Steady-state calculation & pump sizing
District heating network, part 2: perform the steady-state calculation and size the pump
Overview
This part demonstrates how to edit the system configuration, perform a steady-state calculation, and size the pump. The starting point is the network created in the first part.
Checking the system configuration
In the Systems view, it is shown which systems are assigned at which point.
House transfer station
Double-clicking the entry opens the plant editor. The simple house transfer station contains:
- A heat exchanger with a pressure loss of 0.5 bar
- A valve that regulates a temperature difference of 20 Kelvin across the heat exchanger
Energy plant
The energy plant contains:
- A circulation pump with an initially constant pressure increase of 2 bar (it will be sized afterwards)
- A simple heat generator with a constant supply temperature of 80 °C
Performing the steady-state calculation
- Switch to the Steady-state analysis tab.
- Open the dialog — here you can configure supply temperature, temperature difference, static pressure (pressure in the pressure maintenance system), and the simultaneity.
- Create the steady-state calculation.
Results of the steady-state calculation
The results show:
- The pressure loss at the worst point and the critical path displayed in color
- By selecting different entries in the table, the pressure losses at each consumer can be displayed
- The pressure profile along the branch, optionally with or without geodetic height
- The pressure limits of the pipes (e.g. PN16 with 16 bar pressure rating)
Important in practice:
In the pressure profile, check not only the worst point but also the absolute pressure at the highest and lowest terrain points. Besides the pressure rating of the pipes (e.g. PN16), it is crucial that the pressure never falls below the evaporation pressure of the supply temperature anywhere — otherwise cavitation and air ingress are a risk. Especially in hilly terrain, the geodetic height determines the required pressure maintenance.
Additional display options
Additional quantities can be displayed in color in the network: specific pressure loss, mass flow, volume flow, and further results. Selecting an element shows additional results on the right side.
Detail results
Under Details you find a tabular overview of every component in the network — i.e. every component in the systems and in the pipe network, including pipe fittings, with the respective pressure loss, mass flow, volume flow, and absolute pressure.
Sizing the pump
- Switch to Pump sizing.
- In the upper table the energy plant is displayed. Below it, suitable pumps are suggested.
- Select the desired pump and click Assign pump.
- The pump from the database is automatically stored in the system — the correct curves are assigned directly.
Verifying the pump in the system
Via Edit system and double-clicking the energy plant, you can verify that the correct pump curves are stored.