This function computes a fictitious thermal resistance between
the pipe outer wall and a fictitious, average temperature of the
plane that contains the pipes. The equation is the same as is
implemented in TRNSYS 17. Different equations are used for

- floor heating systems (if
```
sysTyp ==
Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.SystemType.Floor
```

),
- radiant heating or cooling systems in ceilings and walls (if
```
sysTyp ==
Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.SystemType.Ceiling_Wall_or_Capillary
```

and `disPip/dPipOut ≥ 5.8`

), and
- capillary tube systems (if
```
sysTyp ==
Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.SystemType.Ceiling_Wall_or_Capillary
```

and `disPip/dPipOut < 5.8`

).

#### Limitations

The resistance `Rx`

is based on a steady-state heat
transfer analysis. Therefore, it is only valid during steady-state.
For a fully dynamic model, a finite element method for the radiant
slab would need to be implemented.

function AverageResistance
input Modelica.SIunits.Distance disPip "pipe distance";
input Modelica.SIunits.Diameter dPipOut "pipe outside diameter";
input Modelica.SIunits.ThermalConductivity k "pipe level construction element thermal conductivity";
input Buildings.Fluid.HeatExchangers.RadiantSlabs.Types.SystemType sysTyp "Type of radiant system";
input Modelica.SIunits.ThermalConductivity kIns "floor slab insulation thermal conductivity";
input Modelica.SIunits.Thickness dIns "floor slab insulation thickness";
output Modelica.SIunits.ThermalInsulance Rx "Thermal insulance";
end AverageResistance;

- April 17, 2012, by Michael Wetter:

Added term `1/s`

in computation of
`infSum`

.
- April 5, 2012, by Michael Wetter:

Revised implementation.
- April 3, 2012, by Xiufeng Pang:

First implementation.

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