ps version

We have a closed-loop air system. After the pump, there is a valve V1 which controls the total air flow. Next is the heat exchanger box, out of which flow 2 branches of the system, one for the plenum air, which should see of order 70 cfm or 13.2 m/s through a 2" tube. The other branch should see about 30 cfm. The flow is measured for both branches. Valve V2 is used to proportion these flows. The pressure in the MVD should be neutral, so on the return legs, valves V3 and V4 can be used to balance the effects of the resistance of the heat exchanger box.

What do we observe? Turn on the system, and adjust V3 and V4 such that the MVD pressure is neutral. This happened when V3 and V4 are completely closed. After some confusion, we arrived at the following conclusion: we are not conserving mass. On the supply side, there were numerous leaks, but on the return side there wer much fewer leaks. The net effect is that air is lost from the supply side, which is not made up on the return side, and the entire system becomes under-pressurized.

Solution:First of all, the suply side leaks have to be eliminated.