Heat flux analysis with transient heat conduction

In summary, the conversation discusses a one-dimensional heating system with a heating source in the center and two PVC elements on either side. The heat distribution in other dimensions is negligible due to insulation. The thickness and surface area of one PVC element are given, and the heat flux is measured during heating with different power levels. The question is whether any physical properties of the heated material can be determined from the results, such as thermal resistance or the heating power of the source. The attempt at a solution involves calculating the heat flux increase over time, as well as considering the convection coefficient of the room. However, it is unclear if this information is sufficient to calculate the thermal resistance or other physical properties.
  • #1
Zaffax
1
0

Homework Statement


I have one dimensional heating system. In the center is heating source which is heating two PVC elements located on both sides of the heating source. Heat distribution in other dimensions is negligible because of insulation. Thickness of one PVC element is 0,051 m and surface area 9,19 * 10-3 m2. During heating I measured exiting heat flux of one PVC element with heat flux sensor. I got following results:
physics_forum.png

Before red line the heating power is 14,4 W and after red line 1,6 W. The heat is divided in half between the elements, so initially there's 7,2 W heat flowing to one PVC element. The reason I changed heating power was that I wanted to measure heat flux with steady state and power of 1,6 W (which was successful as the heat flux reaches value of about 80 W/m2 compared to the theoretical value of 86 W/m2 if heating is approximated to be one dimensional), and by heating the elements at first with 14,4 W I could make the experiment be quicker. I didn't have equipment to measure temperature on the hot and cold side of the element, but the room temperature was 18 Celsius.

The question is: from the results during transient heating before system reaches steady state can I determine any physical properties of the heated material such as thermal resistance, or if the physical properties of the material were known could I determine for example the heating power of the heating source? Before the red line heat flux on the cold surface of PVC element is rising steadily at constant rate for over 3000 seconds so I was thinking maybe I could solve something out of the derivative constant (which is 0,0138 W/m2s during the 3000s period between t = 2000s & t = 5000s) since it most likely is related one way or another to the thermal resistance of material, but after checking through transient heating theory and equations I couldn't think of any way to use them on these results, so I must humbly ask for your advice on this matter since my knowledge is hitting wall and it's about time to use ladder to help get past it.

Homework Equations



kaavat.png


The Attempt at a Solution


The constant heat flux increase in time is already calculated above. Heat power on the cold surface at given time can be calculated by multiplying measured heat flux with surface area. I was thinking that I could also calculate surface temperature from the equation of convection, if I knew the convection coefficient of the room in which this experiment was made. My guess is that radiation is negligible, since the subject was covered with aluminium foil, so all the heat flux measured by heat flux sensor is taken away by convection.
 
Physics news on Phys.org
  • #2
I'm not sure if this is enough information to calculate thermal resistance of the material or any other physical properties.
 

FAQ: Heat flux analysis with transient heat conduction

What is heat flux analysis with transient heat conduction?

Heat flux analysis with transient heat conduction is a method used to analyze the flow of heat through a material over time. It takes into account the changing temperature and properties of the material, as well as the heat transfer occurring through conduction.

Why is heat flux analysis with transient heat conduction important?

This analysis is important because it allows us to understand how heat is transferred through a material in real-time, which is crucial for designing and optimizing systems that rely on heat transfer, such as engines or electronic devices.

How is heat flux calculated in transient heat conduction?

Heat flux is calculated by dividing the amount of heat transferred through a material by the area and the time interval. It is expressed in units of watts per square meter (W/m²).

What factors affect heat flux in transient heat conduction?

The main factors that affect heat flux in transient heat conduction are the material properties, such as thermal conductivity and specific heat, and the temperature difference between the two sides of the material. Other factors include the geometry and boundary conditions of the system.

How is heat flux analysis with transient heat conduction used in practical applications?

This analysis is used in various practical applications, such as in the design of heating and cooling systems, thermal management of electronic devices, and modeling of heat transfer in materials processing. It is also used in research and development for understanding and optimizing heat transfer processes.

Back
Top