.BuildingSystems.Fluid.FixedResistances.BaseClasses.PlugFlowHeatLoss

Information

Component that calculates the heat losses at the end of a plug flow pipe when the flow goes in the design direction.

Main equations

The governing equations are

T_out = T_b + (T_in - T_b) exp((t_out - t_in)/tau_char)

with

tau_char = R C

Assumptions and limitations

This model is based on the following assumptions:

• The water temperature is uniform in the cross section.
• There is no axial heat transfer in the water or surrounding.
• The boundary temperature along the pipe is uniform.
• Heat losses are steady-state.

Implementation

Heat losses are only considered in design flow direction. For heat loss consideration in both directions, use one of these models at both ends of a BuildingSystems.Fluid.FixedResistances.BaseClasses.PlugFlow model. The outlet temperature is calculated as in the equation above, using the inlet temperature at port_a and the instantaneous time delay and boundary temperature. The boundary temperature can be either the air temperature or the undisturbed ground temperature, depending on the definition of the thermal resistance R.

This component requires the delay time and the instantaneous ambient temperature as an input. This component is to be used in single pipes or in more advanced configurations where no influence from other pipes is considered.

Revisions

• December 6, 2017, by Michael Wetter:
  Reformulated call to medium function.
  This is for issue 869.
• October 20, 2017, by Michael Wetter:
  Revised implementation to avoid graphical and textual modeling. Revised variable names and documentation to follow guidelines.
• November 6, 2015 by Bram van der Heijde:
  Make time delay input instead of calculation inside this model.
• September, 2015 by Marcus Fuchs:
  First implementation.