This test attempts to assess how even a distribution of fluid to the risers this design achieves. If the distribution is uneven, then the efficiency of the collector will suffer. Even though this design is very common, there is surprisingly little data that I could find on the evenness of the distribution.
The picture shows the my 11 ft wide collector used for the test.
Same collector with glazing removed to show manifolds and risers.
The test was done by removing the glazing from the collector, and with full sun on the collector, and normal fluid flow through the collector, the temperature of each riser was measured with an IR gun style thermometer.
The idea being that if a good fluid distribution is being achieved, the risers should all have a similar temperature profile with the lower part being near the tank temperature, and the temperature gradually increasing as you go up the riser.
Riser No | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
top | 124 | 123 | 123 | 124 | 126 | 129 | 124 | 128 | 126 | 132 | 127 | 125 | 129 | 125 | 128 | 126 | 123 | 123 | 122 | |
mid | 123 | 122 | 121 | 123 | 124 | 124 | 120 | 125 | 123 | 125 | 125 | 125 | 125 | 124 | 123 | 123 | 123 | 123 | 120 | |
bottom | 122 | 117 | 119 | 117 | 119 | 117 | 115 | 119 | 118 | 119 | 120 | 121 | 119 | 117 | 117 | 115 | 116 | 120 | 115 | |
Time | 12:47 PM | 12:56 PM | ||||||||||||||||||
Temp rise | 2 | 6 | 4 | 7 | 7 | 12 | 9 | 9 | 8 | 13 | 7 | 4 | 10 | 0 | 8 | 11 | 11 | 7 | 3 | 7 |
Happily, the distribution is pretty even, with most risers showing similar temperature patterns. There are variations, but probably not enough to seriously effect efficiency.
It does appear that the evenness of the distribution can be effected by relatively small changes in the details of how the plumbing is done. Have a look at the full report for more details on this.
All the gory details on riser flow distribution test...
If you have additional data on riser flow pattern tests or analysis, please let me know.
Gary