When you want to apply a total heat source option in the part of the region, you must consider the cell geometry (especially volume) at the target region.
Details
When you want to give a heat source at the part of the region, you have options: volumetric heat or total heat source. The selection of the options above depends on the situation (or given value from the reference data). If you want to use the total heat source option at the part of the region with field functions using cell centroid or position, you must consider the geometry or distribution of the cell in the target region. Since the total heat source input by field function or user code depends on the volume of the target and the cell, the input value you computed may work differently from what you intended. h_cell = h_total * ( V_cell / V_total ) The input value depends on the volume of the cell volume and the target space volume, as shown above, and both volume factors are directly affected by the cell morphology in the target space. Thus, you should check the cell volume and geometry in the target region before giving the total heat source. Another field function consists of the cell position or centroid in the heat source field function or cell sets can be a good checker for this problem.