Paw - 01/2020

Product range Solex

Solar transfer stations

Selection table solar transfer stations - Solex

Specific flow

rate in l/(m2 x h)

Collector surface in m2

90/

100

120

140/

160

180/

200

240

280

320

360/

400

Mini

Midi

Maxi

Mega

***

Mini

Midi

Maxi

Mega

***

Mini

Midi

Maxi

Mega

***

Mini

Midi

Maxi

Mega

***

High-flow system with harp collectors

Dimensioning of a Solex module

Different collector types with the same size of collector field need

very different

flow rates for an effective operation without interruption. The

hydraulic connection of the collector field as well as the shape of

the collector can in

fluence the optimal flow of the solar circuit, too.

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 difference. 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 litres 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 litres 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

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.

*** precise dimensioning required

01/2020 • Printed in Germany

260

PAW GmbH & Co. KG • 31789 Hameln • Germany • Phone: +49-5151-9856-0 • Fax: +49-5151-9856-98 • info@paw.eu • www.paw.eu