A second check valve was installed in the system on Friday, March 25, to prevent reverse thermosiphoning. Figure 6 shows the subsequent change in hourly average collector inlet and outlet temperature.
The reverse thermosiphoning described earlier in this paper caused the apparent positive (but actually negative) heat flow that occurred at night from January through March.
All 90-degree turns should be accomplished by using two 45-degree elbows because thermosiphoning water does not like to make 90-degree turns, and this ensures a smoother flow.
The check valve used in the lower thermosiphoning line that runs from the drum to the lower water jacket inlet is important, and keeps the heated water from backing up in an opposite direction from what we want.