Details on "Calculation Parameters" (District Networks)
Information about the Calculation Parameters tab in the Settings for the Rohrnetzberechnung Quartiersnetze.
In this section, specify the global settings and limit values for Rohrnetzberechnung Quartiersnetze.
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Sizing
In this section, you define the design temperatures and limit values for the pipe network calculation. Meaningful default values for calculating district networks have already been set for all parameters; you can adjust these to meet the requirements of your project if necessary.
Design Temperature for Consumers - Flow: Sets the design temperature for consumers in the flow.
Design Temperature for Consumers – Return: Sets the design temperature for consumers in the return.
Max. Velocity in Distribution Pipes: Sets the limit value for the highest velocity in the distribution pipes.
Max. Velocity in Service Pipes: Sets the limit value for the max. velocity in service pipes.
Max. Pipe Friction Pressure Loss in Distribution Pipes: Sets the limit value for the maximum pipe friction pressure loss in the distribution pipes.
Max. Pipe Friction Pressure Loss in Service Pipes: Specifies the limit value for the maximum pipe friction pressure loss in the service pipes.
Max. System Pressure: Sets the limit value for the highest pressure in the district networks.
Temperature Boosted Cold Water: Sets the temperature for boosted cold water.
Consider Elevation Data
Enabled: The elevation data entered is taken into account in the calculation to determine the geodetic elevation data for the pipes and to consider it in the calculation. In the calculation dialog, the elevations of the individual Pipe Route Sections are displayed in the column H.
You can label elevation points in the drawing using the Label Objects function in the Elevation Points section.
Medium
Opens the Medium dialog where you can edit the currently used medium or load another medium.
Diversity
Drop-down list for selecting the diversity method used in the calculation. Diversity determines how many consumers in the district network are drawing heat at the same time and thus directly influences the sizing of the pipes and pumps. The following options are available:
- 100%: All consumers are considered at full capacity at the same time. This method is usually used as a worst-case approach or for test scenarios without reduction through diversity.
- DS 439: This is a Danish standard for typical load profiles in local and district networks. Due to the consideration of realistic usage distributions, the DS 439 is suitable for practical network simulations.
- VDI 2072: The VDI 2072 should be used for systems in which centrally heated domestic hot water is supplied via fresh water stations or central systems. This guideline realistically determines the simultaneous tapping rates that serve as the basis for sizing storage and transfer systems as well as the network. By combining usage profiles and empirical data, this method yields results that are significantly more practical than, for example, a simple generalized estimate according to Winter.
Typical applications include systems where multiple users draw hot water simultaneously but not continuously, such as apartment buildings with fresh water stations and complexes with central heating and decentralized fresh water stations, including hotels, residential complexes, or public buildings.
- Winter: In this method, it is simply assumed that there is an increased simultaneous demand during the heating period. Because of the increased overlap resulting from the combination of heating and domestic hot water demands, this method is suitable for modeling conservative load peaks during winter operation. It should be noted that, in practice, the domestic water and heating loads do not occur simultaneously. The use of this process therefore results in high mass flow rates and large pipe dimensions.
Min. Diversity: Sets the minimum value for diversity.
Sizing Strategy
Drop-down list to define the strategy used for sizing of the district network. Sizing is carried out in up to three steps, depending on the selected strategy.
| Step | |
|---|---|
| 1 Basic Sizing | A network with the smallest possible nominal diameters is created in consideration of the specified limit values. All pipes are sized in such a way that the specified values for maximum velocities and maximum pipe friction pressure losses are not exceeded. The specified maximum system pressure is not yet considered in this step. With the Sizing Strategy none, only this step is performed. |
| 2 Magnification | This is performed for the sizing strategies Sequential, R-value, and Pressure Loss. Selected trench sections are enlarged as long as the required pump pressure of the critical hydraulic path is greater than the specified maximum system pressure. The order, in which the trench sections are dimensioned, depends on the selected Sizing Strategy. |
| 3 Partial reduction of nominal diameters | This is performed for the sizing strategies Sequential, R-value, and Pressure Loss. Finally, an attempt is made to reduce the enlarged pipes again as far as the system pressure conditions allow. The pipes that were enlarged last are tested first (LIFO principle - last in first out). |
The following sizing strategies are available:
- None: Only the basic sizing (step 1) is carried out and a network with the smallest possible nominal diameters is created under consideration of the corresponding conditions.
- Sequential: All three steps of the sizing process are carried out. In Step 2, the individual sections are sorted from the consumer to the energy hub, and the pipes are increased in size in that order, taking the relevant conditions into account.
- R-Value: All three steps of the sizing process are carried out. In step 2, the individual trench sections are sorted in descending order according to their pipe friction pressure loss and an attempt is made to enlarge the pipes in this order, considering the corresponding conditions.
- Pressure Loss: All three steps of the sizing process are carried out. In step 2, the individual trench sections are sorted in descending order according to their pressure losses and an attempt is made to enlarge the pipes in this order, considering the corresponding conditions.
Heat Gain
In this section, you specify the values for the parameters used in the heat gain calculation.
Ground Temperature: Determines the average ground temperature at the project site.
Oversizing: Specifies the thickness of the ground layer above the pipes.
Lambda Ground: Specifies the thermal conductivity of the ground at the project site.
Pipe Spacing: Specifies the distance between the supply and return pipes in UNO piping systems.
Include Ageing Factors
Enabled: The input fields for the factors of moisture and aging are enabled, and the calculation takes into account heat losses resulting from the deterioration of pipe insulation due to moisture and aging.
fm Influence Factor from Humidity: Specifies the factor affecting the degradation of pipe insulation due to moisture.
Influence Factor from Aging: Specifies the factor accounting for the deterioration of pipe insulation due to aging.
Permissible Temperature Deviation from Design Values: Specifies the tolerance for temperature deviations from the design temperatures of the flow and return pipes.
Permissible Temperature Loss in Supply: Sets the tolerance for the temperature loss in the flow.