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 adjusted 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, ...). A on/off valve is integrated in 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 in the ratio 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 off 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 hold constant and for proportional head the pump head (H) goes to the H/2 at 0 flow. It is also possible to chance and 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 doted duty point (2 m, 7,84 m³/h). The selected pump is in this particular case to small and will have an influence on 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 incorrect the software will show this as an error. The actual flow will is also be shown on the label.

Related models:

TOKEN - NzU4fFhrSk5wWTc1 - Supply pump

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 on constant speed.
Pump in a variable flow situation needs to be set on constant head or proportional head.
Pump used with an external signal needs to be set on constant speed. The speed of the pump will be adjusted accordingly the 0 - 1 signal, where signal 0 is minimum speed and signal 1 is maximum speed.

Electricity consumption

The electric power P_e depends on the effective theoretical pump power (Δp * Q) and the respective efficiency for the pump (η_pump). The pump efficiency is a generic curve based on technical data from manufactures, with a max. 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.

The pump efficiency will reduce as a function of the system flow, this is shown in the plot below. The pump electricity consumption is calculated in time during the simulation taken into account; the differential pressure, flow and the pump efficiency.

P_e = Power (W)
Δp = Differential pressure (Pa)
Q = Flow (kg/s)
η_pomp = Efficiency (%)

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 the month of January and compared on the basis of 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 case of the external pump control the pump speed will be adjusted according the input signal witch 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.