RF
MC
26
SERIES/PARALLEL CONNECTION LAYOUTS AND PANEL ARRAYS
Chapter 4
SERIES/PARALLEL CONNECTION LAYOUTS AND PANEL ARRAYS
The Extrafl ame solar kits are made up from two or more panels that must be connected to each other. There
are three possible connections: in series, in parallel, and mixed in series – parallel. When the collectors are
connected in series, they are passed by the same fl ow and the system fl ow rate that passes through each
collector is the same. The temperature if the heat transfer fl uid increases from the fi rst to the last collector
and this means that the last collectors work at a higher temperature and therefore with lower effi
ciency. The
loss of head of each collector is also added and as a consequence in this confi guration it results convenient
to work with low fl ow rates (low fl ow).
RF = Cold return
MC = Hot fl ow
The parallel connection according to the Tichelmann method allows to obtain the same fl ow for each
collector. In order to prevent dead areas and to guarantee a turbulent fl ow it is useful to adjust the
circulating fl ow rate on each collector to a value exceeding 60 l/h. The fl uid fl ow rate of the system with
parallel connection is divided between the various collectors. If the collectors are n and the total fl ow
rate is x, in each collector there is a fl ow rate equal to x/n. Diff erently from connection in series, the heat
drop between up and downstream is the same for all collectors and therefore they work with the same
effi
ciency value.
The connection in parallel seems more effi
cient with respect to connection in series; on the other hand it
can only be applied to fi elds formed by a small number of collectors (about 5).
Particular connection must be given to the connection of the pipes to the panels in order to guarantee
uniform distribution of the fl ow rate (see fi gure 4.3). Pay attention to the direction of assembly of the panel,
which must be positioned with the down side below.
fi gure 4.1
