modelUPreinsulated
U model for Preinsulated pipes
Extends from BuildingSystems.Technologies.DistrictHeatingNetworks.UndergroundPipes.BaseClasses.DHN_Umodels.UPartialClass.
Information
Main equations
U1 = (Rg+Ri)/((Rg+Ri)^2-Rm^2)
U2 = (Rm)/((Rg+Ri)^2-Rm^2)
Implementation
In case U1 > 4*U2, the value of U2 is set to 0. It means the interaction between pipes is negelcted.
References
On transient heat losses from buried district heating pipes, Bomm 2000.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nPipes (from UPartialClass) | Number of pipes | |
| General › Geometry | |||
| Modelica.Units.SI.Area | SPip (from UPartialClass) | (Modelica.Constants.pi*d_o*d_o/4) - SWat | Cross-sectional wall area of the pipe (area of piping material) |
| Modelica.Units.SI.Area | SWat (from UPartialClass) | (Modelica.Constants.pi*d_i*d_i/4) | Cross-sectional inside area of the pipe |
| Modelica.Units.SI.Diameter | d_i (from PipeInfo) | Pipe's inner diameter | |
| Modelica.Units.SI.Diameter | d_o (from PipeInfo) | d_i/(0.0366*Modelica.Math.log(d_i) + 0.769) | Pipe's outter diameter |
| Modelica.Units.SI.Thickness | th_ins (from PipeInfo) | 0.05 | Insulation's thickness |
| Modelica.Units.SI.Thickness | th_c (from PipeInfo) | 0.005 | Cover's thickness |
| Modelica.Units.SI.Diameter | d_g | 1.313 | Diameter of the undisturbed ground |
| General › Thermal properties | |||
| Modelica.Units.SI.Density | den_p (from UPartialClass) | 8 | Density of the pipe material |
| Modelica.Units.SI.SpecificHeatCapacity | cp_p (from UPartialClass) | 0.49 | Specific heat capacity of the pipe material |
| Modelica.Units.SI.ThermalConductivity | lam_ins (from PipeInfo) | 0.032 | Heat conductivity of the pipe's insulation |
| Modelica.Units.SI.ThermalConductivity | lam_c (from PipeInfo) | 0.43 | Heat conductivity of the covers material |
| Modelica.Units.SI.ThermalConductivity | lam_g | 1.2 | Heat conductivity of the undisturbed ground |
| General › Laying | |||
| Modelica.Units.SI.Length | H_real | Depth of the pipe center | |
| Modelica.Units.SI.Length | E | Distance between pipes' centers | |
| Assumptions | |||
| Modelica.Units.SI.CoefficientOfHeatTransfer | h_gs | 14.6 | Heat transfer coefficient at the ground surface |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealOutput | U (from UPartialClass) |