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New to COMSOL: modeling simple heat diffusion in water
Posted 15 lug 2016, 08:32 GMT-4 1 Reply
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I am currently participating in a summer school about applications of mathematics in Industry. This week we were given a demo of COMSOL by COMSOL employee Temesgen Kindo. I have downloaded the free trial and I am trying to apply it to a project.
I would like to create a simple model of heat diffusion in space and time. The physics packages I am using are "Laminar flow" and "Heat transfer in fluids." Our domain is a two dimensional rectangle consisting entirely of water. The top of the rectangle is exposed to air and the three remaining sides are insulated.
Initially, one small parcel of water (a square in the top right corner) starts at 110F and the remaining water begins at 80F. I want to evolve the system over time and witness that the system moves toward a temperature equilibrium. First, I create a mesh and solve for velocity fluid u (assuming zero initial conditions). Then I take this u and I solve the heat equation over a time interval of 30 minutes. But in my results I do not see any significant heat diffusion and this does not seem physically reasonable to me.
Could you let me know what options I may take on COMSOL to make this model more physically reasonable? When I get this basic model working, I would also like to and inlets and outlet to the walls with inlet and outlet velocities of .5m/s (currently disabled in my file). I would like to observe the effect of this added flow on temperature over time.
Any help is greatly appreciated!
I would like to create a simple model of heat diffusion in space and time. The physics packages I am using are "Laminar flow" and "Heat transfer in fluids." Our domain is a two dimensional rectangle consisting entirely of water. The top of the rectangle is exposed to air and the three remaining sides are insulated.
Initially, one small parcel of water (a square in the top right corner) starts at 110F and the remaining water begins at 80F. I want to evolve the system over time and witness that the system moves toward a temperature equilibrium. First, I create a mesh and solve for velocity fluid u (assuming zero initial conditions). Then I take this u and I solve the heat equation over a time interval of 30 minutes. But in my results I do not see any significant heat diffusion and this does not seem physically reasonable to me.
Could you let me know what options I may take on COMSOL to make this model more physically reasonable? When I get this basic model working, I would also like to and inlets and outlet to the walls with inlet and outlet velocities of .5m/s (currently disabled in my file). I would like to observe the effect of this added flow on temperature over time.
Any help is greatly appreciated!
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1 Reply Last Post 15 lug 2016, 09:59 GMT-4
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Posted:
8 years ago
Hello Jacob,
Water is a rather bad thermal conductor, but in real life most of the heat transfer in your experiment is likely happening by natural convection, rather than by conduction. Your model does not include convection.
See for instance
www.comsol.com/blogs/using-the-boussinesq-approximation-for-natural-convection/
www.comsol.com/model/free-convection-in-a-water-glass-195
to learn more on how to set up a natural convection model.
Best,
Jeff
Water is a rather bad thermal conductor, but in real life most of the heat transfer in your experiment is likely happening by natural convection, rather than by conduction. Your model does not include convection.
See for instance
www.comsol.com/blogs/using-the-boussinesq-approximation-for-natural-convection/
www.comsol.com/model/free-convection-in-a-water-glass-195
to learn more on how to set up a natural convection model.
Best,
Jeff