The basic aim of the experiments conducted was to
determine the thermal performance of thermosyphon
heat-pipe solar collector under real operating conditions
using three different refrigerants. A compact solar collector
using different refrigerants to transfer heat collected
by a flat plate with heat pipes to heat water was designed
and produced, using medium-level technical abilities and
working at low temperature conditions. An extensive
two-phase closed thermosyphon solar collector testing
program lasting for two months revealed that the prototype
heat pipe solar water heaters performed satisfactorily.
The heat pipes did not present start up difficulties. It
was found that the refrigerant of the highest solar thermal
energy collection performance among the working
fluids used in this experimental investigation was
R410A. In future studies, the effect of the number of
the thermosyphon tubes of the collector on the water
temperature rise and the collection efficiency should be
investigated. Theoretical study and more experimental
data are needed to optimize the collector parameters.
The results shown in the present work may be used in
the design and construction of a compact SDHWS.
Generally speaking, refrigerant charged domestic hot
water systems combine good energy behaviour with simplicity
in manufacture, the use of common flat-plate
solar collectors without significant alterations of the
existing production line, good behaviour in freezing
and overheating, and an absence of moving parts or
external pumping power. Also, as the present paper contains
side-by-side performance comparisons of three
identical systems using three different refrigerants, this
study can be useful to system designers in the selection
of an appropriate refrigerant.