Abstract
Most small solar domestic hot water systems, SDHW systems, are not
equipped with circulation piping. In many systems the pipes, in
which the hot water is transported from the solar tank to the
draw-off locations, are relatively long. Hence, the waiting time
for hot water during draw-off is relatively long. In order to
reduce this waiting time to an acceptable level, the flow rate
during draw-off is often very large - typically about 20 l/min -
at least at the start of the draw-off. As long as the flow rate
during draw-off is small, the mixing rate inside the tank is
small. However, if the flow rate is large, as mentioned above, the
mixing rate can be relatively large if the cold water inlet design
is poor. Mixing results in destratification in the solar tank and
with that reduced thermal performance of the SDHW system.
Investigations indicate that the decrease of the yearly thermal
performance caused by mixing during draw-offs can be as high as 23
% if a marketed cold water inlet design is used. Other tested
inlet designs result in a decrease of 2-3 % of the yearly thermal
performance caused by mixing. Based on the investigations
recommendations on the design of the cold water inlet and on a
test method for solar tanks concerning mixing during draw-offs are
given.
Original language | English |
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Title of host publication | Thermal destratification in small standard solar tanks due to mixing during tapping |
Publication date | 1999 |
Publication status | Published - 1999 |
Event | ISES 1999 Solar World Congress: Solar is renewable - Jerusalem, Israel Duration: 4 Jul 1999 → 9 Jul 1999 |
Conference
Conference | ISES 1999 Solar World Congress |
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Country | Israel |
City | Jerusalem |
Period | 04/07/1999 → 09/07/1999 |