This model multiplies the heat flow rate so that
0 = port_b.Q_flow + k * port_a.Q_flow
.
The temperature remains unchanged. Therefore, this model does not conserve energy. It is used in Buildings.Fluid.HeatExchangers.RadiantSlabs.ParallelCircuitsSlab to avoid having to instanciate multiple slab models in parallel, with each having the same mass flow rate and temperatures.