, A is the surface area, and T1-T2 is the temperature difference between the two mediums.

2. How do you determine the overall heat transfer coefficient?

The overall heat transfer coefficient can be determined by considering the individual heat transfer coefficients for each medium and the resistance of each medium to heat transfer. It can be calculated using the formula 1/U = 1/h1 + 1/h2 + 1/h3, where h1, h2, and h3 are the individual heat transfer coefficients for each medium.

3. What factors affect the heat transfer rate between three mediums?

The heat transfer rate between three mediums is affected by factors such as the temperature difference between the mediums, the surface area of the mediums, the material properties of the mediums, and the overall heat transfer coefficient. Other factors such as the presence of insulation or external factors like wind can also affect the heat transfer rate.

4. How does the material of the mediums affect heat transfer?

The material of the mediums can affect heat transfer due to differences in thermal conductivity. Materials with higher thermal conductivity, such as copper, will transfer heat more easily than materials with lower thermal conductivity, such as water or the ground. This affects the overall heat transfer coefficient and can impact the heat transfer rate between the mediums.

5. Why is it important to calculate heat transfer between three mediums?

Calculating heat transfer between three mediums is important in various scientific and engineering fields, such as energy conservation, building design, and thermal management. It allows us to understand how heat is transferred between different materials and environments, and how to optimize heat transfer for efficient energy usage.

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