HEAT_FLOW 2D: How to generate output via OGS or ParaView

Hello everyone,

I’m trying to calculate the heat flow. My model is only 2D.

I tried this in my output file:
#OUTPUT
$PCS_TYPE
HEAT_TRANSPORT
$GEO_TYPE
SURFACE SURF_1
$DAT_TYPE
TOTAL_FLUX
$TIM_TYPE
STEPS 1

The Output will be generated, but the values per timestep are zero.

Do you know which settings have to be set or how can I calculate the heat flux in ParaView?

Thanks!