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).
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.