...
...
...
...
...
...
...
...
...
...
Pump types
Pump type | Name | Description |
|---|---|---|
 | Supply pump | This pump is mounted on the supply pipe and is mostly used on collectors and risers. |
 | Boiler feed pump | This pump is mounted on the return pipe and is used on production units (Boilers, heat pumps, Cogen, ...). |
 | Supply pump with external control | This pump is mounted on the supply pipe. The pump speed is ad tojusted according the external signal (0-1). |
 | Switchable boiler feed pump | This pump is mounted on the return pipe and is used on production units (Boilers, heat pumps, Cogen, ...)An A on/off valve is integrated into the basic circuit. |
Calculation
Pump head
The method of the pump head calculation is for all pump types the same (see above). The pump head is calculated by combining all of the pressure losses within the path of the most resistance (see the blue dots in the example below, this can be shown by hovering over the pump). The total calculated pressure loss is 34.785 Pa (1.667,5 Pa + 33.117 Pa), to calculate the pump head, the density (965 kg/m³ @75°C) and the gravity (9,81 N/kg) is taken into account as explained in the formula below. By clicking on the pump the calculated pump head is (3,68 m) shown in the parameter list, also is it possible to block the pump head by clicking the lock. To have more insight into the ratio of which component takes the most pressure loss this can be seen by hovering over the pump.
...
h = Pump head (m)
p = Total pressure loss (N/m² = Pa)
ρ = Density (kg/m³)
g = Gravity (N/kg)
Pump curve
When the pump head is calculated, a pump curve (generically) is at the same time produced where the calculated pump head and the design flow is the duty point (see blue dot). In function of the chosen operation mode (constant speed, constant head, and proportional head) the pump curve is further shaped by a parabolic line. For constant head, the pump head is held constant and for proportional head, the pump head (H) goes to the H/2 at 0 flow. It is also possible to chance at points in the curve. When the curve is locked the pump head will be selected in function of the design flow and the locked curve, also it is not possible to lock the pump curve and at the same time the pump head because this is contradictory.
...
Parameter validation
When the pump head is locked at 2 m instead of the calculated 3,68 m, the pump curve will be fitted on the blue dotedottedy point (2 m, 7,84 m³/h). The selected pump is in this particular case too small and will influence the actual flow. The red line in the graph below shows the pressure loss curve, the red dot 1 is the needed duty point at (3,68 m and 7,84 m³/h), but the actual duty point (red dot 2) is (2,4 m and 6,91 m³/h). In case the pump is selected incorrectly the software will show this as an error. The actual flow will is also be shown on the label.
...
Simulation
Different pump curves
All the pump types can make use of the different pump curves (constant speed, constant head, and proportional head), dependent on the use of the pump, the pump curve needs to be adjusted.
Pump in a constant flow situation needs to be set at a constant speed.
Pump in a variable flow situation needs to be set on the constant head or proportional head.
The pump used with an external signal needs to be set at a constant speed. The speed of the pump will be adjusted accordingly through the 0 - 1 signal, where signal 0 is minimum speed and signal 1 is maximum speed.
Electricity consumption
The electric power Pe depends on the effective theoretical pump power (Δp * Q) and the respective efficiency for the pump (ηpump). The pump efficiency is a generic curve based on technical data from manufacturers, with a maximum efficiency of 53%. This value can be overridden in the simulation parameters dialog and will be taken into account after executing the Optimize system components action.
...
formula (0 < relativeVolumeFlow < 1) : 0.01 * (((75 * relativeVolumeFlow - 181) * relativeVolumeFlow + 159.38) * relativeVolumeFlow + 0.2927)
Study case
In this example, the 4 pump operation modes (internal and external) are simulated during January and compared based on electricity consumption. This case is a variable flow installation with a constant supply temperature. In partial load, as shown in the plots below the pump head will follow the pump curve as a function of the flow in the installation (blue dot is the design duty point and the red dots are the pump head according to the flow). In the case of the external pump control, the pump speed will be adjusted according to the input signal which comes from the PI control, the minimum pump speed is respected by filling in a minimum modulation percentage (the pump speed is reduced so the most open valve (±60%) will go to 95% open position). There is a big difference in electricity consumption between the 4 pump operation modes respectively 56,7 kWh, 36,2 kWh, 20,9 kWh, and 14,2 kWh within the same installation. Depending on the used concept the electricity consumption will differ.
...