Value of t_outlet_k for circ_pump_pressure

[harrahx3]

Describe the bug
In pandapipes 0.11 the attributes t_outlet_k has been added in the results parameters of the branch elements.

In the case of several pipes converging to the same junction, I understand that this attribute is useful to distinguish between the temperature at the outlet of the individual pipes, and the temperature at the junction resulting from the mixing of the fluids.

However I noticed an unexpected behavior in the case of circulation pumps, where the t_outlet_k doesn't correspond to the output temperature, but is smaller than both the feed and the return temperatures.

To Reproduce
Minimal example code:

I create a simple District Heazting system with only one circ_pump_pressure and one heat_consumer, connected with two pipes.

There is only one loop so there are never two branch elements converging towards the same junction.

import pandapipes

net = pandapipes.create_empty_network(fluid="water", name='net_pipes')

# create junctions
j0 = pandapipes.create_junction(net, pn_bar=10, tfluid_k=350)
j1 = pandapipes.create_junction(net, pn_bar=10, tfluid_k=350)
j2 = pandapipes.create_junction(net, pn_bar=10, tfluid_k=350)
j3 = pandapipes.create_junction(net, pn_bar=10, tfluid_k=350)

# create branch elements
pandapipes.create_pipe_from_parameters(net, from_junction=j0, to_junction=j1, length_km=0.1,
                                       diameter_m=0.05, u_w_per_m2k=10, text_k=273.15+15)
pandapipes.create_pipe_from_parameters(net, from_junction=j2, to_junction=j3, length_km=0.1,
                                       diameter_m=0.05, u_w_per_m2k=10, text_k=273.15+10)

pandapipes.create_circ_pump_const_pressure(net,
                                           return_junction=j3,
                                           flow_junction=j0,
                                           p_flow_bar=10,
                                           plift_bar=8,
                                           t_flow_k=233.15)

pandapipes.create_heat_consumer(net, from_junction=j1, to_junction=j2,
                                qext_w=100e3, controlled_mdot_kg_per_s=1)

pandapipes.pipeflow(net, mode='bidirectional')

print(net.res_circ_pump_pressure)

Result

net.res_circ_pump_pressure

 v_mean_m_per_s  p_from_bar  p_to_bar    t_from_k  t_to_k  t_outlet_k  \
0             NaN         2.0      10.0  306.672499  333.15  289.822499   

   mdot_from_kg_per_s  mdot_to_kg_per_s  vdot_m3_per_s  deltat_k  qext_w  
0                 1.0              -1.0       0.001003       NaN     NaN  

Expected behavior
I expect t_outlet_k being equal to the feed temperature t_to_k

Python environment (please complete the following information):

• OS: Ubuntu 24.04
• pandapipes version : 0.11.0