Product range Solex

Dimensioning

High-Flow system with harp collectors

Dimensioning of a Solex module

Different collector types with the same size of collector field

need very di

fferent flow rates for an e

ffective operation

without interruption. The hydraulic connection of the collector

field as well as the shape of the collector can also in

fluence

the optimal

flow of the solar circuit. Corresponding values

should be agreed with the manufacturer of the collectors.

They can also be found in the technical documents of the

collectors.

The solar systems are roughly divided into High-Flow systems

and Low-Flow systems. High-Flow systems are operated with

a higher

flow rate and a smaller temperature difference

between collector inlet and collector outlet.

In reality, these systems have less pressure drop than Low-

Flow systems. Accordingly, Low-Flow systems work with lower

flow rates and a higher temperature di

fference. The Solex

transfer stations can be used for High-Flow solar thermal

systems as well as for Low-Flow systems.

The values for the speci

fic flow rate given below refer to the

nominal flow rate.

Depending on the control target and the basic conditions, the

flow rate in the partial-load range is adapted by the controller

and can be much smaller than the calculated nominal flow

rate.

Low-Flow system with meander collectors

High-Flow systems have a flow rate of 25 to 40 litres per

square metre of collector surface and hour or 0.42 to 0.67 litre

per square metre of collector surface and minute.

Low-Flow systems have a flow rate of 10 to 20 litres per

square metre of collector surface and hour or 0.17 to 0.33 litre

per square metre of collector surface and minute.

The total

flow rate in a solar thermal system depends on:

• System operation mode (High-Flow/Low-Flow)

• Collector surface

• Performance of the heat exchanger (secondary)

The circulation pump dimensioning depends on:

• Flow rate

• Pressure drop of heat exchanger, collector, piping system

238

01/2024 • Printed in Germany

PAW GmbH & Co. KG • info@paw.eu • www.paw.eu

For the selection table of the proper Solex, we assumed a

minimum head of ~5 m wc (~50 kPa). If the real collector field

(including pipes) has a higher pressure drop, a detailed

dimensioning is inevitable.