Now assume a circulator capable of generating a flow rate of
15 gpm was installed in the secondary circuit, and the piping was scaled up
accordingly. Figure 3 shows the resulting flows:<br><br>
Notice that flow between the closely spaced tees has reversed. This reversal is
the only possibility given the flow rates in the surrounding pipes, and rest
assured it does not damage the system in any way. <br><br>
Also notice that the flow rate in the primary loop, for all practical purposes,
does not change. That’s because the insignificant pressure drop between the
closely spaced tees effectively prevents the primary loop from “feeling” any
change in its hydraulic resistance. Remember, the primary loop doesn’t even
“know” the secondary circuit exits.<br><br>
An even more interesting result is what happens to temperatures and heat
transfer in the secondary circuit. Again, we have to follow the energy into and
out of the tees to predict what will happen.<br><br>
The flow reversal between the tees now creates a mixing point at the upstream
tee-just the opposite of what occurred in the first scenario where the mixing
point was at the downstream tee.<br><br>