Learning Forum

[Laure]

Thanks Nick / Rob for your reply.

I ran three cases in a simplified 2D model. The tank in 6 m long and 2 m deep. The top 0.2 m contain water (fluid) and the rest is sediment (solid). The line heat source in 2 m and is located 0.5 from the top, heating the sediment (solid) for 4 hr. In these cases, I am only considering conduction in sediment.

In case 1, I assigned the thermal conditions of the line source as Heat Flux and input power rate per m2

In case 2, I assigned the thermal conditions of the line source as Heat Flux and input power rate per m3 (assumed cable thickness = 0.01 m)

In case 3, I assigned the thermal conditions of the line source as Coupled and input power rate per m3 (assumed cable thickness = 0.01 m)

Cases 1 & 2 produced the same results. However, Case 3 developed a much lower temperature profile (please refer to image below).

All cases reached a lower maximum temperature compared with the observed maximum value (34 C).

Questions:

1)      What is the correct approach to define heat rate for the line heat source of this problem?

2)      Do you have any idea of the differences between Case 1 (or Case 2) and Case 3?

3)      Why do you think simulated maximum temperature is lower than the observed maximum temperature? Note: I did a sensitivity analysis of solid thermal conductivity, specific heat, and density (using appropriate ranges). In all cases, simulated maximum temperature was lower than observed maximum temperature. 

Thanks in advance.