Last month, we discussed how a constant volume heating, ventilation and air conditioning (HVAC) system would continually pump the same flow rate of chilled water through the entire system regardless of the cooling load.
A recent question I received from an engineer in the Middle East had to do with a “double control” of boiler feed pumps (BFPs) at his power plant. The system was controlled both by set position of the valves as well as variable speed drives. I was intrigued.
Entrained air is typically measured by volume at atmospheric pressure and not by weight. While not a totally inclusive list, the following are the most common reasons for air entrainment in pump systems: