.AixLib.Fluid.DistrictHeatingCooling.Pipes.StaticPipe

Information

Pipe with heat loss using the time delay based heat losses for the transport delay of the fluid. This model determines the pressure drop either through a static factor or using the sum of zeta values.

This Pipe model is applicable for simulation of long pipes such as in district heating and cooling systems.

Implementation

This model is based on AixLib.Fluid.DistrictHeatingCooling.BaseClassesStatic.StaticCore.

Heat losses are implemented by AixLib.Fluid.FixedResistances.BaseClasses.PlugFlowHeatLoss at each end of the pipe (see AixLib.Fluid.FixedResistances.BaseClasses.PlugFlowCore). Depending on the flow direction, the temperature difference due to heat losses is subtracted at the right fluid port.

The pressure drop is implemented using AixLib.Fluid.FixedResistances.HydraulicDiameter.

The thermal capacity of the pipe wall is implemented as a mixing volume of the fluid in the pipe, of which the thermal capacity is equal to that of the pipe wall material. In addition, this mixing volume allows the hydraulic separation of subsequent pipes. Thanks to the vectorized implementation of the (design) outlet port, splits and junctions of pipes can be handled in a numerically efficient way.

This mixing volume is not present in the StaticCore model, which can be used in cases where mixing volumes at pipe junctions need to be added manually.

If Boolean use_zeta is set "true" HydraulicResistance is used.

HydraulicResistance takes into account additional pressure drops due to bends/valves/etc. Therefore the sum of zeta values has to be given prior.

If Boolean use_zeta is set "false" the pressureloss is determine through a static factor which has to given prior.

Assumptions

• Heat losses are for steady-state operation.
• The axial heat diffusion in the fluid, the pipe wall and the ground are neglected.
• The boundary temperature is uniform.
• The thermal inertia of the pipe wall material is lumped on the side of the pipe that is connected to ports_b.

Revisions

• September 25, 2019, by Nils Neuland:
  Revised variable names and documentation to follow guidelines. Corrected malformed hyperlinks.